android camera2 api focus lock

Adding the focus lock as the first part of capturing a still image

This android tutorial describes how to obtain the android camera2 api focus lock, which is required prior to capturing a still image.

GET CODE

You can get it from here https://github.com/mobapptuts/recyclerview_image_gallery.git Tag camera2-lock-focus

or else run this command

git clone —branch camera2-lock-focus https://github.com/mobapptuts/recyclerview_image_gallery.git

CODE SAMPLES

Add some samples to reference the various camera states

private static final int STATE_PREVIEW = 0;
   private static final int STATE__WAIT_LOCK = 1;

In the CameraCaptureSession callback member override the members onCaptureCompleted & onCaptureFailed. The add a new method to the callback called process where if the state is “STATE_WAIT_LOCK” the auto focus state will be checked for focus lock.

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

      private void process(CaptureResult result) {
          switch(mState) {
              case STATE_PREVIEW:
                  // Do nothing
                  break;
              case STATE__WAIT_LOCK:
                  Integer afState = result.get(CaptureResult.CONTROL_AF_STATE);
                  if(afState == CaptureRequest.CONTROL_AF_STATE_FOCUSED_LOCKED) {
                      unLockFocus();
                      Toast.makeText(getApplicationContext(), "Focus Lock Successful", Toast.LENGTH_SHORT).show();
                  }
                  break;
          }
      }
      @Override
      public void onCaptureStarted(CameraCaptureSession session, CaptureRequest request, long timestamp, long frameNumber) {
          super.onCaptureStarted(session, request, timestamp, frameNumber);
      }

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

          process(result);
      }

      @Override
      public void onCaptureFailed(CameraCaptureSession session, CaptureRequest request, CaptureFailure failure) {
          super.onCaptureFailed(session, request, failure);

          Toast.makeText(getApplicationContext(), "Focus Lock Unsuccessful", Toast.LENGTH_SHORT).show();
      }
  };

Create lockFocus & unLockFocus methods

private void lockFocus() {
       try {
           mState = STATE__WAIT_LOCK;
           mPreviewCaptureRequestBuilder.set(CaptureRequest.CONTROL_AF_TRIGGER,
                   CaptureRequest.CONTROL_AF_TRIGGER_START);
           mCameraCaptureSession.capture(mPreviewCaptureRequestBuilder.build(),
                   mSessionCaptureCallback, mBackgroundHandler);
       } catch (CameraAccessException e) {
           e.printStackTrace();
       }
   }

   private void unLockFocus() {
       try {
           mState = STATE_PREVIEW;
           mPreviewCaptureRequestBuilder.set(CaptureRequest.CONTROL_AF_TRIGGER,
                   CaptureRequest.CONTROL_AF_TRIGGER_CANCEL);
           mCameraCaptureSession.capture(mPreviewCaptureRequestBuilder.build(),
                   mSessionCaptureCallback, mBackgroundHandler);
       } catch (CameraAccessException e) {
           e.printStackTrace();
       }
   }

Call the lockFocus from the takePhoto method

public void takePhoto(View view) {
          lockFocus();
  }