@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
    int resWidth = 0;
    int resHeight = 0;
    int width = MeasureSpec.getSize(widthMeasureSpec);
    int widthMode = MeasureSpec.getMode(widthMeasureSpec);
    int height = MeasureSpec.getSize(heightMeasureSpec);
    int 
 
heightMode = MeasureSpec.getMode(heightMeasureSpec);
    if (widthMode != MeasureSpec.EXACTLY || heightMode != MeasureSpec.EXACTLY) {
        //如果不是精確值對應的處理
resWidth = getSuggestedMinimumWidth();//取背景圖的寬度
resWidth = resWidth == 0 ? getDefaultWidht() : resWidth;
resHeight = getSuggestedMinimumHeight();
resHeight = resHeight == 0 
 
? getDefaultWidht() : resHeight;
} else {
        //如果是精確值，則取寬和高中值小的
resWidth = resHeight = Math.min(width, height);
}
    setMeasuredDimension(resWidth, resHeight);
//獲得半徑
mRadius = Math.max(getMeasuredWidth(), getMeasuredHeight());
//menu item個數
final int childCount = getChildCount();
//menu item 尺寸
int childSize = (int
 
) (mRadius * RADIO_DEFAULT_CHILD_DIMENSION);
    int childMode = MeasureSpec.EXACTLY;
//迭代測量
for (int i = 0; i < childCount; i++) {

        final View child = getChildAt(i);
        if (child.getVisibility() == GONE) {
            continue;
}

        //測量menu item
int makeMeasureSpec = -1;
        if (child.getId() == R.id.id_circle_menu_item_center) {
            makeMeasureSpec = MeasureSpec.makeMeasureSpec((int) (mRadius * RADIO_DEFAULT_CENTERITEM_DIMENSION), childMode);
} else {
            makeMeasureSpec = MeasureSpec.makeMeasureSpec(childSize, childMode);
}
        child.measure(makeMeasureSpec, makeMeasureSpec);
}

    mPadding = (int) (RADIO_PADDING_LAYOUT * mRadius);
}