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我一直在尝试在观察者回调中进行绘制，当我尝试锁定画布时，我总是得到一个空返回。SurfaceHolder 似乎还可以。我添加了一个 SurfaceHolder 回调，它在游戏早期被调用。

这是我的观察者更新方法：

// implements Observer
public void update(Observable observable, Object data) {
   Canvas c = null;
   Log.i(TAG, "Surface Observer of CbSurfaceState thread: "
         + Thread.currentThread().getName());
   try {
      synchronized(mCbHolder) {
         c = mCbHolder.lockCanvas(null);
         if(c == null) {
             Log.i(TAG, "lockCanvas returned null");
          } else {
             doDraw(c);
          }
       }
    } finally {
       // do this in a finally so that if an exception is thrown
       // during the above, we don't leave the Surface in an
       // inconsistent state
       if (c != null) {
          mCbHolder.unlockCanvasAndPost(c);
       }
    }
}

这是我在初始化中第一次使用它的地方：

public void initCbSurfaceView(Context context) {
   mContext = context;
   // register our interest in hearing about changes to our surface
   mCbHolder = getHolder();
   Log.i(TAG,"got holder");
   mCbHolder.addCallback(cbSurfaceHolderCallback);
   Log.i(TAG,"added callback");
   // initially in preview mode
   mCbHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
   // previewHolder.(SurfaceHolder); Don't know how to replace, but it
   // won't work without the above.
   ...
   mCbSurfaceState.addObserver(this);
   Log.i(TAG, "Creation of CbSurfaceState thread: "
         + Thread.currentThread().getName());
}

我什至在创建表面时再次设置它，（我最近添加它只是为了确定）

SurfaceHolder.Callback cbSurfaceHolderCallback = new SurfaceHolder.Callback() {
   @Override
   public void surfaceCreated(SurfaceHolder holder) {
      Log.i(TAG, "In surfaceCreated callback");
      mCbHolder = holder;
   }
   ...
};

这是一些日志。我打印了线程，因为起初它是从异步线程开始的，我设法避免了这种情况。：

02-24 20:31:10.380: I/CbSurfaceView(4013): In surfaceCreated callback

02-24 20:31:10.380: I/CbSurfaceView(4013): SurfaceChanged 854X404

02-24 20:31:10.380: I/CbSurfaceView(4013): initPreview width 854 height 404

...

02-24 20:31:25.974: I/CbTouchListener(4013): onTouch Down x 665.7714 y 194.92023

02-24 20:31:25.974: I/CbSurfaceView(4013): Surface Observer of CbSurfaceState thread: main

02-24 20:31:25.981: I/CbSurfaceView(4013): lockCanvas returned null

02-24 20:31:26.005: I/CbSurfaceView(4013): Surface Observer of CbSurfaceState thread: main

02-24 20:31:26.075: I/CbSurfaceView(4013): lockCanvas returned null

我到底做错了什么？我的 doDraw 一直在工作，直到它开始尝试绘制位图。然后我想从lockCanvas中检查null。

我在这里找到了答案How to draw an overlay on a surfaceView used by Camera on Android? 看来你不能在预览上画画。我得到了一个关于 PUSH_BUFFER 类型表面的异常，所以我将它重置为 NORMAL，这样它就不会抱怨了。我无法锁定预览的表面，如果它不是 NORMAL，它会抛出异常。显然你不能动态地改变表面类型。这可能是它被弃用的原因，但是除非您将其设置为 PUSH_BUFFER，否则相机预览将不起作用。我将在顶部添加另一个非 Surface 视图，用于绘制和渲染拍摄的照片。

感谢您的关注，我希望这对某人有所帮助。

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0 回答 0