Question

我有一项任务，要求球根据用户点击的按钮在屏幕上移动，并通过点击另一个按钮让球在红色和绿色之间切换。这一切都有效，但颜色变化。我有一个听众和班级对按钮点击作出反应，但我似乎没有得到改变。是否有更好/更简单的方法来实现这一目标？

提前感谢您的帮助！

我的代码：

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

public class Lab2b extends JFrame {

Lab2b(){
    setTitle("Lab 2");
    Lab2Panel p = new Lab2Panel();
    add(p);
}

public static void main(String[] args){

    Lab2b frame = new Lab2b();
    frame.setTitle("Lab 2 - Ball Mover ");
    frame.setLocationRelativeTo(null);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setSize(600, 400);
    frame.setVisible(true);
    }

}

class Lab2Panel extends JPanel{
Lab2Button canvas = new Lab2Button();
JPanel panel = new JPanel();

Lab2Panel () {

    setLayout(new BorderLayout());

    JButton leftButton = new JButton("left");
    JButton rightButton = new JButton("right");
    JButton upButton = new JButton("up");
    JButton downButton = new JButton("down");
    JButton colorButton = new JButton("Change Color");

    panel.add(leftButton);
    panel.add(rightButton);
    panel.add(upButton);
    panel.add(downButton);
    panel.add(colorButton);

    this.add(canvas, BorderLayout.CENTER);
    this.add(panel, BorderLayout.SOUTH);

    leftButton.addActionListener(new LeftListener(canvas));
    rightButton.addActionListener(new RightListener(canvas));
    upButton.addActionListener(new UpListener(canvas));
    downButton.addActionListener(new DownListener(canvas));
    colorButton.addActionListener(new ColorChangeListener(canvas));
}


}

class Lab2Button extends JPanel {
int radius = 5;
int x = -1;
int y = -1;

protected void paintComponent(Graphics g){
    if (x<0 || y<0) {
        x = getWidth() / 2 - radius;
        y = getHeight() / 2 - radius;
    }
    super.paintComponent(g);
    g.setColor(Color.RED);
    g.drawOval(x,y, 2 * radius, 2 * radius);


}

        public void moveLeft(){

            x -= 5;
            this.repaint();
        }

        public void moveRight(){

            x += 5;
            this.repaint();
        }

        public void moveUp(){
            y -= 5;
            this.repaint();
        }

        public void moveDown(){
            y += 5;
            this.repaint();
        }

        public void colorChange(){
            this.repaint();
        }



}

class LeftListener implements ActionListener{
    private Lab2Button canvas;

    LeftListener(Lab2Button canvas) {
     this.canvas = canvas;
    }

    public void actionPerformed(ActionEvent e){
     canvas.moveLeft();
    }
}

class RightListener implements ActionListener{
    private Lab2Button canvas;

    RightListener(Lab2Button canvas) {
        this.canvas = canvas;
    }

    public void actionPerformed(ActionEvent e){
      canvas.moveRight();
    }
}


class UpListener implements ActionListener{
    private Lab2Button canvas;

    UpListener(Lab2Button canvas) {
        this.canvas = canvas;
    }

    public void actionPerformed(ActionEvent e){
        canvas.moveUp();
    }
}



class DownListener implements ActionListener{
    private Lab2Button canvas;

    DownListener(Lab2Button canvas) {
        this.canvas = canvas;
    }

    public void actionPerformed(ActionEvent e){
     canvas.moveDown();
    }
}

class ColorChangeListener implements ActionListener {
    private Lab2Button canvas;

    ColorChangeListener(Lab2Button canvas) {
        this.canvas = canvas;
    }
    public void actionPerformed(ActionEvent e){
        canvas.colorChange();
    }
}

按钮移动侦听器类代码：

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

class Lab2MoveBallListener extends Lab2Button implements ActionListener { 

    public void actionPerformed(ActionEvent e){ 
        this.moveLeft(); 
    } 
}

好的，改变了这段代码：

public void colorChange(){
            this.repaint();
        }

这个和它在编译时出错：错误：找不到符号 if（g.getColor（）= Color.RED）{

public void colorChange(){

            if (g.getColor() = Color.RED){
                g.setColor(Color.GREEN);
            }
            else{
                g.setColor(Color.RED);
            }

            this.repaint();
        }

Answer 1

看一下使用JColorChooser。它可以根据需要设置球的颜色。见How to Use Color Choosers

这里你对颜色进行了硬编码，因此无法修改球的颜色。使用班级成员Color变量并从getColor分配。

除此之外：请记住在调用drawOval之前设置颜色：

g.setColor(ballColor); g.drawOval(x, y, 2 * radius, 2 * radius);

Answer 2

当您调用方法colorChange()时，您永远不会说要更改颜色，只需重新绘制屏幕即可。你需要在某处改变颜色。要做到这一点，我有一个颜色变量，并在ActionPerformed方法的if语句中为颜色按钮。 if将具有布尔值，如果它为真，则将颜色变量设置为等于此颜色，否则将其设置为等于另一种颜色。现在，g.setColor(Color.RED);代替paintComponent()而不是g.setColor(colorVariable);，{{1}}。希望这有助于解决您的问题。

使用动作侦听器实现颜色更改

2 个答案: