import java.awt.*;
import java.awt.event.*;
import javax.swing.SwingUtilities;
class WinB extends Frame implements MouseListener,MouseMotionListener
{ Button button;
TextField text;
int x, y;
boolean move=false;
WinB()
{ button=new Button("用鼠标拖动我");
text=new TextField("用鼠标拖动我",8);
button.addMouseListener(this);
button.addMouseMotionListener(this);
text.addMouseListener(this);
text.addMouseMotionListener(this);
addMouseMotionListener(this);
setLayout(new FlowLayout());
add(button);
add(text);
addWindowListener(new WindowAdapter(){
public void windowClosing(WindowEvent e){
System.exit(0);
}
});
setBounds(10,10,350,300);
setVisible(true);
validate();
}
public void mousePressed(MouseEvent e){}
public void mouseReleased(MouseEvent e)
{ move=false;
}
public void mouseEntered(MouseEvent e){}
public void mouseExited(MouseEvent e){}
public void mouseClicked(MouseEvent e){}
public void mouseMoved(MouseEvent e){}
public void mouseDragged(MouseEvent e)
{ Component com=null;
if(e.getSource() instanceof Component)
{ if(com!=this)
move=true;
e=SwingUtilities.convertMouseEvent(com, e, this);
if(move)
{ x=e.getX();
y=e.getY();
int w=com.getSize().width;
int h=com.getSize().height;
com.setLocation(x-w/2, y-h/2);
}
}
}
}
public class MouseMotionExa {
/**
* @param args
*/
public static void main(String[] args) {
new WinB();
// TODO Auto-generated method stub
}
}
上述代码是实现通过鼠标移动文本框和按钮，编译通过了，可是用鼠标拖动时开始报错，if(e.getSource() instanceof Component) 我把这句改成if(e.e.getSource()==com)没有错误了，但是鼠标事件不发生，该句判断鼠标事件的对象的类是否是Component，这句话主要起什么作用？
------解决方案--------------------
查看了API，类的关系如下：
java.lang.Object
java.util.EventObject
java.awt.AWTEvent
java.awt.event.ComponentEvent
所以，Component com = e.getComponent()，才对。
修改的WinB的代码如下：
- Java code
package demo;import java.awt.Button;import java.awt.Component;import java.awt.FlowLayout;import java.awt.Frame;import java.awt.TextField;import java.awt.event.MouseEvent;import java.awt.event.MouseListener;import java.awt.event.MouseMotionListener;import java.awt.event.WindowAdapter;import java.awt.event.WindowEvent;import javax.swing.SwingUtilities;public class WinB extends Frame implements MouseListener, MouseMotionListener { Button button; TextField text; int x, y; boolean move = false; WinB() { button = new Button("用鼠标拖动我"); text = new TextField("用鼠标拖动我", 8); button.addMouseListener(this); button.addMouseMotionListener(this); text.addMouseListener(this); text.addMouseMotionListener(this); addMouseMotionListener(this); setLayout(new FlowLayout()); add(button); add(text); addWindowListener(new WindowAdapter() { public void windowClosing(WindowEvent e) { System.exit(0); } }); setBounds(10, 10, 350, 300); setVisible(true); validate(); } public void mousePressed(MouseEvent e) { } public void mouseReleased(MouseEvent e) { move = false; } public void mouseEntered(MouseEvent e) { } public void mouseExited(MouseEvent e) { } public void mouseClicked(MouseEvent e) { } public void mouseMoved(MouseEvent e) { } public void mouseDragged(MouseEvent e) { Component com = e.getComponent(); if (com instanceof Component) { if (com != this) move = true; e = SwingUtilities.convertMouseEvent(com, e, this); if (move) { x = e.getX(); y = e.getY(); int w = com.getSize().width; int h = com.getSize().height; com.setLocation(x - w / 2, y - h / 2); } } }}