Android Camera2 相机拍照流程详解

实现特点

• 实现自动对焦
• 选择性正常触发闪光灯flash
• 复用CaptureRequest.Builder, 参数完全一致
• 拍照注意事项讲解
• 代码片段详解

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cameraDevice
   CameraCaptureSession的mPreviewSession
   CaptureRequest.Builder的captureRequestBuilder
   ImageReader的imageReader
   等
3. 定义一个类似takePicture()的开始拍照方法
4. 自动对焦 对焦, 直接开始拍照, 调用类似captureStillPicture()的方法
5. 自动对焦

 // 设置自动对焦模式
            captureRequestBuilder.set(CaptureRequest.CONTROL_AF_MODE, CaptureRequest.CONTROL_AF_MODE_CONTINUOUS_PICTURE);
            captureRequestBuilder.set(CaptureRequest.CONTROL_AE_PRECAPTURE_TRIGGER, CaptureRequest.CONTROL_AE_PRECAPTURE_TRIGGER_START);

6. 拍摄前, 如果需要闪光的, 需要设置

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

上面这条语句会触发闪光的开启动作

7. 添加拍摄图片的输出

captureRequestBuilder.addTarget(mImageReader.getSurface());

8. 设置当前的拍摄意图

captureRequestBuilder.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.

9. 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);
            captureRequestBuilder.set(CaptureRequest.JPEG_ORIENTATION,
                    (sensorOrientation +
                            mDisplayOrientation * (mFacing == Constants.FACING_FRONT ? 1 : -1) +
                            360) % 360);

10. 停止画面预览

mPreviewSession.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.

11. 开始拍照

  mPreviewSession.capture(captureRequestBuilder.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
                            captureRequestBuilder.removeTarget(imageReader.getSurface());
                            //恢复相机预提为预览
                            captureRequestBuilder.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
                                mPreviewSession.capture(mPreviewRequestBuilder.build(), null, null);
                            } catch (CameraAccessException e) {
                                e.printStackTrace();
                            }
                        }
                    }, null);

12. 完整部分代码

 /**拍照*/
    private void takePicture()
    {
        try
        {
            if (cameraDevice == null)
            {
                return;
            }
                    // 创建拍照请求
            captureRequestBuilder = cameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_STILL_CAPTURE);
            // 设置自动对焦模式
            captureRequestBuilder.set(CaptureRequest.CONTROL_AF_MODE, CaptureRequest.CONTROL_AF_MODE_CONTINUOUS_PICTURE);
            captureRequestBuilder.set(CaptureRequest.CONTROL_AE_PRECAPTURE_TRIGGER, CaptureRequest.CONTROL_AE_PRECAPTURE_TRIGGER_START);
            // 将imageReader的surface设为目标
            captureRequestBuilder.addTarget(imageReader.getSurface());
            // 获取设备方向
            int rotation = getWindowManager().getDefaultDisplay().getRotation();
            // 根据设备方向计算设置照片的方向
            captureRequestBuilder.set(CaptureRequest.JPEG_ORIENTATION
                    , ORIENTATIONS.get(rotation));
            mCaptureRequestBuilder.set(CaptureRequest.CONTROL_AE_EXPOSURE_COMPENSATION, 5);
            // 停止连续取景
            mPreviewSession.stopRepeating();
            mPreviewSession.abortCaptures();
            //拍照
            CaptureRequest captureRequest = captureRequestBuilder.build();
            //设置拍照监听
            mPreviewSession.capture(captureRequest,captureCallback, null);
        }
        catch (CameraAccessException e)
        {
            e.printStackTrace();
        }
    }