Question

i’m trying to create a Bitmap

 BitmapDrawable img = new BitmapDrawable(getResources(), "res/drawable/wrench.png");
 Bitmap wrench = img.getBitmap();
 //Bitmap wrench = BitmapFactory.decodeResource(getResources(), R.drawable.wrench);
 canvas.drawColor(Color .BLACK);
 Log.d("OLOLOLO",Integer.toString(wrench.getHeight()));
 canvas.drawBitmap(wrench, left, top, null);

but when i call wrench.getHeight() program failed with NullPoinerException. (i put the file in drawable directory)
how can i solve my problem?

Answer 1

Ok… I think I have a handle on your problem now. Like I said, you can’t access your drawables via a path, so if you want a human readable interface with your drawables that you can build programatically, declare a HashMap somewhere in your class:

private static HashMap<String, Integer> images = null;

Then initialize it in your constructor:

public myClass() {
  if (images == null) {
    images = new HashMap<String, Integer>();
    images.put("Human1Arm", R.drawable.human_one_arm);
    // for all your images - don't worry, this is really fast and will only happen once
  }
}

Now for access –

String drawable = "wrench";
// fill in this value however you want, but in the end you want Human1Arm etc
// access is fast and easy:
Bitmap wrench = BitmapFactory.decodeResource(getResources(), images.get(drawable));
canvas.drawColor(Color .BLACK);
Log.d("OLOLOLO",Integer.toString(wrench.getHeight()));
canvas.drawBitmap(wrench, left, top, null);