Better Bookmark Display Viewholder in Home Screen of the Open Event Android App

Earlier in the Open Event Android app we had built the homescreen with the bookmarks showing up at the top as a horizontal list of cards but it wasn’t very user-friendly in terms of UI. Imagine that a user bookmarks over 20-30 sessions, in order to access them he/she might have to scroll horizontally a lot in order to access his/her bookmarked session. So this kind of UI was deemed counter-intuitive. A new UI was proposed involving the viewholder used in the schedule page i.e DayScheduleViewHolder, where the list would be vertical instead of horizontal. An added bonus was that this viewholder conveyed the same amount of information on lesser white space than the earlier viewholder i.e SessionViewHolder.

Old Design
New Design










Above are two images, one in the initial design, the second in the new design. In the earlier design the number of bookmarks visible to the user at a time was at most 1 or 2 but now with the UI upgrade a user can easily see up-to 5-6 bookmarks at a time. Additionally there is more relevant content visible to the user at the same time.

Additionally this form of design also adheres to Google’s Material Design guidelines.

Code Comparison of the two Iterations

Initial Design
sessionsListAdapter = new SessionsListAdapter(getContext(), mSessions, bookmarkedSessionList);
 bookmarksRecyclerView.setLayoutManager(new LinearLayoutManager(getContext(),LinearLayoutManager.HORIZONTAL,false));

Here we are using the SessionListAdapter for the bookmarks. This was previously being used to display the list of sessions inside the track and location pages. It is again being used here to display the horizontal list of bookmarks.To do this we are using the function setBookmarkView(). Here mSessions consists the list of bookmarks that would appear in the homescreen.

Current Design
 bookMarksListAdapter = new DayScheduleAdapter(mSessions,getContext());
 bookmarksRecyclerView.setLayoutManager(new LinearLayoutManager(getContext()));

Now we are using the DayScheduleAdapter which is the same adapter used in the schedule page of the app. Now we use a vertical layout instead of a horizontal layout  but with a new viewholder design. I will be talking about the last line in the code snippet shortly.

ViewHolder Design (Current Design)

<RelativeLayout android:id="@+id/content_frame">
    <LinearLayout android:id="@+id/ll_sessionDetails">
        <TextView android:id="@+id/slot_title"/>
            <TextView android:id="@+id/slot_start_time”/>
            <TextView android:id="@+id/slot_underscore"/>
            <TextView android:id="@+id/slot_end_time"/>

           <TextView android:id="@+id/slot_comma"/>
            <TextView android:id="@+id/slot_location”/>
            <Button android:id="@+id/slot_track"/>
            <ImageButton android:id="@+id/slot_bookmark"/>

    <View android:id=”@+id/divider”/>

This layout file is descriptive enough to highlight each element’s location.

In this viewholder we can also access to the track page from the track tag and can also remove bookmarks instantly.

The official widget to make a scroll layout in android is ScrollView. Basically, adding a RecyclerView inside ScrollView can be difficult . The problem was that the scrolling became laggy and weird.  Fortunately, with the appearance of Material Design , NestedScrollView was released and this becomes much easier.


With this small snippet of code we are able to insert a RecyclerView inside the NestedScrollView without any scroll lag.
So now we have successfully updated the UI/UX for the homescreen  to meet the requirements as given by the Material Design guidelines.


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Maintain Aspect Ratio Mixin on Open Event Frontend

The welcome page of the Open-Event-Frontend is designed to contain cards that represent an event. A user is directed to the event-details page by clicking on the corresponding card. The page consists of an image that serves as the banner for the event and an overlapping div to provide some contrast against the image. A comment may also be added onto the image and along with the overlapping div it is wrapped in a container div.

Since we have given a specific height to the contrasting div, the background image shrinks according to the screen size but the contrasting div does not whenever we go from a large screen to a smaller screen.

Mobile view (before):-

We want our contrasting div also to resize in accordance to the image. To do it, we first define a sass mixin to maintain a common aspect ratio for image and overlapping div. Let us see it’s code.

