Controlling Camera Actions Using Voice Interaction in Phimpme Android

In this blog, I will explain how I implemented Google voice actions to control camera features on the Phimpme Android project. I will cover the following features I have implemented on the Phimpme project:

  • Opening the application using Google Voice command.
  • Switching between the cameras.
  • Clicking a Picture and saving it through voice command.

Opening application when the user gives a command to Google Now.                       When the user gives command “Take a selfie” or “Click a picture” to Google Now it directly opens Phimpme camera activity.

 First                                                                                                                                        We need to add an intent filter to the manifest file so that Google Now can  detect Phimpme camera activity

       <action android:name=""/>

       <category android:name="android.intent.category.DEFAULT"/>
       <category android:name="android.intent.category.VOICE"/>

category android:name=”android.intent.category.VOICE” is added to the IMAGE_CAPTURE intent filter for the Google Now to detect the camera activity. For the Google Now assistance to accept the command in the camera activity we need to add the following in the STILL_IMAGE_CAMERA intent filter in the camera activity.

   <action android:name=""/>

   <category android:name="android.intent.category.DEFAULT"/>
   <category android:name="android.intent.category.VOICE"/>

So, now when the user says “OK Google” and “Take a Picture” the camera activity on Phimpme opens.

Integrating Google Voice assistance in Camera Activity

Second,                                                                                                                               After opening the camera application the Google Assistance should ask a question.

The cameraActivity in Phimpme can be opened in two ways, such as:

  • When opened from a different application.
  • When given the command to Goole Now assistance.

We need to check whether the camera activity is prompted from Google assistance or not to activate voice command. We will check it in onResume function.

public void onResume() {
if (CameraActivity.this.isVoiceInteraction()) {

If is.VoiceInteraction gives “true” then voice Assistance prompts.             Assistance to ask which camera to use

Third,                                                                                                                                 After the camera activity opens the Google assistance should ask which camera to use either front or back.

To take any voice input from the user, we to store the expected commands in VoiceInteractor.PickoptionRequest. This function listens to the command by the user. We need to add synonyms for the same command.

To choose the rear camera

VoiceInteractor.PickOptionRequest.Option rear = new VoiceInteractor.PickOptionRequest.Option(getResources().getString(R.string.camera_rear), 0);

I added synonyms like the rear, normal and back.

To choose front camera

VoiceInteractor.PickOptionRequest.Option front = new VoiceInteractor.PickOptionRequest.Option(getResources().getString(R.string.camera_front), 1);

I added synonyms like the front, selfie camera and forward. 

For assistance to ask any question such as “Which camera to use we” I have used getVoiceinteractor and inflating VoiceInteractor.PickOptionRequest.option[] array with options front and rear.

     .submitRequest(new VoiceInteractor.PickOptionRequest(
           new VoiceInteractor.Prompt(getResources().getString(“Which camera would you like to use?”),
           new VoiceInteractor.PickOptionRequest.Option[]{front, rear},
           null) {

The google assistance waits for a response from the user for only a few seconds and it goes inactive. If the user gives any unexpected command the assistance will ask the question one more time.

Check if the user gives an expected command or not.

We will override OnOptionResult(boolean finished, Options[] selection, Bundle result) function.if  (finished && selections.length == 1) if the speech length matches with any of the options provided it checks which option was used.

Check the command given by the user to switch between the cameras.

Two array objects are passed 0 and 1.  If the command given was “rear” then selection[0].getindex() = 0 and camera activity switches to the rear camera and if the the command given by the user is rear then selection[0].getIndex = 1 and camera activity switches to front camera.

public void onPickOptionResult(boolean finished, Option[] selections, Bundle result) {
  if (finished && selections.length == 1) {
     Message message = Message.obtain();
     message.obj = result;
     if (selections[0].getIndex() == 0)
     {  rearCamera();
     if (selections[0].getIndex() == 1)


Click Picture when the user says “Cheese

After switching the camera the assistant prompts the message”Say cheese”. We need to add voiceInteractor.prompt(“Say cheese”).

