Android way to use Bitmaps from Camera.setPreviewCallback
<pre><code>camera.setPreviewCallback(new Camera.PreviewCallback() {
    private long timestamp=0;
    public synchronized void onPreviewFrame(byte[] data, Camera camera) {
        Log.e("CameraTest","Time Gap = "+(System.currentTimeMillis()-timestamp));
        timestamp=System.currentTimeMillis();

        Bitmap mFaceBitmap = BitmapFactory.decodeByteArray(data, 0, data.length);
        if (mFaceBitmap!=null) FaceDetection.calculate(mFaceBitmap);

        camera.addCallbackBuffer(data);
        return;
    }
});
</code></pre>

<p>I have a camera View, and in front of a simple View (where I can draw something). 
I'd like to draw on the front of View, when I can find the face of a human. 
But <code>mFaceBitmap</code> is ever and ever return null, why? </p>

<p>If this is a bad idea, how can I do this better?</p>