 @mixin aspect-ratio($width, $height) {
    position: relative;
    &:before {
      display: block;
      content: "";
      width: 100%;
      padding-top: ($height / $width) * 100%;
    > .content {
      position: absolute;
      top: 0;
      left: 0;
      right: 0;
      bottom: 0;
    > img {
      position: absolute;
      top: 0;
      left: 0;
      right: 0;
      bottom: 0;

So what does this mixin actually doing is we are passing the height and width of the image and we are defining a pseudo element for our image and give it a margin top of (height/width)*100 since this value is related to image width (height: 0; padding-bottom: 100%; would also work, but then we have to adjust the padding-bottom value every time we change the width). Now we just position the content element and image as absolute with all four orientations set to 0. This just covers the parent element completely, no matter which size it has.

Now we can simply use our mixin by adding the following line of code in out container div

@include aspect-ratio(2, 1);

Here we want to maintain a 2:1 aspect ratio and the user is also expected to upload the image in the same aspect ratio. Therefore, we pass width as 2 and height as 1 to our mixin.

Now when we resize our screen both the image and the overlapping div resize maintaining 2:1 aspect ratio.

Mobile view (after):-


  • mademyday blog describes a method of using pseudo elements to maintain an element’s aspect ratio.
  • css-tricks snippet.
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Image Cropper On Ember JS Open Event Frontend

In Open Event Front-end, we have a profile page for every user who is signed in where they can edit their personal details and profile picture. To provide better control over profile editing to the user, we need an image cropper which allows the user to crop the image before uploading it as their profile picture. For this purpose, we are using a plugin called Croppie. Let us see how we configure Croppie in the Ember JS front-end to serve our purpose.

All the configuration related to Croppie lies in a model called cropp-model.js.

 onVisible() {
    this.$('.content').css('height', '300px');
      customClass : 'croppie',
      viewport    : {
        width  : 400,
        height : 200,
        type   : 'square'
      boundary: {
        width  : 600,
        height : 300

  onHide() {
    const $img = this.$('img');
    if ($img.parent().is('div.croppie')) {

  actions: {
    resetImage() {
    cropImage() {
      this.$('img').croppie('result', 'base64', 'original', 'jpeg').then(result => {
        if (this.get('onImageCrop')) {

There are two functions: onVisible() and onHide(), which are called every time when we hit reset button in our image cropper model.

  • When a user pushes reset button, the onHide() function fires first which basically destroys a croppie instance and removes it from the DOM.
  • onVisible(), which fires next, sets the height of the content div. This content div contains our viewport and zoom control. We also add a customClass of croppie to the container in case we are required to add some custom styling. Next, we set the dimensions and the type of viewport which should be equal to the dimensions of the cropped image. We define type of cropper as ‘square’ (available choices are ‘square’ and ‘circle’). We set the dimensions of our boundary. The interesting thing to notice here is that we are setting only the height of the boundary because if we pass only the height of the boundary, the width will be will be calculated using the viewport aspect ratio. So it will fit in all the screen sizes without overflowing.

The above two functions are invoked when we hit the reset button. When the user is satisfied with the image and hits ‘looks good’ button, cropImage() function is called where we are get the resulting image by passing some custom options provided by croppie like base64 bit encoding and size of cropped image which we are set to ‘original’ here and the extension of image which is we set here as ‘.jpeg’. This function returns the image of desired format which we use to set profile image.


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Addition of Bookmark Icon in Schedule ViewHolder in Open Event Android App

In the Open Event Android app we only had a list of sessions in the schedule page without  the ability to bookmark the session unless we went into the SessionDetailPage or visited the session list via the tracks page or the locations page. This was obviously very inconvenient. There were several iterations of UI design for the same. Taking cues from the Google I/O 17 App I thought that the addition of the Bookmark Icon in the Schedule ViewHolder would be helpful to the user. In this blog post I will be talking about how this feature was implemented.

Layout Implementation for the Bookmark Icon

    app:srcCompat="@drawable/ic_bookmark_border_white_24dp" />

The bookmark Icon was modelled as an ImageButton inside the item_schedule.xml file which serves as the layout file for the DayScheduleViewHolder.

Bookmark Icon Functionality in DayScheduleAdapter

The Bookmark Icon had mainly 3 roles :

  1. Add the session to the list of bookmarks (obviously)
  2. Generate the notification giving out the bookmarked session details.
  3. Generate a Snackbar if the icon was un-clicked which allowed the user to restore the bookmarked status of the session.
  4. Update the bookmarks widget.

Now we will be seeing how was all this done. Some of this was already done previously in the SessionListAdapter. We just had to modify some of the code to get our desired result.

       Session not bookmarked                      Session bookmarked                      

First we just set a different icon to highlight the Bookmarked and the un-bookmarked status. This code snippet highlights how this is done.

if(session.isBookmarked()) {
 } else {

We check if the session is bookmarked by calling a function isBookmarked() and choose one of the 2 bookmark icons depending upon the bookmark status.

If a session was found out to be bookmarked and the Bookmark Icon was we use the WidgetUpdater.updateWidget() function to remove that particular session from the  Bookmark Widget of the app. During this a  Snackbar is also generated “Bookmark Removed” with an UNDO option which is functional.

realmRepo.setBookmark(sessionId, false).subscribe();
 if ("MainActivity".equals(context.getClass().getSimpleName())) {
    Snackbar.make(slot_content, R.string.removed_bookmark, Snackbar.LENGTH_LONG)
            .setAction(R.string.undo, view -> {
                realmRepo.setBookmark(sessionId, true).subscribe();

else {
    Snackbar.make(slot_content, R.string.removed_bookmark, Snackbar.LENGTH_SHORT).show();

If a session wasn’t bookmarked earlier but the Bookmark Icon was clicked we would firstly need to update the bookmark status within our local Realm Database.

realmRepo.setBookmark(sessionId, true).subscribe();

We would also create a notification to notify the user.

NotificationUtil.createNotification(session, context).subscribe(
        () -> Snackbar.make(slot_content,
        throwable -> Snackbar.make(slot_content,

The static class Notification Util is responsible for the generation of notifications. The internal working of that class is not necessary right now. What this snippet of code does is that It creates a Snackbar upon successful notification with the text “Bookmark Added” and if any error occurs a Snackbar with the text “Error Creating Notification” is generated.


This snippet of code is responsible for the colors that are assigned to the Bookmark Icons for different tracks and this color is obtained in the following manner.

int storedColor = currentSession.getTrack().getColor()

So now we have successfully added the Bookmark Icon to the ScheduleViewHolder inside the schedule of the app.


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Addition Of Track Tags In Open Event Android App

In the Open Event Android app we only had a list of sessions in the schedule page without  knowing which track each session belonged to. There were several iterations of UI design for the same. Taking cues from the Google I/O 17 App we thought that the addition of track tags would be informative to the user.  In this blog post I will be talking about how this feature was implemented.

TrackTag Layout in Session

                tools:text="Track" />

The important part here is the track tag was modelled as a <Button/> to give users a touch feedback via a ripple effect.

Tag Implementation in DayScheduleAdapter

All the dynamic colors for the track tags was handled separately in the DayScheduleAdapter.

final Track sessionTrack = currentSession.getTrack();
       int storedColor = Color.parseColor(sessionTrack.getColor());
       holder.slotTrack.getBackground().setColorFilter(storedColor, PorterDuff.Mode.SRC_ATOP);

       holder.slotTrack.setOnClickListener(v -> {
            Intent intent = new Intent(context, TrackSessionsActivity.class);
            intent.putExtra(ConstantStrings.TRACK, sessionTrack.getName());

            intent.putExtra(ConstantStrings.TRACK_ID, sessionTrack.getId());

As the colors associated with a track were all stored inside the track model we needed to obtain the track from the currentSession. We could get the storedColor by calling getColor() on the track object associated with the session.

In order to set this color as the background of the button we needed to set a color filter with a PorterDuff Mode called as SRC_ATOP.

The name of the parent class is an homage to the work of Thomas Porter and Tom Duff, presented in their seminal 1984 paper titled “Compositing Digital Images”. In this paper, the authors describe 12 compositing operators that govern how to compute the color resulting of the composition of a source (the graphics object to render) with a destination (the content of the render target).

Ref :

To exactly understand what does the mode SRC_ATOP do we can refer to the image below for understanding. There are several other modes with similar functionality.


      SRC IMAGE             DEST IMAGE           SRC ATOP DEST

Now we also set an onClickListener for the track tag so that it directs us to the tracks Page.

So now we have successfully added track tags to the app.


