Creating an Installer for PSLab Desktop App

PSLab device is made useful with applications running on two platforms. One is Android and the other one is a desktop application developed using Python frameworks. Desktop application uses half a dozen of dependent libraries and they are required to be installed prior to installing the application itself.

For someone with zero or less knowledge on how to install packages in a Linux environment, this task will be quite difficult. To ease up the process of installing the desktop application in a computer, we can use a script to run specific commands which will install the dependencies and the application.

Dependencies required by PSLab  Desktop app

  • PyQt 4.7
  • Python 2.6, 2.7 or 3.x
  • NumPy, Scipy
  • pyqt4-dev-tools
  • Pyqtgraph
  • pyopengl and qt-opengl
  • iPython-qtconsole

These dependencies can be made installed using a bash script running with root permission. A bash script will have the file extension “.sh” and a header line;

#!/bin/bash

A bash script needs to be made executable by the user himself. To do this, user needs to type a one line command in the terminal as follows and enter his password;

sudo chmod +x <Name_of_the_script>.sh

The keyword “sudo” interprets as “Super User DO” and the line follows will be executed with root permission. In other words with administrative privileges to modify system settings such as copying content to system folders.

The keyword “chmod” stands for “Change Mode” which will alter the mode of a file. In current context, the file is made executable by adding the executable property to the bash script using “+x” syntax.

Once the script is made executable, it can be executed using;

sudo ./<Name_of_the_script>.sh

An installer can be made attractive by using different colors rather than the plain old text outputs. For this purpose we can use color syntax in bash script. They are represented using ANSI escape codes and following is a list of commonly used colors;

Black        0;30     Dark Gray     1;30
Red          0;31     Light Red     1;31
Green        0;32     Light Green   1;32
Brown/Orange 0;33     Yellow        1;33
Blue         0;34     Light Blue    1;34
Purple       0;35     Light Purple  1;35
Cyan         0;36     Light Cyan    1;36
Light Gray   0;37     White         1;37

As in any programming language, rather than using the same line in many places, we can define variables in a bash script. The syntax will be the variable name followed by an equal sign with the value. There cannot be spaces around the equal sign or it will generate an error.

GREEN='\033[0;32m'

These variables can be accessed using a special syntax as follows;

${GREEN}

Finally we can output a message to the console using the “echo” command

echo -e "${GREEN}Welcome to PSLab Desktop app installer${NOCOLOR}"

Note that the keyword “-e” is used to enable interpretation of the following backslash escapes.

In order to install the packages and libraries, we use two package management tools. One is “apt” which stands for “Advanced Packaging Tool” and the second is “pip” which is used to download python related packages from “Python Package Index”. The following two lines illustrates how the two commands can be accessed.

apt-get install python-pip python-dev build-essential -y

pip install pyqtgraph

The keyword “-y” avoids the confirmation prompt in console to allow installation by pressing “Y” key every time it installs a package from “apt”.

Resources:

Restoring State after Orientation Change in Loklak Wok Android

During orientation change i.e. from portrait to landscape mode in Android, the current activity restarts again. As the activity restarts again, all the defined variables loose their previous value, for example the scroll position of a RecyclerView, or the data in the rows of RecyclerView etc. Just imagine a user searched some tweets in Loklak Wok Android, and as the user’s phone is in “Auto rotation” mode, the orientation changes from portrait to landscape. As a result of this, the user loses the search result and has to do the search again. This leads to a bad UX.

Saving state in onSavedInstanceState

The state of the app can be saved by inserting values in a Bundle object in onSavedInstanceState callback. Inserting values is same as adding elements to a Map in Java. Methods like putDouble, putFloat, putChar etc. are used where the first parameter is a key and the second parameter is the value we want to insert.

@Override
public void onSaveInstanceState(Bundle outState) {
   if (mLatitude != null && mLongitude != null) {
       outState.putDouble(PARCELABLE_LATITUDE, mLatitude);
       outState.putDouble(PARCELABLE_LONGITUDE, mLongitude);
   }
...
}

 

The values can be retrieved back when onCreate or onCreateView of the Activity or Fragment is called. Bundle object in the callback parameter is checked, whether it is null or not, if not the values are retrieved back using the keys provided at the time of inserting. The latitude and longitude of a location in TweetPostingFragment are retrieved in the same fashion

public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
   ...
   if (savedInstanceState != null) { // checking if bundle is null
       // extracting from bundle
       mLatitude = savedInstanceState.getDouble(PARCELABLE_LATITUDE);
       mLongitude = savedInstanceState.getDouble(PARCELABLE_LONGITUDE);
       // use extracted value
   }
}

Restoring Custom Objects, using Parcelable

But what if we want to restore custom object(s). A simple option can be serializing the objects using the native Java Serialization or libraries like Gson. The problem in these cases is performance, they are quite slow. Parcelable can be used, which leads the pack in performance and moreover it is provided by Android SDK, on top of that, it is simple to use.

