>首先以camera2 api android为例,有一个开源谷歌示例代码. https://github.com/googlesamples/android-Camera2Basic

>对于要绘制矩形的部分(触摸要对焦)的第二步,请按照以下步骤操作 –

>创建一个扩展到SurfaceView的自定义类.

>在此自定义类中调用onTouchListener方法以检测手指坐标并使用android中的paint类绘制矩形.

– 在您的TextureView上方添加此自定义类,该类显示来自camera2的预览.

>将自定义视图变为透明.

>最后当您在设备屏幕上的某个点触摸时,将调用onTouchListener,它将在您在相机预览上方添加的自定义视图的画布上绘制.

>最后清除你的画布,这样就不会在自定义视图中添加矩形,因为你需要在一个时间点使用一个矩形.

>如果一段时间没有触摸,矩形也会消失.使用自定义视图中的处理程序执行此操作

我在这里给你一个经过测试的代码来做到这一点.我希望它可以帮助你.最好的运气.

private class CustomView extends SurfaceView {

private final Paint paint;

private final SurfaceHolder mHolder;

private final Context context;

public CustomView(Camera2BasicFragment context) {

super(context.getActivity().getBaseContext());

mHolder = getHolder();

mHolder.setFormat(PixelFormat.TRANSPARENT);

this.context = context.getActivity().getBaseContext();

paint = new Paint(Paint.ANTI_ALIAS_FLAG);

paint.setColor(Color.WHITE);

paint.setStyle(Paint.Style.STROKE);

}

@Override

protected void onDraw(Canvas canvas) {

super.onDraw(canvas);

}

@Override

public boolean onTouchEvent(MotionEvent event) {

if (event.getAction() == MotionEvent.ACTION_DOWN) {

invalidate();

if (mHolder.getSurface().isValid()) {

final Canvas canvas = mHolder.lockCanvas();

Log.d("touch", "touchRecieved by camera");

if (canvas != null) {

Log.d("touch", "touchRecieved CANVAS STILL Not Null");

canvas.drawColor(Color.TRANSPARENT, PorterDuff.Mode.CLEAR);

canvas.drawColor(Color.TRANSPARENT);

canvas.drawCircle(event.getX(), event.getY(), 100, paint);

mHolder.unlockCanvasAndPost(canvas);

new Handler().postDelayed(new Runnable() {

@Override

public void run() {

Canvas canvas1 = mHolder.lockCanvas();

if(canvas1 !=null){

canvas1.drawColor(0, PorterDuff.Mode.CLEAR);

mHolder.unlockCanvasAndPost(canvas1);

}

}

}, 1000);

}

mHolder.unlockCanvasAndPost(canvas);

}

}

return false;

}

}