Android - Rounded square line progress bar

I'm trying to create a rounded square line progress bar to draw a progress around an image.

So far, I have the following XML which defines my rounded square line:

<shape xmlns:android="http://schemas.android.com/apk/res/android" >

    <stroke
        android:width="6dp"
        android:color="@android:color/holo_green_light" />

    <padding
        android:left="5dp"
        android:right="5dp"
        android:bottom="5dp"
        android:top="5dp" />

    <corners android:radius="50dp" />

</shape>

I'm aware of this solution: https://github.com/mrwonderman/android-square-progressbar but I'm not interested in as the effect is not the one I want.

I've tried to create a plain circle on top of the rounded square line and tried to merge the two with PorterDuff, but so far I was also not able to create the progress bar effect. Drawing a pie of that circle to draw the progress.

I've also tried to create the rounded square programaticaly in case the XML inflating was considered as a plain image and all pixels were taken into account during the PorterDuff merge. But same result.

try this simple custom class:

class V extends View {
    Path path = new Path();
    Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);
    float length;
    float[] intervals = {0, 0};

    public V(Context context) {
        super(context);
        paint.setColor(Color.GREEN);
        paint.setStyle(Paint.Style.STROKE);
        paint.setStrokeWidth(20);
    }

    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        path.reset();
        RectF rect = new RectF(0, 0, w, h);
        float inset = paint.getStrokeWidth();
        rect.inset(inset, inset);

        path.addRoundRect(rect, 100, 100, Path.Direction.CW);
        length = new PathMeasure(path, false).getLength();
        intervals[0] = intervals[1] = length;
        PathEffect effect = new DashPathEffect(intervals, length);
        paint.setPathEffect(effect);
    }

    public void setProgress(int progress) {
        PathEffect effect = new DashPathEffect(intervals, length - length * progress / 100);
        paint.setPathEffect(effect);
        invalidate();
    }

    @Override
    protected void onDraw(Canvas canvas) {
        canvas.drawPath(path, paint);
    }
}

test code (put in inside Activity#onCreate):

    LinearLayout ll = new LinearLayout(this);
    ll.setOrientation(LinearLayout.VERTICAL);
    SeekBar sb = new SeekBar(this);
    ll.addView(sb);
    final V v = new V(this);
    ll.addView(v);
    setContentView(ll);

    SeekBar.OnSeekBarChangeListener sbcl = new SeekBar.OnSeekBarChangeListener() {
        @Override
        public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
            v.setProgress(progress);
        }
        @Override public void onStartTrackingTouch(SeekBar seekBar) {}
        @Override public void onStopTrackingTouch(SeekBar seekBar) {}
    };
    sb.setOnSeekBarChangeListener(sbcl);