等待，直到线程执行结束执行下一个方法

Question

之前，我一直认为我的管理界面和呼叫项目对象以进口物品的方法在我的DB一个JFrame子类：

public TestGUI() throws IOException 
{ 

    initComponents(); 

    Item.importItems(progressBar); // static method that execute a new thread to import item witouth freeze my UI (I update a progressBar in it) 

    table.refresh(); //Metodh that I need to execute only after "importItems()" methods is completed 

} 

Item对象实现Runnable在一个新的线程

public Item implements Runnable 
{ 

    private JProgressBar progressBar; 

    public void importItems (JProgressBar progressBar) throws IOException //Metodo per importare articoli da un file esterno. Usa i Thread. 
    { 

     this.progressBar = progressBar; 

     Thread importThread = new Thread (new RefreshTable(),"Importer Thread"); 

     importThread.start(); 

    } 

    void run() 
    { 

     // I execute here all the DB operation that i need. I also update the progress bar    here 

    } 


} 

执行导入操作如何修改代码来执行table.refresh()只有Item.importImtes(progressBar)结束它的运行后？谢谢！

Answer 1

如果你想一个线程等待另一个，你可以随时使用CountDownLatch也。使用一个也意味着你不必等到一些线程完成。如果你让你的问题对我们更好理解，我们可以帮助你了解更多细节。

你需要共享的CountDownLatch例如线程之间：

public TestGUI() throws IOException{ 
     initComponents(); 
     private final CountDownLatch latch = new CountDownLatch(1); 
     Item.importItems(progressBar, latch); // static method that execute a new thread to import item witouth freeze my UI (I update a progressBar in it) 
     latch.await(); 
     table.refresh(); //Metodh that I need to execute only after "importItems()" methods is completed 
} 

而在另一边：

public Item implements Runnable { 
    private JProgressBar progressBar; 
    public void importItems (JProgressBar progressBar, CountDownLatch latch) throws IOException { //Metodo per importare articoli da un file esterno. Usa i Thread. 

     this.progressBar = progressBar; 

     Thread importThread = new Thread (new RefreshTable(),"Importer Thread"); 

     importThread.start(); 

    } 

    void run() { 

     // I execute here all the DB operation that i need. I also update the progress bar here 
     //After everything finishes: 
     latch.countDown(); // you want this to be executed in a finally block of the try catch 
    } 


} 

Answer 2

在线程上使用.join（）方法。

Answer 3

<线程> .join（）方法会阻塞当前线程，直到<线程>已完成。

Answer 4

这是你应该如何使用它：

class ProgressBar extends Thread{ 
    public void run(){ 
     System.out.println("Progress Bar - start"); 
     try { 
      Thread.currentThread().sleep(2000); 
     } catch (InterruptedException e) {} 
     System.out.println("Progress Bar - end"); 
    } 
} 
public class ThreadDemo { 
    public static void main(String[] args) throws InterruptedException { 
     System.out.println("Main Thread Start"); 
     Thread t1 = new Thread(new ProgressBar()); 
     t1.start(); 
     t1.join(); 
     System.out.println("Main Thread End"); 
    } 
} 

OUTPUT：

Main Thread Start 
Progress Bar - start 
Progress Bar - end 
Main Thread End 

Answer 5

退房SwingWorker和SwingUtilities如果你使用Swing。
它们含有辅助线程API

Answer 6

你可以做的是底了移动table.refresh();码子线程代码并使用SwingUtilities.InvokeLater将其转发到GUI线程事件队列：

public void run() { 
     //... 
     SwingUtilities.InvokeLater(
      new Runnable() { 
       public void run() { 
        table.refresh(); 
       } 
      });   
} 

这样你就可以在GUI线程上执行它，但只有当子线程完成它的工作时。