java - 安装后运行的第一个应用程序中相机无法工作

Question

我在我的 Android 应用程序中实现了一个简单的 QR 扫描仪代码。该代码似乎工作正常，但由于某种原因，安装后，第一次打开应用程序时，CameraView 保持黑色。只有在我第二次启动应用程序后它才能工作(关闭后，onResume不会改变任何东西)

这是我的代码:

private static Context context;

private CameraSource cameraSource;
private SurfaceView cameraView;
private final int MY_PERMISSIONS_REQUEST_CAMERA = 1;
private String token = "";
private String tokenanterior = "";
private static Activity mActivity;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    context = this;
    mActivity = this;

    // verifico si el usuario dio los permisos para la camara
    if (ActivityCompat.checkSelfPermission(MainActivity.this, Manifest.permission.CAMERA)
            != PackageManager.PERMISSION_GRANTED) {

        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
            // verificamos la version de ANdroid que sea al menos la M para mostrar
            // el dialog de la solicitud de la camara
            if (shouldShowRequestPermissionRationale(
                    Manifest.permission.CAMERA)) ;
            requestPermissions(new String[]{Manifest.permission.CAMERA},
                    MY_PERMISSIONS_REQUEST_CAMERA);
        }
    }

    cameraView = (SurfaceView) findViewById(R.id.camera_view);
    initQR();

}

public void initQR() {

    // creo el detector qr
    BarcodeDetector barcodeDetector =
            new BarcodeDetector.Builder(this)
                    .setBarcodeFormats(Barcode.ALL_FORMATS)
                    .build();

    // creo la camara
    cameraSource = new CameraSource
            .Builder(this, barcodeDetector)
            .setRequestedPreviewSize(1600, 1024)
            .setAutoFocusEnabled(true) //you should add this feature
            .build();

    // listener de ciclo de vida de la camara
    cameraView.getHolder().addCallback(new SurfaceHolder.Callback() {
        @Override
        public void surfaceCreated(SurfaceHolder holder) {

            // verifico si el usuario dio los permisos para la camara
            if (ActivityCompat.checkSelfPermission(MainActivity.this, Manifest.permission.CAMERA)
                    != PackageManager.PERMISSION_GRANTED) {

                if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
                    // verificamos la version de ANdroid que sea al menos la M para mostrar
                    // el dialog de la solicitud de la camara
                    if (shouldShowRequestPermissionRationale(
                            Manifest.permission.CAMERA)) ;
                    requestPermissions(new String[]{Manifest.permission.CAMERA},
                            MY_PERMISSIONS_REQUEST_CAMERA);
                }
                return;
            }else {
                try {
                    cameraSource.start(cameraView.getHolder());
                } catch (IOException ie) {
                    Log.e("CAMERA SOURCE", ie.getMessage());
                }
            }
        }

        @Override
        public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
        }

        @Override
        public void surfaceDestroyed(SurfaceHolder holder) {
            cameraSource.stop();
        }
    });

    // preparo el detector de QR
    barcodeDetector.setProcessor(new Detector.Processor<Barcode>() {
        @Override
        public void release() {
        }
}

有什么想法吗？

编辑:根据@r2rek的回答，我在类中实现了onRequestPermissionResult()函数，如下所示:

@Override
public void onRequestPermissionsResult(int requestCode,
                                       String[] permissions, int[] grantResults) {
    switch (requestCode) {
        case MY_PERMISSIONS_REQUEST_CAMERA: {
            // If request is cancelled, the result arrays are empty.
            if (grantResults.length > 0
                    && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                // permission was granted, yay! Do the
                // contacts-related task you need to do.
                Log.i("Results:", "HE GAVE EM");
                initQR();
            } else {
                // permission denied, boo! Disable the
                // functionality that depends on this permission.
            }
            return;
        }

    }
}

但这并没有解决问题，initQR 被执行了两次(因为我被要求获得拍摄视频和拍照的许可)。但在首次安装时，它仍然无法在 SurfaceView 上正确显示相机流。

Answer 1

这里正在努力解决同样的问题。 问题是，当您在权限对话框后通过 initQR() 重新创建扫描仪时，不会再次调用 surfaceCreated 回调。因此，cameraSource.start 未被调用，您将面临黑屏。

在其他情况下也会出现同样的问题 - 例如当您通过 USB 电缆将手机连接到笔记本电脑时，会弹出安全对话框并削弱相机源。

观察 - 在这些情况下总是会调用 onPause() 和 onResume()。有时扫描仪会恢复(翻转、 sleep 后)，有时则不会。

我的解决方案(黑客)是将延迟恢复逻辑放入 onPause() 和 onResume() 方法:

@Override
protected void onPause() {
    super.onPause();
    cameraSource.release();
    cameraSourceStarted = false;
}

@Override
protected void onResume() {
    super.onResume();
    initialiseDetectorsAndSources();

    final Handler handler = new Handler(Looper.getMainLooper());
    handler.postDelayed(new Runnable() {
        @Override
        public void run() {
            if (!cameraSourceStarted) {
                try {
                    if (ActivityCompat.checkSelfPermission(MainActivity.this, Manifest.permission.CAMERA) == PackageManager.PERMISSION_GRANTED) {
                        cameraSource.start(surfaceView.getHolder());
                    } else {
                        ActivityCompat.requestPermissions(MainActivity.this, new
                                String[]{Manifest.permission.CAMERA}, REQUEST_CAMERA_PERMISSION);
                    }

                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }, 500);
}

当cameraSource正常启动时，我还在surfaceCreated中设置了 boolean 变量cameraSourceStarted = true - 因此恢复什么也不做。