android - 停止 CaptureCallback 请求

Question

我正在尝试使用 Camera2 API 通过 Zbar 读取 QR 码。不幸的是，当我在成功扫描二维码后尝试完成 Activity 时遇到以下错误:

Handler (android.os.Handler) {282a7034} sending message to a Handler on a dead thread
java.lang.IllegalStateException: Handler (android.os.Handler) {282a7034} sending message to a Handler on a dead thread
    at android.os.MessageQueue.enqueueMessage(MessageQueue.java:325)
    at android.os.Handler.enqueueMessage(Handler.java:631)
    at android.os.Handler.sendMessageAtTime(Handler.java:600)
    at android.os.Handler.sendMessageDelayed(Handler.java:570)
    at android.os.Handler.post(Handler.java:326)
    at android.hardware.camera2.dispatch.HandlerDispatcher.dispatch(HandlerDispatcher.java:61)
    at android.hardware.camera2.dispatch.MethodNameInvoker.invoke(MethodNameInvoker.java:88)
    at android.hardware.camera2.dispatch.DuckTypingDispatcher.dispatch(DuckTypingDispatcher.java:53)
    at android.hardware.camera2.dispatch.ArgumentReplacingDispatcher.dispatch(ArgumentReplacingDispatcher.java:74)
    at android.hardware.camera2.dispatch.BroadcastDispatcher.dispatch(BroadcastDispatcher.java:54)
    at android.hardware.camera2.dispatch.MethodNameInvoker.invoke(MethodNameInvoker.java:88)
    at android.hardware.camera2.impl.CallbackProxies$DeviceCaptureCallbackProxy.onCaptureCompleted(CallbackProxies.java:120)
    at android.hardware.camera2.impl.CameraDeviceImpl$CameraDeviceCallbacks$4.run(CameraDeviceImpl.java:1362)
    at android.os.Handler.handleCallback(Handler.java:739)
    at android.os.Handler.dispatchMessage(Handler.java:95)
    at android.os.Looper.loop(Looper.java:135)
    at android.os.HandlerThread.run(HandlerThread.java:61)

这些是相关的代码 fragment :

private CameraCaptureSession.CaptureCallback mCaptureCallback
        = new CameraCaptureSession.CaptureCallback() {

    @Override
    public void onCaptureCompleted(CameraCaptureSession session, CaptureRequest request,
                                   TotalCaptureResult result) {
        Bitmap barcodeBmp = mTextureView.getBitmap();
        if(barcodeBmp == null)
            return;
        int width = barcodeBmp.getWidth();
        int height = barcodeBmp.getHeight();

        Image mQRCode = new Image(width, height, "RGB4");
        final ImageScanner scanner = new ImageScanner();
        scanner.setConfig(0, Config.X_DENSITY, 3);
        scanner.setConfig(0, Config.Y_DENSITY, 3);
        scanner.setConfig(0, Config.ENABLE, 0); //Disable all the Symbols
        scanner.setConfig(Symbol.QRCODE, Config.ENABLE, 1); //Only QRCODE is enable

        int[] pixels = new int[(width * height)];
        barcodeBmp.getPixels(pixels, 0, width, 0, 0, width, height);
        mQRCode.setData(pixels);
        int scanResult = scanner.scanImage(mQRCode.convert("Y800"));

        Log.i(TAG, "Result = " + scanResult);

        if(scanResult != 0) {

            Log.i(TAG, "Getting results");
            SymbolSet syms = scanner.getResults();
            Log.i(TAG, "Have results");
            for(Symbol sym : syms) {
                Intent returnIntent = new Intent();
                returnIntent.putExtra("Result", sym.getData());
                setResult(RESULT_OK, returnIntent);
                closeCamera();
                stopBackgroundThread();
                mActivity.finish();
            }

        }
    }

};

private void closeCamera() {
    try {
        mCameraOpenCloseLock.acquire();
        if (null != mCaptureSession) {
            mCaptureSession.close();
            mCaptureSession = null;
        }
        if (null != mCameraDevice) {
            mCameraDevice.close();
            mCameraDevice = null;
        }
        if (null != mImageReader) {
            mImageReader.close();
            mImageReader = null;
        }
    } catch (InterruptedException e) {
        throw new RuntimeException("Interrupted while trying to lock camera closing.", e);
    } finally {
        mCameraOpenCloseLock.release();
    }
}

private void stopBackgroundThread() {
    if(mBackgroundThread != null) {
        mBackgroundThread.quitSafely();
        try {
            mBackgroundThread.join(1);
            mBackgroundThread = null;
            mBackgroundHandler = null;
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

如何停止调用 CaptureCallback 并将结果干净地返回到我的主要 Activity ？

Answer 1

您正在调用 CameraDevice#close()，但这不会立即关闭相机。您应该保持线程运行直到设备完成。

您的代码可能基于 Google’s Camera2 sample app .要整齐地完成所有事情，请停止 CameraDevice.StateCallback 中的线程，而不是覆盖 #onClosed(CameraDevice) 方法:

private CameraDevice.StateCallback mStateCallback
        = new CameraDevice.StateCallback() {

    // ...

    @Override
    public void onClosed(CameraDevice camera) {
        // Keep the thread alive until the camera is closed.
        stopBackgroundThread();
    }

};

看起来当前行为可能是自 documentation for CameraDevice#close() 以来的错误说:

Immediately after this call, besides the final onClosed(CameraDevice) calls, no further callbacks from the device or the active session will occur, and any remaining submitted capture requests will be discarded, as if abortCaptures() had been called, except that no success or failure callbacks will be invoked.