Event Management

Read more about the article Dynamic Base URL Support in the Open Event Organizer App

Dynamic Base URL Support in the Open Event Organizer App

Open Event API Server acts as a backend for Open Event Organizer Android App. The server has a development instance running on the web for developers. Developers use this instance to try out new feature additions, bug fixings and other such changes in the source code. And when confirmed working, these changes are updated to the main running instance which is kept live throughout for the users. Similarly for Android app developers, to test the app with both the instances, we have implemented the dynamic base URL support in the app. The app has a default base URL set to development instance or main instance dependent on the debug mode. That means the app will use a server on developer instance when used under debug mode and will use a main instance server if used under release mode. The app also provides an option to enter an alternate URL while login in the app which replaces default base URL in the app for the session.

In the organizer app, we are using Retrofit + Okhttp for handling network requests and dagger for dependency injection. The OkhttpClient provider in NetworkModule class looks like:

@Provides
@Singleton
OkHttpClient providesOkHttpClient(HostSelectionInterceptor interceptor) {
   return new OkHttpClient.Builder()
       .addNetworkInterceptor(new StethoInterceptor())
       .build();
}

 

Retrofit had a support for mutable base URL in the earlier versions but the feature is no longer available in the recent versions. We are using Interceptor class for changing base URL. The class has a method named intercept, which gets called at each network request. In this method, base URL is reset to the new URL.

So first you have to extend Interceptor class and reset base URL in the intercept method. The Interceptor class in the app looks like:

public final class HostSelectionInterceptor implements Interceptor {
   private String host;
   private String scheme;

   public HostSelectionInterceptor(){
       //Intentionally left blank
   }

   public void setInterceptor(String url) {
       HttpUrl httpUrl = HttpUrl.parse(url);
       scheme = httpUrl.scheme();
       host = httpUrl.host();
   }

   @Override
   public Response intercept(Chain chain) throws IOException {
       Request original = chain.request();

       // If new Base URL is properly formatted then replace the old one
       if (scheme != null && host != null) {
           HttpUrl newUrl = original.url().newBuilder()
               .scheme(scheme)
               .host(host)
               .build();
           original = original.newBuilder()
               .url(newUrl)
               .build();
       }
       return chain.proceed(original);
   }
}

 

The class has a private string field host to save base URL. The method setInterceptor is used to change the base URL. Once the base URL is changed, thereafter all the network requests use changed URL to call. So now our interceptor is ready which can be used to support dynamic base URL in the app. This interceptor is added to Okhttp builder using its method addInterceptor.

@Provides
@Singleton
HostSelectionInterceptor providesHostSelectionInterceptor() {
   return new HostSelectionInterceptor();
}

@Provides
@Singleton
OkHttpClient providesOkHttpClient(HostSelectionInterceptor interceptor) {
   return new OkHttpClient.Builder()
       .addInterceptor(interceptor)
       .addNetworkInterceptor(new StethoInterceptor())
       .build();
}

 

And now you are able to change base URL just by using the setInterceptor method of Interceptor class from anywhere in the app. And by then all the network calls use the updated base URL.

Application

I will show you here, how exactly this works in the Open Event Organizer app. On the login page, we have provided an option to enter an alternate base URL.

                                

We have kept a default URL checked. The default URL is set as per debug mode. This is done by setting the fields in the build.gradle. The code looks like:

buildTypes {
       release {
           ...
           buildConfigField "String", "DEFAULT_BASE_URL", '"https://www.eventyay.com/api/v1/"'
       }
       debug {
           buildConfigField "String", "DEFAULT_BASE_URL", '"https://open-event-dev.herokuapp.com/api/v1/"'
       }
   }

 

The field is used in the app as:

private final String DEFAULT_BASE_URL = BuildConfig.DEFAULT_BASE_URL;

 

On login, the loginPresenter calls setInterceptor method of the Interceptor to update the URL according to the user’s input. And the base URL is changed in the app for further network requests.

Links:
1. Gist link for Interceptor implementation code – https://gist.github.com/swankjesse/8571a8207a5815cca1fb
2. Google dagger dependency injector Github Repo
3. Retrofit http client Github Repo
4. Okhttp client Github Repo

Continue ReadingDynamic Base URL Support in the Open Event Organizer App
Read more about the article Implementing Sponsors API in Open Event Frontend to Display Sponsors

Implementing Sponsors API in Open Event Frontend to Display Sponsors

This article will illustrate how the sponsors have been displayed on the public event page in Open Event Frontend using the Open-Event-Orga sponsors API. As we know that the project is an ember application so, it uses Ember data to consume the API. For fetching the sponsors, we would be mainly focusing on the following API endpoint: 

GET /v1/events/{event_identifier}/sponsors

 

In the application we need to display the sponsors is the event’s public page which contains the event details, ticketing information, speaker details etc. along with the list of sponsors so, we will be only concerned with the public/index route in the application. As the sponsors details are nested within the events model so we need to first fetch the event and then from there we need to fetch the sponsors list from the model.

The model to fetch the event details looks like this:

model(params) {
return this.store.findRecord('event', params.event_id, { include: 'social-links' });
}

 

But we can easily observe that there is no parameter related to sponsor in the above model. The reason behind this is the fact that we want our sponsors to be displayed only on the event’s index route rather than displaying them on all the sub routes under public route. To display the sponsors on the public/index route our modal looks like this:

model() {
    const eventDetails = this._super(...arguments);
    return RSVP.hash({
      event   : eventDetails,
      sponsors: eventDetails.get('sponsors')
   });
}

 

As we can see in the above code that we have used this._super(…arguments) to fetch the event details from the event’s public route model which contains all the information related to the event thereby eliminating the need of another API call to fetch sponsors. Now using the ember’s get method we are fetching the sponsors from the eventDetails and putting it inside the sponsors JSON object for using it lately to display sponsors in public/index route.

