错误:Only the original thread that created a view hierarchy can touch its views——Handler的使用

今天写了一个更新UI的小例子,没想到出了log打印了这样一个错误:Only the original thread that created a view hierarchy can touch its views。goolgle了一下找到了原因。

原来android中相关的view和控件不是线程安全的,我们必须单独做处理。这里借此引出Handler的使用。

 

 Handler的官方描述:


A Handler allows you to send and process Message and Runnable objects associated with a thread’s MessageQueue. Each Handler instance is associated with a single thread and that thread’s message queue. When you create a new Handler, it is bound to the thread / message queue of the thread that is creating it — from that point on, it will deliver messages and runnables to that message queue and execute them as they come out of the message queue


.Handler的使用场合:

 

1、 to schedule messages and runnables to be executed as some point in the future;

      安排messages和runnables在将来的某个时间点执行。

2、 to enqueue an action to be performed on a different thread than your own.

      将action入队以备在一个不同的线程中执行。即可以实现线程间通信。比如当你创建子线程时,你可以再你的子线程中拿到父线程中创建的Handler对象,就可以通过该对象向父线程的消息队列发送消息了。由于Android要求在UI线程中更新界面,因此,可以通过该方法在其它线程中更新界面。


通过Handler更新UI实例:

步骤:

1、创建Handler对象(此处创建于主线程中便于更新UI)。

2、构建Runnable对象,在Runnable中更新界面。

3、在子线程的run方法中向UI线程post,runnable对象来更新UI。

 

详细代码如下:

*java线程的详细讲解链接

 

转自:http://blog.csdn.net/djx123456/article/details/6325983

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