自定義ViewGroup 支持Margin

通常自定義VIewGroup步驟:
1.繼承ViewGroup
2.重寫onMeasure
3.重寫onLayout
4.重寫onDraw

此時,MarginLayoutParams cParams = (MarginLayoutParams) view1.getLayoutParams();會報異常
異常內容爲:

java.lang.ClassCastException: android.view.ViewGroup$LayoutParams cannot be cast to android.view.ViewGroup$MarginLayoutParams

因此要支持Margin還有必須 重寫generateLayoutParams方法
實例 :

@Override
    public ViewGroup.LayoutParams generateLayoutParams(AttributeSet attrs)
    {
        return new MarginLayoutParams(getContext(), attrs);
    }

這樣就能夠支持Margin 進行操做了