在Android平台下,进行多线程编程时,经常需要在主线程之外的一个单独的线程中进行某些处理,然后更新用户界面显示。但是,在主线线程之外的线程中直接更新页面显示的问题是
报异常:android.view.ViewRoot$CalledFromWrongThreadException:
Only the original thread that created a view hierarchy can touch its
views.
【只有原始创建这个视图层次(view hierachy)的线程才能修改它的视图(view)】
也就是说必须在一般必须在程序的主线程(也就是ui)线程中进行更新界面显示的工作。可以采用下面的方法之一来解决:
法1:
在Activity.onCreate(Bundle savedInstanceState)中创建一个Handler类的实例,
在这个Handler实例的handleMessage回调函数中调用更新界面显示的函数。
/**
* 启动线程用来刷新登录提示文字,N秒刷新一次
*
*/
private class FreshWordsThread extends Thread
{
@Override
public void run()
{
try
{
mLoadingWords = "test";
mLoadhandler.sendEmptyMessage(REFRESH);
}
catch (InterruptedException e)
{
e.printStackTrace();
Thread.currentThread().interrupt();
}
}
}
//主线程中的handler
class LoadHandler extends Handler
{
/**
* 接受子线程传递的消息机制
*/
@Override
public void handleMessage(Message msg)
{
super.handleMessage(msg);
int what = msg.what;
Log.i(TAG, "Main handler message code: " + what);
switch (what)
{
case REFRESH:
{
// 刷新页面的文字
mLoadingText.setText(mLoadingWords);
break;
}
}
}
}
法2:利用Activity.runOnUiThread(Runnable)把更新ui的代码创建在Runnable中,然后在需要更新ui时,把这个Runnable对象传给Activity.runOnUiThread(Runnable)。
这样Runnable对像就能在ui程序中被调用。
FusionField.currentActivity.runOnUiThread(new Runnable()
{
public void run()
{
Toast.makeText(FusionField.currentActivity, "Success",
Toast.LENGTH_LONG).show();
}
});
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