Question

我有一个JLabel和一个JButton。在下面的代码中，我尝试在执行for循环之前更改按钮单击时的JLabel文本，但是在循环执行后JLabel文本会更改。这是代码 -

private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         

        int n = JOptionPane.showConfirmDialog(null, "Print??");
        if(n==JOptionPane.YES_OPTION)
                {
                    jLabel1.setText("Please Wait...");
                    System.out.println("Hello");

                    for(int i = 0 ; i<65000;i++)
                    {
                        System.out.println("printing");
                    }

                }
    }

然而，在循环执行之前打印Hello。我在for循环中做了一些其他事情，这也需要一些时间，直到循环执行我想显示Please Wait ....但它在执行循环后显示。问题是什么。请帮忙......

Answer 1

Thread t1 = new Thread() {
            public void run() {
            lbl.setText("Please wait...");
            pnl.updateUI();
        }
    };
    Thread t2 = new Thread() {

        public void run() {
            for (int i = 0; i < 10000; i++) {
                pnl.updateUI();
                System.out.println("Printing");
            }
            lbl.setText("Done!!!");
        }
    };

全局声明此内容并点击按钮后写t1.start()和t2.start();

Answer 2

It is better if you use Thread concept in this issue.

**EDIT**

Thread thread1 = new Thread () {
  public void run () {
//   set your label code here 
  }
};
Thread thread2 = new Thread () {
  public void run () {
    // iterate your loop here 
  }
};
thread1.start();
thread2.start();

Answer 3

这只是因为当方法完成其执行后，其更改后的按钮文本，所以你应该使用线程概念，因为jogi说..

public class YouClass implements Runnable {

public void run() {
   // set text here 
}

public void run() {
   // use loop here  
}

public static void main(String args[]) {
    (new Thread(new YouClass())).start();
    (new Thread(new YouClass())).start();
}

}

Answer 4

if (n == JOptionPane.YES_OPTION) {
        new Thread(new Runnable() {
            @Override
            public void run() {
                jLabel1.setText("Please Wait...");
                System.out.println("Hello");
                for (int i = 0; i < 65000; i++) {
                    System.out.println("printing");
                }
                jLabel1.setText("Done...");
            }
        }).start();
    }

Java中的JOptionPane的ConfirmDialog

4 个答案: