java - 在同一 Activity android上使用前后摄像头

Question

我知道这个问题已经被问过很多次了，但我别无选择，只能再次问这个问题。我正在使用 camera2 api 在同一屏幕上显示前后摄像头。我创建了两个纹理 View ，每个 View 都有两个相机实例。即使这样，我也会遇到异常。

这是我的 MainActivity.java 代码:

public class MainActivity extends AppCompatActivity {

    private static final String TAG = "AndroidCameraApi";
    private TextureView textureView,textureView1;
    private static final SparseIntArray ORIENTATIONS = new SparseIntArray();
    static {
        ORIENTATIONS.append(Surface.ROTATION_0, 90);
        ORIENTATIONS.append(Surface.ROTATION_90, 0);
        ORIENTATIONS.append(Surface.ROTATION_180, 270);
        ORIENTATIONS.append(Surface.ROTATION_270, 180);
    }
    private String cameraId,cameraId1;
    protected CameraDevice cameraDevice,cameraDevice1;
    protected CameraCaptureSession cameraCaptureSessions,cameraCaptureSessions1;
    protected CaptureRequest.Builder captureRequestBuilder,captureRequestBuilder1;
    private Size imageDimension,imageDimension1;
    private static final int REQUEST_CAMERA_PERMISSION = 200;
    private Handler mBackgroundHandler,mBackgroundHandler1;
    private HandlerThread mBackgroundThread,mBackgroundThread1;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_android_camera_api);
        textureView = (TextureView) findViewById(R.id.texture);
        textureView1 = (TextureView) findViewById(texture1);
        assert textureView != null;
        assert textureView1 != null;
        textureView.setSurfaceTextureListener(textureListener);
        textureView1.setSurfaceTextureListener(textureListener1);

    }
    TextureView.SurfaceTextureListener textureListener = new TextureView.SurfaceTextureListener() {
        @Override
        public void onSurfaceTextureAvailable(SurfaceTexture surface, int width, int height) {
            //open your camera here
            openCamera();
        }
        @Override
        public void onSurfaceTextureSizeChanged(SurfaceTexture surface, int width, int height) {
            // Transform you image captured size according to the surface width and height
        }
        @Override
        public boolean onSurfaceTextureDestroyed(SurfaceTexture surface) {
            return false;
        }
        @Override
        public void onSurfaceTextureUpdated(SurfaceTexture surface) {
        }
    };

    TextureView.SurfaceTextureListener textureListener1 = new TextureView.SurfaceTextureListener() {
        @Override
        public void onSurfaceTextureAvailable(SurfaceTexture surface, int width, int height) {
            //open your camera here
            openBackCamera();
        }
        @Override
        public void onSurfaceTextureSizeChanged(SurfaceTexture surface, int width, int height) {
            // Transform you image captured size according to the surface width and height
        }
        @Override
        public boolean onSurfaceTextureDestroyed(SurfaceTexture surface) {
            return false;
        }
        @Override
        public void onSurfaceTextureUpdated(SurfaceTexture surface) {
        }
    };

    private final CameraDevice.StateCallback stateCallback = new CameraDevice.StateCallback() {
        @Override
        public void onOpened(CameraDevice camera) {
            //This is called when the camera is open
            Log.e(TAG, "onOpened");
            cameraDevice = camera;
            createCameraPreview();
        }
        @Override
        public void onDisconnected(CameraDevice camera) {
            cameraDevice.close();
        }
        @Override
        public void onError(CameraDevice camera, int error) {
            cameraDevice.close();
            cameraDevice = null;
        }
    };


    private final CameraDevice.StateCallback stateCallback1 = new CameraDevice.StateCallback() {
        @Override
        public void onOpened(CameraDevice camera) {
            //This is called when the camera is open
            Log.e(TAG, "onOpened");
            cameraDevice1 = camera;
            createCameraPreview1();
        }
        @Override
        public void onDisconnected(CameraDevice camera) {
            cameraDevice1.close();
        }
        @Override
        public void onError(CameraDevice camera, int error) {
            cameraDevice1.close();
            cameraDevice1 = null;
        }
    };


