定时器时闪烁，当它到达0

Question

导入库

public class Countdown1 extends Applet implements Runnable { 
// getting user input 

    String input = JOptionPane.showInputDialog("Enter seconds: "); 
// converting string to integer 

    int counter = Integer.parseInt(input); 

    Thread countdown; 

    public void start() { 
     countdown = new Thread(this); 
     countdown.start(); 

    } 

// executed by thread 
    public void run() { 

     Timer timer; 

     timer = new Timer(1000, new ActionListener() /* counting down time inputted */ { 
      public void actionPerformed(ActionEvent evt) { 
       if (counter > 0) { 

        counter--; 
// repainting each second 

        repaint(); 
       } 
      } 
     }); 
// timer started 

     timer.start(); 

    } 

    public void paint(Graphics g) { 
//painting text and time 

     g.setFont(new Font("Times New Roman", Font.BOLD, 35)); 
     g.drawString("Seconds: " + String.valueOf(counter), 260, 210); 
     setBackground(Color.orange); 
     setForeground(Color.magenta); 

// change background to cyan when timer reaches 0 
     if (counter == 0) { 
      setBackground(Color.cyan); 
     } 
    } 
} 

Answer 1

的问题是不是你的Timer（虽然我做题，需要一个单独的线程中启动它），问题是绝对基于paint。

像Applet这样的顶级容器没有双缓冲，这意味着每个绘画动作都倾向于被迫发送到底层的Graphics设备。

现在，您可以通过以上雇员或走到这一些双缓冲过程你能...

• 从JApplet扩展，而不是
• 创建一个从东西延伸的自定义组件，像JPanel并重写它的paintComponent方法来代替，将您的自定义绘画移动到此方法
• 改为将此组件添加到小程序。

应该解决眼前的问题......

你也应该避免调用setForeground或setBackground任何paint方法中。事实上，你应该避免调用可能调用repaint任何paint方法中的任何方法...

看看Performing Custom Painting

我敢肯定，这String input = JOptionPane.showInputDialog("Enter seconds: ");是一个坏主意。相反，你应该提供某种控制或选项的用户界面中更改该值...

原油例如

import java.awt.Color; 
import java.awt.Font; 
import java.awt.Graphics; 
import java.awt.event.ActionEvent; 
import java.awt.event.ActionListener; 
import javax.swing.JApplet; 
import javax.swing.JOptionPane; 
import javax.swing.JPanel; 
import javax.swing.Timer; 

public class Countdown1 extends JApplet { 

    @Override 
    public void init() { 
     add(new CounterPane()); 
    } 

    public class CounterPane extends JPanel { 

     String input = JOptionPane.showInputDialog("Enter seconds: "); 

     int counter = Integer.parseInt(input); 

     public CounterPane() { 

      Timer timer; 

      timer = new Timer(1000, new ActionListener() /* counting down time inputted */ { 
       public void actionPerformed(ActionEvent evt) { 
        System.out.println(counter); 
        if (counter > 0) { 

         counter--; 

         setBackground(Color.orange); 
         setForeground(Color.magenta); 

         if (counter <= 0) { 
          setBackground(Color.cyan); 
         } 

         repaint(); 
        } 
       } 
      }); 

      timer.start(); 

     } 

     @Override 
     protected void paintComponent(Graphics g) { 
      super.paintComponent(g); 
      g.setFont(new Font("Times New Roman", Font.BOLD, 35)); 
      g.setColor(getForeground()); 
      g.drawString("Seconds: " + String.valueOf(counter), 260, 210); 
     } 

    } 
}