Android中实现view的更新UI有两组方法的问题

Android中实现view的更新有两组方法,

一组是invalidate,另一组是postInvalidate,其中前者是在UI线程自身中使用,而后者在非UI线程中使用。

SDK中说:

public void invalidate()
Invalidate the whole view. If the view is visible, onDraw(Canvas) will be called at some point in the future. This must be called from a UI thread. To call from a non-UI thread, call postInvalidate().

public void postInvalidate ()
Cause an invalidate to happen on a subsequent cycle through the event loop. Use this to invalidate the View from a non-UI thread.

google的文档的说明实在是简单,往往看了开发中都会遇到这两个问题:
1. 没有任何异常,view没能刷新。
2. android应用异常终止,打开logcat会看到这样的异常信息, Only the original thread that created a view hierarchy can touch its views。

最后,通过查文档,上网查询才知道,invalidate和postInvalidate方法需要使用android提供的handler,才能实现重绘 ,而在文档的说明中却只字不提,真是简单啊。具体是在需要重绘的地方调用handler的sendMessage方法发送消息,紧接着会os会触发 handler中的handlerMessage方法,在handlerMessage方法中再调用view的invalidate或者 postInvalidate方法就能实现重绘。

class CustomizeView extends WhichView {  
 
    public CustomizeView(Context context) {  
        super(context);  
        final Handler handler = new Handler();  
 
        new Thread(new Runnable() {  
            @Override 
            public void run() {  
                // delay some minutes you desire.  
                /*try { 
                    Thread.sleep(3000); 
                } catch (InterruptedException e) { 
                }*/ 
                handler.post(new Runnable() {  
                    public void run() {  
                        concreteUpdateUI();  
                        invalidate();  
                    }  
                });  
            }  
        }).start();  
    }  
 
    protected void concreteUpdateUI() {  
        // Add concrete movement for UI updates.  
        // ...  
    }  

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