創建一個新的事件處理程序和源代碼

Question

我有一個用戶界面（UI）類。它創建了一些線程（讓我們稱之爲T）來完成一些工作。我希望我的UI類在T完成工作時得到通知。 我想我需要在UI類（onClick（）等）中創建一個事件處理程序，並從T觸發它。 問題：這可能嗎？怎麼樣 ？ //要清楚，UI類已經有一些事件處理程序，它們是由我沒寫的函數觸發的。像onClick（）等。

Answer 1

這是一個相當普遍的要求，因爲您通常希望儘可能少地在UI線程上進行操作。

如果您正在使用鞦韆，請看SwingWorker課程。如果你不使用鞦韆，你可能想看看ExecutorService和FutureTask。

import java.util.concurrent.Callable; 
import java.util.concurrent.ExecutionException; 
import java.util.concurrent.ExecutorService; 
import java.util.concurrent.Executors; 
import java.util.concurrent.FutureTask; 

public class Futures { 

    public static void main(String[] args) { 

     UI ui = new UI(); 
     FutureHandle<String> handle = new FutureHandle<String>(new BigJob()); 
     FutureHandle<String> handle2 = new FutureHandle<String>(new BigJob()); 

     ui.doUIStuff("Things can happen on the UI thread"); 
     ui.startHeavyLiftingJob(handle); 
     ui.doUIStuff("I've got a big job running, but I'm still responsive"); 
     ui.startHeavyLiftingJob(handle2); 

    } 


    /** 
    * Your UI class. Don't want to do anything big 
    * on the UI's thread. 
    */ 
    static class UI implements Listener<String> { 

     private ExecutorService threadPool = Executors.newFixedThreadPool(5); 

     public void doUIStuff(String msg) { 
      System.out.println(msg); 
     } 

     public void startHeavyLiftingJob(FutureHandle<String> handle) { 
      System.out.println("Starting background task"); 
      handle.setListener(this); 
      threadPool.execute(handle); 
     } 

     public void callback(String result) { 
      System.out.println("Ooh, result ready: " + result); 
     } 

    } 


    /** 
    * A handle on a future which makes a callback to a listener 
    * when the callable task is done. 
    */ 
    static class FutureHandle<V> extends FutureTask<V> { 

     private Listener<V> listener; 

     public FutureHandle(Callable<V> callable) { 
      super(callable); 
     } 

     @Override 
     protected void done() { 
      try { 
       listener.callback(get()); 
      } catch (InterruptedException e) { 
       //handle execution getting interrupted 
      } catch (ExecutionException e) { 
       //handle error in execution 
      } 
     } 

     public void setListener(Listener<V> listener) { 
      this.listener = listener; 
     } 

    } 

    /** 
    * Class that represents something you don't want to do on the UI thread. 
    */ 
    static class BigJob implements Callable<String> { 

     public String call() throws Exception { 
      Thread.sleep(2000); 
      return "big job has finished"; 
     } 

    } 


    interface Listener<V> { 
     public void callback(V result); 
    } 
}