The objects of class which needs to be restored implements Parcelable interface and the class must provide a static final object called CREATOR which implements Parcelable.Creator interface.

writeToParcel and describeContents method need to be override to implement Parcelable interface. In writeToParcel method the member variables are put inside the parcel, in our case describeContents method is not used, so, simply 0 is returned. Status class which stores the data of a searched tweet implements parcelable.

@Override
public int describeContents() {
   return 0;
}

@Override
public void writeToParcel(Parcel dest, int flags) {
   dest.writeString(mText);
   dest.writeInt(mRetweetCount);
   dest.writeInt(mFavouritesCount);
   dest.writeStringList(mImages);
   dest.writeParcelable(mUser, flags);
}

 

NOTE: The order in which variables are pushed into Parcel needs to be maintained while variables are extracted from the parcel to recreate the object. This is the reason why no “key” is required to push data into a parcel as we do in bundle.

The CREATOR object implements the creation of object from a Parcel. The CREATOR object overrides two methods createFromParcel and newArray. createFromParcel is the method in which we implement the way an object is created from a parcel.

public static final Parcelable.Creator<Status> CREATOR = new Creator<Status>() {
   @Override
   public Status createFromParcel(Parcel source) {
       return new Status(source); // a private constructor to create object from parcel
   }

   @Override
   public Status[] newArray(int size) {
       return new Status[size];
   }
};

 

The private constructor, note that the order in which variables were pushed is maintained while retrieving the values.

private Status(Parcel source) {
   mText = source.readString();
   mRetweetCount = source.readInt();
   mFavouritesCount = source.readInt();
   mImages = source.createStringArrayList();
   mUser = source.readParcelable(User.class.getClassLoader());
}

 

The status objects are restored the same way, latitude and longitude were restored. putParcelableArrayList in onSaveInstaceState and getParcelableArrayList in onCreateView methods are used to push into Bundle object and retrieve from Bundle object respectively.

@Override
public void onSaveInstanceState(Bundle outState) {
   super.onSaveInstanceState(outState);
   ArrayList<Status> searchedTweets = mSearchCategoryAdapter.getStatuses();
   outState.putParcelableArrayList(PARCELABLE_SEARCHED_TWEETS, searchedTweets);
   ...
}


// retrieval of the pushed values in bundle
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                            Bundle savedInstanceState) {
   ...
   if (savedInstanceState != null) {
       ...
       List<Status> searchedTweets =
               savedInstanceState.getParcelableArrayList(PARCELABLE_SEARCHED_TWEETS);
       mSearchCategoryAdapter.setStatuses(searchedTweets);
   }
   ...
   return view;
}

Resources:

Testing Presenter of MVP in Loklak Wok Android

Imagine working on a large source code, and as a new developer you are not sure whether the available source code works properly or not, you are surrounded by questions like, Are all these methods invoked properly or the number of times they need to be invoked? Being new to source code and checking manually already written code is a pain. For cases like these unit-tests are written. Unit-tests check whether the implemented code works as expected or not. This blog post explains about implementation of unit-tests of Presenter in a Model-View-Presenter (MVP) architecture in Loklak Wok Android.

Adding Dependencies to project

In app/build.gradle file

defaultConfig {
   ...
   testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
}

dependencies {
   ...
   androidTestCompile 'org.mockito:mockito-android:2.8.47'
   androidTestCompile 'com.android.support:support-annotations:25.3.1'
   androidTestCompile 'com.android.support.test.espresso:espresso-core:2.2.2'
}

Setup for Unit-Tests

The presenter needs a realm database and an implementation of LoklakAPI interface. Along with that a mock of the View is required, so as to check whether the methods of View are called or not.

The LoklakAPI interface can be mocked easily using Mockito, but the realm database can’t be mocked. For this reason an in-memory realm database is created, which will be destroyed once all unit-test are executed. As the presenter is required for each unit-test method we instantiate the in-memory database before all the tests start i.e. by annotating a public static method with @BeforeClass, e.g. setDb method.

@BeforeClass
public static void setDb() {
   Realm.init(InstrumentationRegistry.getContext());
   RealmConfiguration testConfig = new RealmConfiguration.Builder()
           .inMemory()
           .name("test-db")
           .build();
   mDb = Realm.getInstance(testConfig);
}

 

NOTE: The in-memory database should be closed once all unit-tests are executed. So, for closing the databasse we create a public static method annotated with @AfterClass, e.g. closeDb method.

@AfterClass
public static void closeDb() {
   mDb.close();
}

 

Now, before each unit-test is executed we need to do some setup work like instantiating the presenter, a mock instance of API interface generated  by using mock static method and pushing in some sample data into the database. Our presenter uses RxJava and RxAndroid which depend on IO scheduler and MainThread scheduler to perform tasks asynchronously and these schedulers are not present in testing environment. So, we override RxJava and RxAndroid to use trampoline scheduler in place of IO and MainThread so that our test don’t encounter NullPointerException. All this is done in a public method annotated with @Before e.g. setUp.

