Java输入错误

好吧，我放弃。我已经是C++程序员几年了，但我尝试学习java，因为它是一种流行的语言。在我学习的过程中，我学到了很多东西，但最终我开始尝试使用输入系统，这样当我点击这个红色菱形多边形时，它会变成绿色，但经过几天的沮丧之后。。。娜达。我仍然只有一颗红钻石。它可能很小，但我就是找不到

import java.awt.*;
import java.awt.event.*;
import java.applet.*;

public class Vici extends Applet
{
    /**
     * 
     */
    private static final long serialVersionUID = 1L;
    private Space castle;

    public Vici()
    {
        castle = new Space();
        castle.addMouseListener(new SpaceInput());
    }



    public void paint(Graphics g)
    {
        Graphics2D g2d = (Graphics2D)g;


        int width = getSize().width;
        int height = getSize().height;

        g2d.setColor(Color.BLACK);
        g2d.fillRect(0, 0,  width, height);


        castle.paint(g2d);


    }

    class SpaceInput implements MouseListener
    {

        public void mouseEntered(MouseEvent m) { }
        public void mouseExited(MouseEvent m) { }
        public void mouseReleased(MouseEvent m)
        {
            switch(m.getButton())
            {
                case MouseEvent.BUTTON1:
                    castle.setColor(Color.GREEN);
                    castle.repaint();
                    repaint();
            }
        }
        public void mouseClicked(MouseEvent m)
        {
            switch(m.getButton())
            {
                case MouseEvent.BUTTON1:
                    castle.setColor(Color.GREEN);
                    castle.repaint();
                    repaint();
            }
        }
        public void mousePressed(MouseEvent m)
        {
            switch(m.getButton())
            {
                case MouseEvent.BUTTON1:
                    castle.setColor(Color.GREEN);
                    castle.repaint();
                    repaint();
            }
        }
    }

}








import java.awt.*;
import java.awt.event.*;
import java.awt.geom.*;

public class Space extends Canvas 
{
    private Polygon poly;
    private Color c;
    private int[] polyX = { 0, 24, 0, -24 };
    private int[] polyY = { 24, 0, -24, 0 };

    public void init()
    {
        poly = new Polygon( polyX, polyY, polyX.length);
        c = Color.red;
    }

    Space()
    {
        init();
    }

    void setColor(Color c)
    {
        this.c = c;
    }

    public void paint(Graphics g)
    {       
        Graphics2D g2d = (Graphics2D)g;

        AffineTransform identity = new AffineTransform();

        g2d.setTransform(identity);

        g2d.translate(100, 100);

        g2d.setColor(c);
        g2d.fill(poly);
    }

    public void update( Graphics g )
    {
        paint( g );
    }
}

---

我去掉了无关的“SpaceInput”类，并将鼠标侦听器添加到applet（而不是“castle”）。一切都成功了：）

@查兹·贝尔蒂诺-

我认为整个问题在于使用“Canvas”（自Java1.2以来就过时了）与“JPanel”（取代了自J2SE2.0以来结合使用的旧“Panel”和“Canvas”）

下面是另一个示例，其行为与您预期的一样。主要区别在于它使用Swing JPanel而不是AWT画布：

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

public class HelloAWT extends Applet {

    private Diamond diamond;
    private static final int height = 350;
    private static final int width = 350;

    public void init () {
        setBackground(Color.green);
        resize (width, height);
        diamond = new Diamond ();
        diamond.init (Color.green);
        add(diamond);
    }

    public void paint(Graphics g)
    {
System.out.println ("HelloAWT@paint()...");
        String msg = "Hello AWT!";
        g.setFont(new Font ("Arial", Font.BOLD, 18));
        FontMetrics fm = g.getFontMetrics ();
        int x = (getWidth() - fm.stringWidth(msg)) / 2;
        int y = (getHeight() / 2) + 50;
        g.drawString(msg, x, y);
        diamond.repaint ();
    }
}

class Diamond extends JPanel implements MouseListener {
    private static final int height = 100;
    private static final int width = 100;
    private Color c = Color.red;
    private Color bkgd;
    private int[] polyX;
    private int[] polyY;
    private Polygon poly;

    public void init (Color bkgd) {
System.out.println ("Diamond@init(): bkgd=" + bkgd + "...");        
        setPreferredSize (new Dimension(width, height));
        this.bkgd = bkgd;
        polyX = new int[] { width/2, width, width/2, 0 };
        polyY= new int[] { 0, height/2, height, height/2 };
System.out.println ("polyX=" + polyX[0] + "," + polyX[1] + "," + polyX[2] + "," + polyX[3] + "...");        
System.out.println ("polyY=" + polyY[0] + "," + polyY[1] + "," + polyY[2] + "," + polyY[3] + "...");        
        poly = new Polygon( polyX, polyY, polyX.length);
        addMouseListener (this);
    }

