在运行时更改Android Camera 2的Flash设置

Question

基本上，我想要做的是通过应用程序中的按钮单击更改CONTROL_AE_MODE。用户可以使用AUTO闪光（ON_AUTO_FLASH），如果ON（ON_ALWAYS_FLASH）或OFF（CONTROL_AE_MODE_OFF）则使用。

在这个例子中：https://github.com/googlesamples/android-Camera2Basic/blob/master/Application/src/main/java/com/example/android/camera2basic/Camera2BasicFragment.java

第818行，他们设置闪光灯一次：

// Use the same AE and AF modes as the preview.
            captureBuilder.set(CaptureRequest.CONTROL_AF_MODE,
                    CaptureRequest.CONTROL_AF_MODE_CONTINUOUS_PICTURE);
            setAutoFlash(captureBuilder);

            // Orientation
            int rotation = activity.getWindowManager().getDefaultDisplay().getRotation();
            captureBuilder.set(CaptureRequest.JPEG_ORIENTATION, ORIENTATIONS.get(rotation));

            CameraCaptureSession.CaptureCallback CaptureCallback
                    = new CameraCaptureSession.CaptureCallback() {

                @Override
                public void onCaptureCompleted(@NonNull CameraCaptureSession session,
                                               @NonNull CaptureRequest request,
                                               @NonNull TotalCaptureResult result) {
                    showToast("Saved: " + mFile);
                    Log.d(TAG, mFile.toString());
                    unlockFocus();
                }
            };

            mCaptureSession.stopRepeating();
            mCaptureSession.capture(captureBuilder.build(), CaptureCallback, null);

然后在840行构建CaptureSession。

有没有办法在预览后更改CONTROL_AE_MODE？

我试过改造会议，这有点奏效：

if(flashMode == CameraView.CAMERA_FLASH_ON){
            Log.e("CAMERA 2", "FLASH ON");
            mPreviewCaptureRequestBuilder.set(CaptureRequest.CONTROL_AE_MODE, CaptureRequest.CONTROL_AE_MODE_ON_ALWAYS_FLASH);
        }else if(flashMode == CameraView.CAMERA_FLASH_OFF){
            Log.e("CAMERA 2", "FLASH OFF");
            mPreviewCaptureRequestBuilder.set(CaptureRequest.CONTROL_AE_MODE, CaptureRequest.CONTROL_AE_MODE_OFF);
        }else if(flashMode == CameraView.CAMERA_FLASH_AUTO){
            Log.e("CAMERA 2", "FLASH AUTO");
            mPreviewCaptureRequestBuilder.set(CaptureRequest.CONTROL_AE_MODE, CaptureRequest.CONTROL_AE_MODE_ON_AUTO_FLASH);
        }
        mFlashMode = flashMode;
        if (mCameraCaptureSession != null) {
            mCameraCaptureSession.close();
            mCameraCaptureSession = null;
       }
  createCameraPreviewSession();

出于某种原因，CONTROL_AE_MODE_OFF会将整个预览变为黑色。我试着在文档中查找更新方法但没有找到任何内容。

任何教程或文档都非常感谢。

Answer 1

我不知道为什么你的预览变黑，但你不需要手动关闭捕获会话。来自.close()方法的文档：

直接使用

createCaptureSession(List , CameraCaptureSession.StateCallback,
  Handler)

而不关闭是快速切换到新会话的推荐方法，因为可以更有效地重用未更改的目标输出。

因此，您可以重用现有的CaptureRequest.Builder，设置更改的值，构建新的PreviewRequest，并使用此新请求启动新会话，如下所示：

try {
    // Change some capture settings
    mPreviewRequestBuilder.set(CaptureRequest.CONTROL_AE_MODE, CaptureRequest.CONTROL_AE_MODE_ON);
    // Build new request (we can't just edit existing one, as it is immutable)
    mPreviewRequest = mPreviewRequestBuilder.build();
    // Set new repeating request with our changed one
    mCaptureSession.setRepeatingRequest(mPreviewRequest, mCaptureCallback, mBackgroundHandler);
} catch (CameraAccessException e) {
    e.printStackTrace();
}

它会快得多（几乎没有任何可见的预览冻结）。

Answer 2

正如@ cyborg86pl在切换闪光模式时提到的那样，你不应该切换CONTROL_AE_MODE。相反，你可以在FLASH_MODE之间切换。这是我案例的一个工作示例：

  when (currentFlashState) {
        FlashState.AUTO -> {
          previewRequestBuilder.set(CaptureRequest.CONTROL_AE_MODE, CaptureRequest.CONTROL_AE_MODE_ON_AUTO_FLASH)
        }
        FlashState.ON -> {
          previewRequestBuilder.set(CaptureRequest.CONTROL_AE_MODE, CaptureRequest.CONTROL_AE_MODE_ON)
          previewRequestBuilder.set(CaptureRequest.FLASH_MODE, CameraMetadata.FLASH_MODE_TORCH)
        }
        FlashState.OFF -> {
          previewRequestBuilder.set(CaptureRequest.CONTROL_AE_MODE, CaptureRequest.CONTROL_AE_MODE_ON)
          previewRequestBuilder.set(CaptureRequest.FLASH_MODE, CaptureRequest.FLASH_MODE_OFF)
        }
      }
 previewRequest = previewRequestBuilder.build()
 captureSession.setRepeatingRequest(previewRequest, captureCallback, backgroundHandler)

Answer 3

你想要的是禁用闪光灯，而不是自动曝光（AE），因此你想使用CONTROL_AE_MODE_ON而不是CONTROL_AE_MODE_OFF。

如documentation中所述：

CONTROL_AE_MODE_ON

相机设备的自动曝光程序处于活动状态，没有闪光控制。