@Before
public void setUp() throws Exception {
   // mocking view and api
   mMockView = mock(SuggestContract.View.class);
   mApi = mock(LoklakAPI.class);

   mPresenter = new SuggestPresenter(mApi, mDb);
   mPresenter.attachView(mMockView);

   queries = getFakeQueries();
   // overriding rxjava and rxandroid
   RxJavaPlugins.setIoSchedulerHandler(scheduler -> Schedulers.trampoline());
   RxAndroidPlugins.setMainThreadSchedulerHandler(scheduler -> Schedulers.trampoline());

   mDb.beginTransaction();
   mDb.copyToRealm(queries);
   mDb.commitTransaction();
}

 

Some fake suggestion queries are created which will be returned as observable when API interface is mocked. For this, simply two query objects are created and added to a List after their query parameter is set. This is implemented in getFakeQueries method.

private List<Query> getFakeQueries() {
   List<Query> queryList = new ArrayList<>();

   Query linux = new Query();
   linux.setQuery("linux");
   queryList.add(linux);

   Query india = new Query();
   india.setQuery("india");
   queryList.add(india);

   return queryList;
}

 

After that, a method is created which provides the created fake data wrapped inside an Observable as implemented in getFakeSuggestionsMethod method.

private Observable<SuggestData> getFakeSuggestions() {
   SuggestData suggestData = new SuggestData();
   suggestData.setQueries(queries);
   return Observable.just(suggestData);
}

 

Lastly, the mocking part is implemented using Mockito. This is really simple, when and thenReturn static methods of mockito are used for this. The method which would provide the fake data is invoked inside when and the fake data is passed as a parameter to thenReturn. For example, stubSuggestionsFromApi method

private void stubSuggestionsFromApi(Observable observable) {
   when(mApi.getSuggestions(anyString())).thenReturn(observable);
}

Finally, Unit-Tests

All the tests methods must be annotated with @Test.

Firstly, we test for a successful API request i.e. we get some suggestions from the Loklak Server. For this, getSuggestions method of LoklakAPI is mocked using stubSuggestionFromApi method and the observable to be returned is obtained using getFakeSuggestions method. Then, loadSuggestionFromAPI method is called, the one that we need to test. Once loadSuggestionFromAPI method is invoked, we then check whether the method of the View are invoked inside loadSuggestionFromAPI method, this is done using verify static method. The unit-test is implemented in testLoadSuggestionsFromApi method.

@Test
public void testLoadSuggestionsFromApi() {
   stubSuggestionsFromApi(getFakeSuggestions());

   mPresenter.loadSuggestionsFromAPI("", true);

   verify(mMockView).showProgressBar(true);
   verify(mMockView).onSuggestionFetchSuccessful(queries);
   verify(mMockView).showProgressBar(false);
}

 

Similarly, a failed network request for obtaining is suggestions is tested using testLoadSuggestionsFromApiFail method. Here, we pass an IOException throwable – wrapped inside an Observable – as parameter to stubSuggestionsFromApi.

@Test
public void testLoadSuggestionsFromApiFail() {
   Throwable throwable = new IOException();
   stubSuggestionsFromApi(Observable.error(throwable));

   mPresenter.loadSuggestionsFromAPI("", true);
   verify(mMockView).showProgressBar(true);
   verify(mMockView).showProgressBar(false);
   verify(mMockView).onSuggestionFetchError(throwable);
}

 

Lastly, we test if our suggestions are saved in the database by counting the number of saved suggestions and asserting that, in testSaveSuggestions method.

@Test
public void testSaveSuggestions() {
   mPresenter.saveSuggestions(queries);
   int count = mDb.where(Query.class).findAll().size();
  // queries is the List that contains the fake suggestions
   assertEquals(queries.size(), count);
}

Resources:

Handling Data Requests in Open Event Organizer Android App

Open Event Organizer is a client side application of Open Event API Server created for event organizers and entry managers. The app maintains a local database and syncs it with the server when required. I will be talking about handling data requests in the app in this blog.

The app uses ReactiveX for all the background tasks including data accessing. When a user requests any data, there are two possible ways the app can perform. The one where app fetches the data directly from the local database maintained and another where it requests data from the server. The app has to decide one of the ways. In the Organizer app, AbstractObservableBuilder class takes care of this. The relevant code is:

final class AbstractObservableBuilder<T> {

   private final IUtilModel utilModel;
   private boolean reload;
   private Observable<T> diskObservable;
   private Observable<T> networkObservable;

   ...
   ...

