Question

我遇到了这个问题...当我画一条线时，字符跟在我画的线上但计算机在其他地方描绘了一条线： enter image description here

所以有人都知道发生了什么事吗？ My code:

@SuppressWarnings({"serial","rawtypes","unchecked"})
public class someGame extends JFrame implements MouseListener, KeyListener{

ArrayList lines = new ArrayList();
Point2D.Double start;
final Color BROWN = new Color(156,93,82);
Slider thread;
Rectangle cow = null;
boolean drawGuy = false;
public someGame(){
    super("Some Game");
    setSize(700,700);
    setVisible(true);
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    addMouseListener(this);
    addKeyListener(this);
}

public void paint(Graphics g){
    super.paint(g);
    g.setColor(Color.black);
    for(int i = 0; i < lines.size(); i++){
        Line2D.Double temp = (Line2D.Double) lines.get(i);
        int x1 = Integer.parseInt(""+Math.round(temp.getX1()));
        int x2 = Integer.parseInt(""+Math.round(temp.getX2()));
        int y1 = Integer.parseInt(""+Math.round(temp.getY1()));
        int y2 = Integer.parseInt(""+Math.round(temp.getY2()));

        g.drawLine(x1,x2,y1,y2);
    }

    if(drawGuy){
        try{
            URL url = this.getClass().getResource("resources/img/world/char.png");
            Image image = Toolkit.getDefaultToolkit().getImage(url);
            g.drawImage(image, cow.x, cow.y, this);
        } catch(Exception exc){}
    }
}

public void mouseClicked(MouseEvent e){}
public void mouseEntered(MouseEvent e){}
public void mouseExited(MouseEvent e){}
public void mousePressed(MouseEvent e){
    start = new Point2D.Double(e.getX(),e.getY());
}
public void mouseReleased(MouseEvent e){
    Point2D.Double end = new Point2D.Double(e.getX(),e.getY());
    lines.add(new Line2D.Double(start,end));
    repaint();
}
public void keyPressed(KeyEvent e){}
public void keyReleased(KeyEvent e){}
public void keyTyped(KeyEvent e){
    if(e.getKeyChar()=='p'||e.getKeyChar()=='P'){
        thread = new Slider();
        thread.start();
        thread.action(true);
    }
    if(e.getKeyChar()=='q'||e.getKeyChar()=='Q'){
        thread.action(false);
        drawGuy = false;
        thread = null;
    }
}
private class Slider extends Thread{
    double velocity, gravity;
    boolean go = false;
    public void run(){
        if(go){
            initGuy();
            velocity = 0;
            gravity = 1;
        }
        while(go){
            try{
                Line2D.Double lineTaken = null;
                boolean onLine = false;
                int firstOnLine = -1;
                for(int i = lines.size()-1; i>=0; i--){
                    Line2D.Double temp = (Line2D.Double) lines.get(i);
                    if(temp.intersects(cow.x,cow.y,50,50)){
                        lineTaken = temp;
                        onLine = true;
                        if(firstOnLine!=i){
                            firstOnLine = i;
                            gravity = 0;
                        }
                        break;
                    }
                }
                if(onLine){
                    double grav = (lineTaken.y2-lineTaken.y1)/50;
                    double vlct = (lineTaken.x2-lineTaken.x1)/100;
                    if(velocity<5)velocity+=vlct;
                    if(gravity<2.5)gravity+=grav;
                }
                else{
                    gravity+=.2;
                }
                cow.x+=velocity;
                cow.y+=gravity;

                Thread.sleep(75);
                repaint();
            }catch(Exception e){break;}
        }
    }
    public void action(boolean b){
        go = b;
    }
    public void initGuy(){
        Line2D.Double firstLine = (Line2D.Double) lines.get(0);
        int x = Integer.parseInt(""+Math.round(firstLine.x1));
        int y = Integer.parseInt(""+Math.round(firstLine.y1));
        cow = new Rectangle(x+30,y-20,30,30);
        drawGuy = true;
    }
}

很抱歉大码，但我不知道出了什么问题...... 非常感谢任何回答:)的人 ......是的，主要方法是someGame g = new someGame();

Answer 1

1）如果没有充分理由，绝不能使用paint(..)。而是扩展JPanel类并覆盖paintComponent(...)。

2）除非添加功能

，否则不要扩展JFrame类

3）不要忘记所有Swing组件的创建和操作应该在EDT上完成 - Event Dispatch Thread

4）Java命名约定是CamelCase，类名的每个新单词都应以大写字母开头，即SomeGame

5）不要使用setSize而是覆盖组件getPreferredSize并返回所需的尺寸，然后在pack()上调用JFrame，然后再设置可见。

6）使用Keybindings代替KeyListener

7）使用MouseAdapter代替MouseListener

8）不要扩展Thread类rather implement Runnable并创建start()方法以在runnable类中启动线程（我没有在下面的代码中实现它）

9）除了在绘制方法中绘制对象的必要性之外，做加载图像等长时间运行的任务或做任何其他工作不是一个好主意你应该在类初始化或至少在组件绘制方法之外加载图片等。（我没有在下面的代码中实现这个）

10）关于线条绘制不正确的最大问题是：

g.drawLine(x1,x2,y1,y2);

应为drawLine(int x1,int y1,int x2,int y2)：

g.drawLine(x1,y1,x2,y2);

这是代码（现在没时间解释，希望你能理解）：

我在@MadProgrammer的评论中添加了一些额外的内容，例如投射到Graphics2D并使用RenderHints进行抗锯齿。

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Image;
import java.awt.Rectangle;
import java.awt.RenderingHints;
import java.awt.Toolkit;
import java.awt.event.ActionEvent;
import java.awt.event.KeyEvent;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.geom.Line2D;
import java.awt.geom.Point2D;
import java.net.URL;
import java.util.ArrayList;
import javax.swing.AbstractAction;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.KeyStroke;
import javax.swing.SwingUtilities;

public class SomeGame {

    public SomeGame() {
        JFrame frame = new JFrame("Some Game");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        DrawPanel dp = new DrawPanel();
        frame.add(dp);

        frame.pack();
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                new SomeGame();
            }
        });

    }
}

class DrawPanel extends JPanel {

    ArrayList lines = new ArrayList();
    Point2D.Double start;
    final Color BROWN = new Color(156, 93, 82);
    Slider thread;
    Rectangle cow = null;
    boolean drawGuy = false;

    public DrawPanel() {
        addMouseListener(new MouseAdapter() {
            @Override
            public void mouseReleased(MouseEvent me) {
                super.mouseReleased(me);
                Point2D.Double end = new Point2D.Double(me.getX(), me.getY());
                lines.add(new Line2D.Double(start, end));
                repaint();
            }

            @Override
            public void mousePressed(MouseEvent me) {
                super.mousePressed(me);
                start = new Point2D.Double(me.getX(), me.getY());
            }
        });
        setKeyBindings();
    }

    private void setKeyBindings() {
        getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW).put(KeyStroke.getKeyStroke(KeyEvent.VK_P, 0), "P");
        getActionMap().put("P", new AbstractAction() {
            @Override
            public void actionPerformed(ActionEvent ae) {
                thread = new Slider(DrawPanel.this);
                thread.action(true);
                thread.start();
            }
        });
        getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW).put(KeyStroke.getKeyStroke(KeyEvent.VK_Q, 0), "q");
        getActionMap().put("Q", new AbstractAction() {
            @Override
            public void actionPerformed(ActionEvent ae) {
                thread.action(false);
                drawGuy = false;
                thread = null;
            }
        });
    }

    @Override
    public Dimension getPreferredSize() {
        return new Dimension(700, 700);
    }

    @Override
    public void paintComponent(Graphics g) {
        super.paintComponent(g);

        //lets go 2D :)
        Graphics2D g2d = (Graphics2D) g;

        //turn on anti aliasing
        g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);


        g2d.setColor(Color.black);

        for (int i = 0; i < lines.size(); i++) {
            Line2D.Double temp = (Line2D.Double) lines.get(i);
            int x1 = Integer.parseInt("" + Math.round(temp.getX1()));
            int x2 = Integer.parseInt("" + Math.round(temp.getX2()));
            int y1 = Integer.parseInt("" + Math.round(temp.getY1()));
            int y2 = Integer.parseInt("" + Math.round(temp.getY2()));

            g2d.drawLine(x1, y1, x2, y2);
        }

        if (drawGuy) {
            try {
                URL url = this.getClass().getResource("resources/img/world/char.png");
                Image image = Toolkit.getDefaultToolkit().getImage(url);
                g.drawImage(image, cow.x, cow.y, this);
            } catch (Exception exc) {
            }
        }
    }

    private class Slider extends Thread {

        double velocity, gravity;
        boolean go = false;
        private final DrawPanel dp;

        private Slider(DrawPanel dp) {
            this.dp = dp;
        }

        public void run() {
            if (go) {
                initGuy();
                velocity = 0;
                gravity = 1;
            }
            while (go) {
                try {
                    Line2D.Double lineTaken = null;
                    boolean onLine = false;
                    int firstOnLine = -1;
                    for (int i = lines.size() - 1; i >= 0; i--) {
                        Line2D.Double temp = (Line2D.Double) lines.get(i);
                        if (temp.intersects(cow.x, cow.y, 50, 50)) {
                            lineTaken = temp;
                            onLine = true;
                            if (firstOnLine != i) {
                                firstOnLine = i;
                                gravity = 0;
                            }
                            break;
                        }
                    }
                    if (onLine) {
                        double grav = (lineTaken.y2 - lineTaken.y1) / 50;
                        double vlct = (lineTaken.x2 - lineTaken.x1) / 100;
                        if (velocity < 5) {
                            velocity += vlct;
                        }
                        if (gravity < 2.5) {
                            gravity += grav;
                        }
                    } else {
                        gravity += .2;
                    }
                    cow.x += velocity;
                    cow.y += gravity;

                    Thread.sleep(75);
                    SwingUtilities.invokeLater(new Runnable() {
                        @Override
                        public void run() {
                            dp.repaint();
                        }
                    });
                } catch (Exception e) {
                    break;
                }
            }
        }

        public void action(boolean b) {
            go = b;
        }

        public void initGuy() {
            Line2D.Double firstLine = (Line2D.Double) lines.get(0);
            int x = Integer.parseInt("" + Math.round(firstLine.x1));
            int y = Integer.parseInt("" + Math.round(firstLine.y1));
            cow = new Rectangle(x + 30, y - 20, 30, 30);
            drawGuy = true;
        }
    }
}

为什么它在错误的地方画线？

1 个答案: