Android上实现自定义相机应用程序的最佳实践[页5]

javaCopy codepublic class CameraActivity extends AppCompatActivity {
    private TextureView textureView;
    private CameraDevice cameraDevice;
    private CameraCaptureSession cameraCaptureSession;
    private CaptureRequest.Builder captureRequestBuilder;
    private ImageReader imageReader;
    private HandlerThread backgroundThread;
    private Handler backgroundHandler;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_camera);

        textureView = findViewById(R.id.texture_view);
        textureView.setSurfaceTextureListener(surfaceTextureListener);
    }

    private TextureView.SurfaceTextureListener surfaceTextureListener = new TextureView.SurfaceTextureListener() {
        @Override
        public void onSurfaceTextureAvailable(SurfaceTexture surface, int width, int height) {
            openCamera();
        }

        @Override
        public void onSurfaceTextureSizeChanged(SurfaceTexture surface, int width, int height) {
            // Ignored, Camera does all the work for us
        }

        @Override
        public boolean onSurfaceTextureDestroyed(SurfaceTexture surface) {
            return false;
        }

        @Override
        public void onSurfaceTextureUpdated(SurfaceTexture surface) {
            // Invoked every time there's a new Camera preview frame
        }
    };

    private void openCamera() {
        CameraManager cameraManager = (CameraManager) getSystemService(Context.CAMERA_SERVICE);
        String cameraId = null;
        try {
            String[] cameraIds = cameraManager.getCameraIdList();
            for (String id : cameraIds) {
                CameraCharacteristics characteristics = cameraManager.getCameraCharacteristics(id);
                if (characteristics.get(CameraCharacteristics.LENS_FACING) == CameraCharacteristics.LENS_FACING_BACK) {
                    cameraId = id;
                    break;
                }
            }
            CameraCharacteristics characteristics = cameraManager.getCameraCharacteristics(cameraId);
            StreamConfigurationMap streamConfigurationMap = characteristics.get(CameraCharacteristics.SCALER_STREAM_CONFIGURATION_MAP);
            Size[] sizes = streamConfigurationMap.getOutputSizes(SurfaceTexture.class);
            Size previewSize = sizes[0];
            int width = previewSize.getWidth();
            int height = previewSize.getHeight();
            imageReader = ImageReader.newInstance(width, height, ImageFormat.JPEG, 1);
            imageReader.setOnImageAvailableListener(onImageAvailableListener, backgroundHandler);
            cameraManager.openCamera(cameraId, cameraStateCallback, backgroundHandler);
        } catch (CameraAccessException e) {
            e.printStackTrace();
        }
    }

    private CameraDevice.StateCallback cameraStateCallback = new CameraDevice.State