快速瞭解Android onMeasure() onLayout()

標籤：android   onmeasure   onlayout   

通過重寫ViewGroup學習onMeasure() onLayout()方法

@Override

protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
   //擷取模式和大小，邊界參數共有3種模式：UNSPECIFIED一般為0, EXACTLY準確尺寸, AT_MOST自適應尺寸  
int w_mode = MeasureSpec.getMode(widthMeasureSpec);
int w_size = MeasureSpec.getSize(widthMeasureSpec);
int h_mode = MeasureSpec.getMode(heightMeasureSpec);
int h_size = MeasureSpec.getSize(heightMeasureSpec);
//計算自訂的所有子控制項的大小  
 measureChildren(widthMeasureSpec, heightMeasureSpec);
//通知父控制項，寬高需要多大地方放置子控制項
//setMeasuredDimension(resolveSize(size, widthMeasureSpec),resolveSize(size, heightMeasureSpec));
setMeasuredDimension(w_size, h_size);
Log.e("onMeasure","寬mode=" + w_mode + "寬size="+ w_size
+ "高mode=" + h_mode+ "高size=" +h_size);
// super.onMeasure(widthMeasureSpec,heightMeasureSpec);

}

//onLayout是為了指定視圖的顯示位置，方法執行的前後順序是在onMeasure之後，因為視圖肯定是只有知道大小才能指定位置放置
@Override  
    protected void onLayout(boolean changed, int l, int t, int r, int b) {  
        // 記錄總高度  
        int mTotalHeight = 0;  
        // 遍曆所有子視圖  
        int childCount = getChildCount();  
        for (int i = 0; i < childCount; i++) {  
            View childView = getChildAt(i);  
            // 擷取在onMeasure中計算的視圖尺寸  
            int measureHeight = childView.getMeasuredHeight();  
            int measuredWidth = childView.getMeasuredWidth();  
  
            childView.layout(l, mTotalHeight, measuredWidth, mTotalHeight   + measureHeight);  
            mTotalHeight += measureHeight;  
        }  
    }

快速瞭解Android onMeasure() onLayout()