Android Camera2自动曝光

CaptureRequest.Builder builder.set(CaptureRequest.CONTROL_MODE, CameraMetadata.CONTROL_MODE_AUTO);

List<int[]> ae_fps_ranges = new ArrayList<>();
for (Range<Integer> r : characteristics.get(CameraCharacteristics.CONTROL_AE_AVAILABLE_TARGET_FPS_RANGES)) {
    ae_fps_ranges.add(new int[] {r.getLower(), r.getUpper()});
}
Collections.sort(ae_fps_ranges, new CameraController.RangeSorter());

builder.set(CaptureRequest.CONTROL_AE_TARGET_FPS_RANGE, ae_target_fps_range);

switch(flash_value) {
   case "flash_off":
       builder.set(CaptureRequest.CONTROL_AE_MODE, CameraMetadata.CONTROL_AE_MODE_ON);
       builder.set(CaptureRequest.FLASH_MODE, CameraMetadata.FLASH_MODE_OFF);
       break;
   case "flash_auto":
       // note we set this even in fake flash mode (where we manually turn torch on and off to simulate flash) so we
       // can read the FLASH_REQUIRED state to determine if flash is required
   /*if( use_fake_precapture || CameraController2.this.want_expo_bracketing )
       builder.set(CaptureRequest.CONTROL_AE_MODE, CameraMetadata.CONTROL_AE_MODE_ON);
   else*/
       builder.set(CaptureRequest.CONTROL_AE_MODE, CameraMetadata.CONTROL_AE_MODE_ON_AUTO_FLASH);
       //这里FLASH_MODE可以设置为任意值，因为AE_MODE优先级高
       builder.set(CaptureRequest.FLASH_MODE, CameraMetadata.FLASH_MODE_OFF);
       break;
   case "flash_on":
       // see note above for "flash_auto" for why we set this even fake flash mode - arguably we don't need to know
       // about FLASH_REQUIRED in flash_on mode, but we set it for consistency...
   /*if( use_fake_precapture || CameraController2.this.want_expo_bracketing )
       builder.set(CaptureRequest.CONTROL_AE_MODE, CameraMetadata.CONTROL_AE_MODE_ON);
   else*/
       builder.set(CaptureRequest.CONTROL_AE_MODE, CameraMetadata.CONTROL_AE_MODE_ON_ALWAYS_FLASH);
       builder.set(CaptureRequest.FLASH_MODE, CameraMetadata.FLASH_MODE_OFF);
       break;
   case "flash_torch":
       builder.set(CaptureRequest.CONTROL_AE_MODE, CameraMetadata.CONTROL_AE_MODE_ON);
       builder.set(CaptureRequest.FLASH_MODE, CameraMetadata.FLASH_MODE_TORCH);
       break;
   case "flash_red_eye":
       // not supported for expo bracketing or burst
       if( CameraController2.this.burst_type != BurstType.BURSTTYPE_NONE )
           builder.set(CaptureRequest.CONTROL_AE_MODE, CameraMetadata.CONTROL_AE_MODE_ON);
       else
           builder.set(CaptureRequest.CONTROL_AE_MODE, CameraMetadata.CONTROL_AE_MODE_ON_AUTO_FLASH_REDEYE);
       builder.set(CaptureRequest.FLASH_MODE, CameraMetadata.FLASH_MODE_OFF);
       break;
   case "flash_frontscreen_auto":
   case "flash_frontscreen_on":
   case "flash_frontscreen_torch":
       builder.set(CaptureRequest.CONTROL_AE_MODE, CameraMetadata.CONTROL_AE_MODE_ON);
       builder.set(CaptureRequest.FLASH_MODE, CameraMetadata.FLASH_MODE_OFF);
       break;
}

CameraCaptureSession.CaptureCallback{
    @Override
    public void onCaptureCompleted(@NonNull CameraCaptureSession session, @NonNull CaptureRequest request, @NonNull TotalCaptureResult result) {
        long capture_result_exposure_time = result.get(CaptureResult.SENSOR_EXPOSURE_TIME);
        long capture_result_sensitivity = result.get(CaptureResult.SENSOR_SENSITIVITY);
    }
}