   @NonNull
   private Callable<Observable<T>> getReloadCallable() {
       return () -> {
           if (reload)
               return Observable.empty();
           else
               return diskObservable
                   .doOnNext(item -> Timber.d("Loaded %s From Disk on Thread %s",
                       item.getClass(), Thread.currentThread().getName()));
       };
   }

   @NonNull
   private Observable<T> getConnectionObservable() {
       if (utilModel.isConnected())
           return networkObservable
               .doOnNext(item -> Timber.d("Loaded %s From Network on Thread %s",
                   item.getClass(), Thread.currentThread().getName()));
       else
           return Observable.error(new Throwable(Constants.NO_NETWORK));
   }

   @NonNull
   private <V> ObservableTransformer<V, V> applySchedulers() {
       return observable -> observable
           .subscribeOn(Schedulers.io())
           .observeOn(AndroidSchedulers.mainThread());
   }

   @NonNull
   public Observable<T> build() {
       if (diskObservable == null || networkObservable == null)
           throw new IllegalStateException("Network or Disk observable not provided");

       return Observable
               .defer(getReloadCallable())
               .switchIfEmpty(getConnectionObservable())
               .toList()
               .flatMap(items -> diskObservable.toList())
               .flattenAsObservable(items -> items)
               .compose(applySchedulers());
   }
}

 

DiskObservable is a data request to the local database and networkObservable is a data request to the server. The build function decides which one to use and returns a correct observable accordingly. The class object takes a boolean field reload which is used to decide which observable to subscribe. If reload is true, that means the user wants data from the server, hence networkObservable is returned to subscribe. Also switchIfEmpty in the build method checks whether the data fetched using diskObservable is empty, if found empty it switches the observable to the networkObservable to subscribe.

This class object is used for every data access in the app. For example, this is a code snippet of the gettEvents method in EventRepository class.

@Override
public Observable<Event> getEvents(boolean reload) {
   Observable<Event> diskObservable = Observable.defer(() ->
       databaseRepository.getAllItems(Event.class)
   );

   Observable<Event> networkObservable = Observable.defer(() ->
       eventService.getEvents(JWTUtils.getIdentity(getAuthorization()))
           ...
           ...
           .flatMapIterable(events -> events));

   return new AbstractObservableBuilder<Event>(utilModel)
       .reload(reload)
       .withDiskObservable(diskObservable)
       .withNetworkObservable(networkObservable)
       .build();
}

 

Links:
1. Documentation of ReactiveX API
2. Github repository link of RxJava – Reactive Extension for JVM

Implement Internationalization in SUSI Android With Weblate

When you build an Android app, you must consider about users for whom you are building an app. It may be possible that you users are from the different region. To support the most users your app should show text in locale language so that user can use your app easily. Our app SUSI Android is also targeting users from different regions. Internationalization is a way that ensures our app can be adapted to various languages without requiring any change to source code. This also allows projects to collaborate with non-coders more easily and plugin translation tools like Weblate.

Benefits of using Internationalization are:

  • It reduces the time for localization i.e it will localize your app automatically.
  • It helps us to keep and maintain only single source code for different regions.

To achieve Internationalization in Android app you must follow below steps:

  • Move all the required contents of your app’s user interface into the resource file.
  • Create new directories inside res to add support for Internationalization. Each directory’s name should follow rule <resource type>-(language code). For example values-es contains string resource for es language code i.e Spanish.
  • Now add different locale content in the respective folder.

We need to create separate directories for different locale because to show locale specific content, Android check specific folder i.e res/<resource type>-(language code) like res/values-de and show content from that folder. That’s why we need to move all the required content into resource file so that each required content can be shown in the specific locale.

How Internationalization is implemented in SUSI Android

In SUSI Android there is not any locale specific image but only string. So I created only locale specific value resource folder to add locale specific strings. To create locale specific values folder I follow the above-mentioned rule i.e <resource type>-(language code).

After that, I added specific language string in the respective folder.

Instead of hard-coded strings, we used strings from string.xml file so that it will change automatically according to the region.

android:text=“@string/reset”

and

showToast(getString(R.string.wrong_password))

In absence of resource directory for any specific locale, Android use default resource directory.

Integrate Weblate in SUSI Android

Weblate is a web based translation tool. The best part of Weblate is its tight version control integration which makes it easy for translators to contribute because translator does not need to fork your repo and send pull request for each change but Weblate handle this part i.e translator translate strings of the project in Weblate site and Weblate will send pull request for those changes.

Weblate can host your free software projects for free but it depends on them. Here is the link of SUSI Android project hosted on Weblate. If your project is good then they can host your project for free. But for that, you have to apply from this link and select ask for hosting. Now fill up form as shown in below picture.

Once your project is hosted on Weblate, they will email you about it. After that, you have to integrate Weblate in your project so that Weblate can automatically push translated strings to your project and also Weblate get notify about changes in your repository. Here is the link on how to add Weblate service and Weblate user to your project.