    public void paint(Graphics g)
    {       
System.out.println ("Diamond()@paint(), bounds=" + getHeight() + "," + getWidth () + "...");
        Graphics2D g2d = (Graphics2D)g;
        g2d.setColor(bkgd);
        g2d.fillRect(0, 0, width, height);
        g2d.setColor(c);
        g2d.fill(poly);
    }

    public void mouseEntered(MouseEvent m) {
System.out.println ("mouseEntered()...");
    }

    public void mouseExited(MouseEvent m) {
System.out.println ("mouseExited()...");            
    }

    public void mouseReleased(MouseEvent m) {
System.out.println ("mouseReleased()...");          
    }

    public void mouseClicked(MouseEvent m) {
System.out.println ("mouseClicked(), current color=" + c + "...");
        if (c == Color.red)
            c = Color.blue;
        else
            c = Color.red;
        repaint ();
    }

    public void mousePressed(MouseEvent m) {
System.out.println ("mousePressed()...");           
    }

}

---

错误是什么？我们不会检查您的代码并发现错误@Hemant Metalia-问题是鼠标侦听器从未被调用，因此颜色从未改变。这是一个合理的问题……小程序不是学习Java GUI编程的好方法。制作应用程序。第一。不要使用AWT，使用Swing。大多数曾经知道如何使用AWT的人已经忘记了细节。Paulsm4我正在使用eclipse，您的代码在单击时会使其变为绿色，即使单击的不是菱形。你能改变你的代码吗？这样它只会在只点击钻石时改变颜色。如果是这样的话，试试他的代码，但是把

addMouseListener（this）

改成

castle。addMouseListener（this）

Gobernador，这和我的问题一样。好的，更近一点，但是点击空间是正方形的，不是菱形。1）鼠标侦听器应用于整个面板（面板的整个矩形），2）您可以编写一个函数，以获取鼠标x/y并确定您是否在面板的特定区域内，如果您需要3）主要问题-为什么没有检测到鼠标单击-已解决。对的

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

public class HelloAWT extends Applet {

    private Diamond diamond;
    private static final int height = 350;
    private static final int width = 350;

    public void init () {
        setBackground(Color.green);
        resize (width, height);
        diamond = new Diamond ();
        diamond.init (Color.green);
        add(diamond);
    }

    public void paint(Graphics g)
    {
System.out.println ("HelloAWT@paint()...");
        String msg = "Hello AWT!";
        g.setFont(new Font ("Arial", Font.BOLD, 18));
        FontMetrics fm = g.getFontMetrics ();
        int x = (getWidth() - fm.stringWidth(msg)) / 2;
        int y = (getHeight() / 2) + 50;
        g.drawString(msg, x, y);
        diamond.repaint ();
    }
}

class Diamond extends JPanel implements MouseListener {
    private static final int height = 100;
    private static final int width = 100;
    private Color c = Color.red;
    private Color bkgd;
    private int[] polyX;
    private int[] polyY;
    private Polygon poly;

    public void init (Color bkgd) {
System.out.println ("Diamond@init(): bkgd=" + bkgd + "...");        
        setPreferredSize (new Dimension(width, height));
        this.bkgd = bkgd;
        polyX = new int[] { width/2, width, width/2, 0 };
        polyY= new int[] { 0, height/2, height, height/2 };
System.out.println ("polyX=" + polyX[0] + "," + polyX[1] + "," + polyX[2] + "," + polyX[3] + "...");        
System.out.println ("polyY=" + polyY[0] + "," + polyY[1] + "," + polyY[2] + "," + polyY[3] + "...");        
        poly = new Polygon( polyX, polyY, polyX.length);
        addMouseListener (this);
    }

    public void paint(Graphics g)
    {       
System.out.println ("Diamond()@paint(), bounds=" + getHeight() + "," + getWidth () + "...");
        Graphics2D g2d = (Graphics2D)g;
        g2d.setColor(bkgd);
        g2d.fillRect(0, 0, width, height);
        g2d.setColor(c);
        g2d.fill(poly);
    }

    public void mouseEntered(MouseEvent m) {
System.out.println ("mouseEntered()...");
    }

    public void mouseExited(MouseEvent m) {
System.out.println ("mouseExited()...");            
    }

    public void mouseReleased(MouseEvent m) {
System.out.println ("mouseReleased()...");          
    }

    public void mouseClicked(MouseEvent m) {
System.out.println ("mouseClicked(), current color=" + c + "...");
        if (c == Color.red)
            c = Color.blue;
        else
            c = Color.red;
        repaint ();
    }

    public void mousePressed(MouseEvent m) {
System.out.println ("mousePressed()...");           
    }

}