Till now, we’ve fetched and stored the sponsors now our next task is to display the sponsors list on the event’s index page. The code for displaying the sponsors list on the index page is 

{{public/sponsor-list sponsors=model.sponsors}}

 

The sample user interface without  for displaying the sponsors looks like this:  

Fig. 1: The sample user interface for displaying the sponsors

After replacing the real time data with the sample one, the user interface (UI) for the sponsors looks like this.

Fig. 2: The user interface for sponsors with real time data

The entire code for implementing the sponsors API can be seen here.

To conclude, this is how we efficiently fetched the sponsors list using the Open-Event-Orga sponsors API, ensuring that there is no unnecessary API call to fetch the data.  

Resources:

Continue ReadingImplementing Sponsors API in Open Event Frontend to Display Sponsors
Read more about the article Presenter Abstraction Layer in Open Event Organizer Android App

Presenter Abstraction Layer in Open Event Organizer Android App

Open Event Organizer App design follows Model View Presenter (MVP) architecture which enables heavy unit testing. MVP is a trending architecture design followed these days. If you are not aware of MVP architecture, then please refer any of the tutorial (few links are given at the end of this blog) about it before reading this. In the design, the code becomes little repetitive as the application size increases due to so many presenters and views, which degrades the code readability. So to avoid this and keep the functionality code clean in the App, we have created a Presenter Abstraction Layer which contains the repetitive code and the layer is extended wherever required in the app. I will be talking about the Presenter Abstraction Layer implementation through the App in this blog.

First of all, create a base interface. The base interface contains methods which every presenter will have. The base interface for presenter in the App looks like:

public interface IBasePresenter {
   void start();
   void detach();
}

 

In the method start, presenter loads all the required data from the model and sends it to the view. And releases all the resources in detach. These two methods are required in all the presenters. This interface is extended by other two interfaces which will be actually used by the views. The relevant code is:

public interface IPresenter<V> extends IBasePresenter {
   void attach(V view);
}

public interface IDetailPresenter<K, V> extends IBasePresenter {
   void attach(K key, V view);
}

 

Method attach is used to attach view and the data id (if required) to the presenter. In the app, most of the presenters require an extra data which is used in loading data from the model. Hence two interfaces are extended from the base interface. Now comes the implementation part.

public abstract class BasePresenter<V> implements IPresenter<V> {
   private V view;
   private CompositeDisposable compositeDisposable;

   @Override
   @CallSuper
   public void attach(V view) {
       this.view = view;
       this.compositeDisposable = new CompositeDisposable();
   }

   @Override
   @CallSuper
   public void detach() {
       view = null;
       compositeDisposable.dispose();
   }

   protected V getView() {
       return view;
   }

   protected CompositeDisposable getDisposable() {
       return compositeDisposable;
   }
}

 

The App uses ReactiveX Observables for async operations which contain fragment/activity context hence these need to be disposed at some lifecycle of fragment/activity. detach nulls the view and disposes the compositeDisposable. This method is called at the onStop lifecycle of fragment/activity. The observable subscriptions are one of the major reasons for memory leaks if not disposed at correct lifecycle in Android. So the detach method is called at onStop lifecycle when activity goes into background or fragment is switched by FragmentTransaction. Another base presenter class looks like:

public  abstract class BaseDetailPresenter<K, V> extends BasePresenter<V> implements IDetailPresenter<K, V> {
   private K id;

   @Override
   @CallSuper
   public void attach(K id, V view) {
       super.attach(view);
       this.id = id;
   }

   protected K getId() {
       return id;
   }
}

 

This class extends the previous one except for the attach method. As the presenters extending this, require an extra data id which is passed through this method. So the id can be used in the presenter extending this class using getId. The presenters in the app extend one of these two classes. This helps in making a firm app structure and the development process easier. Abstraction layer should be used wherever same code is repeated. This increases code readability and decreases the chances of creating bugs especially when a team is working on the same project.

Links:
1. MVP for Android: how to organize the presentation layer, by Antonio Leiva
2. Android Code That Scales, With MVP, by Nathan Barraille
3. Ted Mosby – Software Architect, by Hannes Dorfmann

Continue ReadingPresenter Abstraction Layer in Open Event Organizer Android App
Read more about the article Customizing Serializers in Open Event Front-end

Customizing Serializers in Open Event Front-end

Open Event Front-end project primarily uses Ember Data for API requests, which handles sending the request to correct endpoint, serializing and deserializing the request/response. The Open Event API project uses JSON API specs for implementation of the API, supported by Ember data.

While sending request we might want to customize the payload using a custom serializer. While implementing the Users API in the project, we faced a similiar problem. Let’s see how we solved it.

Creating a serializer for model

A serializer is created for a model, in this example we will create a user serializer for the user model. One important thing that we must keep in mind while creating a serializer is to use same name as that of model, so that ember can map the model with the serializer. We can create a serializer using ember-cli command:

ember g serializer user

 
Customizing serializer

In Open Event Front-end project every serializer extends the base serializer application.js which defines basic serialization like omitting readOnly attributes from the payload.

The user serializer provides more customization for the user model on top of application model. We override the serialize function, which lets us manipulate the payload of the request. We use `snapshot.id` to differentiate between a create request & an update request. If `snapshot.id` exists then it is an update request else it is a create request.