If it is not possible to host your project on Weblate for free then you can host it by own. You can follow below steps:

  • First, we deploy Weblate on our localhost using the installation guide given on Weblate site. I install Weblate from git. I cloned latest source code using Git
git clone https://github.com/WeblateOrg/weblate.git
  • Now change directory to where you cloned weblate source code and install all the required dependencies and optional dependencies using code
pip install -r requirements.txt

and

pip install -r requirements-optional.txt
  • After doing that we copy weblate/settings_example.py to weblate/settings.py. Then we configure settings.py and use the following command to migrate the settings.
./manage.py migrate
  • Now create an admin using following command.
./manage.py createadmin
  • After that add a project from your Admin dashboard (Web translations-> Projects-> Add Project) by filling all details.
  • Once the project is added, we add the component (Web translations-> Components-> Add Component) to link our Translation files.
  • To change any translation we make changes and push it to the repository where our SSH key generated from Weblate is added. A full guide to do that is mentioned in this link.

Reference

How to use Realm in SUSI Android to Save Data

Sometimes we need to store information on the device locally so that we can use information offline and also query data faster. Initially, SQLite was only option to store information on the device. But working with SQLite is difficult sometimes and also it makes code difficult to understand. Also, SQL queries take a long time. But now we have realm a better alternative of SQLite. The Realm is a lightweight mobile database and better substitute of SQLite. The Realm has own C++ core and store data in a universal, table-based format by a C++ core. This allows Realm to allow data access from multiple languages as well as a range of queries. In this blog post, I will show you why we used Realm and how we save data in SUSI Android using Realm.

“How about performance? Well, we’re glad you asked 🙂 For all the API goodness & development productivity we give you, we’re still up to 100x faster than some SQLite ORMs and on average ~10x faster than raw SQLite and common ORMs for typical operations.” (compare: https://blog.realm.io/realm-for-android/)

Advantages of Realm over SQLite are following:

  • It is faster than SQLite as explained on the Realm blog. One of the reasons realm is faster than SQLite is, the traditional SQLite + ORM abstraction is leaky because ORM simply converts  Objects and their methods into SQL statements. Realm, on the other hand, is an object database, meaning your objects directly reflect your database.
  • It is easier to use as it uses objects for storing data. When we use SQLite we need boilerplate code to convert values to and from the database, setting up mappings between classes and tables, fields and columns, foreign keys, etc. Whereas in Realm data is directly exposed as objects and can be queried without any conversion.

Prerequisites

To include this library in your project you need

  • Android studio version 1.5.1 or higher.
  • JDK version 7.0 or higher.
  • Android API level 9 or higher.

How to use realm in Android

To use Realm in your project we must add the dependency of the library in build.gradle(project) file 

 dependencies {
       classpath “io.realm:realm-gradle-plugin:3.3.1”
   }

and build.gradle(module) file.

apply plugin: realm-android
dependencies {
compile io.realm:android-adapters:1.3.0
}

Now you have to instantiate Realm in your application class. Setting a default configuration in your Application class, will ensure that it is available in the rest of your code.

RealmConfiguration realmConfiguration = new RealmConfiguration.Builder(this)
                                                              .deleteRealmIfMigrationNeeded().build();
Realm.setDefaultConfiguration(realmConfiguration);

Now we need to create a model class. A model class is use to save data in Realm and retrieve saved data and it must extend RealmObject class. For eg.

public class Person extends RealmObject {
   private String name;
   public String getName() {
       return name;
   }
   public void setName(String name) {
       this.name = name;
   }
}

Field in the model class uses to define columns. For eg. ‘name’ is a column name. Method like setName() use to save data  and getName() use to retrieve saved data.

Now create an instance of the Realm in the activity where you want to use it. It will be used to read data from the Realm and write data to the Realm.

Realm realm = Realm.getInstance(this);

Before you start a new transaction you must call beginTransaction(). It will open database.

realm.beginTransaction();

To write data to the Realm you need to create an instance of the model class. createObject used to create an instance of RealmObject class. Our model class is RealmObject type so we use createObject() to create an instance of the model class.

Person person = realm.createObject(Person.class);

Write data to realm.

person.setName(“MSDHONI”);

And after it you must call commitTransaction(). commitTransaction() use to end transaction.

realm.commitTransaction();

Reading data from Realm is easier than writing data to it. You need to create an instance of the Realm.

Realm realm = Realm.getInstance(this);

To create query use where the method and pass the class of object you want to query. After creating query you can fetch all data using findAll() method.

realm.where(Person.class).findAll();

Reference

Functionality and Customization of the Meilix Metapackage meilix-default-settings

Meilix has is made of build file and metapackages. Build file is responsible for executing commands and successfully implementing the work of metapackages.

Metapackages in Meilix
Name of metapackages used in Meilix are: meilix-artwork, meilix-default-settings.

meilix-default-settings

meilix-default-settings have 3 major folders debian, etc and usr and a Makefile. We are only concerned with etc and usr folder here.
etc and usr folders are folders in which if changes are made that can be seen the ISO. One can assume this as two folders present in the root folder of a Linux Distro.

