Question

java 新手提问 鼠标事件

如图所示，文本框中有默认的文字，当鼠标点击文本框时候，文本框里面的文字会消失，填写完所有文本框信息，点击按钮注册。

Answer 1

源代码如下：

public class Reg extends javax.swing.JFrame
{

public Reg()
{
initComponents();
setTitle("注册界面");
setLocationRelativeTo(null);
}

private void initComponents()
{

button1 = new java.awt.Button();
textField1 = new java.awt.TextField();
textField2 = new java.awt.TextField();
textField3 = new java.awt.TextField();
textField4 = new java.awt.TextField();
textField5 = new java.awt.TextField();

setDefaultCloseOperation

(javax.swing.WindowConstants.EXIT_ON_CLOSE);

button1.setActionCommand("\u6ce8\u518c");
button1.setLabel("\u6ce8\u518c");
//添加鼠标单击事件
button1.addActionListener(new

java.awt.event.ActionListener()
{
public void actionPerformed

(java.awt.event.ActionEvent evt)
{
button1ActionPerformed(evt);
}
});

textField1.setText("\u59d3");
//添加获得焦点的事件
textField1.addFocusListener(new

java.awt.event.FocusAdapter()
{
public void focusGained

(java.awt.event.FocusEvent evt)
{
textField1FocusGained(evt);
}
});

textField2.setText("\u540d");
//添加获得焦点的事件
textField2.addFocusListener(new

java.awt.event.FocusAdapter()
{
public void focusGained

(java.awt.event.FocusEvent evt)
{
textField2FocusGained(evt);
}
});

textField3.setText("\u90ae\u7bb1");
//添加获得焦点的事件
textField3.addFocusListener(new

java.awt.event.FocusAdapter()
{
public void focusGained

(java.awt.event.FocusEvent evt)
{
textField3FocusGained(evt);
}
});

textField4.setText("\u5bc6\u7801");
//添加获得焦点的事件
textField4.addFocusListener(new

java.awt.event.FocusAdapter()
{
public void focusGained

(java.awt.event.FocusEvent evt)
{
textField4FocusGained(evt);
}
});

textField5.setText("textField5");

javax.swing.GroupLayout layout = new

javax.swing.GroupLayout(
getContentPane());
getContentPane().setLayout(layout);
layout.setHorizontalGroup

(layout.createParallelGroup(

javax.swing.GroupLayout.Alignment.LEADING).addGroup(
layout.createSequentialGroup

().addContainerGap().addGroup(

layout.createParallelGroup(

javax.swing.GroupLayout.Alignment.LEADING,

false).addComponent(textField1,

javax.swing.GroupLayout.DEFAULT_SIZE,

javax.swing.GroupLayout.DEFAULT_SIZE,

Short.MAX_VALUE).addComponent(textField3,

javax.swing.GroupLayout.DEFAULT_SIZE, 98,

Short.MAX_VALUE).addComponent(textField4,

javax.swing.GroupLayout.DEFAULT_SIZE,

javax.swing.GroupLayout.DEFAULT_SIZE,

Short.MAX_VALUE)).addGap(54, 54, 54)
.addComponent

(textField2,

javax.swing.GroupLayout.PREFERRED_SIZE, 82,

javax.swing.GroupLayout.PREFERRED_SIZE)
.addContainerGap(77,

Short.MAX_VALUE)).addGroup(

javax.swing.GroupLayout.Alignment.TRAILING,
layout.createSequentialGroup

().addContainerGap(313,

Short.MAX_VALUE).addComponent(textField5,

javax.swing.GroupLayout.PREFERRED_SIZE, 8,

javax.swing.GroupLayout.PREFERRED_SIZE)).addGroup(
layout.createSequentialGroup

().addGap(114, 114, 114)
.addComponent

(button1,

javax.swing.GroupLayout.PREFERRED_SIZE, 92,

javax.swing.GroupLayout.PREFERRED_SIZE)
.addContainerGap

(115, Short.MAX_VALUE)));
layout
.setVerticalGroup(layout

.createParallelGroup(

javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(

layout

.createSequentialGroup()

.addComponent(

textField5,

javax.swing.GroupLayout.PREFERRED_SIZE,

9,

javax.swing.GroupLayout.PREFERRED_SIZE)

.addGap(48, 48, 48)

.addGroup(

layout

.createParallelGroup(

javax.swing.GroupLayout.Alignment.LEADING)

.addComponent(

textField2,

javax.swing.GroupLayout.PREFERRED_SIZE,

javax.swing.GroupLayout.DEFAULT_SIZE,

javax.swing.GroupLayout.PREFERRED_SIZE)

.addGroup(

layout

.createSequentialGroup()

