Android截屏SurfaceView黑屏问题的解决办法

Z时代
2024-01-10
分类：综合

最近项目中有截屏的需求，普通的view截屏方法网上一搜一大把，但是SurfaceView截屏黑屏问题很多文章说的并不清楚，自己参考了一些别的博客，再加上自己的思考，算是找到了一种解决方案。

1、首先看我们一般是怎么用SurfaceView的


public class SuperSurfaceView extends SurfaceView implements SurfaceHolder.Callback {
 SurfaceHolder surfaceHolder;
 public SuperSurfaceView(Context context) {
  super(context);
  surfaceHolder = this.getHolder();
  surfaceHolder.addCallback(this);
 }
 @Override
 public void surfaceChanged(SurfaceHolder holder, int format, int width,
        int height) {
 }
 @Override
 public void surfaceCreated(SurfaceHolder holder) {
  new Thread(new MyThread()).start();
 }
 @Override
 public void surfaceDestroyed(SurfaceHolder holder) {
 }
 class MyThread implements Runnable {
  @Override
  public void run() {
   Canvas canvas = surfaceHolder.lockCanvas(null);//获取画布
   Paint mPaint = new Paint();
   mPaint.setColor(Color.BLUE);
   canvas.drawRect(new RectF(100, 100, 1000, 550), mPaint);
   surfaceHolder.unlockCanvasAndPost(canvas);//解锁画布，提交画好的图像
  }
 }
}

从以上代码中，可以看到在MyThread的run方法中创建了一块画布，进行SurfaceView的绘制，但是我们知道SurfaceView是双缓冲机制，这个Canvas上的内容我们拿不到，所以截屏出来是黑屏。所以，要拿到这个画布上的内容，就自己创建一个画布，将这些内容画到自己的Canvas上，就可以了。

2、拿到SurfaceView画布上的bitmap，看修改过后的代码


public abstract class SuperSurfaceView extends SurfaceView implements SurfaceHolder.Callback {
 SurfaceHolder surfaceHolder;
 public SuperSurfaceView(Context context) {
  super(context);
  surfaceHolder = this.getHolder();
  surfaceHolder.addCallback(this);
 }
 @Override
 public void surfaceChanged(SurfaceHolder holder, int format, int width,
        int height) {
 }
 @Override
 public void surfaceCreated(SurfaceHolder holder) {
  new Thread(new MyThread()).start();
 }
 @Override
 public void surfaceDestroyed(SurfaceHolder holder) {
 }
 class MyThread implements Runnable {
  @Override
  public void run() {
   Canvas canvas = surfaceHolder.lockCanvas(null);//获取画布
   doDraw(canvas);
   surfaceHolder.unlockCanvasAndPost(canvas);//解锁画布，提交画好的图像
  }
 }
 //将绘制图案的方法抽象出来，让子类实现，调用getBitmap方法时就会调用此方法
 protected abstract void doDraw(Canvas canvas);
 //调用该方法将doDraw绘制的图案绘制在自己的canvas上
 public Bitmap getBitmap() {
  Bitmap bitmap = Bitmap.createBitmap(getWidth(), getHeight(), Bitmap.Config.ARGB_8888);
  Canvas canvas = new Canvas(bitmap);
  doDraw(canvas);
  return bitmap;
 }
}

3、下面看MainActivity中如何使用


Button bt = (Button) findViewById(R.id.bt);
FrameLayout fl = (FrameLayout) findViewById(R.id.fl);
//用到surfaceview需继承SuperSurfaceView才能截到屏，否则截出来是黑屏
SuperSurfaceView surfaceView = new SuperSurfaceView(this) {
 @Override
 protected void doDraw(Canvas canvas) {
  Paint mPaint = new Paint();
  mPaint.setColor(Color.BLUE);
  canvas.drawRect(new RectF(100, 100, 1000, 550), mPaint);
 }
};
fl.addView(surfaceView);
bt.setOnClickListener(new View.OnClickListener() {
 @Override
 public void onClick(View v) {
  //调用该方法即可得到surfaceview上绘制的图案
  Bitmap bitmap = surfaceView.getBitmap();
 }
});