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[操作系统]android Activity runOnUiThread() 方法使用


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();    }  }