Question

Here’s what I’m trying to do: I’m trying to load a sequence of bitmaps to display an animation. That means that I need to have a descent fps (24 fps). I need to load no more than 10 seconds of animations or about 300 bitmaps. And since it’s a live wallpaper I’m limited to manually drawing each frame.

Here’s what I tried so far:

1. The obvious strategy: load each bitmap each frame and draw it. This is slow.
2. Use caching. I put the bitmap loading in a seperate thread. A cache of about 20 bitmaps continously load in the background. However, I still get poor performance (about 10 fps). The culprit is slow bitmap loading.
3. I was going to try using OpenGL but then I realized that even with OpenGL, the slow bitmap loading will still be a problem. Right? (Or am I wrong?)

So what other strategies can I use?

Here’s what I had in mind: if I use openGL, I can use smaller bitmaps (because it gives better scaling). Perhaps then I can have a bigger cache – say perhaps 3 seconds. With a larger cache, the slow bitmap loading will not be a problem, right?

Any other strategies?

---

Oh and this is my current bitmap loading function:

void loadNthBitmap(int i, int n) {
    try {
    buf = new 
        BufferedInputStream(assets.
                open(folder+"/"
                     +imageList[n])
                );
    tmpBitmap = BitmapFactory.
        decodeStream(buf);
    rbitmap[i] = Bitmap.createBitmap
        (tmpBitmap,
         0,0,imageWidth,imageHeight,
         transMatrix,false);
    }
    catch(IOException e) {}
}

where imageList is pre-defined list of assets and transMatrix is a rotation and scaling matrix.

Answer 1

What you’re trying to do (i.e. full-frame animation) is not easy. Almost all Android animation (from the Lunar Lander example in the SDK to Angry Birds) consists of moving small sprites on a relatively static background.

The “obvious” solution to your problem would be to turn your animation into an mpeg and then decode it as a video live wallpaper, replicating the approach that this guy took here: http://forum.xda-developers.com/showthread.php?t=804720 (alternative link http://android.ccpcreations.com/vlw/)