JLabel油漆點

Question

import java.awt.Graphics; 
import javax.swing.*; 

public class Demo 
{ 
    JFrame jf; 
    JLabel[] labels; 
    JPanel panel; 

    public Demo() 
    { 
     jf = new JFrame(); 
     jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 

     labels = new JLabel[10]; 
     Box vbox = Box.createVerticalBox(); 
     for (int i = 0; i < 10; i++) 
     { 
      labels[i] = new JLabel(); 
      vbox.add(labels[i]); 
     } 
     panel = new JPanel(); 
     panel.add(vbox); 
     jf.add(panel); 
     jf.setSize(300, 250); 
     jf.setVisible(true); 
    } 
    public static void main(String[] args) 
    { 
     SwingUtilities.invokeLater(new DemoRunnable()); 
    } 
    public void updateState() 
    { 
     for (JLabel l : labels) 
     { 
      if (Math.random() > 0.5) 
       l.setText("777777777777777777777777777777777777"); 
      else 
       l.setText("10000000000000000000000000000000000000"); 
     } 
    } 
} 
class DemoRunnable implements Runnable 
{ 
    Demo demo; 

    DemoRunnable() 
    { 
     this.demo = new Demo(); 
    } 
    @Override 
    public void run() 
    { 
     Thread t = new Thread(new Runnable() 
     { 

      @Override 
      public void run() 
      { 
       while (true) 
       { 
        try 
        { 
         Thread.sleep(0); 
        } 
        catch (InterruptedException e) 
        { 
         e.printStackTrace(); 
        } 
        demo.updateState(); 
       } 
      } 
     }); 
     t.start(); 

    } 
} 

我看到這樣的效果，當這個程序執行。是否有可能消除它（零點必須是點）？

Answer 1

我在回答代碼示例只，

import java.awt.EventQueue; 
import java.awt.GridLayout; 
import javax.swing.*; 

public class Demo { 

    private JFrame jf; 
    private JLabel[] labels; 
    private JPanel panel; 

    public Demo() { 
     labels = new JLabel[10]; 
     Box vbox = Box.createVerticalBox(); 
     for (int i = 0; i < 10; i++) { 
      labels[i] = new JLabel(); 
      labels[i].setText("10000000000000000000000000000000000000"); 
      vbox.add(labels[i]); 
     } 
     panel = new JPanel(); 
     panel.setLayout(new GridLayout()); 
     panel.add(vbox); 
     jf = new JFrame(); 
     jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
     jf.add(panel); 
     jf.pack(); 
     jf.setVisible(true); 
    } 

    public static void main(String[] args) { 
     SwingUtilities.invokeLater(new DemoRunnable()); 
    } 

    public void updateState() { 
     for (final JLabel l : labels) { 
      if (Math.random() > 0.5) { 
       EventQueue.invokeLater(new Runnable() { 

        @Override 
        public void run() { 
         l.setText("777777777777777777777777777777777777"); 
        } 
       }); 
      } else { 
       EventQueue.invokeLater(new Runnable() { 

        @Override 
        public void run() { 
         l.setText("10000000000000000000000000000000000000"); 
        } 
       }); 
      } 
     } 
    } 
} 

class DemoRunnable implements Runnable { 

    private Demo demo; 

    DemoRunnable() { 
     this.demo = new Demo(); 
    } 

    @Override 
    public void run() { 
     Thread t = new Thread(new Runnable() { 

      @Override 
      public void run() { 
       while (true) { 
        try { 
         Thread.sleep(250); 
        } catch (InterruptedException e) { 
         e.printStackTrace(); 
        } 
        demo.updateState(); 
       } 
      } 
     }); 
     t.start(); 
    } 
} 

Answer 2

代替setSize()使用pack()採取組件的仔細計算首選大小的優勢。您還需要初始化您的標籤：

labels[i] = new JLabel("10000000000000000000000000000000000000"); 

還要考慮javax.swing.Timer，而不是一個單獨的線程。

附錄：方便的是，每個Swing Timer共享一個公用後臺線程，並且在事件分派線程上調用actionPerformed()。替代方案是SwingWorker，圖示爲here。