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POHow does Android's setDrawingCacheEnabled() work?
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copied!<p>I have a UI where the root layout is a RelativeLayout. It has a number of Views, such as fields, buttons, etc.</p> <p>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.</p> <p>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".</p> <pre><code>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); } } </code></pre> <p>Now in the DetailPanel I try to use the cache. I was hoping that bitmap rendering via the cache would improve performance:</p> <pre><code>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); } } } </code></pre> <p>The Bitmap is non-null and is the right size, but it is completely black.</p> <p>Why is my bitmap black? That code may be obscenely wrong; I've tried a million different things and just cannot figure it out.</p>

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