java - Android:移动bmp留下痕迹(Surface View和Canvas)

我试图为Android应用程序制作精灵动画，但遇到了一个小问题。我正在一个surfaceview上绘图，我在现有布局的基础上添加了这个视图。在这个surfaceview上，我想设置一些精灵的动画，以便它们沿着一条路径行走。
所以这就是我现在面临的结果：
行走的精灵正在留下一条小径。所以我决定用谷歌搜索这个问题，显然我必须先清除画布，然后再在上面绘图。
这是我以前的方法：

public void onDraw(Canvas canvas) {
    update();
    int srcX = currentFrame * width;
    int srcY = directionX * height;
    Rect src = new Rect(srcX, srcY, srcX + width, srcY + height);
    Rect dst = new Rect(x, y, x + width, y + height);
    canvas.drawBitmap(bmp, src, dst, null);

}

这是我后来用的方法

public void onDraw(Canvas canvas) {
    canvas.drawRGB(0, 0, 0);
    update();
    int srcX = currentFrame * width;
    int srcY = directionX * height;
    Rect src = new Rect(srcX, srcY, srcX + width, srcY + height);
    Rect dst = new Rect(x, y, x + width, y + height);
    canvas.drawBitmap(bmp, src, dst, null);

}

所以我现在有了这个结果

这很好，因为它没有留下更多的线索，但我看不到下面的布局。不管怎样，我能得到最好的两个世界吗？我原以为清理画布会有用，但显然效果不如预期。
我会把我的代码贴在下面
表面视图：

public class MonsterView extends SurfaceView {

private Bitmap monsterImg;
private SurfaceHolder holder;
private MonsterThread mainThread;
private Sprite monsterSprite;
private int x;
private int xSpeed = 1;

public MonsterView(Context context) {
    super(context);
    this.mainThread = new MonsterThread(this);
    this.x = 0;


    holder = getHolder();
    holder.setFormat(PixelFormat.TRANSPARENT);

    holder.addCallback(new SurfaceHolder.Callback() {

        @Override
        public void surfaceCreated(SurfaceHolder holder) {
            mainThread.setRunning(true);
            mainThread.start();
        }

        @Override
        public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {

        }

        @Override
        public void surfaceDestroyed(SurfaceHolder holder) {
            boolean retry = true;
            mainThread.setRunning(false);
            while (retry) {
                try {
                    mainThread.join();
                    retry = false;
                } catch (InterruptedException e) {
                }
            }

        }
    });
    setZOrderOnTop(true);
    monsterImg = BitmapFactory.decodeResource(getResources(), R.drawable.fire);
    monsterSprite = new Sprite(this,monsterImg);
}

@Override
public void onDraw(Canvas canvas) {
    if (x == getWidth() - monsterImg.getWidth()) {
        xSpeed = -1;
    }
    if (x == 0) {
        xSpeed = 1;
    }
    x = x + xSpeed;
    monsterSprite.onDraw(canvas);
}

线程：

public class MonsterThread extends Thread {
private MonsterView monsterSurface;
private boolean running;
static final long FPS = 35;

public MonsterThread(MonsterView monsterSurface){
    this.monsterSurface = monsterSurface;
    this.running = false;
}

@Override
public void run() {
    long ticksPS = 1000 / FPS;
    long startTime;
    long sleepTime;

    while(running){
        Canvas c = null;
        startTime = System.currentTimeMillis();
        try{
            c = monsterSurface.getHolder().lockCanvas();
            synchronized (monsterSurface.getHolder()){

                monsterSurface.onDraw(c);
            }
        } finally {
            if( c!= null){
                monsterSurface.getHolder().unlockCanvasAndPost(c);

            }
        }
        sleepTime = ticksPS-(System.currentTimeMillis() - startTime);
        try {
            if(sleepTime > 0)
                sleep(sleepTime);
            else
                sleep(10);
        } catch (Exception e){}
    }
}

public MonsterView getMonsterSurface() {
    return monsterSurface;
}

public void setMonsterSurface(MonsterView monsterSurface) {
    this.monsterSurface = monsterSurface;
}

public boolean isRunning() {
    return running;
}

public void setRunning(boolean running) {
    this.running = running;
}

雪碧：

public class Sprite {
private static final int BMP_ROWS = 4;
private static final int BMP_COLUMNS = 3;
private int x = 0;
private int y = 0;
private int xSpeed = 5;
private MonsterView monsterView;
private Bitmap bmp;
private int currentFrame = 0;
private int width;
private int height;

private int directionX;

public Sprite(MonsterView monsterView, Bitmap bmp) {
    this.monsterView = monsterView;
    this.bmp=bmp;
    this.width = bmp.getWidth() / BMP_COLUMNS;
    this.height = bmp.getHeight() / BMP_ROWS;
    this.directionX = 2;
}

private void update() {
    if (x > monsterView.getWidth() - width - xSpeed) {
        xSpeed = -5;
        directionX = 1;
    }
    if (x + xSpeed < 0) {
        xSpeed = 5;
        directionX = 2;
    }
    x = x + xSpeed;
    currentFrame = ++currentFrame % BMP_COLUMNS;
    Log.d("test", ""+currentFrame);
}

public void onDraw(Canvas canvas) {
    update();
    int srcX = currentFrame * width;
    int srcY = directionX * height;
    Rect src = new Rect(srcX, srcY, srcX + width, srcY + height);
    Rect dst = new Rect(x, y, x + width, y + height);
    canvas.drawBitmap(bmp, src, dst, null);

}

最佳答案

有很多方法可以处理这个问题，但是一般来说，方法是通过维护一个背景层（这只是另一个图像）和精灵层。不是清除，而是在每一帧你闪动（复制）你的背景到表面（这会抹去一切），然后你闪动你的精灵。