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Addition Of Settings Page Animations in Open Event Android App

In order to bring in some uniform user flow in the  Open Event Android  there was a need to implement slide animation for various screens. It turned out that the settings page didn’t adhere to such a rule. In this blog post I’ll be highlighting how this was implemented in the app.

Android Animations

Animations for views/layouts in android were built in order to have elements of the app rely on real life motion and physics. These are mainly used to choreograph motion among various elements within a page or multiple pages. Here we would be implementing a simple slide_in and a slide_out animation for the settings page. Below I highlight how to write a simple animator.


<?xml version="1.0" encoding="utf-8"?>

       android:toXDelta="0%" />


This xml file maily is what does the animation for us in the app. We just need to provide the translate element with the position fromXDelta from where the view would move to another location that would be toXDelta.

@android:integer/config_shortAnimTime is a default int variable for animation durations.

Here toXDelta=”0%” signifies that initial position of the page i.e the settings page that is the screen itself. And the 100% in fromXDelta signifies the virtual screen space to the right of the actual screen(OUTSIDE THE SCREEN OF THE PHONE).

Using this animation it appears that the screen is sliding into the view of the user from the right.

We will be using overridePendingTransition to override the default enter and exit animations for the activities which is fade_in and fade_out as of Android Lollipop.

The two integers you provide for overridePendingTransition(int enterAnim, int exitAnim) correspond to the two animations – removing the old Activity and adding the new one.

We have already defined the enterAnim here that is slide_in_left. For the exit animation we would define another animation that would be stay_in_place.xml that would have both fromXDelta and toXDelta as 0% as their values. This was done to just avoid any exit animation.

We need to add this line after the onCreate call within the SettingActivity.

 protected void onCreate(Bundle savedInstanceState) {

       //Some Code
       overridePendingTransition(R.anim.slide_in_right,    R.anim.stay_in_place);
     //Some Code

Now we are done.

We can see below that the settings page animates with the prescribed animations below.



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Documenting Open Event API Using API-Blueprint

FOSSASIA‘s Open Event Server API documentation is done using an api-blueprint. The API Blueprint language is a format used to describe API in an API blueprint file, where a blueprint file (or a set of files) is such that describes an API using the API Blueprint language. To follow up with the blueprint, an apiary editor is used. This editor is responsible for rendering the API blueprint and printing the result in user readable API documented format. We create the API blueprint manually.

Using API Blueprint:-
We create the API blueprint by first adding the name and metadata for the API we aim to design. This step looks like this :-


# Open Event API Server

The Open Event API Server

# Group Authentication

The API uses JWT Authentication to authenticate users to the server. For authentication, you need to be a registered user. Once you have registered yourself as an user, you can send a request to get the access_token.This access_token you need to then use in Authorization header while sending a request in the following manner: `Authorization: JWT <access_token>`

API blueprint starts with the metadata, here FORMAT and HOST are defined metadata. FORMAT keyword specifies the version of API Blueprint . HOST defines the host for the API.

The heading starts with # and the first heading is regarded as the name of the API.

NOTE – Also all the heading starts with one or more # symbol. Each symbol indicates the level of the heading. One # symbol followed by heading serves as the top level i.e. one # = Top Level. Similarly for  ## = second level and so on. This is in compliance with normal markdown format.
        Following the heading section comes the description of the API. Further, headings are used to break up the description section.

Resource Groups:
    By using group keyword at the starting of a heading , we create a group of related resources. Just like in below screenshot we have created a Group Users.

# Group Users

For using the API you need(mostly) to register as an user. Registering gives you access to all non admin API endpoints. After registration, you need to create your JWT access token to send requests to the API endpoints.

| Parameter | Description | Type | Required |
| `name`  | Name of the user | string | - |
| `password` | Password of the user | string | **yes** |
| `email` | Email of the user | string | **yes** |


    In the Group Users we have created a resource Users Collection. The heading specifies the URI used to access the resource inside of the square brackets after the heading. We have used here parameters for the resource URI which takes us into how to add parameters to the URI. Below code shows us how to add parameters to the resource URI.

