Share Events in the Open Event Organizer Android App

In the Open Event Organizer Android App, after creating an event the organizer was unable to share it. We handled this challenge and came up with options to share Event with other social media apps. Along with that user can send Email to users containing event description with just a click. All this through a UI that our user will love interacting with. Let’s see how we implemented this.

Specifications

We designed a UI given below which offer four functionalities to the user in a single screen.

  1. The Event Name and Date are shown in the CardView.
  2. User can copy Event External URL by clicking on Copy URL option.
  3. User can send Email containing information about the Event like ( Name, Description, Starting and Ending Date-Time for the Event) via Email by clicking on Email option.
  4. User can share the same information described in point three via other social media/chatting apps etc by clicking on many more option.

The is the Event Model class ia a POJO containing the associated attributes.

We will use Retrofit to fetch Event object from server through a GET request in EventApi class.

@GET(“events/{id}?include=tickets”)
Observable<Event> getEvent(@Path(“id”) long id);

Then we will use the getEvent method of EventRepositoryImpl class to make the request for us using EventApi class and then pass on the Response Event object to the ViewModel by wrapping it in RxJava Observable. We are accepting a boolean field named reload which decdes whether we need to reuse the existing Event object from Local Database  or fetch a new object from server.

@Override
public Observable<Event> getEvent(long eventId, boolean reload) {
Observable<Event> diskObservable = Observable.defer(() ->
repository
.getItems(Event.class, Event_Table.id.eq(eventId))
.filter(Event::isComplete)
.take(1)
);

Observable<Event> networkObservable = Observable.defer(() ->
eventApi
.getEvent(eventId)
.doOnNext(this::saveEvent));

return repository.observableOf(Event.class)
.reload(reload)
.withDiskObservable(diskObservable)
.withNetworkObservable(networkObservable)
.build();
}

In ShareEventVewModel, we are calling the getEvent from EventRepositoryImpl class, construct a LiveData object from it so that UI could observe changes on it. Methods getShareableInformation, getShareableUrl, getShareableSubject provide the shareable information to the UI which is further shared with other apps.

public class ShareEventViewModel extends ViewModel {

protected LiveData<Event> getEvent(long eventId, boolean reload) {
if (eventLiveData.getValue() != null && !reload)
return eventLiveData;

compositeDisposable.add(eventRepository.getEvent(eventId, reload)
.doOnSubscribe(disposable -> progress.setValue(true))
.doFinally(() -> progress.setValue(false))
.subscribe(event -> {
this.event = event;
eventLiveData.setValue(event);
},
throwable -> error.setValue(ErrorUtils.getMessage(throwable))));

return eventLiveData;
}

public String getShareableInformation() {
return Utils.getShareableInformation(event);
}

}

In ShareEventFragment class does the work of binding the UI to the model using data binding. It observes the LiveData objects supplied by presenter and reflect the changes in UI to the LiveData object.

public class ShareEventFragment extends BaseFragment implements ShareEventView {

public void shareEvent() {
Intent shareIntent = new Intent();
shareIntent.setAction(Intent.ACTION_SEND);
shareIntent.putExtra(Intent.EXTRA_TEXT, shareEventViewModel.getShareableInformation());
shareIntent.setType(“text/plain”);
startActivity(Intent.createChooser(shareIntent, getResources().getText(R.string.send_to)));
}

public void shareByEmail() {
Intent shareIntent = new Intent();
shareIntent.setAction(Intent.ACTION_SENDTO);
shareIntent.setType(“message/rfc822”);
shareIntent.setData(Uri.parse(“mailto:”));
shareIntent.putExtra(Intent.EXTRA_SUBJECT, shareEventViewModel.getEmailSubject());
shareIntent.putExtra(Intent.EXTRA_TEXT, shareEventViewModel.getShareableInformation());
try {
startActivity(Intent.createChooser(shareIntent, getResources().getText(R.string.send_to)));
} catch (android.content.ActivityNotFoundException ex) {
ViewUtils.showSnackbar(binding.getRoot(), “There are no email clients installed”);
}
}

public void copyUrlToClipboard() {
ClipboardManager clipboard = (ClipboardManager) getActivity().getSystemService(Context.CLIPBOARD_SERVICE);
String eventUrl = shareEventViewModel.getShareableUrl();
if (eventUrl == null) {
ViewUtils.showSnackbar(binding.getRoot(), “Event does not have a Public URL”);
} else {
ClipData clip = ClipData.newPlainText(“Event URL”, shareEventViewModel.getShareableUrl());
clipboard.setPrimaryClip(clip);
ViewUtils.showSnackbar(binding.getRoot(), “Event URL Copied to Clipboard”);
}
}
}

The layout file contains the Event object bind to the UI using Two way Data Binding. Here is an extract from the layout file. For viewing entire file, please refer here.

References

  1. Official documentation of Retrofit 2.x http://square.github.io/retrofit/
  2. Official documentation for RxJava 2.x https://github.com/ReactiveX/RxJava
  3. Official documentation for ViewModel https://developer.android.com/topic/libraries/architecture/viewmodel
  4. Codebase for Open Event Organizer App https://github.com/fossasia/open-event-orga-app
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Change Password Feature for Open Event Android Organizer App

In Open Event Organizer Android App, the users were able to successfully login and sign up but in case they wanted to change their login password they could not. So, we added a feature to allow users to change their existing password. This blog explains the technical details to implement this feature following MVVM architecture and using highly efficient libraries like Retrofit, RxJava, Raziz Labs DbFlow, Data Binding.

Specifications

We will implement a page where users can enter their old password and new password along with a confirm password field. Their will be a login button to send the password change request to server. Server then return a response and we will provide feedback regarding the request. We are following MVP architecture so there will be a Model class, Fragment class, Presenter class and Network Layer to make network requests.

Let’s start with creating ChangePassword model class. There are three fields to store old password, new password and new confirmed password. Several Lombok annotations like @Data, @AllArgsConstructor, @NoArgsConstructor are used to avoid boilerplate code for getters, setters and constructors. @JsonNaming annotation is used to translate the Java Object names to KebabCase when they are serialized.

@Data
@AllArgsConstructor
@NoArgsConstructor
@JsonNaming(PropertyNamingStrategy.KebabCaseStrategy.class)
public class ChangePassword {

public String oldPassword;
public String newPassword;

@JsonIgnore
public String confirmNewPassword;
}

The layout file is binded to model using Data Binding. There will be three TextInputEditText fields for user input. An option to toggle password visibility and a login button.

The Fragment class binds layout file to the Fragment and handle UI stuff. Presenter is called to make Login request when login button is pressed.

public class ChangePasswordFragment extends BaseFragment<ChangePasswordPresenter> implements ChangePasswordView {

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
binding = DataBindingUtil.inflate(inflater, R.layout.change_password_fragment, container, false);
validator = new Validator(binding);

AppCompatActivity activity = ((AppCompatActivity) getActivity());
activity.setSupportActionBar(binding.toolbar);

ActionBar actionBar = activity.getSupportActionBar();
if (actionBar != null) {
actionBar.setHomeButtonEnabled(true);
actionBar.setDisplayHomeAsUpEnabled(true);
}

return binding.getRoot();
}

@Override
public void onStart() {
super.onStart();
getPresenter().attach(this);
binding.setOrganizerPassword(getPresenter().getChangePasswordObject());
getPresenter().start();

binding.btnChangePassword.setOnClickListener(view -> {
if (!validator.validate())
return;

String url = binding.url.baseUrl.getText().toString().trim();
getPresenter().setBaseUrl(url, binding.url.overrideUrl.isChecked());
getPresenter().changePasswordRequest(binding.oldPassword.getText().toString(),
binding.newPassword.getText().toString(),
binding.confirmNewPassword.getText().toString());

});
}

When the Login button is pressed, changePasswordRequest() method is called which makes an asynchronous call to ChangePasswordModel in order to perform the task of sending and receiving data from network in a different thread than the UI thread. Along with making requests, this method also verifies the password typed in confirm password field and send the the error as well as success message to the fragment.

public class ChangePasswordPresenter extends AbstractBasePresenter<ChangePasswordView> {

public void changePasswordRequest(String oldPassword, String newPassword, String confirmPassword) {
if (!newPassword.equals(confirmPassword)) {
getView().showError(“Passwords Do Not Match”);
return;
}

organizerPasswordObject.setOldPassword(oldPassword);
organizerPasswordObject.setNewPassword(newPassword);
organizerPasswordObject.setConfirmNewPassword(confirmPassword);

changePasswordModel.changePassword(organizerPasswordObject)
.compose(disposeCompletable(getDisposable()))
.compose(progressiveErroneousCompletable(getView()))
.subscribe(() -> getView().onSuccess(“Password Changed Successfully”), Logger::logError);
}
}

We are using Retrofit to make POST Request to server using the REST API. @Body annotation denotes the object request body which here contains a Map<String, ChangePassword> object. The Response from server is captured in Observable<ChangePasswordResponse> which is an RxJava Observable.