    protected void startBackgroundThread() {
        mBackgroundThread = new HandlerThread("Camera Background");
        mBackgroundThread.start();
        mBackgroundHandler = new Handler(mBackgroundThread.getLooper());
    }
    protected void stopBackgroundThread() {
        mBackgroundThread.quitSafely();
        try {
            mBackgroundThread.join();
            mBackgroundThread = null;
            mBackgroundHandler = null;
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

    protected void startBackgroundThread1() {
        mBackgroundThread1 = new HandlerThread("Camera Background");
        mBackgroundThread1.start();
        mBackgroundHandler1 = new Handler(mBackgroundThread1.getLooper());
    }
    protected void stopBackgroundThread1() {
        mBackgroundThread1.quitSafely();
        try {
            mBackgroundThread1.join();
            mBackgroundThread1 = null;
            mBackgroundHandler1 = null;
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }


    protected void createCameraPreview() {
        try {
            SurfaceTexture texture = textureView.getSurfaceTexture();
            assert texture != null;
            texture.setDefaultBufferSize(imageDimension.getWidth(), imageDimension.getHeight());
            Surface surface = new Surface(texture);
            captureRequestBuilder = cameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW);
            captureRequestBuilder.addTarget(surface);
            cameraDevice.createCaptureSession(Arrays.asList(surface), new CameraCaptureSession.StateCallback(){
                @Override
                public void onConfigured(@NonNull CameraCaptureSession cameraCaptureSession) {
                    //The camera is already closed
                    if (null == cameraDevice) {
                        return;
                    }
                    // When the session is ready, we start displaying the preview.
                    cameraCaptureSessions = cameraCaptureSession;
                    updatePreview();
                }
                @Override
                public void onConfigureFailed(@NonNull CameraCaptureSession cameraCaptureSession) {
                    Toast.makeText(MainActivity.this, "Configuration change", Toast.LENGTH_SHORT).show();
                }
            }, null);
        } catch (CameraAccessException e) {
            e.printStackTrace();
        }
    }

    protected void createCameraPreview1() {
        try {
            SurfaceTexture texture1 = textureView1.getSurfaceTexture();
            assert texture1 != null;
            texture1.setDefaultBufferSize(imageDimension1.getWidth(), imageDimension1.getHeight());
            Surface surface = new Surface(texture1);
            captureRequestBuilder1 = cameraDevice1.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW);
            captureRequestBuilder1.addTarget(surface);
            cameraDevice1.createCaptureSession(Arrays.asList(surface), new CameraCaptureSession.StateCallback(){
                @Override
                public void onConfigured(@NonNull CameraCaptureSession cameraCaptureSession) {
                    //The camera is already closed
                    if (null == cameraDevice1) {
                        return;
                    }
                    // When the session is ready, we start displaying the preview.
                    cameraCaptureSessions1 = cameraCaptureSession;
                    updatePreview1();
                }
                @Override
                public void onConfigureFailed(@NonNull CameraCaptureSession cameraCaptureSession) {
                    Toast.makeText(MainActivity.this, "Configuration change", Toast.LENGTH_SHORT).show();
                }
            }, null);
        } catch (CameraAccessException e) {
            e.printStackTrace();
        }
    }


    private void openCamera() {
        CameraManager manager = (CameraManager) getSystemService(Context.CAMERA_SERVICE);
        Log.e(TAG, "is camera open");
        try {
            cameraId = manager.getCameraIdList()[0];
            CameraCharacteristics characteristics = manager.getCameraCharacteristics(cameraId);
            StreamConfigurationMap map = characteristics.get(CameraCharacteristics.SCALER_STREAM_CONFIGURATION_MAP);
            assert map != null;
            imageDimension = map.getOutputSizes(SurfaceTexture.class)[0];
            // Add permission for camera and let user grant the permission
            if (ActivityCompat.checkSelfPermission(this, Manifest.permission.CAMERA) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, Manifest.permission.WRITE_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED) {
                ActivityCompat.requestPermissions(MainActivity.this, new String[]{Manifest.permission.CAMERA, Manifest.permission.WRITE_EXTERNAL_STORAGE}, REQUEST_CAMERA_PERMISSION);
                return;
            }
            manager.openCamera(cameraId, stateCallback, null);
        } catch (CameraAccessException e) {
            e.printStackTrace();
        }
        Log.e(TAG, "openCamera X");
    }