While manipulation user properties like email, contact etc we do not need to pass ‘password’ in the payload. We make use of ‘adapterOptions’ property associated with the ‘save()’ method. If the adapterOptions are associated and the ‘includePassword’ is set then we add ‘password’ attribute to the payload.

import ApplicationSerializer from 'open-event-frontend/serializers/application';
import { pick, omit } from 'lodash';

export default ApplicationSerializer.extend({
  serialize(snapshot, options) {
    const json = this._super(...arguments);
    if (snapshot.id) {
      let attributesToOmit = [];
      if (!snapshot.adapterOptions || !snapshot.adapterOptions.includePassword) {
        attributesToOmit.push('password');
      }
      json.data.attributes = omit(json.data.attributes, attributesToOmit);
    } else if (options && options.includeId) {
      json.data.attributes = pick(json.data.attributes, ['email', 'password']);
    }
    return json;
  }
});

If we want to add the password in the payload we can simply add ‘includePassword’ property to the ‘adapterOptions’ and pass it in the save method for operations like changing the password of the user.

user.save({
  adapterOptions: {
    includePassword: true
  }
})

Thank you for reading the blog, you can check the source code for the example here.
Resources

Learn more about how to customize serializers in ember data here

Continue ReadingCustomizing Serializers in Open Event Front-end
Read more about the article Displaying Upcoming Sessions at a Microlocation Open Event Android

Displaying Upcoming Sessions at a Microlocation Open Event Android

“When I am attending a session in a room, I don’t get information on what is coming up.”

The issue that the user expressed was that he wanted to know what were the upcoming sessions at a microlocation. While I took up this issue in Open Event Android a few days back, I was thinking of ways about how this can be implemented. The app should be easy-to-use even for non-developers and thus, any new feature shouldn’t be too complex in its implementation. We decided upon doing the following:

  • Adding an “upcoming” option in the options menu of the Location activity.
  • This option’s purpose was to trigger the app to show information about the upcoming session in that microlocation.

Initial changes in LocationActivity.java

First of all, we added a new icon in the options menu of LocationActivity.java. One of the things that we learnt there was to use ifRoom|collapseActionView option for the app:showAsAction  

attribute as frequently as possible. This option ensures that the title in the option’s menu is visible at all times irrespective of the options being visible along with their icons.

So in case, the title is too big and there is very little room for the options to appear individually, then instead of squeezing down the title, the “ifRoom” attribute will collapse the option icons and insert a 3-dotted drop-down option list with all the options appearing in the drop-down.

Something like this:

The icon’s XML element and UI looked something like this:

<item
       android:id="@+id/upcoming_sessions"
       android:icon="@drawable/ic_timeline_white_24dp"
       android:title="@string/upcoming"
       app:showAsAction="ifRoom|collapseActionView"
app:actionViewClass="android.support.v7.widget.Button"/>

About the drawable icon that you see in the screenshot above, it was a tough find. Before I talk about how I came across this icon, I will talk about adding an icon in Android Studio.

How to add an icon in Android Studio?

Adding an item in Android studio means adding a drawable at a basic level. You can find all drawables under the app/src/main/res/drawable folder.

To add a new drawable, right-click on the drawable folder and go to new –>Vector asset. A window similar to what is shown below will appear.

Now, on selecting the “icon” option you will be taken to a huge list of icons that you can add in your app and then use them subsequently. But the problem here is that it is tough at times to find the icon that will be fit for your purpose. Like in my case, there was no direct icon for “upcoming”. This is when we had to do something more. We had to browse to this amazing site by Google: https://material.io/icons/ This site shows all the available icons in a much more interactive way and it was a lot more easier for me to come across the icon we wanted using this site.

The vector drawable file for the icon we chose looks like this:

<vector xmlns:android="http://schemas.android.com/apk/res/android"
       android:width="24dp"
       android:height="24dp"
       android:viewportWidth="24.0"
       android:viewportHeight="24.0">
   <path
       android:fillColor="#FFFFFF"
       android:pathData="M23,8c0,1.1 -0.9,2 -2,2 -0.18,0 -0.35,-0.02 -0.51,-0.07l-3.56,3.55c0.05,0.16 0.07,0.34 0.07,0.52 0,1.1 -0.9,2 -2,2s-2,-0.9 -2,-2c0,-0.18 0.02,-0.36 0.07,-0.52l-2.55,-2.55c-0.16,0.05 -0.34,0.07 -0.52,0.07s-0.36,-0.02 -0.52,-0.07l-4.55,4.56c0.05,0.16 0.07,0.33 0.07,0.51 0,1.1 -0.9,2 -2,2s-2,-0.9 -2,-2 0.9,-2 2,-2c0.18,0 0.35,0.02 0.51,0.07l4.56,-4.55C8.02,9.36 8,9.18 8,9c0,-1.1 0.9,-2 2,-2s2,0.9 2,2c0,0.18 -0.02,0.36 -0.07,0.52l2.55,2.55c0.16,-0.05 0.34,-0.07 0.52,-0.07s0.36,0.02 0.52,0.07l3.55,-3.56C19.02,8.35 19,8.18 19,8c0,-1.1 0.9,-2 2,-2s2,0.9 2,2z"/>
</vector>

What would the upcoming icon do?

Keeping in mind the necessity for the feature to be less complex, I decided that the upcoming icon will lead the user to a dialog box that shows the status of upcoming sessions in that micro location. The implementation for this feature involved 2 main things:

  1. Finding out the upcoming session from the list of sessions in the microlocation.
  2. Generate a dialog box that shows information about that session.

Finding position of upcoming session in Recycler View

Upcoming session will be a session whose starting time comes after the current time. So the approach was simple.

