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两点连线问题

摘要: 两点连线问题

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

public class DrawLine extends JFrame
{
public DrawLine()
{
this.addMouseListener(new MouseAdapter()
{
public void mousePressed(MouseEvent e)
{
int x1,y1;
x1 = e.getX();
y1 = e.getY();
}
public void mouseReleased(MouseEvent e)
{
int x2,y2;
x2 = e.getX();
y2 = e.getY();
getGraphics().drawLine(x1,y1,x2,y2);//此处getGraphics()为什么不对呢??
}
}
);
}
public static void main(String[] args)
{
DrawLine fm = new DrawLine();
fm.setSize(300,300);
fm.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
fm.setVisible(true);
}
}

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/**
*注意变量的做用域,x1,y1,在mouseReleased()里的嘛.
*/
import javax.swing.*;
import java.awt.event.*;
import java.awt.*;
import java.awt.image.*;

public class DrawLine extends JFrame
{
int x1,y1;
public DrawLine()
{
this.addMouseListener(new MouseAdapter()
{
public void mousePressed(MouseEvent e)
{
x1 = e.getX();
y1 = e.getY();
}
public void mouseReleased(MouseEvent e)
{
int x2,y2;
x2 = e.getX();
y2 = e.getY();
getGraphics().drawLine(x1,y1,x2,y2);//此处getGraphics()为什么不对呢??
}
}
);
}
public static void main(String[] args)
{
DrawLine fm = new DrawLine();
fm.setSize(300,300);
fm.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
fm.setVisible(true);
}
}

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谢谢!!

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