Android 2.1 View's getDrawingCache() method always returns null

Question

I'm working with Android 2.1 and have the following problem: Using the method View.getDrawingCache() always returns null. getDrawingCache() should return a Bitmap, which is the presentation of View's content.

Example code:

public void onCreate(final Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);

  setContentView(R.layout.main);

  final View view = findViewById(R.id.ImageView01);
  view.setDrawingCacheEnabled(true);
  view.buildDrawingCache();
  final Bitmap bmp = view.getDrawingCache();
  System.out.println(bmp);

}

I've already tried different ways to configure the View object for generating the drawing cache (e.g. View.setWillNotDraw(boolean) and View.setWillNotCacheDrawing(boolean)), but nothing works.

What is the right way, or what I'm doing wrong?

PS: In real code I want to apply getDrawingCache() on a ViewGroup like RelativeLayout. Is the behaviour the same when using a ViewGroup?

Answer 1

Bitmap screenshot;
view.setDrawingCacheEnabled(true);
screenshot = Bitmap.createBitmap(view.getDrawingCache());
view.setDrawingCacheEnabled(false);

You need Bitmap.createBitmap(view.getDrawingCache()); as the Bitmap from which the reference is received by getDrawingCache() gets recycled.

Answer 2

use

onLayout(x, y, width, height);

for ex:

onLayout(0, 0, 100, 100);

before calling getDrawingCache

Answer 3

Never do these things in onCreate! You can do it in a View.onClickListener or other place.