  1. Run a loop on a sorted list of all sessions in a microlocation.
  2. Find out every session’s start time.
  3. Compare the start time of every session with the current time.
  4. Find the first session whose start time comes after the current time.
  5. Store that session’s position, name, ID and other stuff like track name and track color.
  6. Break out of the loop.

This was the basic logic or algorithm, so to say. Here’s the implementation in the upcomingSession() function:

public void upcomingSession(){
   String upcomingTitle = "";
   String track = "";
   String color = null;
   Date current = new Date();
   for (Session sess:sortedSessions){
       try {
           Date start = DateUtils.getDate(sess.getStartsAt());
           if (start.after(current)){
               upcomingTitle = sess.getTitle();
               track = sess.getTrack().getName();
               color = sess.getTrack().getColor();
               break;
           }
       } catch (ParseException e) {
           e.printStackTrace();
       }
   }

Now, displaying a dialog box consisting of all the necessary information is an easy thing to do once you have the required information. So, I’ll just provide some code for it here without explaining much about it.

The initialisations:

public void upcomingSessionsInitial(){
   upcomingDialogBox = new Dialog(this);
           upcomingDialogBox.setContentView(R.layout.upcoming_dialogbox);
           trackImageIcon = (ImageView)upcomingDialogBox.findViewById(R.id.track_image_drawable);
           upcomingSessionText = (TextView) upcomingDialogBox.findViewById(R.id.upcoming_session_textview);
           upcomingSessionTitle = (TextView) upcomingDialogBox.findViewById(R.id.upcoming_Session_title);
           Button dialogButton = (Button) upcomingDialogBox.findViewById(R.id.upcoming_button);
           dialogButton.setOnClickListener(new View.OnClickListener() {
               @Override
               public void onClick(View view) {
                   upcomingDialogBox.dismiss();
               }
           });
}

The calling:

switch (item.getItemId()){
       case R.id.action_map_location:
           FragmentManager fragmentManager = getSupportFragmentManager();
           FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();

           Bundle bundle = new Bundle();
           bundle.putBoolean(ConstantStrings.IS_MAP_FRAGMENT_FROM_MAIN_ACTIVITY, false);
           bundle.putString(ConstantStrings.LOCATION_NAME, location);

           Fragment mapFragment = ((OpenEventApp)getApplication())
                   .getMapModuleFactory()
                   .provideMapModule()
                   .provideMapFragment();
           mapFragment.setArguments(bundle);
           fragmentTransaction.replace(R.id.content_frame_location, mapFragment, FRAGMENT_TAG_LOCATION).addToBackStack(null).commit();

           sessionRecyclerView.setVisibility(View.GONE);
           noSessionsView.setVisibility(View.GONE);
           menu.setGroupVisible(R.id.menu_group_location_activity, false);
           return true;
       case android.R.id.home:
           onBackPressed();
           getSupportFragmentManager().popBackStack();
           sessionRecyclerView.setVisibility(View.VISIBLE);
           return true;
       case R.id.upcoming_sessions:
           upcomingDialogBox.show();
           return true;
       default:
           return true;
   }
}

Final result:

This is the final result or solution that we generated for the issue that was addressed by one of the users:

Some useful links are:

Continue ReadingDisplaying Upcoming Sessions at a Microlocation Open Event Android
Read more about the article File Upload Validations on Open Event Frontend

File Upload Validations on Open Event Frontend

In Open Event Frontend we have used semantics ui’s form validations to validate different fields of a form. There are certain instances in our app where the user has to upload a file and it is to be validated against the suggested format before uploading it to the server. Here we will discuss how to perform the validation.

Semantics ui allows us to validate by facilitating pass of an object along with rules for its validation. For fields like email and contact number we can pass type as email and number respectively but for validation of file we have to pass a regular expression with allowed extension.The following walks one through the process.

fields : {
  file: {
    identifier : 'file',
    rules      : [
      {
        type   : 'empty',
        prompt : this.l10n.t('Please upload a file')
      },
      {
        type   : 'regExp',
        value  : '/^(.*.((zip|xml|ical|ics|xcal)$))?[^.]*$/i',
        prompt : this.l10n.t('Please upload a file in suggested format')
      }
    ]
  }
}

Here we have passed file element (which is to be validated) inside our fields object identifier, which for this field is ‘file’, and can be identified by its id, name or data-validate property of the field element. After that we have passed an array of rules against which the field element is validated. First rule gives an error message in the prompt field in case of an empty field.

The next rule checks for allowed file extensions for the file. The type of the rule will be regExp as we are passing a regular expression which is as follows-

/^(.*.((zip|xml|ical|ics|xcal)$))?[^.]*$/i

It is little complex to explain it from the beginning so let us breakdown it from end-

 

$ Matches end of the string
[^.]* Negated set. Match any character not in this set. * represents 0 or more preceding token
( … )? Represents if there is something before (the last ?)
.*.((zip|xml|ical|ics|xcal)$) This is first capturing group ,it contains tocken which are combined to create a capture group ( zip|xml|ical|ics|xcal ) to extract a substring
^ the beginning of the string

Above regular expression filters all the files with zip/xml/ical/xcal extensions which are the allowed format for the event source file.

References

  • Ivaylo Gerchev blog on form validation in semantic ui
  • Drmsite blog on semantic ui form validation
  • Semantic ui form validation docs
  • Stackoverflow regex for file extension
Continue ReadingFile Upload Validations on Open Event Frontend
Read more about the article Adding Sentry Integration in Open Event Orga Android App

Adding Sentry Integration in Open Event Orga Android App

Sentry is a service that allows you to track events, issues and crashes in your apps and provide deep insights with context about them. This blog post will discuss how we implemented it in Open Event Orga App (Github Repo).