Its directory is like this:

meilix-artwork

meilix-artwork has 1 main folder named as usr which contain share folder in which plymouth configuration is made. One can make changes here and it will directly seen in the Linux Distro.

Its directory looks like this:

How these meta packages actually work?
To get the answer one has to jump into the debian folder of any of the metapackage. It contains a control file. This contains information of the metapackages.

Source: meilix-default-settings
Section: x11
Priority: extra
Maintainer: meilix <vanhonit@gmail.com>
Build-Depends: debhelper (>= 8.0.0)
Standards-Version: 3.9.2
Homepage: http://mbm.vn

Package: meilix-default-settings
Architecture: all
Depends: ${shlibs:Depends}, ${misc:Depends}
Description: default settings for meilix
 Various system settings tailored for meilix.

One can update the metapackage from here and tweak with its depends. One come to know about the maintainer of the metapackage which can contacted in case of any issue. We can also know for which architecture this metapackage is made and about its description.
The whole debian does the work but after making any changes in the metapackage, it needs to be rebuild which is performed by debuild.sh. This is how a metapackages in Meilix works.

References:
Linux MetapackagesMatthartley from linux.com
Creating a MetapackageAjmitch from askubuntu.com

Creating Custom Borders for Widgets and Layouts in PSLab Android

User Interface (UI) is one of the most important part of any software development. In PSLab Android App while developing the UI, custom borders are used for various widgets and layouts. This makes the UI look more appealing and widgets and layouts look more highlighted.

In Android, we can do a range of border customization. We can make border rounded, define its thickness and even change its color. Let’s see how to achieve this.

First, go to drawable folder in the tree view on the left size of the Android studio. Then go to new and click on Drawable resource file.

Then a New Resource File dialog box will appear. Type the filename and then click OK.

After this, a new XML file is created. Now we can write the code for creating custom borders. For this, we have to define few elements.

<?xml version="1.0" encoding="UTF-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android">
....
</shape>

Shape Drawables allows defining background, borders, and gradients for the Views.

<solid android:color="#FFFFFF"/>

Here we are setting the background color of the widget/layout to which the border is applied to.

<stroke android:width="3dip" android:color="#B1BCBE" />

Now we are applying the 3dip width to the border and set its color. This shape requires the <stroke> element to define the width and color of the line.

<corners android:radius="10dip"/>

In order to make the corners of the border round, <corner> element is used to define the radius of the corners. We are taking it to be 10dip.

<padding android:left="0dip" android:top="0dip" android:right="0dip" android:bottom="0dip" />

The padding is expressed in pixels for the left, top, right and bottom parts of the view. Padding is used to offset the content of the view by a specific number of pixels.

After applying this border on a layout we get the following results.

Similarly making following changes in the element values help us to make border for the Text View

<solid android:color="@android:color/white" />
<stroke android:width="1dip" android:color="#ffcdd2" />
<corners android:radius="2dp"/>

Other examples

Control Activity

Logical Analyzer Activity

Resources

  1. Stack Overflow Solution to How to make a layout with rounded corners?
  2. Youtube Video on How to create a layout with rounded corner borders in Android? by Sylvain Saurel

Implementing Direct URL in loklak Media Wall

Direct URL is a web address which redirects the user to the preset customized media wall so that the media wall can directly be used to be displayed on the screen. Loklak media wall provides direct URL which has information related to customizations set by the user included in the web address. These customizations, as the query parameters are detected when the page is initialized and actions are dispatched to make changes in the state properties, and hence, the UI properties and the expected behaviour of media wall.

In this blog, I would be explaining how I implemented direct URL in loklak media wall and how customizations are detected to build on initialization of component, a customized media wall.

Flow Chart

Working

Media Wall Direct URL effect

This effect detects when the WALL_GENERATE_DIRECT_URL action is dispatched and creates a direct URL string from all the customization state properties and dispatches a side action WallShortenDirectUrlAction() and stores direct URL string as a state property. For this, we need to get individual wall customization state properties and create an object for it and supply it as a parameter to the generateDirectUrl() function. Direct URL string is returned from the function and now, the action is dispatched to store this string as a state property.

