Manual Focus using android camera2 API

Question

I want to develop an Android Camera App for myself (can share it if there are interested people) that has a manual focus while video recording.

I've added a SeekBar to the google sample Camera2 app but I can't find the way to implement the manual focus.

I found Manual focus in camera2, android but it doesn't work on my LG G4. The stock camera app is almost perfect since it doesn't allow the manual focus in video mode.

Does anyone of you have an idea ?

EDIT: here's the code of the SeekBar listener:

@Override
public void onStopTrackingTouch(SeekBar seekBar) {}

@Override
public void onStartTrackingTouch(SeekBar seekBar) {
    mPreviewBuilder.set(CaptureRequest.CONTROL_AF_MODE, CameraMetadata.CONTROL_AF_MODE_OFF);
}

@Override
public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
    float minimumLens = characteristics.get(CameraCharacteristics.LENS_INFO_MINIMUM_FOCUS_DISTANCE);
    float num = (((float)progress) * minimumLens / 100);
    mPreviewBuilder.set(CaptureRequest.LENS_FOCUS_DISTANCE, num);
}

Answer 1

You need to check if the device you're running on actually supports manual controls in camera2.

The key is whether the available capabilities of the camera device lists MANUAL_SENSOR. If so, then you can control the lens by setting the autofocus mode to OFF, and then setting the lens focus distance to your desired value. If MANUAL_SENSOR is not listed, then the device very likely doesn't support manual focus control (Some manufacturers use private interfaces for their default camera app to implement manual focus control, unfortunately).

These should all go into the repeating request you're using to control preview.

Answer 2

Eddy Talvala described everything correctly in his answer, but if you still feel complicated, here is a code snippet that sets focus to infinity (which has value 0f):

CameraCharacteristics characteristics = manager.getCameraCharacteristics(cameraId);
int[] capabilities = characteristics
    .get(CameraCharacteristics.REQUEST_AVAILABLE_CAPABILITIES);

boolean isManualFocusSupported = IntStream.of(capabilities)
    .anyMatch(x -> x == CameraCharacteristics.REQUEST_AVAILABLE_CAPABILITIES_MANUAL_SENSOR);

if (isManualFocusSupported) {
    previewBuilder.set(CaptureRequest.CONTROL_AF_MODE, CaptureRequest.CONTROL_AF_MODE_OFF);
    previewBuilder.set(CaptureRequest.LENS_FOCUS_DISTANCE, 0f);
}