We need to store the synonyms in VoiceInteractor.PickOption.Options options. I have added synonyms like ready, go, take it, OK, and Cheese to click a picture. If the user gives an unexpected output the assistance checks selection.length ==1 or not and prompts the message “Say cheese” again.

private void asktakePicture() {
  VoiceInteractor.PickOptionRequest.Option option = new VoiceInteractor.PickOptionRequest.Option(getResources().getString(R.string.cheese), 2);
        .submitRequest(new VoiceInteractor.PickOptionRequest(
              new VoiceInteractor.Prompt(getResources().getString(R.string.say_cheese)),
              new VoiceInteractor.PickOptionRequest.Option[]{option},
              null) {
           public void onPickOptionResult(boolean finished, Option[] selections, Bundle result) {
              if (finished && selections.length == 1) {
                 Message message = Message.obtain();
                 message.obj = result;
              } else {
           public void onCancel() {


Now, Users can start camera activity on Phimpme through voice command “Take a Selfie”. They can switch between the cameras through voice command “Selfie camera” or “back camera”, “back” or “front” and finally click a picture by giving voice command “Cheese”, “Click it” and related synonyms.



Generating the Mozilla All Hands Open Event Android App

The main aim of FOSSASIA Open Event Android App is to give an event organiser the ability to generate the app through a single click by providing the necessary json and binary files. The app was tested on the Mozilla All Hands 2017 event which is an annual conference held for Mozilla employees to showcase their experience and also interact with each other.  The sample files for the event can be found here. ( The data for the event was taken from here. (

What was required for building the sample for Mozilla All Hands 2017 event?

  • images folder containing the necessary images of speaker having support for local images too, the logo of the event, the background image of the event.
  • event json file which has all the event specific information like the name of the event, the schedule of the event, the description of the event etc.
  • forms json file having session and speaker form data.
  • meta json file having the root url of the event.
  • microlocations json file having all the locations where the sessions are going to happen.
  • session_types json file consisting data of all the type of session which will occur in the event (the length of session, the name of type and the id).
  • sessions json file consisting session specific data like the title of the session, start time and end time of session, which track that session belongs to etc.
  • speakers json file consisting of speaker specific data like the name of the speaker, image of the speaker, social links of the speaker etc.
  • sponsors json file consisting list of all sponsors of the event.
  • tracks json file consisting of tracks specific data.
  • config.json file which consists of the api url, app name.

After generating the required zip containing the above json files, the zip is uploaded to this site ( and we get an apk after filling the required information. This means all the event organiser is able to generate the sample app by providing the necessary information about the event.

The sample can be found here:

Folder Link:

Zip Link:

How did the Mozilla All Hands 2017 sample app look like?

The screenshots of the sample apk can be seen below:



What were the issues found in the sample app?

As compared to the previous sample apk like Google IO Open Event Android App some issues like support for local speaker images, background issue of the logo were solved. However there were certain issues which we observed on testing the app with the Mozilla All Hands 2017 event:

  1. The theme of the app remains the same no matter which event it is. It is important to give the event organiser the ability to customise the theme of the app.
  2. Certain information in the app like the event information is hard-coded and needs to be taken from the assets folder instead of strings.xml.

Related Links

Using Jackson Library in Open Event Android App for JSON Parsing

Jackson library is a popular library to map Java objects to JSON and vice-versa and has a better parsing speed as compared to other popular parsing libraries like GSON, JSONP etc. This blog post gives a basic explanation on how we utilised the Jackson library in the Open Event Android App.

To use the Jackson library we need to add the dependency for it in the app/build.gradle file.

compile 'com.squareup.retrofit2:converter-jackson:2.2.0'

After updating the app/build.gradle file with the code above we were able to use Jackson library in our project.

Example of Jackson Library JSON Parsing

To explain how the mapping is done let us take an example. The file given below is the sponsors.json file from the android app.

