I have a UI where the root layout is a RelativeLayout. It has a number of Views, such as fields, buttons, etc.
There are also two other panels that are initially invisible. When the user clicks a button, one of these panels slides in from the left, another slides in from the bottom. The problem is the frame rate is pathetic on a Nexus S.
I want to use setDrawingCacheEnabled(true) in order to (I hope) speed up the animation of these two panels. As a simplified example, here is roughly how I slide in one of these panels. I'll call it "detailPanel".
public class MyActivity extends Activity { // Initially invisible. private View detailPanel; // A simple slide animation. private Animation detailEnterAnimation; ... public void someButtonClicked(View view) { detailPanel.startAnimation(detailEnterAnimation); detailPanel.setVisibility(View.VISIBLE); detailPanel.setDrawingCacheEnabled(true); } }
Now in the DetailPanel I try to use the cache. I was hoping that bitmap rendering via the cache would improve performance:
public class DetailPanel extends LinearLayout { public void draw(Canvas canvas) { Bitmap cache = getDrawingCache(); if (cache != null) { canvas.drawBitmap(cache, 0, 0, null); } else { super.draw(canvas); } } }
The Bitmap is non-null and is the right size, but it is completely black.
Why is my bitmap black? That code may be obscenely wrong; I've tried a million different things and just cannot figure it out.
Android View setDrawingCacheEnabled(boolean enabled) Enables or disables the drawing cache.
getDrawingCache() has been deprecated.
Basically, it creates a bitmap from the ListView item and drag it.
From Android documentation (http://developer.android.com/reference/android/view/View.html#setDrawingCacheEnabled%28boolean%29):
Enabling the drawing cache is similar to setting a layer when hardware acceleration is turned off. When hardware acceleration is turned on, enabling the drawing cache has no effect on rendering because the system uses a different mechanism for acceleration which ignores the flag. If you want to use a Bitmap for the view, even when hardware acceleration is enabled, see setLayerType(int, android.graphics.Paint) for information on how to enable software and hardware layers.
Maybe this is your case?
You may want to build your drawing cache before using it, otherwise It will give you a blank bitmap
public void someButtonClicked(View view) { detailPanel.startAnimation(detailEnterAnimation); detailPanel.setVisibility(View.VISIBLE); detailPanel.setDrawingCacheEnabled(true); detailPanel.buildDrawingCache(); //may be you need to add this? }
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