考虑以下只获取IP和端口号的类：
package view;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.net.InetAddress;
import javax.swing.*;
import javax.swing.border.EmptyBorder;
/**
* Server side
* @author X
*
*/
class ServerConnector implements ActionListener
{
private JFrame m_frame = null;
private JTextField m_serverIP;
private JTextField m_serverPort; // you can use also JPasswordField
private JButton m_submitButton;
// location of the jframe
private final int m_centerX = 500;
private final int m_centerY = 300;
// dimensions of the jframe
private final int m_sizeX = 1650;
private final int m_sizeY = 150;
private String m_ip;
private String m_port;
private boolean ready = false;
/**
* Ctor
*/
ServerConnector()
{
m_frame = new JFrame("Sever Side Listener");
m_frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
m_serverIP = new JTextField(20);
m_serverPort = new JTextField(20);
JPanel gui = new JPanel(new BorderLayout(3,3));
gui.setBorder(new EmptyBorder(5,5,5,5));
gui.setSize(m_sizeX , m_sizeY);
m_frame.setContentPane(gui);
JPanel labels = new JPanel(new GridLayout(0,1));
JPanel controls = new JPanel(new GridLayout(0,1));
gui.add(labels, BorderLayout.WEST);
gui.add(controls, BorderLayout.CENTER);
labels.add(new JLabel("Server IP: "));
controls.add(m_serverIP);
labels.add(new JLabel("Server Port: "));
controls.add(m_serverPort);
m_submitButton = new JButton("Start Listening");
m_submitButton.addActionListener(this);
gui.add(m_submitButton, BorderLayout.SOUTH);
m_frame.setLocation(m_centerX , m_centerY);
m_frame.setSize(m_sizeX , m_sizeY);
m_frame.pack();
m_frame.setVisible(true);
}
public static void main(String[] args) {
new ServerConnector();
}
@Override
public void actionPerformed(ActionEvent event) {
Object object = event.getSource();
if (object == this.m_submitButton)
{
// grab all values from the connection box
// if one of them is missing then display an alert message
String ip = this.m_serverIP.getText().trim();
String port = this.m_serverPort.getText().trim();
if (ip.length() == 0)
{
JOptionPane.showMessageDialog(null, "Please enter IP address !");
return;
}
if (port.length() == 0)
{
JOptionPane.showMessageDialog(null, "Please enter Port number!");
return;
}
int s_port = 0;
try
{
// try parse the Port number
// throws exception when an incorrect IP address
// is entered , and caught in the catch block
s_port = Integer.parseInt(port);
}
catch(Exception exp)
{
JOptionPane.showMessageDialog(null, "Port number is incorrect!");
return;
}
try
{
// try parse the IP address
// throws exception when an incorrect IP address
// is entered , and caught in the catch block
InetAddress.getByName(ip);
}
catch(Exception exp)
{
JOptionPane.showMessageDialog(null, "IP address is incorrect!");
return;
}
m_frame.dispose();
this.m_ip = ip;
this.m_port = port;
ready = true;
// new ServerGUI(ip , s_port);
}
}
public boolean isReady()
{
return this.ready;
}
/**
*
* @return
*/
public String[] getIPandPort()
{
String[] ipPort = new String[2];
ipPort[0] = this.m_ip;
ipPort[1] = this.m_port;
return ipPort;
}
}
这将是控制器类
public class ServerController {
String m_ip;
int m_port;
public static void main(String args[])
{
ServerConnector sc = new ServerConnector();
while (!sc.isReady())
{
// run
}
// get IP and port
String[] ipPort = sc.getIPandPort();
System.out.println("IP is :" + ipPort[0] + " and port is :" + ipPort[1]);
}
}
现在ServerController处于while（true）循环中，直到用户输入IP和端口。
如何避免这种依赖（避免while循环）？
答案 0 :(得分：2)
首先，摆脱while (true)循环，因为它的唯一目的是弄乱你的代码。
一般的解决方案是从阻止程序流的代码中获取用户的信息。但是如果在不能阻止其事件线程的GUI中需要这样做，则会出现问题。
One Swing解决方案正如我们之前在your previous question中所讨论的那样：使用模态对话框来获取信息。对话框的模态将暂停调用代码中的程序流，直到处理完对话框。
如果你想避免使用模态对话框，那么另一个通用的事件驱动解决方案是使用观察者设计模式 - 让另一个对象 通知 当信息或状态发生变化时。使用PropertyChangeSupport和PropertyChangeListeners可以很容易地实现这一点，尽管还有其他方法，包括使用Swing库中提供的XxxxListeners。
例如监听器使用和带Swing的MVC：
修改
例如，标有// !!评论的更改：
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
import java.net.InetAddress;
import javax.swing.*;
import javax.swing.border.EmptyBorder;
import javax.swing.event.SwingPropertyChangeSupport;
public class ServerController {
String m_ip;
int m_port;
private static String[] ipPort;
public static void main(String args[]) {
final ServerConnector sc = new ServerConnector();
sc.addPropertyChangeListener(new PropertyChangeListener() {
@Override
public void propertyChange(PropertyChangeEvent evt) {
if (ServerConnector.READY.equals(evt.getPropertyName())) {
if (sc.isReady()) {
ipPort = sc.getIPandPort();
System.out.println("IP is :" + ipPort[0] + " and port is :" + ipPort[1]);
}
}
}
});
}
}
class ServerConnector implements ActionListener {
public static final String READY = "ready"; //!!
private SwingPropertyChangeSupport pcSupport = new SwingPropertyChangeSupport(this); //!!
private boolean ready = false;
private JFrame m_frame = null;
private JTextField m_serverIP;
private JTextField m_serverPort; // you can use also JPasswordField
private JButton m_submitButton;
// location of the jframe
private final int m_centerX = 500;
private final int m_centerY = 300;
// dimensions of the jframe
private final int m_sizeX = 1650;
private final int m_sizeY = 150;
private String m_ip;
private String m_port;
/**
* Ctor
*/
ServerConnector() {
m_frame = new JFrame("Sever Side Listener");
m_frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
m_serverIP = new JTextField(20);
m_serverPort = new JTextField(20);
JPanel gui = new JPanel(new BorderLayout(3, 3));
gui.setBorder(new EmptyBorder(5, 5, 5, 5));
gui.setSize(m_sizeX, m_sizeY);
m_frame.setContentPane(gui);
JPanel labels = new JPanel(new GridLayout(0, 1));
JPanel controls = new JPanel(new GridLayout(0, 1));
gui.add(labels, BorderLayout.WEST);
gui.add(controls, BorderLayout.CENTER);
labels.add(new JLabel("Server IP: "));
controls.add(m_serverIP);
labels.add(new JLabel("Server Port: "));
controls.add(m_serverPort);
m_submitButton = new JButton("Start Listening");
m_submitButton.addActionListener(this);
gui.add(m_submitButton, BorderLayout.SOUTH);
m_frame.setLocation(m_centerX, m_centerY);
m_frame.setSize(m_sizeX, m_sizeY);
m_frame.pack();
m_frame.setVisible(true);
}
public static void main(String[] args) {
new ServerConnector();
}
@Override
public void actionPerformed(ActionEvent event) {
Object object = event.getSource();
if (object == this.m_submitButton) {
// grab all values from the connection box
// if one of them is missing then display an alert message
String ip = this.m_serverIP.getText().trim();
String port = this.m_serverPort.getText().trim();
if (ip.length() == 0) {
JOptionPane.showMessageDialog(null, "Please enter IP address !");
return;
}
if (port.length() == 0) {
JOptionPane.showMessageDialog(null, "Please enter Port number!");
return;
}
int s_port = 0;
try {
// try parse the Port number
// throws exception when an incorrect IP address
// is entered , and caught in the catch block
s_port = Integer.parseInt(port);
}
catch (Exception exp) {
JOptionPane.showMessageDialog(null, "Port number is incorrect!");
return;
}
try {
// try parse the IP address
// throws exception when an incorrect IP address
// is entered , and caught in the catch block
InetAddress.getByName(ip);
}
catch (Exception exp) {
JOptionPane.showMessageDialog(null, "IP address is incorrect!");
return;
}
m_frame.dispose();
this.m_ip = ip;
this.m_port = port;
setReady(true); //!!
// !! ready = true;
// new ServerGUI(ip , s_port);
}
}
// !! added
public void setReady(boolean ready) {
boolean oldValue = this.ready;
boolean newValue = ready;
this.ready = ready;
pcSupport.firePropertyChange(READY, oldValue, newValue);
}
//!! added
public void addPropertyChangeListener(PropertyChangeListener listener) {
pcSupport.addPropertyChangeListener(listener);
}
//!! added
public void removePropertyChangeListener(PropertyChangeListener listener) {
pcSupport.removePropertyChangeListener(listener);
}
public boolean isReady() {
return this.ready;
}
/**
*
* @return
*/
public String[] getIPandPort() {
String[] ipPort = new String[2];
ipPort[0] = this.m_ip;
ipPort[1] = this.m_port;
return ipPort;
}
}