.addComponent(

textField1,

javax.swing.GroupLayout.PREFERRED_SIZE,

javax.swing.GroupLayout.DEFAULT_SIZE,

javax.swing.GroupLayout.PREFERRED_SIZE)

.addGap(

53,

53,

53)

.addComponent(

textField3,

javax.swing.GroupLayout.PREFERRED_SIZE,

javax.swing.GroupLayout.DEFAULT_SIZE,

javax.swing.GroupLayout.PREFERRED_SIZE)

.addGap(

53,

53,

53)

.addComponent(

textField4,

javax.swing.GroupLayout.PREFERRED_SIZE,

javax.swing.GroupLayout.DEFAULT_SIZE,

javax.swing.GroupLayout.PREFERRED_SIZE)))

.addGap(20, 20, 20)

.addComponent(

button1,

javax.swing.GroupLayout.PREFERRED_SIZE,

javax.swing.GroupLayout.DEFAULT_SIZE,

javax.swing.GroupLayout.PREFERRED_SIZE)

.addGap(32, 32, 32)));

pack();
}// </editor-fold>

/**
* 密码框响应事件
*/
private void textField4FocusGained(java.awt.event.FocusEvent

evt)
{
// TODO add your handling code here:
textField4.setText("");
}

/**
* 邮箱框响应事件
*/
private void textField3FocusGained(java.awt.event.FocusEvent

evt)
{
// TODO add your handling code here:
textField3.setText("");
}

/**
* 名框响应事件
*/
private void textField2FocusGained(java.awt.event.FocusEvent

evt)
{
// TODO add your handling code here:
textField2.setText("");
}

/**
* 姓框响应事件
*/
private void textField1FocusGained(java.awt.event.FocusEvent

evt)
{
// TODO add your handling code here:
if (textField1.getText().trim() != null)
textField1.setText("");
}

/**
* 按钮响应事件
*/
private void button1ActionPerformed

(java.awt.event.ActionEvent evt)
{
// TODO add your handling code here:
System.out.println("注册按钮被按下了");
System.out.println("姓：" + textField1.getText());
System.out.println("名：" + textField2.getText());
System.out.println("邮箱：" + textField3.getText());
System.out.println("密码：" + textField4.getText());
}

/**
* @param args the command line arguments
*/
public static void main(String args[])
{
java.awt.EventQueue.invokeLater(new Runnable()
{
public void run()
{
new Reg().setVisible(true);
}
});
}

private java.awt.Button button1;//注册按钮
private java.awt.TextField textField1;//姓
private java.awt.TextField textField2;//名
private java.awt.TextField textField3;//邮箱
private java.awt.TextField textField4;//密码
private java.awt.TextField textField5;
}

Answer 2

import java.awt.BorderLayout;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;

import javax.swing.JFrame;
import javax.swing.JTextField;

public class FrameTest extends JFrame {
private JTextField tf1, tf2;

public FrameTest() {
super("测试");

tf1 = new JTextField("姓");
tf2 = new JTextField("名");

tf1.addMouseListener(new MouseListener() {

public void mouseReleased(MouseEvent e) {
}

public void mousePressed(MouseEvent e) {
}

public void mouseExited(MouseEvent e) {
if (tf1.getText().trim().equals("")) {
tf1.setText("姓");
}
}

public void mouseEntered(MouseEvent e) {
if (tf1.getText().trim().equals("姓")) {
tf1.setText(null);
}
}

public void mouseClicked(MouseEvent e) {
}
});
tf2.addMouseListener(new MouseListener() {

public void mouseReleased(MouseEvent e) {
}

public void mousePressed(MouseEvent e) {
}

public void mouseExited(MouseEvent e) {
if (tf2.getText().trim().equals("")) {
tf2.setText("名");
}
}

public void mouseEntered(MouseEvent e) {
if (tf2.getText().trim().equals("名")) {
tf2.setText(null);
}
}

public void mouseClicked(MouseEvent e) {
}
});

this.add(tf1, BorderLayout.NORTH);
this.add(tf2, BorderLayout.SOUTH);
this.setSize(300, 200);
this.setLocationRelativeTo(null);
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
this.setVisible(true);
}

public static void main(String[] args) {
new FrameTest();
}

}

你参考一下，还不会就回复我

追问

mousePressed(); mouseReleased();mouseClicked();mouseEntered()；mouseExited(); 是不是总要一起用？比如你上面tf1鼠标事件中只有mouseEntered()；mouseExited()有代码，其他mousePressed(); mouseReleased();mouseClicked()都是空方法.

追答

不是总要的，因为我在那里用的是接口，接口就一定要实现里面的抽象方法，你完全可以用自定义类，然后继承mouse适配器，再重写Enter和Exit方法，就不用出现Press等其他空方法