    “description”: “”,
    “id”: 1,
    “level”: 3,
    “name”:  KI Group,
    “type”: Gold,
    “url: “”,
    “logo-url”: “” 

The sponsors.json consists of mainly 7 attributes namely description, id, level, name, type, url and logo url for describing one sponsor of the event. The file for converting the json response to Java POJO objects was done as follows utilizing the Jackson library:

public class Sponsors extends RealmObject {
    private int id;

    private String type;

    private String description;

    private String level;

    private String name;

    private String url;

    private String logoUrl;

As we can see from the above code snippet, the JSON response is converted to Java POJO objects simply by using the annotation [email protected](“”)” which does the work for us.

Another example which makes this library amazing are the setter and getter annotations which help us use a single variable for two different json attributes if need be. We faced this situation when we were moving from the old api to the new json api. In that case we wanted support for both, old and new json attributes. In that case we simply used the following code snippet which made our transition to new api easier.

public class Sponsors extends RealmObject {
    private int id;
    private String type;
    private String description;
    private String level;
    private String name;
    private String url;
    private String logoUrl;

    public void setLogo(String logoUrl) {
        this.logoUrl = logoUrl;

    public void setLogo(String logoUrl) {
        this.logoUrl = logoUrl;

As we can see the setter annotations allow easy naming of variable to multiple attributes if need be thus making the code easily adaptable with less overload.

Related Links:

Using Flask SocketIO Library in the Apk Generator of the Open Event Android App

Recently Flask SocketIO library was used in the apk generator of the Open Event Android App as it gave access to the low latency bi-directional communications between the client and the server side. The client side of the apk generator was written in Javascript which helped us to use a SocketIO official client library to establish a permanent connection to the server.

The main purpose of using the library was to display logs to the user when the app generation process goes on. This gives the user an additional help to check what is the mistake in the file uploaded by them in case an error occurs. Here the library established a connection between the server and the client so that during the app generation process the server would send real time logs to the client so that they can be viewed by the user displayed in the frontend.

To use this library we first need to download it using pip command:

pip install flask-socketio

This library depends on the asynchronous services which can be selected amongst the following listed below:

  1. Eventlet
  2. Gevent
  3. Flask development server based on Werkzeug

Amongst the three listed, eventlet is the best performant option as it has support for long polling and WebSocket transports.

The next thing was importing this library in the flask application i.e the apk generator of the app as follows:

from flask_socketio import SocketIO

current_app = create_app()
socketio = SocketIO(current_app)

if __name__ == '__main__':

The main use of the above statement ( is that with this the startup of the web server is encapsulated. When the application is run in debug mode it is preferred to use the Werkzeug development server. However in production mode the use of eventlet web server or gevent web server is recommended.

We wanted to show the status messages currently shown to the user in the form of logs. For this firstly the file was looked upon which had the status messages and these were sent to the client side of the generator by establishing a connection between them using this library. The code written on the server side to send messages to the client side was as follows:

def handle_message(message):
    if message not None:
        namespace = “/” + self.identifier;
        send(message, namespace = namespace)

As we can see from the above code the message had to be sent to that particular namespace. The main idea of using namespace was that if there were more than one users using the generator at the same time, it would mean the send() method would send the messages to all the clients connected which would lead to the mixing up of status messages and hence it was important to use namespace so that a message was sent to that particular client.

Once the server sent the messages to the client we needed to add functionality to the our client side to receive the messages from them and also update the logs area with suitable content received. For that first the socket connection was established once the generate button was clicked which generated the identifier for us which had to be used as the namespace for that process.

socket = io.connect(location.protocol + "//" + + "/" + identifier, {reconnection: false});

This piece of code established the connection of the socket and helps the client side to receive and send messages from and to the server end.

Next thing was receiving messages from the server. For this the following code snippet was added:

socket.on('message', function(message) {

This piece of code receives the messages from the server for unnamed events. Once the connection is established and the messages are received, the logs are updated with each message being appended so as to show the user the real time information about their build status of their app.

This was how the idea of logs being shown in the apk generator was incorporated by making the required changes in the server and client side code using the Flask SocketIO library.

Related Links:

Writing Tests for class of the Open Event Android App class of Open Event Android App was a util class written to perform the date manipulation functions and ensure the code base got more simpler and deterministic. However it was equally important to test the result from this util class so as to ensure the result returned by it was what we wanted. A test class named “” was written to ensure all the edge cases of conversion of the dates string from one timezone to another timezone were handled properly.

