Today, I'm talking about integrating Google's "+1" button to the Android application. This allows users to share your application in "Google+".

Firstly, you need to add a dependency to the gradle file.

dependencies {
    compile "com.google.android.gms:play-services:7.3.0"
}

Afterward, we need to add a "+1" button to your layout. A size of the PlusOneButton button may be standard, tall, small or medium. We need to change the size attribute for changing the size of the button.

Size of the "+1" button
<com.google.android.gms.plus.PlusOneButton
        xmlns:plus="http://schemas.android.com/apk/lib/com.google.android.gms.plus"
        android:id="@+id/plus_one_button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        plus:size="standard"
        plus:annotation="none" />

The next step is updating an activity.

public class MainActivity extends AppCompatActivity {
    private static final int PLUS_ONE_REQUEST_CODE = 0;
    private static final String APP_URL = "https://play.google.com/store/apps/details?id=app_package";
    private PlusOneButton mPlusOneButton;
    private GoogleApiClient mGoogleApiClient;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_plus_one);
        mPlusOneButton = (PlusOneButton) findViewById(R.id.plus_one_button);
        mGoogleApiClient = new GoogleApiClient.Builder(this)
                .addApi(Plus.API)
                .addScope(Plus.SCOPE_PLUS_LOGIN)
                .useDefaultAccount()
                .build();
    }

    @Override
    protected void onResume() {
        super.onResume();
        mPlusOneButton.initialize(APP_URL, PLUS_ONE_REQUEST_CODE);
    }

    @Override
    protected void onStart() {
        super.onStart();
        mGoogleApiClient.connect();
    }
    
    @Override
    protected void onStop() {
        super.onStop();
        mGoogleApiClient.disconnect();
    }
}

The last step is to change the app_package to your application package.

+1 button application demo