Android Camera2 相机拍照

实现特点

• 不需要自动对焦
• 正常触发闪光灯flash
• 复用CaptureRequest.Builder, 参数完全一致

流程

1. 按照常规方式打开预览
2. 设置好相应的全局变量:
   • CameraDevice的mCamera
   • CameraCaptureSession的mCaptureSession
   • CaptureRequest.Builder的mPreviewRequestBuilder
   • ImageReader的mImageReader
     等
3. 定义一个类似takePicture()的开始拍照方法
4. 不用对焦, 直接开始拍照, 调用类似captureStillPicture()的方法
5. 拍摄前, 如果需要闪光的, 需要设置

mPreviewRequestBuilder.set(CaptureRequest.CONTROL_AE_PRECAPTURE_TRIGGER, CaptureRequest.CONTROL_AE_PRECAPTURE_TRIGGER_START);

这条语句会触发闪光的开启动作

6. 添加拍摄图片的输出

mPreviewRequestBuilder.addTarget(mImageReader.getSurface());

7. 设置当前的拍摄意图

mPreviewRequestBuilder.set(CaptureRequest.CONTROL_CAPTURE_INTENT, CameraMetadata.CONTROL_CAPTURE_INTENT_STILL_CAPTURE);

这条设置页会影响到闪光的正常开启. 如果不需要闪光灯的话, 设置了也没事.

8. 设置图片的方向
   因为物理相机的镜头方向可能和手机的朝向不一致(手机倒着拿), 所以设置这个是确保拍摄出来的图片永远是正向的

  int sensorOrientation = mCameraCharacteristics.get(
                    CameraCharacteristics.SENSOR_ORIENTATION);
            mPreviewRequestBuilder.set(CaptureRequest.JPEG_ORIENTATION,
                    (sensorOrientation +
                            mDisplayOrientation * (mFacing == Constants.FACING_FRONT ? 1 : -1) +
                            360) % 360);

9. 停止画面预览

mCaptureSession.stopRepeating();

也可以不调用这条, 不停止画面. 不过这样会出现闪光灯闪烁2次的问题.

10. 开始拍照

   mCaptureSession.capture(mPreviewRequestBuilder.build(),
                    new CameraCaptureSession.CaptureCallback() {
                        @Override
                        public void onCaptureCompleted(@NonNull CameraCaptureSession session,
                                @NonNull CaptureRequest request,
                                @NonNull TotalCaptureResult result) {
                            

                            //移除输出到ImageReader, 不移除的话,会造成拍照停不下来的问题
                            mPreviewRequestBuilder.removeTarget(mImageReader.getSurface());
                            //恢复相机预提为预览
                            mPreviewRequestBuilder.set(CaptureRequest.CONTROL_CAPTURE_INTENT, CameraMetadata.CONTROL_CAPTURE_INTENT_PREVIEW);
                            try {
                                //不加这句话, 闪光灯无法正常工作, 如果不适用闪光等, 可以不加
                                mCaptureSession.capture(mPreviewRequestBuilder.build(), null, null);
                            } catch (CameraAccessException e) {
                                e.printStackTrace();
                            }
                        }
                    }, null);

11. 结束了.

完整部分代码

    void captureStillPicture() {

        mPreviewRequestBuilder.set(CaptureRequest.CONTROL_AE_PRECAPTURE_TRIGGER,
                CaptureRequest.CONTROL_AE_PRECAPTURE_TRIGGER_START);

        try {

            mPreviewRequestBuilder.addTarget(mImageReader.getSurface());
            mPreviewRequestBuilder.set(CaptureRequest.CONTROL_CAPTURE_INTENT, CameraMetadata.CONTROL_CAPTURE_INTENT_STILL_CAPTURE);

            // Calculate JPEG orientation.
            @SuppressWarnings("ConstantConditions")
            int sensorOrientation = mCameraCharacteristics.get(
                    CameraCharacteristics.SENSOR_ORIENTATION);
            mPreviewRequestBuilder.set(CaptureRequest.JPEG_ORIENTATION,
                    (sensorOrientation +
                            mDisplayOrientation * (mFacing == Constants.FACING_FRONT ? 1 : -1) +
                            360) % 360);
            // Stop preview and capture a still picture.
            mCaptureSession.stopRepeating();
            mCaptureSession.capture(mPreviewRequestBuilder.build(),
                    new CameraCaptureSession.CaptureCallback() {
                        @Override
                        public void onCaptureCompleted(@NonNull CameraCaptureSession session,
                                @NonNull CaptureRequest request,
                                @NonNull TotalCaptureResult result) {
                            mPreviewRequestBuilder.removeTarget(mImageReader.getSurface());
                            mPreviewRequestBuilder.set(CaptureRequest.CONTROL_CAPTURE_INTENT, CameraMetadata.CONTROL_CAPTURE_INTENT_PREVIEW);
                            try {
                                mCaptureSession.capture(mPreviewRequestBuilder.build(), null, null);
                            } catch (CameraAccessException e) {
                                e.printStackTrace();
                            }
//                            unlockFocus();
                        }
                    }, null);
        } catch (CameraAccessException e) {
            Log.e(TAG, "Cannot capture a still picture.", e);
        }
    }