Question

我的教授给了我这个家庭作业，实现了两个按钮并控制了一个风扇。我是GUI的新手，我没有丝毫的线索如何调用我的计时器以使用timer.setDelay();来增加它。任何帮助都将非常感激。我的代码如下：

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


public class Fan extends JFrame implements ActionListener{

    JButton speedup;
    JButton slowdown;


 JPanel testPanel = new MyPanel();//trying to inherit properties of MyPanel
  public Fan() {
    add(testPanel);

GridLayout f = new GridLayout(1,2);
setLayout(f);

JButton speedup = new JButton("Speed Up");
speedup.addActionListener(this);
add(speedup);

JButton slowdown = new JButton("Slow Down");
slowdown.addActionListener(this);
add(slowdown);

}

/* public void actionPerformed(ActionEvent event){
    int delay;
    String cmd = event.getActionCommand();
    if(cmd == "Speed Up" ){

        delay = testPanel.getTimer().getDelay();
        delay++;
        testPanel.getTimer().setDelay(delay);
        }

    else{

         delay = testPanel.getTimer().getDelay();
        delay--;
        testPanel.getTimer().setDelay(delay);
        */ 
//My attempt at getting timer to work commented out


    }




public class MyPanel extends JPanel {

    private static final long serialVersionUID = 1L;
    public Timer timer = new Timer(10, new TimerListener());
    private int alpha = 0; //angle

    public Timer getTimer(){
        return timer; //getter method for timer
    }

    public MyPanel() {
        timer.start();
    }


        protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        alpha = alpha + 1;
        int xc = getWidth()/2;
        int yc = getHeight()/2;
        int rad = (int)(Math.min(getWidth(), getHeight())*0.4);
        int x = xc - rad;
        int y = yc - rad;
        g.fillArc(x, y, 2*rad, 2*rad, 0+alpha, 30);
        g.fillArc(x, y, 2*rad, 2*rad, 90+alpha, 30);
        g.fillArc(x, y, 2*rad, 2*rad, 180+alpha, 30);
        g.fillArc(x, y, 2*rad, 2*rad, 270+alpha, 30);
    }

    class TimerListener implements ActionListener {     

        public void actionPerformed(ActionEvent e){
            repaint();      
        }       
    }   





    public static void main(String[] args) {

        JFrame fan = new Fan();
        fan.setSize(700, 700);
        fan.setLocationRelativeTo(null);
        fan.setDefaultCloseOperation(EXIT_ON_CLOSE);
        fan.setTitle("Spinning Fan");
        fan.setVisible(true);
    }

}

Answer 1

JPanel testPanel = new MyPanel();会将testPanel限制为JPanel的方法（因此您无法使用testPanel.getTimer()）。而是使用MyPanel testPanel = new MyPanel();，然后将能够使用testTimer.getTimer();
if(cmd == "Speed Up" ){。不要将字符串与==进行比较。而是使用equals。所以if ("Speed Up".equals(cmd)) {}
如果你想“加速”一个动画，你应该减少延迟，而不是增加它。反之亦然。

附注

在Event Dispatch Thread上运行Swings应用程序。您可以通过将main中的代码包装在SwingUtilities.invokeLater(...)中来实现此目的。请点击Initial Threads

这是一个固定的例子

import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.Graphics;
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.JPanel;
import javax.swing.SwingUtilities;
import javax.swing.Timer;

public class Fan extends JFrame implements ActionListener {

    JButton speedup;
    JButton slowdown;

    MyPanel testPanel = new MyPanel();// trying to inherit properties of MyPanel

    public Fan() {
        add(testPanel);

        JButton speedup = new JButton("Speed Up");
        speedup.addActionListener(this);

        JButton slowdown = new JButton("Slow Down");
        slowdown.addActionListener(this);

        JPanel panel = new JPanel();
        panel.add(speedup);
        panel.add(slowdown);

        add(panel, BorderLayout.SOUTH);

        pack();
        setLocationRelativeTo(null);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setTitle("Spinning Fan");
        setVisible(true);

    }

    public void actionPerformed(ActionEvent event) {
        int delay;
        String cmd = event.getActionCommand();
        if ("Speed Up".equals(cmd)) {
            delay = testPanel.getTimer().getDelay();
            delay--;
            testPanel.getTimer().setDelay(delay);
        } else {
            delay = testPanel.getTimer().getDelay();
            delay++;
            testPanel.getTimer().setDelay(delay);
        }
    }

    // My attempt at getting timer to work commented out

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {

            public void run() {
                new Fan();
            }
        });
    }
}

class MyPanel extends JPanel {

    private static final long serialVersionUID = 1L;
    public Timer timer = new Timer(10, new TimerListener());
    private int alpha = 0; // angle

    public Timer getTimer() {
        return timer; // getter method for timer
    }

    public MyPanel() {
        timer.start();
    }

    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        alpha = alpha + 1;
        int xc = getWidth() / 2;
        int yc = getHeight() / 2;
        int rad = (int) (Math.min(getWidth(), getHeight()) * 0.4);
        int x = xc - rad;
        int y = yc - rad;
        g.fillArc(x, y, 2 * rad, 2 * rad, 0 + alpha, 30);
        g.fillArc(x, y, 2 * rad, 2 * rad, 90 + alpha, 30);
        g.fillArc(x, y, 2 * rad, 2 * rad, 180 + alpha, 30);
        g.fillArc(x, y, 2 * rad, 2 * rad, 270 + alpha, 30);
    }

    @Override
    public Dimension getPreferredSize() {
        return new Dimension(600, 600);
    }

    class TimerListener implements ActionListener {

        public void actionPerformed(ActionEvent e) {
            repaint();
        }
    }
}

使用JButton控制风扇的速度

1 个答案: