矩形内移动球程序

Question

我正在创建一个移动球程序，该程序的特点是球在矩形的墙壁上移动和弹跳，底部带有开始和停止按钮。

我遇到的问题是我希望球在程序运行时开始移动并从矩形内的线条弹起，这是我的主要问题。下面是我的代码：

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.GridBagLayout;
import java.awt.Rectangle;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.geom.Ellipse2D;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.Timer;

//Does the drawing
class MyDrawing extends JPanel {

private int xpos;
private int ypos;

public void setXPos(final int x) {
    this.xpos = x;
}

public void setYPos(final int y) {
    this.ypos = y;
}

public int getXpos() {
    return xpos;
}

public int getYpos() {
    return ypos;
}

@Override
public void paintComponent(final Graphics g) {
    super.paintComponent(g);
    final Graphics2D g2 = (Graphics2D) g;
    g.setColor(Color.red);
    final Ellipse2D.Double circle = new Ellipse2D.Double(xpos, ypos, 50, 50);
    g2.draw(circle);
    g2.fill(circle);
    final Rectangle box1 = new Rectangle(10, 10, 380, 300);
    g.setColor(Color.BLACK);
    g2.draw(box1);
}
}


public class ControlledBall extends JFrame {
private final JButton       flash = new JButton("Go");
private final JButton       steady = new JButton("Stop");
private final JPanel        panel = new JPanel(new GridBagLayout());
private final MyDrawing     drawing = new MyDrawing();
private final Timer         timer;


//direction
private int dx = 3;
private int dy = 2;

public ControlledBall() {
    panel.add(flash);
    panel.add(steady);
    this.add(panel, BorderLayout.SOUTH);
    this.add(drawing, BorderLayout.CENTER);
    drawing.setXPos(300);
    drawing.setYPos(150);
    steady.addActionListener(new SteadyListener());
    final MoveListener ml = new MoveListener();
    flash.addActionListener(ml);
    timer = new Timer(15, ml);
}

class MoveListener implements ActionListener {
    @Override
    public void actionPerformed(final ActionEvent event) {
        if (!timer.isRunning()){
            timer.start();
        }
        move();
    }
}

class SteadyListener implements ActionListener {
    @Override
    public void actionPerformed(final ActionEvent event) {
        if (timer.isRunning()){
            timer.stop();
        }
    }
}

private void move() {

    int x = drawing.getXpos();
    int y = drawing.getYpos();
    final int dia = 30;
    if (x + dx < 0 || x + dia + dx > getWidth()) {
        dx *= -1;
    }
    if (y + dy < 0 || y + dia + dy > getHeight()) {
        dy *= -1;
    }
    x += dx;
    y += dy;
    drawing.setXPos(x);
    drawing.setYPos(y);
    repaint();
}

public static void main(final String[] args) {
    final JFrame window = new ControlledBall();
    window.setSize(400, 400);
    window.setTitle("Controlled Ball");
    window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    window.setVisible(true);
}
}

Answer 1

问题在于您检查的边界。如果你想检查矩形，你必须将大小实现为变量并将它们输入你的 "bounce"-check 或者你手动添加它（从你的代码中获取矩形的大小）：

 if (x + dx < 10 || x + dia + dx > 380) {
        dx *= -1;
    }
    if (y + dy < 10 || y + dia + dy > 300) {
        dy *= -1;
    }

如果你喜欢真正的距离，使用半球大小的偏移量并将其添加到此代码中。我认为这比速度矢量 dx 和 dy 更好。

矩形内移动球程序

Moving ball inside rectangle program

java

graphics

swing

actionlistener

actionevent