For writing unit tests, first we needed to add these libraries as dependencies in the app’s top level build.gradle file as shown below:

dependencies {
  testCompile 'junit:junit:4.12'

Then a JUnit 4 Test class, which was a Java class containing the required test methods was created. The structure of the class looked like this:

public class DateTest {
[email protected]
   public void methodName() {

Next step was including all the required methods which ensured the util class returned the correct results according to our needs. Various edge cases were taken into account by including functions like converting of date string from local time zone to specified timezone, from international timezone to local timezone, from local timezone to international timezone and many more. Some of the methods which were added in the class are shown below:

  • Test of conversion from local timezone to specified timezone:

This function aimed at ensuring the util class worked well with date conversion from local time zone to a specified timezone. An example as shown below was taken where the conversion of the date string was tested from UTC timezone to Singapore timezone.

public void shouldConvertLocalTimeZoneDateStringToSpecifiedTimeZoneDateString() {

    String dateString1 = "2017-06-02T07:59:10Z";
    String actualString = ISO8601Date.getTimeZoneDateStringFromString(dateString1);
    String expectedString = "Thu, 01 Jun 2017, 23:59, UTC";
    Assert.assertEquals(expectedString, actualString);
  • Test of conversion from local timezone to international timezone:

This function aimed at ensuring the util class worked well with the date conversion from local timezone to international timezone. An example as shown below was taken where the conversion of the date string was tested from Amsterdam timezone to Singapore timezone.

public void shouldConvertLocalTimeZoneDateStringToInternationalTimeZoneDateString() {

    String dateString = "2017-06-02T02:29:10Z";
    String actualString = ISO8601Date.getTimeZoneDateStringFromString(dateString);
    String expectedString = "Thu, 01 Jun 2017, 20:29, GMT+02:00";
    Assert.assertEquals(expectedString, actualString);

Above were some functions added to ensure the conversion of a date string from one timezone to another was correct and thus ensured the util class was working properly and returned the results as required.

The last thing left was running the test to check the results the util class returned. For this we had to do two things:

  1. Sync the project with Gradle.
  2. Run the test by right clicking on the class and selecting “Run” option.

Through this we were able to run the test and check the output of the util class on different cases through the results which could be seen on the Android Monitor in the Android Studio.

Related Links:

  1. This link is about building effective unit tests in android. (
  2. This link is about the unit testing on date processing. (

Expandable ListView In PSLab Android App

In the PSLab Android App, we show a list of experiments for the user to perform or refer to while performing an experiment, using PSLab hardware device. A long list of experiments need to be subdivided into topics like Electronics, Electrical, School Level, Physics, etc. In turn, each category like Electronics, Electrical, etc can have a sub-list of experiments like:

  • Electronics
    • Diode I-V characteristics
    • Zener I-V characteristics
    • Transistor related experiments
  • Electrical
    • Transients RLC
    • Bode Plots
    • Ohm’s Law

This list can continue in similar fashion for other categories as well. We had to  display  this experiment list to the users with a good UX, and ExpandableListView seemed the most appropriate option.

ExpandableListView is a two-level listView. In the Group view an individual item can be expanded to show it’s children. The Items associated with ExpandableListView come from ExpandableListAdapter.









Implementation of Experiments List Using ExpandableListView

First, the ExpandableListView was declared in the xml layout file inside some container like LinearLayout/RelativeLayout.

<LinearLayout xmlns:android=""
       android:dividerHeight="2dp" />

Then we populated the data onto the ExpandableListView, by making an adapter for ExpandableListView by extending BaseExpandableListAdapter and implementing its methods. We then passed a Context, List<String> and Map<String,List<String>> to the Adapter constructor.

