Android setFocusArea and Auto Focus

Question

I've been battling with this feature for couple of days now...

It seems, that camera is ignoring(?) focus areas that I've defined. Here is snippets of the code:

Focusing:

protected void focusOnTouch(MotionEvent event) {
    if (camera != null) {
        Rect rect = calculateFocusArea(event.getX(), event.getY());

        Parameters parameters = camera.getParameters();
        parameters.setFocusMode(Parameters.FOCUS_MODE_AUTO);
        parameters.setFocusAreas(Lists.newArrayList(new Camera.Area(rect, 500)));

        camera.setParameters(parameters);
        camera.autoFocus(this);
    }
}

Focus area calculation:

private Rect calculateFocusArea(float x, float y) {
    int left = clamp(Float.valueOf((x / getSurfaceView().getWidth()) * 2000 - 1000).intValue(), focusAreaSize);
    int top = clamp(Float.valueOf((y / getSurfaceView().getHeight()) * 2000 - 1000).intValue(), focusAreaSize);

    return new Rect(left, top, left + focusAreaSize, top + focusAreaSize);
}

Couple of log events from Camera.AutoFocusCallback#onAutoFocus

Log.d(TAG, String.format("Auto focus success=%s. Focus mode: '%s'. Focused on: %s", focused, camera.getParameters().getFocusMode(), camera.getParameters().getFocusAreas().get(0).rect.toString()));

08-27 11:19:42.240: DEBUG/MyCameraActivity(26268): Auto focus success=true. Focus mode: 'auto'. Focused on: Rect(-109, 643 - -13, 739)
08-27 11:19:55.514: DEBUG/MyCameraActivity(26268): Auto focus success=true. Focus mode: 'auto'. Focused on: Rect(20, 457 - 116, 553)
08-27 11:19:58.037: DEBUG/MyCameraActivity(26268): Auto focus success=true. Focus mode: 'auto'. Focused on: Rect(-159, 536 - -63, 632)
08-27 11:20:00.129: DEBUG/MyCameraActivity(26268): Auto focus success=true. Focus mode: 'auto'. Focused on: Rect(-28, 577 - 68, 673)

Visually it looks like focus succeeds on logged area, but the suddenly it loses focus and focus on center (0, 0), or what takes bigger part of SurfaceView is obtained.

focusAreaSize used in calculation is about 210px (96dp). Testing on HTC One where Camera.getParameters().getMaxNumFocusAreas() is 1.

Initial focus mode (before first tap) is set to FOCUS_MODE_CONTINUOUS_PICTURE.

Am I doing something wrong here? Tinkering with Camera.Area rectangle size or weight doesn't show any noticeable effect.

Answer 1

My problem was much simpler :)

All I had to do is cancel previously called autofocus. Basically the correct order of actions is this:

protected void focusOnTouch(MotionEvent event) {
    if (camera != null) {

        camera.cancelAutoFocus();
        Rect focusRect = calculateTapArea(event.getX(), event.getY(), 1f);
        Rect meteringRect = calculateTapArea(event.getX(), event.getY(), 1.5f);

        Parameters parameters = camera.getParameters();
        parameters.setFocusMode(Parameters.FOCUS_MODE_AUTO);
        parameters.setFocusAreas(Lists.newArrayList(new Camera.Area(focusRect, 1000)));

        if (meteringAreaSupported) {
            parameters.setMeteringAreas(Lists.newArrayList(new Camera.Area(meteringRect, 1000)));
        }

        camera.setParameters(parameters);
        camera.autoFocus(this);
    }
}

Update

@Override
public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
    ...
    Parameters p = camera.getParameters();
    if (p.getMaxNumMeteringAreas() > 0) {
       this.meteringAreaSupported = true;
    }
    ...
}

/**
 * Convert touch position x:y to {@link Camera.Area} position -1000:-1000 to 1000:1000.
 */
private Rect calculateTapArea(float x, float y, float coefficient) {
    int areaSize = Float.valueOf(focusAreaSize * coefficient).intValue();

    int left = clamp((int) x - areaSize / 2, 0, getSurfaceView().getWidth() - areaSize);
    int top = clamp((int) y - areaSize / 2, 0, getSurfaceView().getHeight() - areaSize);

    RectF rectF = new RectF(left, top, left + areaSize, top + areaSize);
    matrix.mapRect(rectF);

    return new Rect(Math.round(rectF.left), Math.round(rectF.top), Math.round(rectF.right), Math.round(rectF.bottom));
}

private int clamp(int x, int min, int max) {
    if (x > max) {
        return max;
    }
    if (x < min) {
        return min;
    }
    return x;
}

Answer 2

Beside setting:

parameters.setFocusMode(Parameters.FOCUS_MODE_AUTO);

you need to set:

parameters.setFocusMode(Parameters.FOCUS_MODE_CONTINUOUS_PICTURE);

if you want real 'live' auto-focus. Also, it will be good to check available focuses:

List<String> focusModes = parameters.getSupportedFocusModes();
LLog.d("focusModes=" + focusModes);
if (focusModes.contains(Parameters.FOCUS_MODE_CONTINUOUS_PICTURE))
    parameters.setFocusMode(Parameters.FOCUS_MODE_CONTINUOUS_PICTURE);

On Samsung S6 you must set this with little delay (~ 500 ms) after getting camera preview.

Answer 3

use FOCUS_MODE_FIXED

if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.GINGERBREAD) {
        mCamera = Camera.open(mCameraId);
    } else {
        mCamera = Camera.open();
    }
cameraParams = mCamera.getParameters();
// set the focus mode
cameraParams.setFocusMode(Camera.Parameters.FOCUS_MODE_FIXED);
// set Camera parameters
mCamera.setParameters(cameraParams);

Answer 4

I had this problem today :/

And after hours of struggling, I found the solution!

It's strange, but it appears that setting focus-mode to "macro" right before setting focus-areas solved the problem ;)

params.setFocusMode(Camera.Parameters.FOCUS_MODE_MACRO);
params.setFocusAreas(focusAreas);
mCamera.setParameters(params);

I have Galaxy S3 with Android 4.1.2

I hope this will work for you either :)