CornerView

public interface CornerView {
    int getCornerRadius();

    void setCornerRadius(int cornerRadius);
}

Implementation

    private int cornerRadius;
    private Path cornersMask;
    private static PorterDuffXfermode pdMode = new PorterDuffXfermode(PorterDuff.Mode.CLEAR);

    public int getCornerRadius() {
        return cornerRadius;
    }

    public void setCornerRadius(int cornerRadius) {
        this.cornerRadius = cornerRadius;
        invalidateShadow();
        initCorners();
    }

    @Override
    protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
        super.onLayout(changed, left, top, right, bottom);

        if (!changed)
            return;

        invalidateShadow();

        if (getWidth() == 0 || getHeight() == 0)
            return;

        initCorners();

        if (rippleDrawable != null)
            rippleDrawable.setBounds(0, 0, getWidth(), getHeight());
    }

    private void initCorners() {
        if (cornerRadius > 0) {
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
                setClipToOutline(true);
                setOutlineProvider(ShadowShape.viewOutlineProvider);
            } else {
                cornersMask = new Path();
                cornersMask.addRoundRect(new RectF(0, 0, getWidth(), getHeight()), cornerRadius, cornerRadius, Path.Direction.CW);
                cornersMask.setFillType(Path.FillType.INVERSE_WINDING);
            }
        } else if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP)
                setOutlineProvider(ViewOutlineProvider.BOUNDS);
        }
    }

    @Override
    public void draw(Canvas canvas) {
        if (cornerRadius > 0 && getWidth() > 0 && getHeight() > 0 && Build.VERSION.SDK_INT <= Build.VERSION_CODES.KITKAT_WATCH) {
            int saveFlags = Canvas.MATRIX_SAVE_FLAG | Canvas.CLIP_SAVE_FLAG | Canvas.HAS_ALPHA_LAYER_SAVE_FLAG | Canvas.FULL_COLOR_LAYER_SAVE_FLAG | Canvas.CLIP_TO_LAYER_SAVE_FLAG;
            int saveCount = canvas.saveLayer(0, 0, getWidth(), getHeight(), null, saveFlags);

            super.draw(canvas);
            if (rippleDrawable != null && rippleDrawable.getStyle() == RippleDrawable.Style.Over)
                rippleDrawable.draw(canvas);

            paint.setXfermode(pdMode);
            canvas.drawPath(cornersMask, paint);

            canvas.restoreToCount(saveCount);
            paint.setXfermode(null);
        } else {
            super.draw(canvas);
            if (rippleDrawable != null && rippleDrawable.getStyle() == RippleDrawable.Style.Over)
                rippleDrawable.draw(canvas);
        }
    }