Android camera2 tap to focus

Question

Trying to implement tap to focus using camera2api.

    CaptureRequest.Builder afBuilder = mPreviewBuilder;

    Rect newRect=new Rect(0,0,200,200);
    MeteringRectangle meteringRectangle=new MeteringRectangle(newRect,METERING_WEIGHT_DONT_CARE);

    MeteringRectangle[] areas = afBuilder.get(CaptureRequest.CONTROL_AF_REGIONS);

    mPreviewBuilder.set(CaptureRequest.CONTROL_AF_REGIONS,areas);
    mPreviewBuilder.set(CaptureRequest.CONTROL_AF_MODE, CameraMetadata.CONTROL_AF_MODE_AUTO);
    mPreviewBuilder.set(CaptureRequest.CONTROL_AF_TRIGGER, CameraMetadata.CONTROL_AF_TRIGGER_START);
    mPreviewSession.setRepeatingRequest(mPreviewBuilder.build(), mCaptureCallback, mBackgroundHandler);

In my call back I am continuously getting stuck in an ACTIVE_SCAN state and occasionally goes into FOCUS_NOT_LOCKED state. I can never seem to get into a FOCUS_LOCKED state and the preview never look focused.

Using a samsung galaxy note 3.

I'm fetching `java.lang.IllegalArgumentException: rect.left must be nonnegative`. could you please guide me! — Kishore Jethava, Dec 19 '16 at 10:53
Might be worth starting a new question on this. Do you have any more information on the issue, code sample etc.? — YRfree Developers, Dec 22 '16 at 09:25
Solved using `SENSOR_INFO_ACTIVE_ARRAY_SIZE`. I had mixed old Camera code with new `Camera2` `MeteringRectangle` — Kishore Jethava, Dec 22 '16 at 09:37

score 2 · Accepted Answer · answered Oct 04 '16 at 17:36

2

For one, you're not actually setting an AF region - you're just reusing the default region from mPreviewBuilder.

Second, even if you set the region to [(0,0,200,200), METERING_WEIGHT_DONT_CARE], that's the top-left corner of the image, and probably not what you want?

Third, and most importantly, you're setting the AF trigger to be repeating. This means that on every frame, you're asking the camera to restart focusing. So it will never complete, because you never let it.

You need to set AF_TRIGGER to START for only a single capture; you'll still want to set the AF_REGION and AF_MODE on repeating request to be consistent through the whole AF scan you're starting.

answered Oct 04 '16 at 17:36

Eddy Talvala

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Thanks. Yeah the rectangles were more of an example for this post. I will try sorting the trigger though, this is for recording video app just to put it into some context. – YRfree Developers Oct 05 '16 at 08:24
Thank you so much it was the repeating trigger issue! – YRfree Developers Oct 05 '16 at 08:51
@YRfreeDevelopers could you kindly update the OP with the code of the fix? – DevonRyder Apr 07 '17 at 14:20
@Eddy Talvala, So i can't set the region manually using coordinates? – Iqbal hossain Aug 29 '18 at 11:32

Android camera2 tap to focus

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