Configuration

First, we need to include the gradle dependency in build.gradle
compile ‘io.sentry:sentry-android:1.3.0’
Now, our project uses proguard for release builds which obfuscates the code and removes unnecessary class to shrink the app. For the crash events to make sense in Sentry dashboard, we need proguard mappings to be uploaded every time release build is generated. Thankfully, this is automatically handled by sentry through its gradle plugin, so to include it, we add this in our project level build.gradle in dependencies block

classpath 'io.sentry:sentry-android-gradle-plugin:1.3.0'

 

And then apply the plugin by writing this at top of our app/build.gradle

apply plugin: 'io.sentry.android.gradle'

 

And then configure the options for automatic proguard configuration and mappings upload

sentry {
   // Disables or enables the automatic configuration of proguard
   // for Sentry.  This injects a default config for proguard so
   // you don't need to do it manually.
   autoProguardConfig true

   // Enables or disables the automatic upload of mapping files
   // during a build.  If you disable this you'll need to manually
   // upload the mapping files with sentry-cli when you do a release.
   autoUpload false
}

 

We have set the autoUpload to false as we wanted Sentry to be an optional dependency to the project. If we turn it on, the build will crash if sentry can’t find the configuration, which we don’t want to happen.

Now, as we want Sentry to configurable, we need to set Sentry DSN as one of the configuration options. The easiest way to externalize configuration is to use environment variables. There are other methods to do it given in the official documentation for config https://docs.sentry.io/clients/java/config/

Lastly, for proguard configuration, we also need 3 other config options, namely:

defaults.project=your-project
defaults.org=your-organisation
auth.token=your-auth-token

 

For getting the auth token, you need to go to https://sentry.io/api/

Now, the configuration is complete and we’ll move to the code

Implementation

First, we need to initialise the sentry instance for all further actions to be valid. This is to be done when the app starts, so we add it in onCreate method Application class of our project by calling this method

// Sentry DSN must be defined as environment variable
// https://docs.sentry.io/clients/java/config/#setting-the-dsn-data-source-name
Sentry.init(new AndroidSentryClientFactory(getApplicationContext()));

 

Now, we’re all set to send crash reports and other events to our Sentry server. This would have required a lot of refactoring if we didn’t use Timber for logging. We are using default debug tree for debug build and a custom Timber tree for release builds.

if (BuildConfig.DEBUG)
   Timber.plant(new Timber.DebugTree());
else
   Timber.plant(new ReleaseLogTree());

 

The ReleaseLogTree extends Timber.Tree which is an abstract class requiring you to override this function:

@Override
protected void log(int priority, String tag, String message, Throwable throwable) {

 }

 

This function is called whenever there is a log event through Timber and this is where we send reports through Sentry. First, we return from the function if the event priority is debug or verbose

if(priority == Log.DEBUG || priority == Log.VERBOSE)
   return;

 

If the event if if info priority, we attach it to sentry bread crumb

if (priority == Log.INFO) {
    Sentry.getContext().recordBreadcrumb(new BreadcrumbBuilder()
          .setMessage(message)
          .build());
}

 

Breadcrumbs are stored and only send with an event. What event comprises for us is the crash event or something we want to be logged to dashboard whenever the user does it. But since info events are just user interactions throughout the app, we don’t want to crowd the issue dashboard with them. However, we want to understand what user was doing before the crash happened, and that is why we use bread crumbs to store the events and only send them attached to a crash event. Also, only the last 100 bread crumbs are stored, making it easier to parse through them.

Now, if there is an error event, we want to capture and send it to the server

if (priority == Log.ERROR) {
   if (throwable == null)
       Sentry.capture(message);
   else
       Sentry.capture(throwable);
}

 

Lastly, we want to set Sentry context to be user specific so that we can easily track and filter through issues based on the user. For that, we create a new class ContextManager with two methods:

  • setOrganiser: to be called at login
  • clearOrganiser: to be called at logout

public void setOrganiser(User user) {
   Map<String, Object> userData = new HashMap<>();
   userData.put("details", user.getUserDetail());
   userData.put("last_access_time", user.getLastAccessTime());
   userData.put("sign_up_time", user.getSignupTime());

   Timber.i("User logged in - %s", user);
   Sentry.getContext().setUser(
       new UserBuilder()
       .setEmail(user.getEmail())
       .setId(String.valueOf(user.getId()))
       .setData(userData)
       .build()
   );
}

 

In this method, we put all the information about the user in the context so that every action from here on is attached to this user.

public void clearOrganiser() {
   Sentry.clearContext();
}

 

And here, we just clear the sentry context.

This concludes the implementation of our sentry client. Now all Timber log events will through sentry and appropriate events will appear on the sentry dashboard. To read more about sentry features and Timber, visit these links:

Sentry Java Documentation (check Android section)

https://docs.sentry.io/clients/java/

Timber Library

https://github.com/JakeWharton/timber

Continue ReadingAdding Sentry Integration in Open Event Orga Android App
Read more about the article Implementing Attendee Detail BottomSheet UI in Open Event Orga App

Implementing Attendee Detail BottomSheet UI in Open Event Orga App

In Open Event Orga App (Github Repo), we allow the option to check the attendee details before checking him/her in or out. Originally, a dialog was shown showing the attendee details, which did not contain much information about the attendee, ticket or the order. The disadvantage of such design was also that it was tied to only one view. We couldn’t show the check in dialog elsewhere in the app, like during QR scanning. So we had to switch back to the attendee view for showing the check in dialog. We decided to create a usable detached component in the form of a bottom sheet containing all required information. This blog will outline the procedure we employed to design the bottom sheet UI.

The attendee check in dialog looked like this:

So, first we decide what we need to show on the check in bottom sheet:

  • Attendee Name
  • Attendee Email
  • Attendee Check In Status
  • Order Status ( Completed, Pending, etc )
  • TIcket Type ( Free, Paid, Donation )
  • Ticket Price
  • Order Date
  • Invoice Number
  • Order ‘Paid Via’

As we are using Android Data Binding in our layout, we’ll start by including the variables required in the layout. Besides the obvious attendee variable, we need presenter instance to handle the check in and check out of the attendee and DateUtils class to parse the order date. Additionally, to handle the visibility of views, we need to include the View class too

<data>
   <import type="org.fossasia.openevent.app.utils.DateUtils" />
   <import type="android.view.View" />

   <variable
       name="presenter"
       type="org.fossasia.openevent.app.event.checkin.contract.IAttendeeCheckInPresenter" />

   <variable
       name="checkinAttendee"
       type="org.fossasia.openevent.app.data.models.Attendee" />
</data>

 

Then, we make the root layout to be CoordinatorLayout and add a NestedScrollView inside it, which contains a vertical linear layout in it. This vertical linear layout will contain our fields.

Note: For brevity, I’ll skip most of the layout attributes from the blog and only show the ones that correspond to the text

Firstly, we show the attendee name:

<TextView
   style="@style/TextAppearance.AppCompat.Headline"
   android:text='@{attendee.firstName + " " + attendee.lastName }'
   tools:text="Name" />

 

The perks of using data binding can be seen here, as we are using string concatenation in layout itself. Furthermore, data binding also handles null checks for us if we add a question mark at the end of the variable name ( attendee.firstName? ).

But our server ensures that both these fields are not null, so we skip that part.

Next up, we display the attendee email

<TextView
   android:text="@{ checkinAttendee.email }"
   tools:text="xyz@example.com" />

 

And then the check in status of the attendee

<TextView
   android:text="@{ checkinAttendee.checkedIn ? @string/checked_in : @string/checked_out }"
   android:textColor="@{ checkinAttendee.checkedIn ? @color/light_green_500 : @color/red_500 }"
   tools:text="CHECKED IN" />

 

Notice that we dynamically change the color and text based on the check in status of the attendee

Now we begin showing the fields with icons to their left. You can use Compound Drawable to achieve this effect, but we use vector drawables which are incompatible with compound drawables on older versions of Android, so we use a horizontal LinearLayout instead.

The first field is the order status denoting if the order is completed or in transient state

<LinearLayout android:orientation="horizontal">

   <ImageView app:srcCompat="@drawable/ic_transfer" />
   <TextView android:text="@{ checkinAttendee.order.status }" />
</LinearLayout>

 

Now, again for keeping the snippets relevant, I’ll skip the icon portion and only show the text binding from now on.

Next, we include the type of ticket attendee has. There are 3 types of ticket supported in Open Event API – free, paid, donation

<TextView
   android:text="@{ checkinAttendee.ticket.type }"  />

 

Next, we want to show the price of the ticket, but only when the ticket is of paid type.

I’ll include the previously omitted LinearLayout part in this snippet because it is the view we control to hide or show the field

<LinearLayout
   android:visibility='@{ checkinAttendee.ticket.type.equalsIgnoreCase("paid") ? View.VISIBLE : View.GONE }'>

   <ImageView app:srcCompat="@drawable/ic_coin" />
   <TextView
       android:text='@{ "$" + checkinAttendee.ticket.price }'
       tools:text="3.78" />
</LinearLayout>

 

As you can see, we are showing this layout only if the ticket type equals paid

The next part is about showing the date on which the order took place

<TextView
   android:text="@{ DateUtils.formatDateWithDefault(DateUtils.FORMAT_DAY_COMPLETE, checkinAttendee.order.completedAt) }" />

 

Here we are using internal DateUtils method to format the date into complete date time from the ISO 8601 standard date present in the order object

Now, we show the invoice number of the order

<TextView
   android:text="@{ checkinAttendee.order.invoiceNumber }" />

 

Lastly, we want to show how the ticket was paid for via

<LinearLayout
   android:visibility='@{ checkinAttendee.order.paidVia.equalsIgnoreCase("free") ? View.GONE : View.VISIBLE }'>

   <ImageView app:srcCompat="@drawable/ic_ray" />
   <TextView  android:text="@{ checkinAttendee.order.paidVia }" />
</LinearLayout>

 

Notice that here too we are controlling the visibility of the layout container and only showing it if the ticket type is paid

This ends our vertical linear layout showing the fields about attendee detail. Now, we add a floating action button to toggle the check in status of attendee

<FrameLayout
   android:layout_gravity="top|end">

   <android.support.design.widget.FloatingActionButton
       android:layout_gravity="center"
       android:onClick="@{() -> presenter.toggleCheckIn() }"
       app:backgroundTint="@{ checkinAttendee.checkedIn ? @color/red_500 : @color/light_green_500 }"
       app:srcCompat="@{ checkinAttendee.checkedIn ? @drawable/ic_checkout : @drawable/ic_checkin }"
       app:tint="@android:color/white" />

   <ProgressBar
       android:layout_gravity="center" />

</FrameLayout>

 

We have used a FrameLayout to wrap a FAB and progress bar together in top end of the bottom sheet. The progress bar shows the indeterminate progress of the toggling of attendee status. And you can see the click binder on FAB triggering the presenter method toggleCheckIn() and how the background color and icon change according to the check in status of the attendee.

This wraps up our layout design. Now we just have to create a BottomSheetDialogFragment, inflate this layout in it and bind the attendee variable and we are all set. The result with all fields visible looks like this:

To learn more about bottom sheet and android data binding, please refer to these links:

Continue ReadingImplementing Attendee Detail BottomSheet UI in Open Event Orga App
Read more about the article Invalidating user login using JWT in Open Event Orga App

Invalidating user login using JWT in Open Event Orga App

User authentication is an essential part of Open Event Orga App (Github Repo), which allows an organizer to log in and perform actions on the event he/she organizes. Backend for the application, Open Event Orga Server sends an authentication token on successful login, and all subsequent privileged API requests must include this token. The token is a JWT (Javascript Web Token) which includes certain information about the user, such as identifier and information about from when will the token be valid, when will it expire and a signature to verify if it was tampered.

Parsing the Token

Our job was to parse the token to find two fields:

  • Identifier of user
  • Expiry time of the token

We stored the token in our shared preference file and loaded it from there for any subsequent requests. But, the token expires after 24 hours and we needed our login model to clear it once it has expired and shown the login activity instead.

To do this, we needed to parse the JWT and compare the timestamp stored in the exp field with the current timestamp and determine if the token is expired. The first step in the process was to parse the token, which is essentially a Base 64 encoded JSON string with sections separated by periods. The sections are as follows:

  • Header ( Contains information about algorithm used to encode JWT, etc )
  • Payload ( The data in JWT – exp. Iar, nbf, identity, etc )
  • Signature ( Verification signature of JWT )

We were interested in payload and for getting the JSON string from the token, we could have used Android’s Base64 class to decode the token, but we wanted to unit test all the util functions and that is why we opted for a custom Base64 class for only decoding our token.

So, first we split the token by the period and decoded each part and stored it in a SparseArrayCompat

public static SparseArrayCompat<String> decode(String token) {
   SparseArrayCompat<String> decoded = new SparseArrayCompat<>(2);

   String[] split = token.split("\\.");
   decoded.append(0, getJson(split[0]));
   decoded.append(1, getJson(split[1]));

   return decoded;
}

 

The getJson function is primarily decoding the Base64 string

private static String getJson(String strEncoded) {
   byte[] decodedBytes = Base64Utils.decode(strEncoded);
   return new String(decodedBytes);
}

The decoded information was stored in this way

0={"alg":"HS256","typ":"JWT"},  1={"nbf":1495745400,"iat":1495745400,"exp":1495745800,"identity":344}

Extracting Information

Next, we create a function to get the expiry timestamp from the token. We could use GSON or Jackson for the task, but we did not want to map fields into any object. So we simply used JSONObject class which Android provides. It took 5 ms on average to parse the JSON instead of 150 ms by GSON

public static long getExpiry(String token) throws JSONException {
   SparseArrayCompat<String> decoded = decode(token);

   // We are using JSONObject instead of GSON as it takes about 5 ms instead of 150 ms taken by GSON
   return Long.parseLong(new JSONObject(decoded.get(1)).get("exp").toString());
}

 

Next, we wanted to get the ID of user from token to determine if a new user is logging in or an old one, so that we can clear the database for new user.

public static int getIdentity(String token) throws JSONException {
   SparseArrayCompat<String> decoded = decode(token);

   return Integer.parseInt(new JSONObject(decoded.get(1)).get("identity").toString());
}

Validating the token

After this, we needed to create a function that tells if a stored token is expired or not. With all the right functions in place, it was just a matter of comparing current time with the stored timestamp

public static boolean isExpired(String token) {
   long expiry;

   try {
       expiry = getExpiry(token);
   } catch (JSONException jse) {
       return true;
   }

   return System.currentTimeMillis()/1000 >= expiry;
}

 

Since the token provides timestamp from epoch in terms of seconds, we needed to divide the current time in milliseconds by 1000 and the function returned true if current timestamp was greater than the expiry time of token.

After writing a few unit tests for both functions, we just needed to plug them in our login model at the time of authentication.

At the time of starting of the application, we use this function to check if a user is logged in or not:

public boolean isLoggedIn() {
   String token = utilModel.getToken();

   return token != null && !JWTUtils.isExpired(token);
}

 

So, if there is no token or the token is expired, we do not automatically login the user and show the login screen.

Implementing login

The next task were

  • Sequest the server to login
  • Store the acquired token
  • Delete database if it is a new user

Before implementing the above logic, we needed to implement a function to determine if the person logging in is previous user, or new one. For doing so, we first loaded the saved user from our database, if the query is empty, surely it is a new user logging in. So we return false, and if there is a user in the database, we match its ID with the logged in user’s ID:

public Single<Boolean> isPreviousUser(String token) {
   return databaseRepository.getAllItems(User.class)
       .first(EMPTY)
       .map(user -> !user.equals(EMPTY) && user.getId() == JWTUtils.getIdentity(token));
}

 

We have added a default user EMPTY in the first operator so that RxJava returns it if there are no users in the database and then we simply map the user to a boolean denoting if they are same or different using the EMPTY user and getIdentity method from JWTUtils

Finally, we use all this information to implement our self contained login request:

eventService
   .login(new Login(username, password))
   .flatMapSingle(loginResponse -> {
       String token = loginResponse.getAccessToken();
       utilModel.saveToken(token);

       return isPreviousUser(token);
   })
   .flatMapCompletable(isPrevious -> {
       if (!isPrevious)
           return utilModel.deleteDatabase();

       return Completable.complete();
   });

 

Let’s see what is happening here. A request using username and password is made to the server which returns a login response containing a JWT, which we store for future use. Next, we flatMapSingle to the Single returned by the isPreviousUser method. And we finally clear the database if it is not a previous user.

Creating these self contained models help reduce complexity in presenter or view layer and all data is handled in one layer making presenter layer model agnostic.

To learn more about JWT and some of the Rx operators I mentioned here, please visit these links:

Continue ReadingInvalidating user login using JWT in Open Event Orga App
Read more about the article Persistence Layer in Open Event Organizer Android App

Persistence Layer in Open Event Organizer Android App

Open Event Organizer is an Event Managing Android App with the core features of Attendee Check In by QR Code Scan and Data Sync with the Open Event API Server. As an event can be large, so the app will be dealing with a large amount of a data. Hence to avoid repetitive network requests for fetching the data, the app maintains a local database containing all the required data and the database is synced with the server. Android provides android.database.sqlite package which contains the API needed to use the database on the Android. But it is really not a good practice to use the sqlite queries everywhere in the app. So there comes a persistence layer. A persistence layer works between the database and the business logic. Open Event Organizer uses Raizlabs’s DbFlow, an ORM based Android Database Library for the same. I will be talking about its implementation through the app in this blog.

First of all, you declare the base class of the database which is used to create the database by Android for the app. You declare all the base constants here. The class looks like:

@Database(
   name = OrgaDatabase.NAME,
   version = OrgaDatabase.VERSION,
   ...
)
public class OrgaDatabase {
   public static final String NAME = "orga_database";
   public static final int VERSION = 2;
   ...
}

OrgaDatabase.java
app/src/main/java/org/fossasia/openevent/app/data/db/configuration/OrgaDatabase.java

Initialise the database in the Application class using FlowManager provided by the library. Choose the Application class to do this to ensure that the library finds the generated code in the DbFlow.

FlowManager.init(
   new FlowConfig.Builder(context)
       .addDatabaseConfig(
           new DatabaseConfig.Builder(OrgaDatabase.class)
           ...
           .build()
       )
       .build());

OrgaApplication.java
app/src/main/java/org/fossasia/openevent/app/OrgaApplication.java

The database is created now. For tables creation, DbFlow uses model classes which must be annotated using the annotations provided by the library. The basic annotations are – @Table, @PrimaryKey, @Column, @ForeignKey etc.

For example, the Attendee class in the app looks like:

@Table(database = OrgaDatabase.class)
public class Attendee ... {

   @PrimaryKey
   public long id;

   @Column
   public boolean checkedIn;
   ...
   ...
   @ForeignKey(
       onDelete = ForeignKeyAction.CASCADE,
       onUpdate = ForeignKeyAction.CASCADE)
   public Order order;
   ...
}

Attendee.java
app/src/main/java/org/fossasia/openevent/app/data/models/Attendee.java

This will create a table named attendee with the columns and relationships annotated. Now comes the part of accessing data from the database. Open Event App uses RxJava’s support to the DbFlow library which enables async data accessing. The getItems method from DataBaseRepository looks like:

public <T> Observable<T> getItems(Class<T> typeClass, SQLOperator... conditions) {
   return RXSQLite.rx(SQLite.select()
       .from(typeClass)
       .where(conditions))
       .queryList()
       .flattenAsObservable(items -> items);
}

 

The method returns an observable emitting the items from the result. For data saving, the method looks like:

DatabaseDefinition database = FlowManager.getDatabase(OrgaDatabase.class);
FastStoreModelTransaction<T> transaction = FastStoreModelTransaction
   .insertBuilder(FlowManager.getModelAdapter(itemClass))
   .addAll(items)
   .build();
database.executeTransaction(transaction);

 

And for updating data, the method looks like:

ModelAdapter<T> modelAdapter = FlowManager.getModelAdapter(classType);
modelAdapter.update(item);

DatabaseRepository.java
app/src/main/java/org/fossasia/openevent/app/data/db/DatabaseRepository.java

DbFlow provides DirectModelNotifier which is used to get notified of the database change anywhere in the app. Open Event App uses PublishSubjects to send notifications on database change event. The implementation of the DatabaseChangeListener in the app looks like:

public class DatabaseChangeListener<T> ... {
   private PublishSubject<ModelChange<T>> publishSubject = PublishSubject.create();
   private DirectModelNotifier.ModelChangedListener<T> modelModelChangedListener;
   ...
   public void startListening() {
       modelModelChangedListener = new DirectModelNotifier.ModelChangedListener<T>() {
           @Override
           public void onTableChanged(@Nullable Class<?> aClass, @NonNull BaseModel.Action action) {
               // No action to be taken
           }
           @Override
           public void onModelChanged(@NonNull T model, @NonNull BaseModel.Action action) {
               publishSubject.onNext(new ModelChange<>(model, action));
           }
       };
       DirectModelNotifier.get().registerForModelChanges(classType, modelModelChangedListener);
   }
   ...
}

DatabaseChangeListener.java
app/src/main/java/org/fossasia/openevent/app/data/db/DatabaseChangeListener.java

The class is used in the app to get notified of the data change and to update the required local data fields using data from item emitted by the publishSubject of the class. This is used in the app where same data is accessed at more than one places. For example, There are two fragments – AttendeesFragment and AttendeeCheckInFragment from which an attendee’s check in status is toggled. So when the status is toggled from AttendeeCheckInFragment, the change must be updated in the AttendeesFragment’s attendees list. This is carried out using DatabaseChangeListener in the AttendeesPresenter which provides attendees list to the AttendeesFragment. And on the change in the attendee’s check in status, AttendeePresenter’s attendeeListener listens for the change and update the attendee in the list accordingly.

Links:
1. Raizlabs’s DbFlow , an ORM Android Database Library Github Repo Link
2. DbFlow documentation
3. Android database managing API android.database.sqlite

Continue ReadingPersistence Layer in Open Event Organizer Android App