java如何构造画笔工具

java如何构造画笔工具

已运行成功，符合要求！
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class Test1 extends JFrame{
DrawPane p;
JButton btn=new JButton("清除");
public Test1() {
p=new DrawPane();
btn.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
p.repaint();
}
});
getContentPane().setLayout(new BorderLayout());
getContentPane().add(p,"Center");
getContentPane().add(btn,"North");
setTitle("画板");
setSize(300,300);
setVisible(true);
}
public static void main(String[] args) {
new Test1();
}
}

class DrawPane extends JPanel {
int x1,y1,x2,y2;
boolean first=true;
public DrawPane() {
x1=x2=y1=y2=0;
MouseAdapter adapter=new MouseAdapter() {
public void mousePressed(MouseEvent e) {
if(e.getButton()==MouseEvent.BUTTON1) {
x1=x2=e.getX();
y1=y2=e.getY();
}
}
public void mouseDragged(MouseEvent e) {
Graphics g=getGraphics();
if(first){
System.out.println("try");
x2=e.getX();
y2=e.getY();
draw(g);
first=false;
}
else{
x1=x2;
y1=y2;
x2=e.getX();
y2=e.getY();
draw(g);
}
}
public void mouseReleased(MouseEvent e) {
if(e.getButton()==MouseEvent.BUTTON1){
x1=x2=y1=y2=0;
}
}
};
addMouseListener(adapter);
addMouseMotionListener(adapter);

}

public void draw(Graphics g) {
g.drawLine(x1,y1,x2,y2);
}
}

这个用来做练习？

看你想在什么组件上画了，JPanel或者定制组件，为其添加Mouse监听器就行了，在监听器里面跟踪鼠标的位置变化，并画出鼠标所在的点

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