Java 秒表 GUI 程序符合但不符合运行

Question

我有一个任务，我必须创建一个 GUI 秒表程序，该程序具有计时器的启动、停止和重置按钮。

到目前为止，我有一个程序可以正确编译，但是当我转到运行该程序时会产生以下错误，所以我不确定如何更正它。

at java.awt.Container.checkNotAWindow(Container.java:492)
at java.awt.Container.addImpl(Container.java:1093)
at java.awt.Container.add(Container.java:419)
at TimerFrame.main(TimerFrame.java:30)

Process completed.

对运行我的程序的任何帮助，或任何其他可以使程序运行更流畅的改进，我们将不胜感激。我刚开始学习 java，因此非常感谢您的帮助。

我也在下面包含了我的代码。

提前致谢！

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

public class TimerFrame {
   public static void main(String[] args){
      new TimerPanel();
      JFrame frame = new JFrame("Stopwatch GUI");
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      TimerPanel panel = new TimerPanel();
      frame.getContentPane().add(panel);
      frame.pack();
      frame.setVisible(true);
   }
}

import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.Timer;

public class TimerPanel extends JFrame implements ActionListener  {
    private int count;
    private JButton start;
    private JButton stop;
    private JButton reset;
    private JLabel label;
    private Timer timer;
    private double time;
    private double extra = 0;

    public TimerPanel(){
        setLayout(new GridLayout(2, 3));

        label = new JLabel("00.00", JLabel.CENTER);

        add(label);

        // Creating a panel (JPanel) for hte buttons to reside in
        JPanel buttons = new JPanel();

        // initilizing buttons
        start = new JButton("Start");
        stop = new JButton("Stop");
        reset = new JButton("Reset");

        // adds the buttons start, stop, and reset to the panel
        buttons.add(start);
        buttons.add(stop);
        buttons.add(reset);

        // adds the panel to the frame
        add(buttons);

        // adding action listeners to the buttons
        start.addActionListener(this);
        stop.addActionListener(this);
        reset.addActionListener(this);

        // initilize timer
        timer = new Timer(0, this);
        timer.setDelay(1000);

        setBackground(Color.pink);
        setPreferredSize(new Dimension(500, 300));
   }

   public void actionPerformed(ActionEvent event){

        //find the source of the action
        if(event.getSource().equals(timer)){
            // records the current time event from timer
            double currentTime = System.currentTimeMillis(); 

            // finds the elapsed time from time and currentTime
            double elapsed = (double) ( currentTime - time) / 1000;

            //adds the extra to the elapsed time
            elapsed = elapsed + extra;

            //displays time in JLabel label
            label.setText(String.format("%.1f", elapsed));

        } else if (event.getSource().equals(start)){
            // the start button has been clicked
            if(!timer.isRunning()){
                time = System.currentTimeMillis(); 
                timer.start();
            }

        } else if (event.getSource().equals(stop)) {
            // the stop button has been clicked
            if(timer.isRunning()){
                //record current time in currentTime
                double currentTime = System.currentTimeMillis();
                // finds the elapsed time from time and currentTime
                double elapsed = (double) ( currentTime - time ) / 1000;
                // (double) -> casts whatever is produced to be a double
                //adds the extra to the elapsed time
                elapsed = elapsed + extra;
                //stop the timer
                timer.stop();
            }
        } else{
            // the reset button has been clicked
            // stops the timer before resetting it
            if(timer.isRunning()){
                timer.stop();
            }
            // resets the timer
            time = System.currentTimeMillis();
            extra = 0;
            label.setText("00.00");
        }
   }
}

Answer 1

public class TimerPanel extends JFrame implements ActionListener  {

好吧，你调用你的 class TimerPanel 但你扩展了一个 JFrame。

如果 class 是 "panel" 那么它应该扩展 JPanel.

  TimerPanel panel = new TimerPanel();
  frame.getContentPane().add(panel);

您收到错误是因为您无法将 JFrame 添加到 JFrame。

Any help with running my program, or any other improvements

为什么要在测试之前写完整个 class？测试应该一步一步来。

所以您首先创建一个框架并对其进行测试。

然后将一些组件添加到框架中并测试布局是否正确。

然后将 ActionListeners 添加到按钮（一次一个）并测试它们。

这样当您遇到问题时，您就知道您刚刚更改了什么。

Java 秒表 GUI 程序符合但不符合运行

Java stopwatch GUI program complies but does not run

java

user-interface

swing

timer

stopwatch

Java 秒表 GUI 程序符合但不符合 运行

Java stopwatch GUI program complies but does not run

java

user-interface

swing

timer

stopwatch

Java 秒表 GUI 程序符合但不符合运行