@Effect()
generateDirectUrl$: Observable<Action>
= this.actions$
.ofType(mediaWallDirectUrlAction.ActionTypes.WALL_GENERATE_DIRECT_URL)
.withLatestFrom(this.store$)
.map(([action, state]) => {
return {
query: state.mediaWallQuery.query,
.
.
.
wallBackground: state.mediaWallCustom.wallBackground
};
})
.map(queryObject => {
const configSet = {
queryString: queryObject.query.displayString,
.
.
.
wallBackgroundColor: queryObject.wallBackground.backgroundColor
}
const shortenedUrl = generateDirectUrl(configSet);
return new mediaWallDirectUrlAction.WallShortenDirectUrlAction(shortenedUrl);
});

Generate Direct URL function

This function generates Direct URL string from all the current customization options value. Now,  keys of the object are separated out and for each element of the object, it checks if there is some current value for the elements and it then first parses the value of the element into URI format and then, adds it to the direct URL string. In such a way, we are creating a direct URL string with these customizations provided as the query parameters.

export function generateDirectUrl(customization: any): string {
const shortenedUrl = ;const activeFilterArray: string[] = new Array<string>();
let qs = ;
Object.keys(customization).forEach(config => {
if (customization[config] !== undefined && customization[config] !== null) {
if (config !== ‘blockedUser’ && config !== ‘hiddenFeedId’) {
qs += `${config}=${encodeURIComponent(customization[config])}&`;
}
else {
if (customization[config].length > 0) {
qs += `${config}= ${encodeURIComponent(customization[config].join(‘,’))}&`;
}
}
}
});
qs += `ref=share`;
return qs;
}

Creating a customized media wall

Whenever the user searches for the URL link on the web, a customized media wall must be created on initialization. The media wall component detects and subscribes to the URL query parameters using the queryParams API of the ActivatedRoute. Now, the values are parsed to a required format of payload and the respective actions are dispatched according to the value of the parameters. Now, when all the actions are dispatched, state properties changes accordingly. This creates a unidirectional flow of the state properties from the URL parameters to the template. Now, the state properties that are supplied to the template are detected and a customized media wall is created.

private queryFromURL(): void {
this.__subscriptions__.push(
this.route.queryParams
.subscribe((params: Params) => {
const config = {
queryString: params[‘queryString’] || ,
imageFilter: params[‘imageFilter’] || ,
profanityCheck: params[‘profanityCheck’] || ,
removeDuplicate: params[‘removeDuplicate’] || ,
wallHeaderBackgroundColor: params[‘wallHeaderBackgroundColor’] || ,
wallCardBackgroundColor: params[‘wallCardBackgroundColor’] || ,
wallBackgroundColor: params[‘wallBackgroundColor’] ||
}
this.setConfig(config);
})
);
}public setConfig(configSet: any) {
if (configSet[‘displayHeader’]) {
const isTrueSet = (configSet[‘displayHeader’] === ‘true’);
this.store.dispatch(new mediaWallDesignAction.WallDisplayHeaderAction(isTrueSet));
}
.
.
if (configSet[‘queryString’] || configSet[‘imageFilter’] || configSet[‘location’]) {
if (configSet[‘location’] === ‘null’) {
configSet[‘location’] = null;
}
const isTrueSet = (configSet[‘imageFilter’] === ‘true’);
const query = {
displayString: configSet[‘queryString’],
queryString: ,
routerString: configSet[‘queryString’],
filter: {
video: false,
image: isTrueSet
},
location: configSet[‘location’],
timeBound: {
since: null,
until: null
},
from: false
}
this.store.dispatch(new mediaWallAction.WallQueryChangeAction(query));
}
}

Now, the state properties are rendered accordingly and a customized media wall is created. This saves a lot of effort by the user to change the customization options whenever uses the loklak media wall.

Reference

MVP in Loklak Wok Android using Dagger2

MVP stands for Model-View-Presenter, one of the most popular and commonly used design pattern in android apps. Where “Model” refers to data source, it can be a SharedPreference, Database or data from a Network call. Going by the word, “View” is the user interface and finally “Presenter”, it’s a mediator between model and view. Whatever events occur in a view are passed to presenter and the presenter fetches the data from the model and finally passes it back to the view, where the data is populated in ViewGroups. Now, the main question, why it is so widely used? One of the obvious reason is the simplicity to implement it and it completely separates the business logic, so, easy to write unit-tests. Though it is easy to implement, its implementation requires a lot of boilerplate code, which is one of its downpoints. But, using Dagger2 the boilerplate code can be reduced to a great extent. Let’s see how Dagger2 is used in Loklak Wok Android to implement MVP architecture.

Adding Dagger2 to the project

In app/build.gradle file

dependencies {
   ...
   compile 'com.google.dagger:dagger:2.11'
    annotationProcessor 'com.google.dagger:dagger-compiler:2.11'
}

 

Implementation

First a contract is created which defines the behaviour or say the functionality of View and Presenter. Like showing a progress bar when data is being fetched, or the view when the network request is successful or it failed. The contract should be easy to read and going by the names of the method one should be able to know the functionality of methods. For tweet search suggestions, the contract is defined in SuggestContract interface.

public interface SuggestContract {

   interface View {

       void showProgressBar(boolean show);

       void onSuggestionFetchSuccessful(List<Query> queries);

       void onSuggestionFetchError(Throwable throwable);
   }

   interface Presenter {

       void attachView(View view);

       void createCompositeDisposable();

       void loadSuggestionsFromAPI(String query, boolean showProgressBar);

       void loadSuggestionsFromDatabase();

       void saveSuggestions(List<Query> queries);

       void suggestionQueryChanged(Observable<CharSequence> observable);

       void detachView();
   }
}

 

A SuggestPresenter class is created which implements the SuggestContract.Presenter interface. I will not be explaining how each methods in SuggestPresenter class is implemented as this blog solely deals with implementing MVP. If you are interested you can go through the source code of SuggestPresenter. Similarly, the view i.e. SuggestFragment implements SuggestContract.View interface.

So, till this point we have our presenter and view ready. The presenter needs to access the model and the view requires to have an instance of presenter. One way could be instantiating an instance of model inside presenter and an instance of presenter inside view. But, this way model, view and presenter would be coupled and that defeats our purpose. So, we just INJECT model into presenter and presenter into view using Dagger2. Injecting here means Dagger2 instantiates model and presenter and provides wherever they are requested.

ApplicationModule provides the required dependencies for accessing the “Model” i.e. a Loklak API client and realm database instance. When we want Dagger2 to provide a dependency we create a method annotated with @Provides as providesLoklakAPI and providesRealm.

@Provides
LoklakAPI providesLoklakAPI(Retrofit retrofit) {
   return retrofit.create(LoklakAPI.class);
}

@Provides
Realm providesRealm() {
   return Realm.getDefaultInstance();
}

 

If we look closely providesLoklakAPI method requires a Retrofit instance i.e. a to create an instance of LoklakAPI the required dependency is Retrofit, which is fulfilled by providesRetrofit method. Always remember that whenever a dependency is required, it should not be instantiated at the required place, rather it should be injected by Dagger2.

@Provides
Retrofit providesRetrofit() {
   Gson gson = Utility.getGsonForPrivateVariableClass();
   return new Retrofit.Builder()
           .baseUrl(mBaseUrl)
           .addCallAdapterFactory(RxJava2CallAdapterFactory.create())
           .addConverterFactory(GsonConverterFactory.create(gson))
           .build();
}

 

As the ApplicationModule class provides these dependencies the class is annotated with @Module.

@Module
public class ApplicationModule {

   private String mBaseUrl;

   public ApplicationModule(String baseUrl) {
       this.mBaseUrl = baseUrl;
   }
   
   
   // retrofit, LoklakAPI, realm @Provides methods
}


After preparing the source to provide the dependencies, it’s time we request the dependencies.

Dependencies are requested simply by using @Inject annotation e.g. in the constructor of SuggestPresenter @Inject is used, due to which Dagger2 provides instance of LoklakAPI and Realm for constructing an object of SuggestPresenter.

public class SuggestPresenter implements SuggestContract.Presenter {

   private final Realm mRealm;
   private LoklakAPI mLoklakAPI;
   private SuggestContract.View mView;
   ...

   @Inject
   public SuggestPresenter(LoklakAPI loklakAPI, Realm realm) {
       this.mLoklakAPI = loklakAPI;
       this.mRealm = realm;
       ...
   }
   
   // implementation of methods defined in contract
}


@Inject can be used on the fields also. When @Inject is used with a constructor the class also becomes a dependency provider, this way creating a method with @Provides is not required in a Module class.

Now, it’s time to connect the dependency providers and dependency requesters. This is done by creating a Component interface, here ApplicationComponent. The component interface defines where are the dependencies required. This is only for those cases where dependencies are injected by using @Inject for the member variables. So, we define a method inject with a single parameter of type SuggestFragment, as the Presenter needs to be injected in SuggestFragment.

@Component(modules = ApplicationModule.class)
public interface ApplicationComponent {


   void inject(SuggestFragment suggestFragment);

}

 

The component interface is instantiated in onCreate method of LoklakWokApplication class, so that it is accessible all over the project.

public class LoklakWokApplication extends Application {

   private ApplicationComponent mApplicationComponent;

   @Override
   public void onCreate() {
       super.onCreate();
      ...
       mApplicationComponent = DaggerApplicationComponent.builder()
               .applicationModule(new ApplicationModule(Constants.BASE_URL_LOKLAK))
               .build();
   }

   public ApplicationComponent getApplicationComponent() {
       return mApplicationComponent;
   }
   
   ...
}


NOTE: DaggerApplicationComponent is created after building the project. So, AndroidStudio will show “Cannot resolve symbol …”, thus build the project : Build > Make Module ‘app’.

Finally, in the onCreateView callback of SuggestFragment we call inject method of DaggerApplicationComponent to tell Dagger2 that SuggestFragment is requesting dependencies.

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                        Bundle savedInstanceState) {
...   
   LoklakWokApplication application = (LoklakWokApplication) getActivity().getApplication();
   application.getApplicationComponent().inject(this);
   suggestPresenter.attachView(this);

   return rootView;
}

Resources: