自定義ViewGroup的基本流程

重寫兩個方法和LayoutParams

onMeasure()
通過measureChildren()來通知每一個子View自己測量（遍歷子View）卖陵。我們只需要考慮ViewGroup的寬高在自適應的情況下該是多大。

@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
    super.onMeasure(widthMeasureSpec,heightMeasureSpec);
    MarginLayoutParams params = null;//布局參數(shù)
    int widthMode = MeasureSpec.getMode(widthMeasureSpec);//測量兩元素Mode和Size
    int widthSize = MeasureSpec.getSize(widthMeasureSpec);
    int heightMode = MeasureSpec.getMode(heightMeasureSpec);
    int heightSize = MeasureSpec.getSize(heightMeasureSpec);
    measureChildren(widthMeasureSpec,heightMeasureSpec);//遍歷子View

    //開始處理wrap_content,如果一個子元素都沒有，就設置為0
    if (getChildCount() == 0) {
        setMeasuredDimension(0,0);
    } else if (widthMode == MeasureSpec.AT_MOST && heightMode == MeasureSpec.AT_MOST) {
        //ViewGroup麻诀，寬掌动，高都是wrap_content糙麦，根據(jù)我們的需求吆鹤，寬度是子控件的寬度宝泵，高度則是所有子控件的總和
        View childOne = getChildAt(0);
        params = (MarginLayoutParams) childOne.getLayoutParams();
        int childWidth = childOne.getMeasuredWidth();
        int childHeight = childOne.getMeasuredHeight();
        setMeasuredDimension(childWidth + params.leftMargin + params.rightMargin,
                childHeight * getChildCount() + params.topMargin + params.bottomMargin);

    } else if (widthMode == MeasureSpec.AT_MOST) {
        //ViewGroup的寬度為wrap_content,則高度不需要管好啰，寬度還是自控件的寬度
        View childOne = getChildAt(0);
        params = (MarginLayoutParams) childOne.getLayoutParams();
        int childWidth = childOne.getMeasuredWidth();
        setMeasuredDimension(childWidth + params.leftMargin + params.rightMargin,heightSize);
    } else if (heightMode == MeasureSpec.AT_MOST) {
        //ViewGroup的高度為wrap_content,則寬度不需要管，高度為子View的高度和
        View childOne = getChildAt(0);
        params = (MarginLayoutParams) childOne.getLayoutParams();
        int childHeight = childOne.getMeasuredHeight();
        setMeasuredDimension(widthSize, childHeight * getChildCount() + params.topMargin + params.bottomMargin);
    }
}

onLayout()
擺放子View的位置

protected void onLayout(boolean changed, int l, int t, int r, int b) {
    int height = 0;
    int count = getChildCount();
    View child;
    Log.e("ri", count + "");
    child = getChildAt(0);
    MarginLayoutParams params = (MarginLayoutParams) child.getLayoutParams();
    int c1 = params.leftMargin;
    int c2 = params.topMargin;
    int c3 = c1 + child.getMeasuredWidth();
    int c4 = c2 + child.getMeasuredHeight();
    child.layout(c1,c2, c3,c4);
    height = c4 + params.bottomMargin;
    for(int i = 1 ;i < count;i++) {
        child = getChildAt(i);
        child.layout(c1, height, c3, height + child.getMeasuredHeight());
        height += child.getMeasuredHeight();
    }
}

params = (MarginLayoutParams) child.getLayoutParams();如果重寫layoutParams相關的代碼儿奶，這樣直接轉(zhuǎn)換會出現(xiàn)問題框往，所以需要重寫下面的代碼:返回MarginLayoutParams類型的對象。

@Override
public LayoutParams generateLayoutParams(AttributeSet attrs) {
    return new MarginLayoutParams(getContext(),attrs);
}
@Override
protected LayoutParams generateDefaultLayoutParams() {
    return new MarginLayoutParams(LayoutParams.MATCH_PARENT,
            LayoutParams.MATCH_PARENT);
}
@Override
protected LayoutParams generateLayoutParams(LayoutParams p) {
    return new MarginLayoutParams(p);
}

onTouchEvent 響應時間