如何在Android Camera2 API中禁用所有自动更新

Question

I'm trying to disable auto-exposure, auto-focus, and auto-white-balance in Google's Camera2Basic sample. Here's my code:

private void disableAutomatics() {
    try {
        mPreviewRequestBuilder.set(CaptureRequest.CONTROL_MODE, CaptureRequest.CONTROL_MODE_OFF);
        mPreviewRequestBuilder.set(CaptureRequest.CONTROL_VIDEO_STABILIZATION_MODE, CaptureRequest.CONTROL_VIDEO_STABILIZATION_MODE_OFF);
        mPreviewRequestBuilder.set(CaptureRequest.LENS_OPTICAL_STABILIZATION_MODE, CaptureRequest.LENS_OPTICAL_STABILIZATION_MODE_OFF);
        mPreviewRequestBuilder.set(CaptureRequest.LENS_FOCUS_DISTANCE, .2f);
        mPreviewRequestBuilder.set(CaptureRequest.SENSOR_EXPOSURE_TIME, 1000000L);

        mPreviewRequest = mPreviewRequestBuilder.build();
        // Set new repeating request with our changed one
        mCaptureSession.setRepeatingRequest(mPreviewRequest, mCaptureCallback, mBackgroundHandler);
    } catch (CameraAccessException e) {
        e.printStackTrace();
    }
}

The problem is I don't know where to place the method in Camera2BasicFragment.java.

Any help would be greatly appreciated.

Answer 1

There are two places where you may want to do those settings:

• If you want to do it before the preview starts, the better place would be inside of the overridden method onConfigured within the createCameraPreviewSession() void (line 696 in the Camera2BasicFragment file provided in the Google's Camera2Basic sample:

   private void createCameraPreviewSession() { try { SurfaceTexture texture = mTextureView.getSurfaceTexture(); assert texture != null; // We configure the size of default buffer to be the size of camera preview we want. texture.setDefaultBufferSize(mPreviewSize.getWidth(), mPreviewSize.getHeight()); // This is the output Surface we need to start preview. Surface surface = new Surface(texture); // We set up a CaptureRequest.Builder with the output Surface. mPreviewRequestBuilder = mCameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW); mPreviewRequestBuilder.addTarget(surface); // Here, we create a CameraCaptureSession for camera preview. mCameraDevice.createCaptureSession(Arrays.asList(surface, mImageReader.getSurface()), new CameraCaptureSession.StateCallback() { @Override public void onConfigured(@NonNull CameraCaptureSession cameraCaptureSession) { // The camera is already closed if (null == mCameraDevice) { return; } // When the session is ready, we start displaying the preview. mCaptureSession = cameraCaptureSession; try { //Place here your custom camera settings // Start displaying the camera preview. mPreviewRequest = mPreviewRequestBuilder.build(); mCaptureSession.setRepeatingRequest(mPreviewRequest, mCaptureCallback, mBackgroundHandler); } catch (CameraAccessException e) { e.printStackTrace(); } } @Override public void onConfigureFailed(@NonNull CameraCaptureSession cameraCaptureSession) { showToast("Failed"); } }, null ); } catch (CameraAccessException e) { e.printStackTrace(); } } 

• If you want to do the settings after the preview has started and in runtime just call your disableAutomatics() from the UI or anywhere else and it should work fine.

Note that you don't have to close the older CaptureSession by calling its CaptureSession.close() method as explained in an answer to this other question because the new replaces the older one.

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On another hand, I am not sure about setting the exposure time value manually as you did in your question:

mPreviewRequestBuilder.set(CaptureRequest.SENSOR_EXPOSURE_TIME, 1000000L);

because you may get unexpected results varying on different devices. What I know is that doing so is usually discouraged and it's preferred instead to let the camera adjust by its own and then call AE (auto-exposure) lock:

mPreviewRequestBuilder.set(CaptureRequest.CONTROL_AE_LOCK, true);

You can check the CONTROL_AE_LOCK reference here .

But if your code needs a fixed exposure time then it should work.