Activity中获取view的高度和宽度为0的原因以及解决方案

在activity中可以调用View.getWidth、View.getHeight()、View.getMeasuredWidth() 、View.getgetMeasuredHeight()来获得某个view的宽度或高度，但是在onCreate()、onStrart()、onResume()方法中会返回0，这是应为当前activity所代表的界面还没显示出来没有添加到WindowPhone的DecorView上或要获取的view没有被添加到DecorView上或者该View的visibility属性为gone 或者该view的width或height真的为0 所以只有上述条件都不成立时才能得到非0的width和height

所以要想获取到的width和height为真实有效的则有以下方法

1.在该View的事件回调里使用这时候该view已经被显示即被添加到DecorView上如点击事件触摸事件焦点事件等

1 View view=findViewById(R.id.tv);  
2     view.setOnClickListener(new OnClickListener() {  
3           
4         @Override  
5         public void onClick(View v) {  
6             int width = v.getWidth();  
7         }  
8     });

2.在activity被显示出来时即添加到了DecorView上时获取宽和高如onWindowFocusChanged() 回调方法

 1 @Override  
 2   public void onWindowFocusChanged(boolean hasFocus) {  
 3     View iv1 = findViewById(R.id.iv1);  
 4 View iv2=findViewById(R.id.iv2);  
 5 String msg1="iv1' width:"+iv1.getWidth()+" height:"+iv1.getHeight()+"  measuredWidth:"+iv1.getMeasuredWidth()+"measuredHeight:"+iv1.getMeasuredHeight();  
 6 String msg2="iv2' width:"+iv2.getWidth()+" height:"+iv2.getHeight()+"  measuredWidth:"+iv2.getMeasuredWidth()+"measuredHeight:"+iv2.getMeasuredHeight();  
 7 i("onWindowFocusChanged() "+msg1);  
 8 i("onWindowFocusChanged() "+msg2);  
 9     super.onWindowFocusChanged(hasFocus);  
10   }

3.或在onResume方法最后开线程300毫秒左右后获取宽和高因为onResume执行完后300毫秒后界面就显示出来了

当然地2种和地3种方法要保证获取宽高的view是在setContentView时设进去的View或它的子View

 1 view.postDelayed(new Runnable() {  
 2               
 3             @Override  
 4             public void run() {  
 5                 View iv1 = findViewById(R.id.iv1);  
 6                 View iv2=findViewById(R.id.iv2);  
 7                 String msg1="iv1' width:"+iv1.getWidth()+" height:"+iv1.getHeight()+"  measuredWidth:"+iv1.getMeasuredWidth()+"measuredHeight:"+iv1.getMeasuredHeight();  
 8                 String msg2="iv2' width:"+iv2.getWidth()+" height:"+iv2.getHeight()+"  measuredWidth:"+iv2.getMeasuredWidth()+"measuredHeight:"+iv2.getMeasuredHeight();  
 9                 i("onWindowFocusChanged() "+msg1);  
10                 i("onWindowFocusChanged() "+msg2);  
11             }  
12         }, 300);

4.在onCreate()或onResume()等方法中需要获取宽高时使用getViewTreeObserver().addOnGlobalLayoutListener()来添为view加回调在回调里获得宽度或者高度获取完后让view删除该回调

 1 view.getViewTreeObserver().addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {  
 2           
 3         @Override  
 4         public void onGlobalLayout() {  
 5             view.postDelayed(new Runnable() {  
 6                   
 7                 @Override  
 8                 public void run() {  
 9                     View iv1 = findViewById(R.id.iv1);  
10                     View iv2=findViewById(R.id.iv2);  
11                     String msg1="iv1' width:"+iv1.getWidth()+" height:"+iv1.getHeight()+"  measuredWidth:"+iv1.getMeasuredWidth()+"measuredHeight:"+iv1.getMeasuredHeight();  
12                     String msg2="iv2' width:"+iv2.getWidth()+" height:"+iv2.getHeight()+"  measuredWidth:"+iv2.getMeasuredWidth()+"measuredHeight:"+iv2.getMeasuredHeight();  
13                     i("onWindowFocusChanged() "+msg1);  
14                     i("onWindowFocusChanged() "+msg2);  
15                 }  
16             }, 300);  
17         }  
18     });

5.在窗口焦点发生变化时获取宽高 onResume完后就会把界面渲染到窗口上渲染完后将执行窗口焦点花生变化回调所以onResume到 onWindowFocusChanged为把界面渲染到窗口的时间

 1 boolean measure;  
 2     View iv1;  
 3     View iv2;  
 4     @Override  
 5     public void onWindowFocusChanged(boolean hasFocus) {  
 6         super.onWindowFocusChanged(hasFocus);  
 7         if(hasFocus && !measure){  
 8             measure=true;  
 9             measure();  
10         }  
11     }  
12     private void findViews(){  
13         iv1 = findViewById(R.id.iv1);  
14         iv2 =findViewById(R.id.iv2);  
15     }  
16     private void measure(){  
17         String msg1="iv1' width:"+iv1.getWidth()+" height:"+iv1.getHeight()+"  measuredWidth:"+iv1.getMeasuredWidth()+"measuredHeight:"+iv1.getMeasuredHeight();  
18         String msg2="iv2' width:"+iv2.getWidth()+" height:"+iv2.getHeight()+"  measuredWidth:"+iv2.getMeasuredWidth()+"measuredHeight:"+iv2.getMeasuredHeight();  
19         i("onWindowFocusChanged() "+msg1);  
20         i("onWindowFocusChanged() "+msg2);  
21     }