问怎样才能检测到相机何时完成了曝光初始化？

EN

// Auto-exposure only seems to start after the first picture has been taken
// And on the Pixel 3 XL, it finishes fastest when you make a lot of captures
captureSession.setRepeatingRequest(request, captureCallback, null);

private CaptureResult firstResult;

private final CameraCaptureSession.CaptureCallback captureCallback = new CameraCaptureSession.CaptureCallback() {

    @Override
    public void onCaptureCompleted(@NonNull CameraCaptureSession session, @NonNull CaptureRequest request, @NonNull TotalCaptureResult result) {
        super.onCaptureCompleted(session, request, result);

        if (firstResult == null)
            firstResult = result;

        boolean aeAcquired;
        Integer aeState = lastResult.get(CaptureResult.CONTROL_AE_STATE);
        if (aeState == null) {
            // This camera doesn't support monitoring of auto-exposure, so we'll just have to wait a bit and then assume it's adjusted.
            long nanosSinceFirstResult = result.get(CaptureResult.SENSOR_TIMESTAMP) - firstResult.get(CaptureResult.SENSOR_TIMESTAMP);
            long millisSinceFirstResult = nanosSinceFirstResult / 1000 / 1000;
            aeAcquired = millisSinceFirstResult >= 750;
        } else {
            aeAcquired = aeState == CameraMetadata.CONTROL_AE_STATE_CONVERGED || aeState == CameraMetadata.CONTROL_AE_STATE_FLASH_REQUIRED;
        }

        if (aeAcquired) {
            // Auto-exposure has finished
        }   
    }

};