## Users Collection [/v1/users{?page%5bsize%5d,page%5bnumber%5d,sort,filter}]
+ Parameters
    + page%5bsize%5d (optional, integer, `10`) - Maximum number of resources in a single paginated response.
    + page%5bnumber%5d (optional, integer, `2`) - Page number to fetchedfor the paginated response.
    + sort (optional, string, `email`) - Sort the resources according to the given attribute in ascending order. Append '-' to sort in descending order.
    + filter(optional, string, ``) - Filter according to the flask-rest-jsonapi filtering system. Please refer: for more.


    An action is specified with a sub-heading inside of  a resource as the name of Action, followed by HTTP method inside the square brackets.
    Before we get on further, let us discuss what a payload is. A payload is an HTTP transaction message including its discussion and any additional assets such as entity-body validation schema.

There are two payloads inside an Action:

  1. Request: It is a payload containing one specific HTTP Request, with Headers and an optional body.
  2. Response: It is a payload containing one HTTP Response.

A payload may have an identifier-a string for a request payload or an HTTP status code for a response payload.

+ Request

    + Headers

            Accept: application/vnd.api+json

            Authorization: JWT <Auth Key>

+ Response 200 (application/vnd.api+json)

Types of HTTP methods for Actions:

  • GET – In this action, we simply send the header data like Accept and Authorization and no body. Along with it we can send some GET parameters like page[size]. There are two cases for GET: List and Detail. For example, if we consider users, a GET for List helps us retrieve information about all users in the response, while Details, helps us retrieve information about a particular user.

The API Blueprint examples implementation of both GET list and detail request and response are as follows.

### List All Users [GET]
Get a list of Users.

+ Request

    + Headers

            Accept: application/vnd.api+json

            Authorization: JWT <Auth Key>

+ Response 200 (application/vnd.api+json)

            "meta": {
                "count": 2
            "data": [
                    "attributes": {
                        "is-admin": true,
                        "last-name": null,
                        "instagram-url": null,


### Get Details [GET]
Get a single user.

+ Request

    + Headers

            Accept: application/vnd.api+json

            Authorization: JWT <Auth Key>

+ Response 200 (application/vnd.api+json)

            "data": {
                "attributes": {
                    "is-admin": false,
                    "last-name": "Doe",
                    "instagram-url": "",


  • POST – In this action, apart from the header information, we also need to send a data. The data must be correct with jsonapi specifications. A POST body data for an users API would look something like this:
### Create User [POST]
Create a new user using an email, password and an optional name.

+ Request (application/vnd.api+json)

    + Headers

            Authorization: JWT <Auth Key>

    + Body

                  "email": "[email protected]",
                  "password": "password",

A POST request with this data, would create a new entry in the table and then return in jsonapi format the particular entry that was made into the table along with the id assigned to this new entry.

  • PATCH – In this action, we change or update an already existing entry in the database. So It has a header data like all other requests and a body data which is almost similar to POST except that it also needs to mention the id of the entry that we are trying to modify.
### Update User [PATCH]
+ `id` (integer) - ID of the record to update **(required)**

Update a single user by setting the email, email and/or name.

Authorized user should be same as user in request body or must be admin.

+ Request (application/vnd.api+json)

    + Headers

            Authorization: JWT <Auth Key>

    + Body

              "data": {
                "attributes": {
                  "password": "password1",
                  "avatar_url": "",
                  "first-name": "Jane",
                  "last-name": "Dough",
                  "details": "example1",
                  "contact": "example1",
                  "facebook-url": "",
                  "twitter-url": "",
                  "instagram-url": "",
                  "google-plus-url": "",
                  "thumbnail-image-url": "",
                  "small-image-url": "",
                  "icon-image-url": ""
                "type": "user",
                "id": "2"

Just like in POST, after we have updated our entry, we get back as response the new updated entry in the database.

  • DELETE – In this action, we delete an entry from the database. The entry in our case is soft deleted by default. Which means that instead of deleting it from the database, we set the deleted_at column with the time of deletion. For deleting we just need to send header data and send a DELETE request to the proper endpoint. If deleted successfully, we get a response as “Object successfully deleted”.
### Delete User [DELETE]
Delete a single user.

+ Request

    + Headers

            Accept: application/vnd.api+json

            Authorization: JWT <Auth Key>

+ Response 200 (application/vnd.api+json)

          "meta": {
            "message": "Object successfully deleted"
          "jsonapi": {
            "version": "1.0"

How to check after manually entering all these? We can use the
apiary website to render it, or simply use different renderer to do it. How? Checkout for my next blog on apiary and aglio.

Learn more about api blueprint here:

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Global Search in Open Event Android

In the Open Event Android app we only had a single data source for searching in each page that was the content on the page itself. But it turned out that users want to search data across an event and therefore across different screens in the app. Global search solves this problem. We have recently implemented  global search in Open Event Android that enables the user to search data from the different pages i.e Tracks, Speakers, Locations etc all in a single page. This helps the user in obtaining his desired result in less time. In this blog I am describing how we implemented the feature in the app using JAVA and XML.

Implementing the Search

The first step of the work is to to add the search icon on the homescreen. We have done this with an id

public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
   super.onCreateOptionsMenu(menu, inflater);
   inflater.inflate(, menu);
   // Get the SearchView and set the searchable configuration
   SearchManager searchManager = (SearchManager)getContext().    getSystemService(Context.SEARCH_SERVICE);
   searchView = (SearchView) menu.findItem(;
  // Assumes current activity is the searchable activity

What is being done here is that the search icon on the top right of the home screen  is being designated a searchable component which is responsible for the setup of the search widget on the Toolbar of the app.

 public boolean onCreateOptionsMenu(Menu menu) {
    MenuInflater inflater = getMenuInflater();
    inflater.inflate(, menu);
    SearchManager searchManager =
            (SearchManager) getSystemService(Context.SEARCH_SERVICE);
    searchView = (SearchView) menu.findItem(;
    if (searchText != null) {
        searchView.setQuery(searchText, true);
    return true; }

We can see that a queryTextListener has been setup in this function which is responsible to trigger a function whenever a query in the SearchView changes.

Example of a Searchable Component

<?xml version="1.0" encoding="utf-8"?>
 <searchable xmlns:android=""
    android:label="@string/app_name" />

For More Info :

If this searchable component is inserted into the manifest in the required destination activity’s body the destination activity is set and intent filter must be set in this activity to tell whether or not the activity is searchable.

Manifest Code for SearchActivity

        android:label="Search App"
        <action android:name="android.intent.action.SEARCH" />
        android:resource="@xml/searchable" />

And the attribute  android:launchMode=”singleTop is very important as if we want to search multiple times in the SearchActivity all the instances of our SearchActivity would get stored on the call stack which is not needed and would also eat up a lot of memory.

Handling the Intent to the SearchActivity

We basically need to do a standard if check in order to check if the intent is of type ACTION_SEARCH.

if (Intent.ACTION_SEARCH.equals(getIntent().getAction())) {
 protected void onNewIntent(Intent intent) {
 public void handleIntent(Intent intent) {
    final String query = intent.getStringExtra(SearchManager.QUERY);

The function searchQuery is called within handleIntent in order to search for the text that we received from the Homescreen.

SearchView Trigger Functions

Next we need to add two main functions in order to get the search working:

  • onQueryTextChange
  • onQueryTextSubmit

The function names are self-explanatory. Now we will move on to the code implementation of the given functions.

 public boolean onQueryTextChange(String query) {
    if(query!=null) {
        searchText = query;
   return true;
 public boolean onQueryTextSubmit(String query) {
    return true;

The role of the searchView.clearFocus() inside the above code snippet is to remove the keyboard popup from the screen to enable the user to have a clear view of the search result.

Here the main search logic is being handled by the function called searchQuery which I’ll talking about now.

Search Logic

private void searchQuery(String constraint) {
    if (!TextUtils.isEmpty(constraint)) {
        String query = constraint.toLowerCase(Locale.getDefault());
//This is the custom recycler view adapter that has been defined for the search
private GlobalSearchAdapter globalSearchAdapter;
 //This stores the results in an Object Array
 private List<Object> result

We are assuming that we have POJO’s(Plain Old Java Objects) for Tracks , Speakers , and Locations and for the Result Type Header.

The code posted below performs the function of getting the required results from the list of tracks. All the results are being fetched asynchronously from Realm and here we have also attached a header for the result type to denote whether the result is of type Track , Speaker or Location. We also see that we have added a changeListener to notify us if any changes have occurred in the set of results.

