JPanel中如何移动多个对象

Question

我想创建多个同时独立移动的方块，我认为最有效的方法是通过 Graphics2D 中的 transform 方法，但我不确定如何让它对每个方块都起作用 square.I 希望方形对象是自包含的并创建自己的转换（实例转换）。这是我到目前为止所拥有的。

变换面板

import javax.swing.*; 
import java.awt.*;
import java.awt.geom.AffineTransform;
import java.util.Random;
import java.util.concurrent.TimeUnit;

public class TranformPanel extends JPanel {
    private int[] xcoords = {250,248,253,255,249}; 
    private int[] ycoords = {250,253,249,245,250}; 
    private double randomx = 0; 
    private double randomy = 0;
    public void paintComponent(Graphics g) 
    { 
        super.paintComponent(g); 
        drawTransform(g,randomx,randomy);
    } 
    private void drawTransform(Graphics g,double randomx,double randomy) 
    {  
        Random rn = new Random(); 
        int xnum = rn.nextInt(10)-5; 
        randomx = xnum; 
        int ynum = rn.nextInt(10)-5; 
        randomy = ynum;

        Rectangle rect = new Rectangle(250,250,10,10);  
        AffineTransform transform = new AffineTransform();   
        Graphics2D g2d = (Graphics2D)g;   

        transform.translate(randomx,randomy);
        g2d.draw(transform.createTransformedShape(rect));  

        }
    }

变形绘图

import java.awt.*; 
import javax.swing.*; 
import java.awt.geom.AffineTransform;
import java.util.Scanner;
import java.util.concurrent.TimeUnit;

public class TransformDraw{ 
    private static TranformPanel panel = new TranformPanel();
    public static void main(String[] args) {    
        // Setup our JFrame details 
        JFrame frame = new JFrame();
        frame.setTitle("Transform Polygon Example");
        frame.setSize(500,500);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setLayout(new BorderLayout());   
        frame.setVisible(true);
        frame.add(panel); 
        Scanner input = new Scanner(System.in); 
        for (int i=0;i<10;i++) 
        { 
        try {
            TimeUnit.SECONDS.sleep(1);
            frame.repaint(); 
        } catch (InterruptedException e) {
            e.printStackTrace();
            }
        } 
    } 
}

感谢提前！

Answer 1

首先创建可以管理其位置（和其他属性）的东西，并且可以是 "painted"

public interface Box {
    public void update(Dimension size);
    public void paint(Graphics2D g2d);
}

所以，这是非常基本的，它所能做的就是更新（在给定区域内）和绘制。您可以根据您的特定需求公开其他属性（例如它的边界框）

接下来，我们需要一个简单的实现，比如...

public class DefaultBox implements Box {

    private Color color;
    private Rectangle bounds;

    private int xDelta;
    private int yDelta;

    public DefaultBox(Color color, Dimension size) {
        this.color = color;
        bounds = new Rectangle(new Point(0, 0), size);

        xDelta = 1 + (int) (Math.random() * 10);
        yDelta = 1 + (int) (Math.random() * 10);
    }

    @Override
    public void update(Dimension size) {
        bounds.x += xDelta;
        bounds.y += yDelta;

        if (bounds.x < 0) {
            bounds.x = 0;
            xDelta *= -1;
        } else if (bounds.x + bounds.width > size.width) {
            bounds.x = size.width - bounds.width;
            xDelta *= -1;
        }
        if (bounds.y < 0) {
            bounds.y = 0;
            yDelta *= -1;
        } else if (bounds.y + bounds.height > size.height) {
            bounds.y = size.height - bounds.height;
            yDelta *= -1;
        }
    }

    @Override
    public void paint(Graphics2D g2d) {
        g2d.setColor(color);
        g2d.fill(bounds);
    }

}

现在，这维护了一个简单的 Rectangle 实例，它描述了对象的位置和大小，它还维护了关于颜色和速度的属性。

当 update 被调用时，它会更新它的位置并进行一些简单的边界检查以确保框保持在指定区域内。

调用paint时，它只是简单地绘制自己。

最后，我们需要一些方法来更新和绘制这些框....

public class TestPane extends JPanel {

    private List<Box> boxes;
    private Color[] colors = {Color.RED, Color.BLACK, Color.BLUE, Color.CYAN, Color.DARK_GRAY, Color.GREEN, Color.LIGHT_GRAY, Color.MAGENTA, Color.ORANGE, Color.PINK, Color.WHITE, Color.YELLOW};

    public TestPane() {
        boxes = new ArrayList<>(25);
        for (int index = 0; index < 100; index++) {
            Color color = colors[(int) (Math.random() * colors.length)];
            int width = 10 + (int) (Math.random() * 9);
            int height = 10 + (int) (Math.random() * 9);
            boxes.add(new DefaultBox(color, new Dimension(width, height)));
        }

        Timer timer = new Timer(40, new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                for (Box box : boxes) {
                    box.update(getSize());
                }
                repaint();
            }
        });
        timer.start();
    }

    @Override
    public Dimension getPreferredSize() {
        return new Dimension(200, 200);
    }

    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        for (Box box : boxes) {
            Graphics2D g2d = (Graphics2D) g.create();
            box.paint(g2d);
            g2d.dispose();
        }
    }

}

好吧，再一次，这很简单。它维护着一个Box的List，一个Swing Timer来定期更新Box的List，调用它们的update方法. Timer 简单地调用 repaint，它（以一种循环的方式）最终调用 paintComponent，然后它只在 Box 的每个实例上调用 paint .

100 盒...

JPanel中如何移动多个对象

how to move multiple objects in JPanel

java

graphics

transform

jpanel

graphics2d