CameraSource.java 文件源码

/**
 * Opens the camera and starts sending preview frames to the underlying detector.  The preview
 * frames are not displayed.
 *
 * @throws IOException if the camera's preview texture or display could not be initialized
 */
@RequiresPermission(Manifest.permission.CAMERA)
public CameraSource start() throws IOException {
    synchronized (mCameraLock) {
        if (mCamera != null) {
            return this;
        }

        mCamera = createCamera();

        // SurfaceTexture was introduced in Honeycomb (11), so if we are running and
        // old version of Android. fall back to use SurfaceView.
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) {
            mDummySurfaceTexture = new SurfaceTexture(DUMMY_TEXTURE_NAME);
            mCamera.setPreviewTexture(mDummySurfaceTexture);
        } else {
            mDummySurfaceView = new SurfaceView(mContext);
            mCamera.setPreviewDisplay(mDummySurfaceView.getHolder());
        }
        mCamera.startPreview();

        mProcessingThread = new Thread(mFrameProcessor);
        mFrameProcessor.setActive(true);
        mProcessingThread.start();
    }
    return this;
}