RoboGuice: (Android findViewById() vs @Inject View)

Roboguice is a dependency injection framework for Android applications, that brings the simplicity and ease of Dependency Injection to Android, using Google’s own Guice library. It smoothes out some of the wrinkles in your Android app development experience make things simple and fun. Do you always forget to check for null when you getIntent().getExtras()? RoboGuice 2 will help you. Think casting findViewById() to a TextView shouldn’t be necessary? RoboGuice is on it.

Using RoboGuice, you can inject your View, Resource, System Service, or any other object. RoboGuice can help you to slim down application code. Less code means less chances of issues/bugs and can help you to save efforts required to write or modify particular code in a project. It helps you to generate readable code which could be easier to follow.

Let’s look at different usage of RoboGuice library.

Usage of RoboGuice library:

• Views Injection:: To initialize views, use @InjectViews, for example: @InjectView(R.id.textView1) TextView textView1;
• Resources Injection: To initialize and get resources, use @InjectResources, for example: @InjectResource(R.string.app_name) String name;
• System services Injection: To initialize and access system services, use @Inject, for example: @Inject LayoutInflater inflater;
• POJO object Injection: To inject and initialize POJO object, use @Inject, for example: @Inject Foo foo;

Installation

To use RoboGuice, you need to download following JAR files :

http://repo1.maven.org/maven2/org/roboguice/roboguice/2.0/roboguice-2.0.jar
http://repo1.maven.org/maven2/com/google/inject/guice/3.0/guice-3.0-no_aop.jar
http://repo1.maven.org/maven2/com/google/code/findbugs/jsr305/1.3.9/jsr305-1.3.9.jar
http://www.java2s.com/Code/Jar/j/Downloadjavaxinject1jar.htm

Let’s look at an example of general activity code:

public class TestActivity extends Activity{

    TextView textView1;

    TextView textView2;

    ImageView imageView1;

    String name;

    Drawable icLauncher;

    LocationManager locManager;

    LayoutInflater inflater;

    NotificationManager notifyManager;

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        // TODO Auto-generated method stub

        super.onCreate(savedInstanceState);

        setContentView(R.layout.layout_test);

        textView1 = (TextView) findViewById(R.id.textView1);

        textView2 = (TextView) findViewById(R.id.textView2);

        imageView1 = (ImageView) findViewById(R.id.imageView1);

        name = getString(R.string.app_name);

        icLauncher = getResources().getDrawable(R.id.ic_launcher);

        locManager = (LocationManager) getSystemService(Activity.LOCATION_SERVICE);

        inflater = (LayoutInflater) getSystemService(Activity.LAYOUT_INFLATER_SERVICE);

        notifyManager = (NotificationManager)        getSystemService(Activity.NOTIFICATION_SERVICE);

        textView1.setText("Hello World! RoboGuice demo");

    }

}

Let’s check the magic of RoboGuice and let’s slim down the code.

Using RoboGuice

To use RoboGuice for the dependency injection, you are required to extends eitherRoboActivity or RoboFragment.

public class TestActivity extends RoboActivity{

    @InjectView(R.id.textView1) TextView textView1;

    @InjectView(R.id.textView2) TextView textView2;

    @InjectView(R.id.imageView1) ImageView imageView1;

    @InjectResource(R.string.app_name) String name;

    @InjectResource(R.drawable.ic_launcher) Drawable icLauncher;

    @Inject LocationManager locManager;

    @Inject LayoutInflater inflater;

    @Inject NotificationManager notifyManager;

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        // TODO Auto-generated method stub

        super.onCreate(savedInstanceState);

        setContentView(R.layout.layout_test);

        textView1.setText(name);

    }

}

Benefits of using RoboGuice

• No need to initialize views, if you want then Inject it using @InjectViews
• No need to initialize System service. If you need then Inject it using @Inject
• No need to initialize Drawable, string and other resources. If you require then Inject it using @InjectResource
• All of these above practices helps you to slim down the code.
• Less code => Less chances of bugs/issues
• Less code => Android developer can save coding efforts and can focus fully on actual business logic of android app

RoboGuice and ActionBarSherlock

As I have mentioned earlier in alert box that you are required to extend either RoboActivity or RoboFragment to use RoboGuice in either Activity or Fragment particularly. But what if you have included ActionBarSherlock in your project to manage compatibility? The problem is you have extended either SherlockActivity or SherlockFragmentActivity for your activity or fragment particularly and now the situation is we could not use RoboGuice with ActionBarSherlock.

But There is one solution for it too, you have to define custom base classes for Activities and Fragments to use RoboGuice and ActionBarSherlock both.

You can download base classes from here: https://github.com/rtyley/roboguice-sherlock or download a JAR file for the same: RoboGuice+Sherlock.jar, include either of them in your project.

You can download a sample code here.

Reference:

http://www.technotalkative.com/lazy-productive-android-developer-1/