How to create a 'transparent circle inside rectangle' shape in XML in Android?

Question

I\'m trying to create the following design in my app.

Design Mockup

Its an overlay on top of the main UI. Trying to create this using a layout on top o

Answer 1

I ran into such a problem that code does not work on api lvl 16 from NSimon. I fixed the code and now it supports api 16+.

public class FocusView extends View {
    private Paint mPaint;
    private Paint mStrokePaint;
    private Path mPath = new Path();

    public FocusView(Context context) {
        super(context);
        initPaints();
    }

    public FocusView(Context context, AttributeSet attrs) {
        super(context, attrs);
        initPaints();
    }

    public FocusView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        initPaints();
    }

    private void initPaints() {
        mPaint = new Paint();
        mPaint.setColor(Color.parseColor("#A6000000"));

        mStrokePaint = new Paint();
        mStrokePaint.setColor(Color.YELLOW);
        mStrokePaint.setStrokeWidth(2);
        mStrokePaint.setStyle(Paint.Style.STROKE);

    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        mPath.reset();

        float radius = 0;
        float strokeWidth = 0;
        if (canvas.getWidth() < canvas.getHeight()) {
            radius = canvas.getWidth() / 2 - 10;
            strokeWidth = (canvas.getHeight() - canvas.getWidth())/2;
        } else {
            radius = canvas.getHeight() / 2 - 10;
            strokeWidth = (canvas.getWidth() - canvas.getHeight())/2;
        }

        mPaint.setStrokeWidth(strokeWidth);

        mPath.addCircle(canvas.getWidth() / 2, canvas.getHeight() / 2, radius, Path.Direction.CW);
        mPath.setFillType(Path.FillType.INVERSE_EVEN_ODD);

        canvas.drawCircle(canvas.getWidth() / 2, canvas.getHeight() / 2, radius, mStrokePaint);

        canvas.drawPath(mPath, mPaint);
    }
}