Similarly this is being done for all the result types that we need i.e Tracks, Locations and Speakers.

public void addResultsFromTracks(String queryString) {

   RealmResults<Track> filteredTracks = realm.where(Track.class)
                                        .like("name", queryString,                     Case.INSENSITIVE).findAllSortedAsync("name");
      filteredTracks.addChangeListener(tracks -> {

       Timber.d("Filtering done total results %d", tracks.size());

We now have a “Global Search” feature in the Open Event Android app. Users had asked for this feature and a learning for us is, that it would have been even better to do more tests with users when we developed the first versions. So, we could have included this feedback and implemented Global Search earlier on.


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Open Event Server: Working with Migration Files

FOSSASIA‘s Open Event Server uses alembic migration files to handle all database operations and updations.  From creating tables to updating tables and database, all works with help of the migration files.
However, many a times we tend to miss out that automatically generated migration files mainly drops and adds columns rather than just changing them. One example of this would be:

def upgrade():
    ### commands auto generated by Alembic - please adjust! ###
    op.add_column('session', sa.Column('submission_date', sa.DateTime(), nullable=True))
    op.drop_column('session', 'date_of_submission')

Here, the idea was to change the has_session_speakers(string) to is_session_speakers_enabled (boolean), which resulted in the whole dropping of the column and creation of a new boolean column. We realize that, on doing so we have the whole data under  has_session_speakers lost.

How to solve that? Here are two ways we can follow up:

  • op.alter_column:

When update is as simple as changing the column names, then we can use this. As discussed above, usually if we migrate directly after changing a column in our model, then the automatic migration created would drop the old column and create a new column with the changes. But on doing this in the production will cause huge loss of data which we don’t want. Suppose we want to just change the name of the column of start_time to starts_at. We don’t want the entire column to be dropped. So an alternative to this is using op.alter_column. The two main necessary parameters of the op.alter_column is the table name and the column which you are willing to alter. The other parameters include the new changes. Some of the commonly used parameters are:

  1. nullable Optional: specify True or False to alter the column’s nullability.
  2. new_column_name – Optional; specify a string name here to indicate the new name within a column rename operation.
  3. type_Optional: a TypeEngine type object to specify a change to the column’s type. For SQLAlchemy types that also indicate a constraint (i.e. Boolean, Enum), the constraint is also generated.
  4. autoincrement –  Optional: set the AUTO_INCREMENT flag of the column; currently understood by the MySQL dialect.
  5. existing_typeOptional: a TypeEngine type object to specify the previous type. This is required for all column alter operations that don’t otherwise specify a new type, as well as for when nullability is being changed on a column.

    So, for example, if you want to change a column name from “start_time” to “starts_at” in events table you would write:
    op.alter_column(‘events’, ‘start_time’, new_column_name=’starts_at’)
def upgrade():
    ### commands auto generated by Alembic - please adjust! ###
    op.alter_column('sessions_version', 'end_time', new_column_name='ends_at')
    op.alter_column('sessions_version', 'start_time', new_column_name='starts_at')
    op.alter_column('events_version', 'end_time', new_column_name='ends_at')
    op.alter_column('events_version', 'start_time', new_column_name='starts_at')

session_version and events_version are the tables name altering columns start_time to starts_at and end_time to ends_at with the op_alter_column parameter new_column_name.

  • op.execute:

Now with alter_column, most of the alteration in the column name or constraints or types is achievable. But there can be a separate scenario for changing the column properties. Suppose I change a table with column “aspect_ratio” which was a string column and had values “on” and “off” and want to convert the type to Boolean True/False. Just changing the column type using alte_column() function won’t work since we need to also modify the whole data. So, sometimes we need to execute raw SQL commands. To do that, we can use the op.execute() function.
The way it is done:

def upgrade():
    ### commands auto generated by Alembic - please adjust! ###
    op.execute("ALTER TABLE image_sizes ALTER full_aspect TYPE boolean USING CASE 
            full_aspect WHEN 'on' THEN TRUE ELSE FALSE END", execution_options=None)

    op.execute("ALTER TABLE image_sizes ALTER icon_aspect TYPE boolean USING CASE 
            icon_aspect WHEN 'on' THEN TRUE ELSE FALSE END", execution_options=None)

    op.execute("ALTER TABLE image_sizes ALTER thumbnail_aspect TYPE boolean USING CASE 
            thumbnail_aspect WHEN 'on' THEN TRUE ELSE FALSE END"execution_options=None)

For a little more advanced use of op.execute() command will be:

op.alter_column('events', 'type', new_column_name='event_type_id')
    op.alter_column('events_version', 'type', new_column_name='event_type_id')
    op.execute('INSERT INTO event_types(name, slug) SELECT DISTINCT event_type_id, 
                lower(replace(regexp_replace(event_type_id, \'& |,\', \'\', \'g\'),
                \' \', \'-\')) FROM events where not exists (SELECT 1 FROM event_types 
                where and event_type_id is not
    op.execute('UPDATE events SET event_type_id = (SELECT id FROM event_types WHERE 
    op.execute('ALTER TABLE events ALTER COLUMN event_type_id TYPE integer USING 

In this example:

  • op.alter_column() renames the column type to event_type_id of events table
  • op.execute() does the following:
  • Inserts into column name of event_types table the value of event_type_idN (which previously contained the name of the event_type) from events table, and
  • Inserts into slug column of event_types table the value of event_type_id where all letters are changed to lowercase; “& ” and “,” to “”; and spaces to “-”.
    1. Checks whether a type with that name already exists so as to disallow any duplicate entries in the event_types table.
    2. Checks whether the event_type_id is null because name of event_types table cannot be null.

You can learn more on Alembic migrations here:

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Integration Testing of an Ember Component in Open Event Frontend

Open Event Frontend uses ember components which are reused several times throughout the project, making these components is one thing but we should also ensure they work as expected. To ensure this we need integration tests.How to write an integration test for event-map component? Three files are generated when we generate our event-map component from the command shell. They are namely:




We are familiar with the above three files as:

  1. event-map.js helps us to provide properties to our event-map.hbs
  2. event-map.hbs is where we define the structure of our component.
  3. event-map-test.js is where we define integration test for our component. Also, which is the current topic for discussion.


In order to test the rendering of the component, we define an integration test for that component. In integration tests we don’t have to launch our whole application and navigate to the location where our component is present. This makes it ideal for testing components. Have a look at the following sample integration test file.

import { test } from 'ember-qunit';
import moduleForComponent from 'open-event-frontend/tests/helpers/component-helper';
import hbs from 'htmlbars-inline-precompile';

moduleForComponent('public/event-map', 'Integration | Component | public/event map');

let event = Object.create({ latitude: 37.7833, longitude: -122.4167, locationName: 'Sample event location address' });

test('it renders', function(assert) {
  this.set('event', event);
  this.render(hbs `{{public/event-map event=event}}`);
  assert.equal(this.$('.address p').text(), 'Sample event location address');

So let’s break down this code line by line-

In the first line we have imported test from ‘ember-qunit’ (default unit testing helper suite     for Ember) which contains all the required test functions. For example, here we are using test function to check to check the rendering of our component. We can use test function multiple times to check multiple components.

Next, we are importing moduleForComponent from ‘open-event-frontend/tests/helpers/component-helper’ helper which helps in finding the component by its name.

Next,  we are importing hbs from ‘htmlbars-inline-precompile’ which basically imports precompile HTMLBars template strings within the tests via ES6 tagged template strings.

The moduleForComponent helper will find the component by name (event-map) and its template. The component we are testing here is a map-related. Therefore, to test this, we need to pass a dummy object consisting of latitude, longitude and locationName. The object data must render correctly in our app.

Inside our test function, this.set(‘event’, event) assigns a variable ( here event ) to our test context.

this.render (hbs `{{public/event-map event=event}}`) lets us create a new instance of the component by declaring the component in template syntax, as we would in our application.

assert.equal(this.$(‘.address p’).text(), ‘Sample event location address’) is basically a check between actual and expected arguments.

For a simple component like a table or a basic UI only component, it is not necessary to pass any object to the component. Only the rendered component can be tested as well. Apart from checking the component rendering we can perform tests on it by using test functions as described above. After writing the integration tests for components, simply run ember test –server on the terminal to see if all the tests have passed or not.      

Find out more about Integration testing in ember –

Ember guides, EmberIgniter

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