@POST(“auth/change-password”)
Observable<ChangePasswordResponse> changePassword(@Body Map<String, ChangePassword> changePassword);

This is the declaration for the method in Network Layer where the actual network request is made. It takes as input the changePassword object from Presenter which is already binded with data. Then it uses RxJava to asynchronously call the Api class and pass in the Map<String, ChangePassword> object. The result is then processed and Completable object is returned to the presenter. The Presenter processes the Completable object and shows user feedback in the form of a message in SnackBar.

References

  1. Official documentation for RxJava by ReactiveX https://github.com/ReactiveX/RxJava
  2. Official documentation for Retrofit by Square Inc https://github.com/square/retrofit
  3. Codebase for Open Event Organizer App on Github https://github.com/fossasia/open-event-orga-app
  4. Open Event Server deployment at heroku https://open-event-api-dev.herokuapp.com/
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Create Session in Open Event Android Organizer Application

Open Event Android Organizer Application offered variety of features to Organizers from all over the world to help them host their Events globally but it didn’t had the functionality to create Sessions in the app itself and associate it to Tracks. This feature addition was crucial since it enables Organizer to create Sessions which every common person enquires about before attending and event. In this Blog Post we will see how we added this functionality in the app.

Open Event Android Organizer Application is a client for Open Event Server which provides the REST API.

Problem

There can be various Sessions associated with Tracks for an Event. Open Event API had the endpoint to implement Creating Session but the Orga app didn’t, so we worked on creating a Session in the app.

The UI for creating a Session is shown above. User can fill in the necessary details and click on the green Floating Action Button to create a Session.

How to implement functionality?

We will follow MVP Architecture and use Retrofit 2.x, RxJava, Dagger, Jackson, Data Binding and other industry standard libraries to implement this functionality.

Firstly, let’s create Session model class specifying the attributes and relationships to set up in database using RazizLabs DbFlow library. The POJO will be serialized into JSON by Jackson library to be passed on as a part of RequestBody to server.

Now we will create SessionApi class that will contain the request details to be passed to Retrofit. @POST denotes a POST request and @Body denotes the requestBody of the request which is a Session object.

public interface SessionApi {
@POST(“sessions”)
Observable<Session> postSession(@Body Session session);
}

This is the CreateSessionFragment class that contains the code binding model to the view. The Fragment class implements the CreateSessionView class overriding the method declarations present there. The @Inject annotation of Dagger is used to load singleton presenter instance lazily to improve app’s performance.

Event-Id and Track-Id’s are retrieved from Bundle from Fragment Transaction. These are then passed on to presenter when Create Session button is pressed. There are other methods to show binding progressbar, snackbar and other UI components to show progress of the background request to server and database.

public class CreateSessionFragment extends BaseFragment<CreateSessionPresenter> implements CreateSessionView {

@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup

container, @Nullable Bundle savedInstanceState) {
binding = DataBindingUtil.inflate(inflater,

R.layout.session_create_layout, container, false);
validator = new Validator(binding.form);

binding.sessionCreate.setOnClickListener(view -> {
if (validator.validate()) {
getPresenter().createSession(trackId, eventId);
}
});

return binding.getRoot();
}

@Override
public void onStart() {
super.onStart();
getPresenter().attach(this);
binding.setSession(getPresenter().getSession());
}
}

In the Presenter createSession method is called when create button is pressed in UI. The method attaches track-id and event-id to Session object. This is necessary for Relationship constraints on Session Model. Then after binding all the data to Session object, we pass it on to SessionRepository. The success response is provided to user by passing success response in getView().onSuccess() method.

public class CreateSessionPresenter extends

AbstractBasePresenter<CreateSessionView> {

public Session getSession() {
return session;
}

public void createSession(long trackId, long eventId) {

Track track = new Track();
Event event = new Event();

track.setId(trackId);
event.setId(eventId);
session.setTrack(track);
session.setEvent(event);

sessionRepository
.createSession(session)
.compose(dispose(getDisposable()))
.compose(progressiveErroneous(getView()))
.subscribe(createdSession ->

getView().onSuccess(“Session Created”), Logger::logError);
}
}

The SessionRepository uses RxJava to make asynchronous Retrofit Call to Server. We throw a Network Error to user if the device does not have Internet Connectivity.

The session object accepted as a parameter in createSession method is passed on to sessionApi. It will return Observable<Session> Response which we will process in doOnNext() method. Then the Session object along with required foreign key relationships with Track and Event is saved in database for offline use.

@Override
public Observable<Session> createSession(Session session) {
if (!repository.isConnected()) {
return Observable.error(new Throwable(Constants.NO_NETWORK));
}return sessionApi
.postSession(session)
.doOnNext(created -> {
created.setTrack(session.getTrack());
created.setEvent(session.getEvent());
repository
.save(Session.class, created)
.subscribe();
})
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread());
}

The above code snippets are from Open Event Orga Application. For exploring the entire codebase please refer here. For details about the REST API used by the app please visit here.

References

  1. Official RxJava Project on Github by ReactiveX https://github.com/ReactiveX/RxJava.
  2. Official Retrofit Project on Github by Square Inc https://github.com/square/retrofit.
  3. Official Open Event Organizer App on Github by FOSSASIA https://github.com/fossasia/open-event-orga-app.
  4. Documentation for REST API of Open Event Server on Heroku by FOSSASIA https://open-event-api-dev.herokuapp.com/.
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Creating Activity for Visualizing Recorded Sensor Data from List Items

In previous blog Using RealmRecyclerView Adapter to Show Recorded Sensor Experiments[2], I  have created a DataLoggerActivity in PSLab Android app containing RecyclerView showing a list having all the recorded experiments where every list item shows the date, time and the sensor instrument used for recording the data, but there arises below questions:-

  • What if the user wants to see the actual recorded data in form of a graph?
  • How the user can see the location recorded along with the data on the map?
  • How can the user export that data?

There is no way I could show all of that information just on a list item so I created another activity called “SensorGraphViewActivity” the layout of that activity is shown in the figure below:

Figure 1 shows the layout of the Activity as produced in Android editor

The layout contains three views:-

  1. At the top there is graph view which I created using Android MP chart which will show the recorded data plotted on it forming the exact same curve that was created while recording it, this way it is useful to visualize the data and also there is also a play button on the top which simulates the data as it was being plotted on the graph in real time.
  2. In the middle, there is a Card view containing two rows which will simply show the date and time of recording.
  3. At the bottom, there is a Map view which shows the location of the user which would be fetched when the user recorded the data.

This is the gist of the layout file created for the activity.

But now the question arises:-

How to show the data in the activity for the item that the user wanted?

For that, I implemented click listener on every list item by simply adding it inside the onBindViewHolder() method

@Override
public void onBindViewHolder(@NonNull final ViewHolder holder, int position) {
   SensorLogged temp = getItem(position);
   holder.sensor.setText(temp.getSensor());
   Date date = new Date(temp.getDateTimeStart());
   holder.dateTime.setText(String.valueOf(sdf.format(date)));
   holder.cardView.setOnClickListener(new View.OnClickListener() {
       @Override
       public void onClick(View view) {
                    ...
       });
}

and inside the click listener I performed following three steps:-

  1. First I stored the position of the item clicked inside a variable.

    int positionVar = holder.getAdapterPosition();
  2. Then I used that position from the variable to fetch related data from the Realm database by simply using getItem() method which returns the SensorLogged[1] RealmObject at that position as I used a special type of RecyclerView Adapter called as RealmRecyclerViewAdapter[2].

    int positionVar = holder.getAdapterPosition();
  3. Then I created an Intent to open the SensorGraphViewActivity and passed the related data (i.e., sensortype, foreignkey, latitude, longitude, timezone, date, time) from SensorLogged[1] object to activity in form of extras.
    Intent intent = new Intent(context, SensorGraphViewActivity.class);
    intent.putExtra(SensorGraphViewActivity.TYPE_SENSOR, item.getSensor());
    intent.putExtra(SensorGraphViewActivity.DATA_FOREIGN_KEY, item.getUniqueRef());
    intent.putExtra(SensorGraphViewActivity.DATE_TIME_START,item.getDateTimeStart());
    intent.putExtra(SensorGraphViewActivity.DATE_TIME_END,item.getDateTimeEnd());
    intent.putExtra(SensorGraphViewActivity.TIME_ZONE,item.getTimeZone());
    intent.putExtra(SensorGraphViewActivity.LATITUDE,item.getLatitude());
    intent.putExtra(SensorGraphViewActivity.LONGITUDE,item.getLongitude());
    
    context.startActivity(intent);
    

And, in the SensorGraphViewActivity, I used getIntent() method to fetch all those extra data in the form of Bundle.
For showing the data in the graph I used the foreign key fetched from the intent and queried all the LuxData[1] RealmObject containing that foreignkey in the form of RealmResult<LuxData>[2] ArrayList and used that list to populate the graph.

Long foreignKey = intent.getLongExtra(DATA_FOREIGN_KEY, -1);
Realm realm = Realm.getDefaultInstance();
entries = new ArrayList<>();
RealmResults<LuxData> results = realm.where(LuxData.class).equalTo(DATA_FOREIGN_KEY, foreignKey).findAll();
for (LuxData item : results) {
   entries.add(new Entry((float) item.getTimeElapsed(), item.getLux()));
}

For the map, I fetched the latitude and longitude again from the intent and used the coordinates to show the location on the open street view map.

Thread thread = new Thread(new Runnable() {
   @Override
   public void run() {
       IMapController mapController = map.getController();
       mapController.setZoom((double) 9);
       GeoPoint startPoint = new GeoPoint(latitude, latitude);
       mapController.setCenter(startPoint);
   }
});

For map purposes, of course, I used a separate thread as it is a heavy and time-consuming process and it could lead the app to lag for a long time which could hamper the User Experience.

Thus after the data being plotted on the map and coordinated being plotted on the map, we can see the layout of the activity as shown in Figure 2.

Figure 2 shows the layout of the activity after being populated with data.

I also created the export button in the toolbar that will use the CSVLogger[3] class implemented inside the PSLab android app to export the data in the form of CSV file and save it in the external storage directory.

Resources

  1. Storing Recorded Sensor Data in Realm Database – My blog where I created the Realm Model classes to store recorded data.
  2. Using RealmRecyclerView Adapter to Show Recorded Sensor Experiments – My previous blog where I created the RecyclerView.
  3. Saving Sensor Data in CSV format – Blog by Padmal storing the data in CSV format.
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Connecting SUSI iOS App to SUSI Smart Speaker

SUSI Smart Speaker is an Open Source speaker with many exciting features. The user needs an Android or iOS device to set up the speaker. You can refer this post for initial connection to SUSI Smart Speaker. In this post, we will see how a user can connect SUSI Smart Speaker to iOS devices (iPhone/iPad).

Implementation –

The first step is to detect whether an iOS device connects to SUSI.AI hotspot or not. For this, we match the currently connected wifi SSID with SUSI.AI hotspot SSID. If it matches, we show the connected device in Device Activity to proceed further with setups.

Choosing Room –

Room name is basically the location of your SUSI Smart Speaker in the home. You may have multiple SUSI Smart Speaker in different rooms, so the purpose of adding the room is to differentiate between them.

When the user clicks on Wi-Fi displayed cell, it starts the initial setups. We are using didSelectRowAt method of UITableViewDelegate to get which cell is selected. On clicking the displayed Wi-Fi cell, a popup is open with a Room Location Text field.

override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
if indexPath.row == 0, let speakerSSID = fetchSSIDInfo(), speakerSSID == ControllerConstants.DeviceActivity.susiSSID {
// Open a popup to select Rooms
presentRoomsPopup()
}
}

When the user clicks the Next button, we send the speaker room location to the local server of the speaker by the following API endpoint with room name as a parameter:

http://10.0.0.1:5000/speaker_config/

Refer this post for getting more detail about how choosing room work and how it is implemented in SUSI iOS.

Sharing Wi-Fi Credentials –

On successfully choosing the room, we present a popup that asks the user to enter the Wi-Fi credentials of previously connected Wi-Fi so that we can connect our Smart Speaker to the wifi which can provide internet connection to play music and set commands over the speaker.

We present a popup with a text field for entering wifi password.

When the user clicks the Next button, we share the wifi credentials to wifi by the following API endpoint:

http://10.0.0.1:5000/wifi_credentials/

With the following params-

  1. Wifissid – Connected Wi-Fi SSID
  2. Wifipassd – Connected Wi-Fi password

In this API endpoint, we are sharing wifi SSID and wifi password with Smart Speaker. If the credentials successfully accepted by speaker than we present a popup for user SUSI account password, otherwise we again present Enter Wifi Credentials popup.

Client.sharedInstance.sendWifiCredentials(params) { (success, message) in
DispatchQueue.main.async {
self.alertController.dismiss(animated: true, completion: nil)
if success {
self.presentUserPasswordPopup()
} else {
self.view.makeToast("", point: self.view.center, title: message, image: nil, completion: { didTap in
UIApplication.shared.endIgnoringInteractionEvents()
self.presentWifiCredentialsPopup()
})
}
}
}

 

Sharing SUSI Account Credentials –

In the method above we have seen that when SUSI Smart Speaker accept the wifi credentials, we proceed further with SUSI account credentials. We open a popup to Enter user’s SUSI account password:

When the user clicks the Next button, we use following API endpoint to share user’s SUSI account credentials to SUSI Smart Speaker:

http://10.0.0.1:5000/auth/

With the following params-

  1. email
  2. password

User email is already saved in the device so the user doesn’t have to type it again. If the user credentials successfully accepted by speaker then we proceed with configuration process otherwise we open up Enter Password popup again.

Client.sharedInstance.sendAuthCredentials(params) { (success, message) in
DispatchQueue.main.async {
self.alertController.dismiss(animated: true, completion: nil)
if success {
self.setConfiguration()
} else {
self.view.makeToast("", point: self.view.center, title: message, image: nil, completion: { didTap in
UIApplication.shared.endIgnoringInteractionEvents()
self.presentUserPasswordPopup()
})
}
}
}

 

Setting Configuration –

After successfully sharing SUSI account credentials, following API endpoint is using for setting configuration.

http://10.0.0.1:5000/config/

With the following params-

  1. sst
  2. tts
  3. hotword
  4. wake

The success of this API call makes successfully connection between user iOS Device and SUSI Smart Speaker.

Client.sharedInstance.setConfiguration(params) { (success, message) in
DispatchQueue.main.async {
if success {
// Successfully Configured
self.isSetupDone = true
self.view.makeToast(ControllerConstants.DeviceActivity.doneSetupDetailText)
} else {
self.view.makeToast("", point: self.view.center, title: message, image: nil, completion: { didTap in
UIApplication.shared.endIgnoringInteractionEvents()
})
}
}
}

After successful connection-

 

Resources –

  1. Apple’s Documentation of tableView(_:didSelectRowAt:) API
  2. Initial Setups for Connecting SUSI Smart Speaker with iPhone/iPad
  3. SUSI Linux Link: https://github.com/fossasia/susi_linux
  4. Adding Option to Choose Room for SUSI Smart Speaker in iOS App
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Adding Marketer and Sales Admin Events Relationship with User on Open Event Server

In this blog, we will talk about how to add API for adding and displaying events in with a user acts as a Marketer and/or Sales Admin on Open Event Server. The focus is on Model Updation and Schema updation of User.

Model Updation

For the Marketer and Sales Admin events, we’ll update User model as follows

Now, let’s try to understand these relationships.

In this feature, we are providing user to act as a marketer and sales admin for a event.

  1. Both the relationships will return the events in which the user is acting as a Marketer and/or Sales Admin.
  2. There are two custom system roles in model CustomSysRole which are Marketer and Sales Admin. A user can act as these custom system roles with respect to an event.
  3. In this relationship, we will return those events from UserSystemRole model in which a user is acting as Marketer Custom System Role and Sales Admin Custom System Role.
  4. We make use of Event and join UserSystemRole and CustomSysRole where we use that user where UserSystemRole.user_id == User.id , CustomSysRole.id == UserSystemRole.role_id, CustomSysRole.name == “Sales Admin” and then we return events in which Event.id == UserSystemRole.event_id
  5. Similarly, for Marketer events we make use of Event and join UserSystemRole and CustomSysRole where we use that user where UserSystemRole.user_id == User.id , CustomSysRole.id == UserSystemRole.role_id, CustomSysRole.name == “Marketer” and then we return events in which Event.id == UserSystemRole.event_id

Schema Updation

For the Marketer and Sales Admin events, we’ll update UserSchema as follows

Now, let’s try to understand this Schema.

In this feature, we are providing user to act as a marketer and sales admin for a event.

  1. For displaying marketer_events relation self_view is displayed by API v1.user_marketer_events and collection of these events is displayed by API v1.event_list
  2. These APIs will return the Events as schema=”EventSchema”. Here, many=True tells us that this is One to many relationship with Events model.

So, we saw how an user can act as a marketer and/or sales admin for many events.

Resources

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Adding Custom System Roles in Open Event Server

In this blog, we will talk about how to add different custom system roles concerning a user on Open Event Server. The focus is on its model and Schema updation.

Model Updation

For the User Table, we’ll update our User Model as follows:

Now, let’s try to understand these hybrid properties.

In this feature, we are providing Admin the rights to see whether a user is acting as a Marketer and / or  Sales Admin of any of the event or not. Here, _is__system_role method is used to check whether an user plays a system role like Marketer, Sales Admin or not. This is done by querying the record from UserSystemRole model. If the record is present then the returned value is True otherwise false.

Schema Updation

For the User Model, we’ll update our Schema as follows:

Now, let’s try to understand this Schema.

Since all the properties will return either True or false so these all properties are set to Boolean in Schema.Here dump_only means, we will return this property in the Schema.

So, we saw how User Model and Schema is updated to show custom system roles concerning a user on Open Event Server.

Resources

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How to pass data between fragments of an Activity in Android app

This blog demonstrates how to pass values of a variable between two fragments of a single activity. The blog will mainly include the demonstration of passing values between fragments while using BottomSheet Navigation as done in PSLab Android application.

This blog contains the work done by me in the Lux Meter instrument of the PSLab Android app of passing data from LuxMeterConfiguration fragment to LuxMeterData fragment as shown in the featured image to set the high limit for the pointer and to set the update period of the Lux Sensor. The blog will solve the difficult task of communication between two fragments of a single activity. For passing data between multiple fragments of different activities, refer to [1].

How to pass data between fragments?

In this blog, I will pass data from Fragment 2 to Fragment 1 only. But vice versa or passing data from both the fragments can also be made using the same given approach.

  • First, make a static method in Fragment 1 which can set the parameters i.e. the value of the variables as soon as the fragment is inflated as follow
public static void setParameters(int one, int two, int three) {
        Fragment1.firstValue = one;
        Fragment1.secondValue = two;
        Fragment1.thirdValue = three;
    }
  • Now, there is one point to mark that Fragment 1 will be inflated only when Fragment 2 gets destroyed. Else, other than default inflation of Fragment 1, there is no way Fragment 1 can be inflated after navigating to Fragment 2.
  • So, override the OnDestroy() method of Fragment 2 and use the setParameters() method to set the value of variables from Fragment 2 to be used in Fragment 1.
@Override
    public void onDestroyView() {
        super.onDestroyView();
        highValue = getValueFromText(highLimit, 0, highLimitMax);
        updatePeriodValue = getValueFromText(updatePeriod, updatePeriodMin, updatePeriodMax + 100);
        Fragment1.setParameters(selectedSensor, highValue, updatePeriodValue);
    }

Here, the highValue, updatePeriodValue and selectedSensor are the variables being used in the Lux Meter fragment in PSLab Android app. But they can be replaced by the necessary variables as per the app.

So, in this way, we can pass data between the fragments of the same Activity in an Android application. Above demonstration can be extended in passing values between multiple fragments of the same Activity by creating different methods in different fragments.

Resources

  1. Blog on how to pass data between fragments of different/same activities: https://www.journaldev.com/14207/android-passing-data-between-fragments
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Prevent Android Activity from Operating while using Bottom Sheet in PSLab App

This blog demonstrates how to prevent the Android Activity in the background from operating while the Bottom Sheet is up in the foreground. The demonstration will be purely from the work I have done under PR #1355 in PSLab Android repository.

Why prevent the Activity from operating?

When using Bottom Sheet in Android, it is preferable to dim the screen behind the Bottom Sheet to provide a good user experience. But the dimming of the screen is itself an indication that the screen won’t work. Also, if the Bottom Sheet is open and while sliding it, if, by mistake, any button in the background of the bottom sheet gets pressed, then if the function related to that button starts executing then it can create a bad user experience.

For example, in PSLab Android app, in Accelerometer instrument, there are record/pause and delete buttons in the toolbar as shown in figure 1. Now, if the bottom sheet is opened and while closing it if the delete button is by mistake pressed by the user, then whole recorded data gets deleted. Thus, it’s a good practice to prevent the background Activity from operating while Bottom Sheet is opened.

Figure 1. Accelerometer Instrument in PSLab Android app

How to prevent the Activity from operating?

In this demonstration, I will use the method followed by PSLab Android app in creating a Bottom Sheet and making the background dim using a View widget. A step by step guide on how to make a Bottom Sheet as in PSLab Android app can be found in [1] and [2].

Strategy

The strategy used in solving this problem is setting an OnClickListener to the View that is used to dim the background and close the Bottom Sheet (if open) and hide the View as soon as the method is called. The View is again made visible when an upward slide gesture is made to open the Bottom Sheet.

Follow the below steps to get the desired results:

  • First, in OnCreate() method, set the OnTouchListener to the view.
view.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
                              if(bottomSheetBehavior.getState()==BottomSheetBehavior.STATE_EXPANDED)
                    bottomSheetBehavior.setState(BottomSheetBehavior.STATE_HIDDEN);
tvShadow.setVisibility(View.GONE);
      }
});
  • Now, override the OnSlide() method of the GestureDetector class and add the following code to it.
@Override
public void onSlide(@NonNull View bottomSheet, float slideOffset) {
    Float value = (float) MathUtils.map((double) slideOffset, 0.0, 1.0, 0.0, 0.8);
    view.setVisibility(View.VISIBLE);
    view.setAlpha(value);
   }

So, now test the Bottom Sheet and you will find that the Bottom Sheet will get closed as soon as the click is made outside it if it is opened. The demonstration of the working of the above code is shown in figure 2.

Figure 2. Demonstration of preventing the background Activity from operating while Bottom Sheet is up

Resources

  1. http://thetechnocafe.com/make-bottom-sheet-android/: Blog on how to make a Bottom Sheet in Android
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How to use Mobile Sensors as Instruments in PSLab Android App

This blog demonstrates how to use built-in mobile sensors in an Android application. This blog will mainly feature my work done in PSLab Android repository of making a Compass and Accelerometer instrument using built-in mobile sensors.

How to access built-in mobile sensors?

Android provides an abstract class called SensorManager which is able to communicate with the hardware i.e. here the sensors in the mobile. But the SensorManager can’t provide continuous data fetched by the sensor. For this, Android provides an interface known as SensorEventListener which receives notifications from SensorManager whenever there is a new sensor data.

How to implement the functionality of sensors in Android app?

Following is a step by step process on how to add support for different sensors in an Android app

  • First, make a new class which extends SensorEventListener and override the default methods.
public class SensorActivity extends Activity implements SensorEventListener {

     public SensorActivity() {
        // Default Constructor      
     }

     @Override
     public void onAccuracyChanged(Sensor sensor, int accuracy) {
     }

     @Override
     public void onSensorChanged(SensorEvent event) {
     }
 }

Here, the SensorActivity() is the default constructor of the class and the onAccuracyChanged() and onSensorChanged() methods will be explained soon.

  • Now declare the SensorManager and use the sensor needed in the app.
private final SensorManager mSensorManager;
private final Sensor mAccelerometer;

     public SensorActivity() {
         mSensorManager = (SensorManager)getSystemService(SENSOR_SERVICE);
         mAccelerometer =        mSensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER);
     }

Here, I have used Sensor.TYPE_ACCELEROMETER to use the built-in Accelerometer in the device. Some of the other options available are:

  1. TYPE_LIGHT – To measure ambient light
  2. TYPE_MAGNETOMETER – To measure magnetic field along different axis
  3. TYPE_GYROSCOPE – To measure movements (sudden changes) in any particular direction

The list of all available sensors in Android can be found in [1].

  • It is necessary to disable the sensors especially when the activity is paused. Failing to do so can drain the battery in just a few hours.

NOTE: The system will not disable sensors automatically when the screen turns off.

So, to save the battery and make the app efficient, we can use the registerListener method to notify the SensorManager to start fetching data from sensor and unregisterListener to notify it to stop.

@Override
protected void onResume() {
         super.onResume();
         mSensorManager.registerListener(this, mAccelerometer, SensorManager.SENSOR_DELAY_NORMAL);
     }

@Override
     protected void onPause() {
         super.onPause();
         mSensorManager.unregisterListener(this);
     }


The onResume() method activates when the app is resumed from a paused state and the onPause() method is called when the app is paused i.e. some other app draws over the current app.

  • Now coming back to onAccuracyChanged() and onSensorChanged() methods, the onAccuracyChanged() method is used to set the accuracy of a sensor. For example, while using GeoLocation sensor, sometimes the position of the mobile isn’t very accurate and so we can define the accuracy level in this method so that the fetched data is used for calculations only if it is in the provided range. And the onSensorChanged() method is the main method where all the data is processed as soon as the new data is notified.

To get the latest value from the sensor, we can use

@Override
public void onSensorChanged(SensorEvent event) {
   data = Float.valueOf(event.values[0]);
   unRegisterListener();
}

Here, the event is an instance of the SensorEvent class which provides the updated data fetched from the sensor. Event.values is used to get the values for any of the three axis including the bias in their values. Following is the list of the index for which we can get a necessary value

values[0] = x_uncalib without bias compensation
values[1] = y_uncalib without bias compensation
values[2] = z_uncalib without bias compensation
values[3] = estimated x_bias
values[4] = estimated y_bias 
values[5] = estimated z_bias

So, in this way, we can add support for any built-in mobile sensor in our Android application.

Resources

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