在android 中我们一般用 Handler 做主线程 和 子线程 之间的通信 。
现在有了一种更为简洁的写法，就是 Activity 里面的 runOnUiThread（ Runnable ）方法。
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)。
Runnable对像就能在ui程序中被调用。如果当前线程是UI线程，那么行动是立即执行。如果当前线程不是UI线程,操作是发布到事件队列的UI线程。
package com.app;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.widget.Toast;
public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//创建一个线程
new Thread(new Runnable() {
@Override
public void run() {
//延迟两秒
try {
Thread.sleep( 2000 );
} catch (InterruptedException e) {
e.printStackTrace();
}
runOnUiThread(new Runnable() {
@Override
public void run() {
Toast.makeText(MainActivity.this, "hah", Toast.LENGTH_SHORT).show();
}
});
}
}).start();
}
}
Activity的runOnUiThread(Runnable)
/**
* Runs the specified action on the UI thread. If the current thread is the UI
* thread, then the action is executed immediately. If the current thread is
* not the UI thread, the action is posted to the event queue of the UI thread.
*
* @param action the action to run on the UI thread
*/
public final void runOnUiThread(Runnable action) {
if (Thread.currentThread() != mUiThread) {
mHandler.post(action);
} else {
action.run();
}
}
