View的getWidth/getHeight与getMeasuredWidth/getMeasuredHeight的区别

转载自http://blog.youkuaiyun.com/u010852801/article/details/45670571

某个View的显示流程是这样的：

Activity.onCreate–>Activity.onStart–>Activity.onResume–>image.onMeasure–>image.onLayout–>onGlobalLayoutListener–>Activity.onWindowFocusChanged–>….–>image.onDraw

onWindowFocusChanged是当activity可见时的调用的，在此之前的函数中调用View.getWidth/getHeight得到的是0，onWindowFocusChanged函数中获View.getWidth/getHeight是合适的。getWidth/getHeight一般是控件添加到Activity之后，显示到屏幕中的实际宽度。而View.getMeasureWidth/getMeasureHeight是配合view.measure使用的，如果未调用View.measure，那么调用view.getMeasureWidth的效果和View.getWidth一样。

如果我们要在onWindowFocusChanged之前的函数，如onCreate中获得View的宽度/高度，有如下三种方法：

方法一：

[java] view plain copy

print ?

1. int width =View.MeasureSpec.makeMeasureSpec(0,View.MeasureSpec.UNSPECIFIED);  
2. int height =View.MeasureSpec.makeMeasureSpec(0,View.MeasureSpec.UNSPECIFIED);  
3. view.measure(width,height);  
4. int height=view.getMeasuredHeight();   
5. int width=view.getMeasuredWidth();  

int width =View.MeasureSpec.makeMeasureSpec(0,View.MeasureSpec.UNSPECIFIED);
int height =View.MeasureSpec.makeMeasureSpec(0,View.MeasureSpec.UNSPECIFIED);
view.measure(width,height);
int height=view.getMeasuredHeight(); 
int width=view.getMeasuredWidth();

方法二：
//增加组件绘制之前的监听

[java] view plain copy

print ?

1. ViewTreeObserver vto =view.getViewTreeObserver();   
2. vto.addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener() {   
3.    @Override  
4.    public boolean onPreDraw() {   
5.      int height =view.getMeasuredHeight();   
6.      int width =view.getMeasuredWidth();       
7.    }  
8. });  

ViewTreeObserver vto =view.getViewTreeObserver(); 
vto.addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener() { 
   @Override
   public boolean onPreDraw() { 
     int height =view.getMeasuredHeight(); 
     int width =view.getMeasuredWidth();     
   }
});

方法三：
//增加整体布局监听

[java] view plain copy

print ?

1. ViewTreeObserver vto = view.getViewTreeObserver();    
2. vto.addOnGlobalLayoutListener(new OnGlobalLayoutListener(){   
3.     @Override   
4.     public void onGlobalLayout() {  
5.       view.getViewTreeObserver().removeGlobalOnLayoutListener(this);       
6.       int height =view.getMeasuredHeight();   
7.       int width =view.getMeasuredWidth();    
8.     }   
9. });  

ViewTreeObserver vto = view.getViewTreeObserver();  
vto.addOnGlobalLayoutListener(new OnGlobalLayoutListener(){ 
    @Override 
    public void onGlobalLayout() {
      view.getViewTreeObserver().removeGlobalOnLayoutListener(this);     
      int height =view.getMeasuredHeight(); 
      int width =view.getMeasuredWidth();  
    } 
});