Android Camera2 相機拍照流程詳解

實現特點

• 實現自動對焦
• 選擇性正常觸發閃光燈flash
• 複用CaptureRequest.Builder, 參數完全一致
• 拍照注意事項講解
• 代碼片段詳解

流程

1. 按照常規方式打開預覽
2. 設置好相應的全局變量:
   CameraDevice的cameraDevice
   CameraCaptureSession的mPreviewSession
   CaptureRequest.Builder的captureRequestBuilder
   ImageReader的imageReader
   等
3. 定義一個類似takePicture()的開始拍照方法
4. 自動對焦 對焦, 直接開始拍照, 調用類似captureStillPicture()的方法
5. 自動對焦

 // 設置自動對焦模式
            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. 拍攝前, 如果需要閃光的, 需要設置

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

上面這條語句會觸發閃光的開啓動作

7. 添加拍攝圖片的輸出

captureRequestBuilder.addTarget(mImageReader.getSurface());

8. 設置當前的拍攝意圖

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

這條設置頁會影響到閃光的正常開啓. 如果不需要閃光燈的話, 設置了也沒事.

9. 設置圖片的方向
   因爲物理相機的鏡頭方向可能和手機的朝向不一致(手機倒着拿), 所以設置這個是確保拍攝出來的圖片永遠是正向的

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

10. 停止畫面預覽

mPreviewSession.stopRepeating();

也可以不調用這條, 不停止畫面. 不過這樣會出現閃光燈閃爍2次的問題.

11. 開始拍照

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

                            //移除輸出到ImageReader, 不移除的話,會造成拍照停不下來的問題
                            captureRequestBuilder.removeTarget(imageReader.getSurface());
                            //恢復相機預提爲預覽
                            captureRequestBuilder.set(CaptureRequest.CONTROL_CAPTURE_INTENT, CameraMetadata.CONTROL_CAPTURE_INTENT_PREVIEW);
                            try {
                                //不加這句話, 閃光燈無法正常工作, 如果不適用閃光等, 可以不加
                                mPreviewSession.capture(mPreviewRequestBuilder.build(), null, null);
                            } catch (CameraAccessException e) {
                                e.printStackTrace();
                            }
                        }
                    }, null);

12. 完整部分代碼

 /**拍照*/
    private void takePicture()
    {
        try
        {
            if (cameraDevice == null)
            {
                return;
            }
                    // 創建拍照請求
            captureRequestBuilder = cameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_STILL_CAPTURE);
            // 設置自動對焦模式
            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);
            // 將imageReader的surface設爲目標
            captureRequestBuilder.addTarget(imageReader.getSurface());
            // 獲取設備方向
            int rotation = getWindowManager().getDefaultDisplay().getRotation();
            // 根據設備方向計算設置照片的方向
            captureRequestBuilder.set(CaptureRequest.JPEG_ORIENTATION
                    , ORIENTATIONS.get(rotation));
            mCaptureRequestBuilder.set(CaptureRequest.CONTROL_AE_EXPOSURE_COMPENSATION, 5);
            // 停止連續取景
            mPreviewSession.stopRepeating();
            mPreviewSession.abortCaptures();
            //拍照
            CaptureRequest captureRequest = captureRequestBuilder.build();
            //設置拍照監聽
            mPreviewSession.capture(captureRequest,captureCallback, null);
        }
        catch (CameraAccessException e)
        {
            e.printStackTrace();
        }
    }