Question

我试图将RedSquare类的对象添加到CatchMeV2类的JFrame中。有什么问题？

public class CatchMeV2 implements ActionListener{
int width = 400;
int height = 450;

public static void main(String[] args) {
    JFrame frame = new JFrame();
    frame.setVisible(true);
    frame.setDefaultCloseOperation(EXIT_ON_CLOSE);
    frame.setResizable(false);
    frame.setSize(400, 400);
    frame.setTitle("CatchMe.V2");
    RedSquare r = new RedSquare();
    frame.add(r);

}

@Override
public void actionPerformed(ActionEvent e) {

    }
}

public class RedSquare extends JPanel implements ActionListener {
int x = 20; int y = 20;
int velX = 4; int velY = 4;
public RedSquare(){
    addActionListener(this);
}
public void paintComponent(Graphics g) {
    super.paintComponent(g);
    g.setColor(Color.green);
    g.fillRect(x, y, 50, 50);
    repaint();
}

@Override
public void actionPerformed(ActionEvent e) {
    x += velX;
    y += velY;
    if (x < 0) {
        velX = 0;
        x = 0;
    }
    if (x > 400 - 50) {
        velX = 0;
        x = 400 - 50;
    }
    if (y < 0) {
        velY = 0;
        y = 0;
    }
    if (y > 400 - 40) {
        velY = 0;
        y = 400 - 40;
    }
    repaint();
    }
}

actionPerformed方法没有做任何事情。有人可以帮忙吗？或者有一个简单的方法来做到这一点？背景：我试图通过使用一个类来制作游戏。我做到了，但问题是我一次只能输入一个关键输入而且它是滞后的。而我的老师说，如果我将它分成不同的类别，它就不会滞后。这是真的吗？

Answer 1

您无法将非可视组件添加到JPanel，因此您需要从组件中扩展RedSquare类，例如JPanel并覆盖paintComponent()方法。

public class CatchMeV2 {

    public static void main(String[] args) {
        JFrame frame = new JFrame();
        frame.setDefaultCloseOperation(EXIT_ON_CLOSE);
        frame.setSize(400, 400);
        frame.setTitle("CatchMe.V2");
        RedSquare r = new RedSquare();
        frame.setContentPane(r);
        frame.setVisible(true);
    }
}

class RedSquare extends JPanel implements ActionListener {

    public RedSquare() {

    }

    @Override    
    protected void paintComponent(Graphics g) {
        super.paintComponent(g); // don't forget to call super method
        g.setColor(Color.green);
        g.fillRect(20, 20, 50, 50);
    }

    @Override
    public void actionPerformed(ActionEvent e) {

    }
}

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你不能使用面板执行的操作，只能用于按钮等。如果你想点击面板做某事，那么你需要使用工具鼠标列表。并将动作代码放入鼠标点击方法。运行此示例

import java.awt.Graphics;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import javax.swing.JFrame;
import static javax.swing.JFrame.EXIT_ON_CLOSE;
import javax.swing.JPanel;

public class CatchMeV2 {

    public static void main(String[] args) {
        JFrame frame = new JFrame();
        frame.setVisible(true);
        frame.setDefaultCloseOperation(EXIT_ON_CLOSE);
        frame.setResizable(false);
        frame.setSize(400, 400);
        frame.setTitle("CatchMe.V2");
        RedSquare r = new RedSquare();
        frame.add(r);
    }
}

class RedSquare extends JPanel implements MouseListener {

    int x = 20;
    int y = 20;
    int velX = 4;
    int velY = 4;

    public RedSquare() {
        addMouseListener(this);
    }

    protected void paintComponent(Graphics g) {
        super.paintComponent(g); 
        g.fillRect(x, y, 50, 50);
    }

    @Override
    public void mouseClicked(MouseEvent e) {
        System.out.println("hi");
        x += velX;
        y += velY;
        if (x < 0) {
            velX = 0;
            x = 0;
        }
        if (x > 400 - 50) {
            velX = 0;
            x = 400 - 50;
        }
        if (y < 0) {
            velY = 0;
            y = 0;
        }
        if (y > 400 - 40) {
            velY = 0;
            y = 400 - 40;
        }
        this.repaint();
    }

    @Override
    public void mousePressed(MouseEvent e) {}

    @Override
    public void mouseReleased(MouseEvent e) {}

    @Override
    public void mouseEntered(MouseEvent e) {}

    @Override
    public void mouseExited(MouseEvent e) {}


}

那时你只想用鼠标点击移动方块所以你仍然可以使用awt鼠标事件但是当你使用键时你必须使用key binding

ActionPerformed方法不能从另一个类工作

1 个答案: