Evil implementation to rounded corner containers.

attrs.xml

<resources>
    
    <declare-styleable name="MaskView">
        <attr name="maskColor" format="color" />
        <attr name="borderColor" format="color" />
        <attr name="cornerRadius" format="dimension" />
        <attr name="maskShape" format="enum">
            <enum name="rounded_rectangle" value="0" />
            <enum name="oval" value="1" />
        </attr>
        <attr name="borderWidth" format="dimension" />
    </declare-styleable>

</resources>

MaskView.java

package com.tietie.foundation.view;

import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.PorterDuff;
import android.graphics.PorterDuffXfermode;
import android.graphics.RectF;
import android.util.AttributeSet;
import android.view.View;

import com.tietie.foundation.R;

public class MaskView extends View {

    public static final int SHAPE_ROUNDED_RECTANGLE = 0;
    public static final int SHAPE_OVAL = 1;

    private int mMaskColor;

    private int mBorderColor;
    private int mBorderWidth;
    private int mCornerRadius;
    private int mMaskShape;

    private RectF mDrawingRect;

    private Paint mPaintEraser;
    private Paint mPaintBorder;

    private Bitmap mDrawingCache;
    private Canvas mDrawingCanvas;

    public MaskView(Context context) {
        super(context);
    }

    public MaskView(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public MaskView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);

        TypedArray a = context.getTheme().obtainStyledAttributes(
                attrs,
                R.styleable.MaskView,
                0, 0);

        try {
            mMaskShape = a.getInt(R.styleable.MaskView_maskShape, SHAPE_ROUNDED_RECTANGLE);
            mMaskColor = a.getColor(R.styleable.MaskView_maskColor, Color.WHITE);
            mBorderColor = a.getColor(R.styleable.MaskView_borderColor, Color.GRAY);
            mBorderWidth = a.getDimensionPixelSize(R.styleable.MaskView_borderWidth, 0);
            mCornerRadius = a.getDimensionPixelSize(R.styleable.MaskView_cornerRadius, 0);
        } finally {
            a.recycle();
        }

        mPaintEraser = new Paint() {{
            this.setAntiAlias(true);
            this.setColor(Color.WHITE);
            this.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR));
        }};

        mPaintBorder = new Paint() {{
            this.setColor(mBorderColor);
            setStrokeWidth(mBorderWidth);
            this.setStyle(Style.STROKE);
        }};

    }

    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        super.onSizeChanged(w, h, oldw, oldh);

        mDrawingRect = new RectF(getPaddingLeft(), getPaddingTop(),
                w - getPaddingLeft() - getPaddingRight(),
                h - getPaddingTop() - getPaddingBottom());

        if (mDrawingCache != null) {
            mDrawingCache.recycle();
        }

        mDrawingCache = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888);
        mDrawingCanvas = new Canvas(mDrawingCache);

        mDrawingCache.eraseColor(mMaskColor);

        switch (mMaskShape) {
            case SHAPE_ROUNDED_RECTANGLE:
                mDrawingCanvas.drawRoundRect(mDrawingRect, mCornerRadius, mCornerRadius, mPaintEraser);
                if (mBorderWidth > 0) {
                    mDrawingCanvas.drawRoundRect(mDrawingRect, mCornerRadius, mCornerRadius, mPaintBorder);
                }
                break;
            case SHAPE_OVAL:
                mDrawingCanvas.drawOval(mDrawingRect, mPaintEraser);
                if (mBorderWidth > 0) {
                    mDrawingCanvas.drawOval(mDrawingRect, mPaintBorder);
                }
                break;
        }
    }

    @Override
    protected void onDraw(Canvas canvas) {
        canvas.drawBitmap(mDrawingCache, 0, 0, null);
    }

}