獲取Android控件的寬和高

在oncreate()方法中獲取控件的寬高，只會獲得0，緣由是oncreate()方法執行完成後控件纔會被度量(measure)，因此咱們在onCreate方法裏面經過view.getHeight()獲取控件的高度或者寬度確定是0,由於它本身尚未被度量,也就是說他本身都不知道本身有多高,而你這時候去獲取它的尺寸,確定是不行的. 解決方法：

//------------------------------------------------方法一

<!-- lang: java -->

int w = View.MeasureSpec.makeMeasureSpec(0,View.MeasureSpec.UNSPECIFIED);  
int h = View.MeasureSpec.makeMeasureSpec(0,View.MeasureSpec.UNSPECIFIED);  
imageView.measure(w, h);  
int height =imageView.getMeasuredHeight();  
int width =imageView.getMeasuredWidth();  
textView.append("\n"+height+","+width);

//-----------------------------------------------方法二

<!-- lang: java -->

ViewTreeObserver vto = imageView.getViewTreeObserver();  
vto.addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener() {  
    public boolean onPreDraw() {  
        int height = imageView.getMeasuredHeight();  
        int width = imageView.getMeasuredWidth();  
        textView.append("\n"+height+","+width);  
        return true;  
    }  
});

//-----------------------------------------------方法三

<!-- lang: java -->

ViewTreeObserver vto2 = imageView.getViewTreeObserver();    
vto2.addOnGlobalLayoutListener(new OnGlobalLayoutListener() {  
    @Override    
    public void onGlobalLayout() {  
        imageView.getViewTreeObserver().removeGlobalOnLayoutListener(this);    
        textView.append("\n\n"+imageView.getHeight()+","+imageView.getWidth());  
    }    
});

方法一: 比其餘的兩個方法多了一次計算,也就是多調用了一次onMeasure()方法,該方法雖然看上去簡單,可是若是要目標控件計算耗時比較大的話(如listView等),不建議使用. 方法二,在繪製前執行回調方法，它的回調方法會調用不少次,而且滑動TextView的時候任然會調用,因此不建議使用. 方法三,當layout或控件的visibility被調用時，執行此回調

方法四：

<!-- lang: java -->
    private void measureItem(View child) {  
         ViewGroup.LayoutParams p = child.getLayoutParams();  
         if (p == null) {  
             p = new ViewGroup.LayoutParams(  
                     ViewGroup.LayoutParams.MATCH_PARENT,  
                     ViewGroup.LayoutParams.WRAP_CONTENT);  
         }  
   
         int childWidthSpec = ViewGroup.getChildMeasureSpec(mWidthMeasureSpec,  
                 mListPadding.left + mListPadding.right, p.width);  
         int lpHeight = p.height;  
         int childHeightSpec;  
         if (lpHeight > 0) {  
             childHeightSpec = MeasureSpec.makeMeasureSpec(lpHeight, MeasureSpec.EXACTLY);  
         } else {  
             childHeightSpec = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED);  
         }  
         child.measure(childWidthSpec, childHeightSpec);  
     }