解析:繼承ViewGroup後的子類如何重寫onMeasure方法

1.首先貼上我試驗成功的代碼
復制代碼 代碼如下:
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {

         int measureWidth = MeasureSpec.getSize(widthMeasureSpec);
         int measureHeigth = MeasureSpec.getSize(heightMeasureSpec);
         setMeasuredDimension(measureWidth, measureHeigth);
         // TODO Auto-generated method stub
         for(int i= 0;i<getChildCount();i++){
             View v = getChildAt(i);
             Log.v(TAG, "measureWidth is " +v.getMeasuredWidth() + "measureHeight is "+v.getMeasuredHeight());
             int widthSpec = 0;
             int heightSpec = 0;
             LayoutParams params = v.getLayoutParams();
             if(params.width > 0){
                 widthSpec = MeasureSpec.makeMeasureSpec(params.width, MeasureSpec.EXACTLY);
             }else if (params.width == -1) {
                 widthSpec = MeasureSpec.makeMeasureSpec(measureWidth, MeasureSpec.EXACTLY);
             } else if (params.width == -2) {
                 widthSpec = MeasureSpec.makeMeasureSpec(measureWidth, MeasureSpec.AT_MOST);
             }

             if(params.height > 0){
                 heightSpec = MeasureSpec.makeMeasureSpec(params.height, MeasureSpec.EXACTLY);
             }else if (params.height == -1) {
                 heightSpec = MeasureSpec.makeMeasureSpec(measureHeigth, MeasureSpec.EXACTLY);
             } else if (params.height == -2) {
                 heightSpec = MeasureSpec.makeMeasureSpec(measureWidth, MeasureSpec.AT_MOST);
             }
             v.measure(widthSpec, heightSpec);

         }
     }

解釋一下：
首先判斷params.width的值是多少，有三種情況。
如果是大於零的話，及傳遞的就是一個具體的值，那麼，構造MeasupreSpec的時候可以直接用EXACTLY。
如果為-1的話，就是MatchParent的情況，那麼，獲得父View的寬度，再用EXACTLY來構造MeasureSpec。
如果為-2的話，就是wrapContent的情況，那麼，構造MeasureSpec的話直接用一個負數就可以了。