通过编辑BitmapFactory.decodeResource方法来提高性能

Question

有3个主要功能

drawImage：

private void drawImage(Canvas canvas) { 
        Bitmap image =
                BitmapFactory.decodeResource(getResources(),
                        getResourceID("img_" + mIndex, "drawable", getApplicationContext()));
        //Draw the image on screen 
         canvas.drawBitmap(image1, mPos.x, mPos.y, null);
    }

drawFrame0：

    private void drawFrame0() {
        final SurfaceHolder SurfaceHolder = getSurfaceHolder();
        SharedPreferences prefs = PreferenceManager
                .getDefaultSharedPreferences(getBaseContext());
        Canvas canvas = null;
        try {
            canvas = SurfaceHolder.lockCanvas();

            if (canvas != null) {
               drawImage(canvas);/****draw layer 0*/
            }
        } finally {
            if (canvas != null) {
                SurfaceHolder.unlockCanvasAndPost(canvas);
            }
        }
    }

LiveWThread：

 private class LiveWThread extends Thread {
        private  boolean continueRunning;

        Engine engine;

        public MoveBallsThread(Engine e) {
            continueRunning = true ;
            engine = e;
        }
        public void stopRunning() {           
            continueRunning = false ;
        }

        public void run() {

            SharedPreferences prefs = PreferenceManager
                    .getDefaultSharedPreferences(getBaseContext());
            try {
                while (continueRunning) {

                    drawFrame0();
                    //incrementCounter22();
                    mIndex++;
                    ...}
                      }

我的问题：无论如何我可以使用BitmapFactory.decodeResource只在应用程序启动时存储我的所有drawables而不使用Thread来循环它，因为每次Thread加载时，图像都必须再次解码，这显然减慢了我的动态壁纸上的图像流量.. 我将以jpg和png格式提供~100个drawables

非常感谢提前。