Question

I’m currently trying to write an app for one special device running Android 2.3.4, that places a system overlay on a precisely defined spot on the screen. This is why I am positioning the layer using absolute values.

I wrote an activity (including two buttons in the layout) that starts and stops a service displaying this overlay.

public class MyActivity extends Activity {

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
}

public void showOverlay(View view) {
    Intent i = new Intent("myPackage.myService");
    startService(i);
}

public void hideOverlay(View view) {
    Intent i = new Intent("myPackage.myService");
    stopService(i);
}
}

And this is my service (which was also added to the manifest file).

public class MyService extends Service {    
ImageView iv;

@Override
    public IBinder onBind(Intent intent) {
    return null;
}

@Override
public void onCreate() {
    super.onCreate();

    int imageRes    =   0;

    final WindowManager.LayoutParams params = new WindowManager.LayoutParams(
            WindowManager.LayoutParams.TYPE_SYSTEM_OVERLAY,
            WindowManager.LayoutParams.FLAG_WATCH_OUTSIDE_TOUCH | WindowManager.LayoutParams.FLAG_LAYOUT_IN_SCREEN,
            PixelFormat.TRANSLUCENT);

    params.gravity  =   Gravity.NO_GRAVITY;
    params.alpha    =   1; 

    switch (findRotation()) {
    case Surface.ROTATION_0:
        params.height = 12; params.width = 600; params.x = 0; params.y = 1012;
        imageRes = R.drawable.horizontal; 
        break;
    case Surface.ROTATION_180: 
        params.height = 12; params.width = 600; params.x = 0; params.y = 0;
        imageRes = R.drawable.horizontal; 
        break;
    case Surface.ROTATION_90: 
        params.height = 600; params.width = 12; params.x = 1012; params.y = 0;
        imageRes = R.drawable.vertical; 
        break;
    case Surface.ROTATION_270: 
        params.height = 600; params.width = 12; params.x = 0; params.y = 0;
        imageRes = R.drawable.vertical; 
        break;
    }

    final WindowManager wm = (WindowManager) getSystemService(WINDOW_SERVICE);        

    iv = new ImageView(getApplicationContext());
    iv.setClickable(false);
    iv.setImageResource(imageRes);
    iv.draw(new android.graphics.Canvas());
    wm.addView(iv, params);
}


private int findRotation() {
     Display display = ((WindowManager) getSystemService(WINDOW_SERVICE)).getDefaultDisplay();
     return display.getRotation();
}


@Override
public void onConfigurationChanged(Configuration newConfig) {
    super.onConfigurationChanged(newConfig);
    onDestroy();    //I don't know how to to make the service reposition the layer, so I used this. Not nice but it works 
    onCreate();   
}


@Override
public void onDestroy() {
    super.onDestroy();
    if(iv != null) {
        ((WindowManager) getSystemService(WINDOW_SERVICE)).removeView(iv);
        iv = null;
    }
}
}

The image to display as overlay has the width (or heigth, I didn’t find a method to rotate drawabled at API level 10, so I used two images, one for horizontal display, one for vertical) of my device’s screen resolution in portrait mode (=600) and a heigth (or width) of 12 pixels. I want it to be positioned where the hardware buttons are, i.e. in portrait mode on the bottom, when turned 90° counter-clockwise on the right, when turned 180° on the top and so on.

This works well for a rotation of 0° and 90° (ccw), but for the other two orientations the image is displayed in the middle of the screen instead of at the top or on the left. What am I doing wrong?

EDIT 2012-04-19:
I have changed the value of params.y for ROTATION_180 to -1012, and this case works now. I don’t think this is expected behaviour, though. A similar change for ROTATION_270 did not work…

Answer 1

OK, I’m sorry, I made a mistake when changing the parameters for ROTATION_270, when I wrote my edit.

I got the code to do what I wanted, here’s what I did:

I changed the y-param for 180° to -1012 and the x-param for 270° to -1012, too. Now, in all four orientations the image is displayed where the hardware buttons are.

I write it down here just for the sake of completeness.

(…)

switch (findRotation()) {
    case Surface.ROTATION_0:
        params.height = 12; params.width = 600; params.x = 0; params.y = 1012;
        imageRes = R.drawable.horizontal; 
        break;
    case Surface.ROTATION_180: 
        params.height = 12; params.width = 600; params.x = 0; params.y = -1012;
        imageRes = R.drawable.horizontal; 
        break;
    case Surface.ROTATION_90: 
        params.height = 600; params.width = 12; params.x = 1012; params.y = 0;
        imageRes = R.drawable.vertical; 
        break;
    case Surface.ROTATION_270: 
        params.height = 600; params.width = 12; params.x = -1012; params.y = 0;
        imageRes = R.drawable.vertical; 
        break;
}

(…)