    private void openBackCamera() {
        CameraManager manager = (CameraManager) getSystemService(Context.CAMERA_SERVICE);
        Log.e(TAG, "is camera open");
        try {
            cameraId1 = manager.getCameraIdList()[1];
            CameraCharacteristics characteristics = manager.getCameraCharacteristics(cameraId1);
            StreamConfigurationMap map = characteristics.get(CameraCharacteristics.SCALER_STREAM_CONFIGURATION_MAP);
            assert map != null;
            imageDimension1 = map.getOutputSizes(SurfaceTexture.class)[0];
            // Add permission for camera and let user grant the permission
            if (ActivityCompat.checkSelfPermission(this, Manifest.permission.CAMERA) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, Manifest.permission.WRITE_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED) {
                ActivityCompat.requestPermissions(MainActivity.this, new String[]{Manifest.permission.CAMERA, Manifest.permission.WRITE_EXTERNAL_STORAGE}, REQUEST_CAMERA_PERMISSION);
                return;
            }
            manager.openCamera(cameraId1, stateCallback1, null);
        } catch (CameraAccessException e) {
            e.printStackTrace();
        }
        Log.e(TAG, "openCamera X");
    }


    protected void updatePreview() {
        if(null == cameraDevice) {
            Log.e(TAG, "updatePreview error, return");
        }
        captureRequestBuilder.set(CaptureRequest.CONTROL_MODE, CameraMetadata.CONTROL_MODE_AUTO);
        try {
            cameraCaptureSessions.setRepeatingRequest(captureRequestBuilder.build(), null, mBackgroundHandler);
        } catch (CameraAccessException e) {
            e.printStackTrace();
        }
    }

    protected void updatePreview1() {
        if(null == cameraDevice1) {
            Log.e(TAG, "updatePreview error, return");
        }
        captureRequestBuilder1.set(CaptureRequest.CONTROL_MODE, CameraMetadata.CONTROL_MODE_AUTO);
        try {
            cameraCaptureSessions1.setRepeatingRequest(captureRequestBuilder1.build(), null, mBackgroundHandler1);
        } catch (CameraAccessException e) {
            e.printStackTrace();
        }
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        if (requestCode == REQUEST_CAMERA_PERMISSION) {
            if (grantResults[0] == PackageManager.PERMISSION_DENIED) {
                // close the app
                Toast.makeText(MainActivity.this, "Sorry!!!, you can't use this app without granting permission", Toast.LENGTH_LONG).show();
                finish();
            }
        }
    }
    @Override
    protected void onResume() {
        super.onResume();
        Log.e(TAG, "onResume");
        startBackgroundThread();
        startBackgroundThread1();
        if (textureView.isAvailable()) {
            openCamera();
        } else {
            textureView.setSurfaceTextureListener(textureListener);
        }

        if (textureView1.isAvailable()) {
            openBackCamera();
        } else {
            textureView1.setSurfaceTextureListener(textureListener1);
        }

    }
    @Override
    protected void onPause() {
        Log.e(TAG, "onPause");
        //closeCamera();
        stopBackgroundThread();
        stopBackgroundThread1();
        super.onPause();
    }
}

布局文件代码:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    >
    <TextureView
        android:id="@+id/texture"
        android:layout_width="match_parent"
        android:layout_height="200dp"
        android:layout_marginBottom="10dp"/>

    <TextureView
        android:id="@+id/texture1"
        android:layout_width="match_parent"
        android:layout_height="200dp"
        />

</LinearLayout>

我得到的异常如下:

java.lang.NullPointerException: Attempt to invoke virtual method 'void android.hardware.camera2.CameraDevice.close()' on a null object reference

我在这条线上遇到异常:

  cameraDevice1.close();

Answer 1

哪个 cameraDevice1.close() 调用失败了？你有没有接到那个相机的 onOpened 电话？

无法保证给定的 Android 设备可以同时打开多个摄像头；唯一知道的方法就是尝试，如果无法完成，第二个摄像头将不会在打开时触发，它会在错误代码为 TOO_MANY_CAMERAS_IN_USE 时触发。

所以如果这发生在这里，那么你将在没有 onOpened 的情况下得到 onError，并且你的 cameraDevice1 将永远不会被设置。