Android Camera2 资源释放导致的内存泄露

先来一段代码看看：

 @Override
    protected void onDestroy() {
        super.onDestroy();
        if (mCaptureRequest != null) {
            mCaptureRequest.removeTarget(mSurface);
            mCaptureRequest = null;
        }
        if (mSurface != null) {
            mSurface.release();
            mSurface = null;
        }
        if (mSurfaceTexture != null){
            mSurfaceTexture.release();
            mSurfaceTexture = null;
        }
        if (mCameraCaptureSession != null) {
            try {
                mCameraCaptureSession.stopRepeating();
                mCameraCaptureSession.abortCaptures();
            } catch (CameraAccessException e) {
                e.printStackTrace();
            }
            mCameraCaptureSession = null;
        }

        if (mCameraDevice != null) {
            mCameraDevice.close();
            mCameraDevice = null;
        }
        if (mChildHandler != null) {
            mChildHandler.removeCallbacksAndMessages(null);
            mChildHandler = null;
        }
        if (mHandlerThread != null) {
            mHandlerThread.quitSafely();
            mHandlerThread = null;
        }

        mCameraManager = null;
        mSessionStateCallback = null;
        mSessionCaptureCallback = null;
        mStateCallback = null;

    }

从上面的代码中可以看出，在destroy时，需要关闭相机相关的资源，并且一定要注意关闭的顺序，如果处理不当就面临的麻烦可能就是内存泄露,注意要释放的资源,否则一直持有会导致内存泄露.
一般情况下会有以下几个操作导致内存泄露:

1. CaptureRequest 如果没有释放Surface, 一定操作释放 mCaptureRequest.removeTarget(mSurface);
2. SurfaceTexture 需要被释放，除了 mSurfaceTexture.release();
   也可以用这种mTextureView.getSurfaceTextureListener().onSurfaceTextureDestroyed(mTextureView.getSurfaceTexture());方式释放SurfaceTextur，但是在上面的public boolean onSurfaceTextureDestroyed(SurfaceTexture surface) 回调中你需要返回true或者自己执行 surface.release(); 这样才会运行onSurfaceTextureDestroyed回调
3. Surface 需要被释放
4. 释放是需要按顺序一个一个释放的
5. 如果你想实现一个工具类来以建造者模式来创建相机拍照,请注意TextureView不能传入工具类里,因为你需要实现setSurfaceTextureListener监听,而这个监听你是无法在工具类里释放它的,它是需要在activity里才能被释放,请切记!
   你最好只传入SurfaceTexture给工具类