Context: for inflating the layout

List<String>: contains titles of unexpanded list

Map<String,List<String>>: contains sub-list mapped with title string

public SavedExperimentAdapter(Context context,
                                 List<String> experimentGroupHeader,
                                 HashMap<String, List<String>> experimentList) {
       this.context = context;
       this.experimentHeader = experimentGroupHeader;
       this.experimentList = experimentList;

In getGroupView() method, we inflate, set title and return group view i.e the main list that we see on clicking and the  sub-list is expanded. You can define your own layout in xml and inflate it. For PSLab Android, we used the default one provided by Android

public View getGroupView(int groupPosition, boolean isExpanded, View convertView, ViewGroup parent) {
   String headerTitle = (String) getGroup(groupPosition);
   if (convertView == null) {
       LayoutInflater inflater = (LayoutInflater) this.context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
       convertView = inflater.inflate(android.R.layout.simple_expandable_list_item_2, null);
   TextView tvExperimentListHeader = (TextView) convertView.findViewById(;
   tvExperimentListHeader.setTypeface(null, Typeface.BOLD);
   TextView tvTemp = (TextView) convertView.findViewById(;
   return convertView;

Similarly, in getChildView() method, we inflate, set data and return child view. We wanted simple TextView as sub-list item thus inflated the layout containing only TextView and setText by taking reference of textView from the inflated view.

public View getChildView(int groupPosition, int childPosition, boolean isLastChild, View convertView, ViewGroup parent) {
   String experimentName = (String) getChild(groupPosition, childPosition);
   if (convertView == null) {
       LayoutInflater inflater = (LayoutInflater) this.context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
       convertView = inflater.inflate(R.layout.experiment_list_item, null);
   TextView tvExperimentTitle = (TextView) convertView.findViewById(;
   return convertView;

The complete code for the Adapter can be seen here.

After creating the adapter we proceeded similarly to the normal ListView. Take the reference for ExpandableListView by findViewById() or BindView if you are using ButterKnife and set the adapter as an instance of adapter created above.

ExpandableListView experimentExpandableList;
experimentAdapter = new SavedExperimentAdapter(context, headerList, map);
Source: PSLab Android


We are planning to divide the experiment sub-list into categories like

  • Electronics
    • Diode
      • Diode I-V
      • Zener I-V
      • Diode Clamping
      • Diode Clipping
    • BJT and FET
      • Transistor CB (Common Base)
      • Transistor CE (Common Emitter)
      • Transistor Amplifier
      • N-FET output characteristic
    • Op-Amps
  • Electrical

This is a bit more complex than it looks, I tried using an ExpandableListView as a child for a group item but ran into some errors. I will write a post as soon as this view hierarchy has been achieved.


Share Images on Pinterest from Phimpme Android Application

After successfully establishing Pinterest authentication in Phimpme our next goal was to share the image on the Pinterest website directly from Phimpme, without using any native Android application.

Adding Pinterest Sharing option in Sharing Activity in Phimpme

To add various sharing options in Sharing Activity in the Phimpme project, I have applied a ScrollView for the list of the different sharing options which include: Facebook, Twitter, Pinterest, Imgur, Flickr and Instagram. All the App icons with the name are arranged in a TableLayout in the activity_share.xml file. Table rows consist of two columns. In this way, it is easier to add more app icons for future development.


Adding Pinterest app icon on the icons_drawable array. This array is then used to inflate the icon on the list view.

private int[] icons_drawables = {R.drawable.ic_facebook_black, R.drawable.ic_twitter_black,R.drawable.ic_instagram_black, R.drawable.ic_wordpress_black, R.drawable.ic_pinterest_black);

Adding Pinterest text on the titles_text array. This array is then used to inflate the names of the various sharing activity.

private int[] titles_text = {R.string.facebook, R.string.twitter, R.string.instagram,
       R.string.wordpress, R.string.pinterest);

Prerequisites to share Image on Pinterest

To share an Image on Pinterest a user has to add a caption and Board ID. Our first milestone was to get the input of the Board ID  by the user. I have achieved this by taking the input in a Dialog Box. When the user clicks on the Pinterest option, a dialog box pops and then the user can add their Board ID.

