AndroidTagGroup实现云标签效果，各种背景效果的标签，并且支持添加，
大体实现：有一个TagsManager管理TagGroup，自定义TagGroup，对TagGroup设置setTags(tags);
TagGroup extends ViewGroup，TagGroup 由多个TagView组成，TagView继承TextView 。
本例子来源：https://github.com/2dxgujun/AndroidTagGroup
主要绘制代码如下：
   @Override
        protected void onDraw(Canvas canvas) {
            canvas.drawArc(mLeftCornerRectF, -180, 90, true, mBackgroundPaint);
            canvas.drawArc(mLeftCornerRectF, -270, 90, true, mBackgroundPaint);
            canvas.drawArc(mRightCornerRectF, -90, 90, true, mBackgroundPaint);
            canvas.drawArc(mRightCornerRectF, 0, 90, true, mBackgroundPaint);
            canvas.drawRect(mHorizontalBlankFillRectF, mBackgroundPaint);
            canvas.drawRect(mVerticalBlankFillRectF, mBackgroundPaint);

            if (isChecked) {
                canvas.save();
                canvas.rotate(45, mCheckedMarkerBound.centerX(), mCheckedMarkerBound.centerY());
                canvas.drawLine(mCheckedMarkerBound.left, mCheckedMarkerBound.centerY(),
                        mCheckedMarkerBound.right, mCheckedMarkerBound.centerY(), mCheckedMarkerPaint);
                canvas.drawLine(mCheckedMarkerBound.centerX(), mCheckedMarkerBound.top,
                        mCheckedMarkerBound.centerX(), mCheckedMarkerBound.bottom, mCheckedMarkerPaint);
                canvas.restore();
            }
            canvas.drawPath(mBorderPath, mBorderPaint);
            super.onDraw(canvas);
        }