在java屏幕上显示鼠标坐标的问题 [英] problem displaying mouse coordinates on the screen in java

问题描述

我试图在我的JPanel中显示鼠标坐标（数学坐标），但是我将每个坐标放在另一个坐标上，可以找出原因。
这里是我的代码：

  import java.awt。*; 
 import java.awt.event.MouseEvent; 
 import java.awt.geom.Line2D; 
 import java.awt.geom.Point2D; 
 import java.applet。*; 
 
 import javax.swing.JPanel; 
 import javax.swing.event.MouseInputAdapter; 
 
 public class drawarea extends JPanel {
 
 int n; 
 private point mouseCoords = null; 
 int UNIT = 20; 
 
 drawarea（）{
 super（）; 
 setBackground（Color.white）; 
 addMouseMotionListener（new MouseInputAdapter（）{
 
 public void mouseMoved（MouseEvent e）{
 super.mouseMoved（e）; 
 mouseCoords = new Point（e.getX （），e.​​getY（））; 
 repaint（）; 
} 
 
 / ** 
 * @see java.awt.event.MouseListener＃mouseExited （MouseEvent）
 * / 
 public void mouseExited（MouseEvent e）{
 super.mouseExited（e）; 
 mouseCoords = null; 
 repaint（）; 
} 
}）; 
 setCursor（new Cursor（Cursor.CROSSHAIR_CURSOR））; 
} 
 
 public void paint（Graphics g）{
 
 // draw axis x and y 
 g.setColor（Color.red）; 
 g.drawLine（0，r.height / 2，r.width，r.height / 2）; 
 g.drawLine（r.width / 2，0，r.width / 2，r.height）; 
 
 Graphics2D g2 =（Graphics2D）g; 
 g2.setRenderingHint（RenderingHints.KEY_ANTIALIASING，
 RenderingHints.VALUE_ANTIALIAS_ON）; 
 dessinBoule（g2）; 
 
 $ b $ private void dessinBoule（Graphics2D g）{
 //如果鼠标不在ara里面
 //我想要坐标显示
 if（mouseCoords == null）{
 return; 
} 
 g.setColor（Color.BLACK）; 
 
 int decPolice = 15; 
 
 g.drawString（x =+ getFormatedString（+ mouseCoords.x）
 +，y =+ getFormatedString（+ mouseCoords.y），2，15 ）; 
 
 $ b $ private String getFormatedString（String s）{
 if（s.length（）> 4）{
 return s.substring（0，3） ; 
} 
 return s; 
} 
} 
  

谢谢。
<您正在绘制图形区域，所以g.drawString（...）会在已经存在的地方绘制一个字符串。您必须首先清除其中的内容，通过以背景颜色绘制矩形，或者使用可以使用单独的paint（...）方法管理的单独组件。

I'm trying to display mouse coordinates (math coordinates) in my JPanel , but i get each coordinates on top of the other ,can' figure out why . here's my code :

import java.awt.*;
import java.awt.event.MouseEvent;
import java.awt.geom.Line2D;
import java.awt.geom.Point2D;
import java.applet.*;

import javax.swing.JPanel;
import javax.swing.event.MouseInputAdapter;

public class drawarea extends JPanel {

    int n;
    private Point mouseCoords = null;
    int UNIT = 20;

    drawarea() {
        super();
        setBackground(Color.white);
        addMouseMotionListener(new MouseInputAdapter() {

            public void mouseMoved(MouseEvent e) {
                super.mouseMoved(e);
                mouseCoords = new Point(e.getX(), e.getY());
                repaint();
            }

            /**
             * @see java.awt.event.MouseListener#mouseExited(MouseEvent)
             */
            public void mouseExited(MouseEvent e) {
                super.mouseExited(e);
                mouseCoords = null;
                repaint();
            }
        });
        setCursor(new Cursor(Cursor.CROSSHAIR_CURSOR));
    }

    public void paint(Graphics g) {

        //draw axis x and y
        g.setColor(Color.red);
        g.drawLine(0, r.height / 2, r.width, r.height / 2);
        g.drawLine(r.width / 2, 0, r.width / 2, r.height);

        Graphics2D g2 = (Graphics2D) g;
        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
            RenderingHints.VALUE_ANTIALIAS_ON);
        dessinBoule(g2);
    }

    private void dessinBoule(Graphics2D g) {
        // if mouse isnt inside the ara where
        // i want the coordinates to bes displayed
        if (mouseCoords == null) {
            return;
        }
        g.setColor(Color.BLACK);

        int decPolice = 15;

        g.drawString("x = " + getFormatedString("" + mouseCoords.x)
            + " , y = " + getFormatedString("" + mouseCoords.y), 2, 15);
    }

    private String getFormatedString(String s) {
        if (s.length() > 4) {
            return s.substring(0, 3);
        }
        return s;
    }
}

thanks.

解决方案

You're drawing on your graphics area, so g.drawString(...) draws a string on top of what is already there. You must either erase what is there first, by drawing a rectangle in the background colour, or use a separate component that you can manage with a separate paint(...) method.

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