private void openPinterestDialogBox() {
   AlertDialog.Builder captionDialogBuilder = new AlertDialog.Builder(SharingActivity.this, getDialogStyle());
   final EditText captionEditText = getCaptionDialog(this, captionDialogBuilder);


   captionDialogBuilder.setNegativeButton(getString(R.string.cancel).toUpperCase(), null);
   captionDialogBuilder.setPositiveButton(getString(R.string.post_action).toUpperCase(), new DialogInterface.OnClickListener() {
       public void onClick(DialogInterface dialog, int which) {
           //This should be empty it will be overwrite later
           //to avoid dismiss of the dialog on the wrong password

   final AlertDialog passwordDialog = captionDialogBuilder.create();;

   passwordDialog.getButton(AlertDialog.BUTTON_POSITIVE).setOnClickListener(new View.OnClickListener() {
       public void onClick(View v) {
           String captionText = captionEditText.getText().toString();
           boardID =captionText;

A user can fetch the Board ID by following the steps:

Board ID is necessary because it specifies where the image needs to be posted.

Creating custom post function for Phimpme

The image is posted using a function in PDKClient class. PDKClient is found in the PDK module which we get after importing Pinterest SDK. Every image is posted on Pinterest is called a Pin. So we will call createPin function. I have made my custom createPin function so that it also accepts Bitmaps as a parameter. In the Pinterest SDK it only accepts image URL to share, The image should already be on the internet to be shared. For this reason, we to add a custom create Pin function to accept Bitmaps as an option.

public void createPin(String note, String boardId, Bitmap image, String link, PDKCallback callback) {
   if (Utils.isEmpty(note) || Utils.isEmpty(boardId) || image == null) {
       if (callback != null) callback.onFailure(new PDKException("Board Id, note, Image cannot be empty"));

   HashMap<String, String> params = new HashMap<String, String>();
   params.put("board", boardId);
   params.put("note", note);
   params.put("image_base64", Utils.base64String(image));
   if (!Utils.isEmpty(link)) params.put("link", link);
   postPath(PINS, params, callback);

Compressing Bitmaps

Since Pinterest SDK cannot accept Bitmap I have added a function to compress the Bitmap and encode it to strings.

public static String base64String(Bitmap bitmap) {
   ByteArrayOutputStream baos = new ByteArrayOutputStream();
   bitmap.compress(Bitmap.CompressFormat.JPEG, 100, baos);
   String b64Str = Base64.encodeToString(baos.toByteArray(), Base64.NO_WRAP);
   return b64Str;

Calling createPin function from the sharingActivity

From the sharingActivity we will call createPin activity. We will pass caption of the image, Board ID, Image bitmap and link(which is optional) as parameters.

       .getInstance().createPin(caption, boardID, image, null, new PDKCallback() {

If the image is posted successfully then onSuccess function is called which pops a snackbar and shows the success message. Otherwise, onFailure function is called which displays failure message on a snackbar.

public void onSuccess(PDKResponse response) {
   Log.d(getClass().getName(), response.getData().toString());
   Snackbar.make(parent, R.string.pinterest_post, Snackbar.LENGTH_LONG).show();


public void onFailure(PDKException exception) {
   Log.e(getClass().getName(), exception.getDetailMessage());
   Snackbar.make(parent, R.string.Pinterest_fail, Snackbar.LENGTH_LONG).show();
   //Toast.makeText(SharingActivity.this, boardID + caption, Toast.LENGTH_SHORT).show();



In Phimpme user can now send Image on Pinterest directly from the application. This is done without the use of the native Pinterest application.



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).


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: ''


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

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



For getting the auth token, you need to go to

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


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
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());
   Timber.plant(new ReleaseLogTree());


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

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)


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

if (priority == Log.INFO) {
    Sentry.getContext().recordBreadcrumb(new BreadcrumbBuilder()


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)


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);
       new UserBuilder()


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() {


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)

Timber Library

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

   <import type="" />
   <import type="android.view.View" />

       type="" />

       type="" />


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:

   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

   android:text="@{ }"
   tools:text="[email protected]" />


And then the check in status of the attendee

   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 }" />


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

   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

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

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


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

   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

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


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

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

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


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


       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" />

       android:layout_gravity="center" />



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: