Java:SwingPropertyChangeSupport
我试图制作一个MVC Java Swing程序,它利用SwingPropertyChangeSupport在模型更新时通知视图。我遇到的问题是,通知似乎没有发生 我在下面准备了一份SSCCE。在SSCCE中,有一个Swing GUI,它有一个按钮和一个文本字段。当您单击该按钮时,模型中的计数器将递增,并且该视图应该得到通知,以便它可以更新自身。然而,尽管我已经检查了oldValue和newValue是否彼此不同,但似乎没有发送/接收到通知(我不确定是哪一个——可能两者都有)。如果有人能帮助我了解我的错误所在,我将不胜感激。谢谢Java:SwingPropertyChangeSupport,java,swing,propertychangelistener,propertychangesupport,Java,Swing,Propertychangelistener,Propertychangesupport,我试图制作一个MVC Java Swing程序,它利用SwingPropertyChangeSupport在模型更新时通知视图。我遇到的问题是,通知似乎没有发生 我在下面准备了一份SSCCE。在SSCCE中,有一个Swing GUI,它有一个按钮和一个文本字段。当您单击该按钮时,模型中的计数器将递增,并且该视图应该得到通知,以便它可以更新自身。然而,尽管我已经检查了oldValue和newValue是否彼此不同,但似乎没有发送/接收到通知(我不确定是哪一个——可能两者都有)。如果有人能帮助我了解
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;
import javax.swing.event.SwingPropertyChangeSupport;
public class Main extends JFrame {
public Main() {
PropertyChangeView theGui = new PropertyChangeView();
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setResizable(true);
add(theGui);
pack();
setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
new Main();
}
});
}
}
class PropertyChangeView extends JPanel {
private JButton button;
private JTextField textfield;
private GridBagConstraints gbc;
private PropertyChangeController controller;
public PropertyChangeView() {
super(new GridBagLayout());
controller = new PropertyChangeController();
button = new JButton("Click me to increment the count");
textfield = new JTextField(10);
button.addActionListener(new ButtonListener());
addPropertyChangeListener(new MyPropertyChangeListener());
gbc = new GridBagConstraints();
gbc.gridheight = 1;
gbc.gridwidth = 1;
gbc.anchor = GridBagConstraints.LINE_START;
gbc.fill = GridBagConstraints.BOTH;
gbc.gridx = 0;
gbc.gridy = 0;
add(button, gbc);
gbc.gridx = 1;
gbc.gridy = 0;
add(textfield, gbc);
}
private class MyPropertyChangeListener implements PropertyChangeListener {
@Override
public void propertyChange(PropertyChangeEvent evt) {
System.out.println("Event received " + evt);
if (evt.getPropertyName().equals(PropertyChangeModel.CHANGED)) {
textfield.setText(evt.getNewValue().toString());
}
}
}
private class ButtonListener implements ActionListener {
@Override
public void actionPerformed(ActionEvent e) {
controller.setCounter(controller.getCounter() + 1);
System.out.println("counter now = " + controller.getCounter());
}
}
}
class PropertyChangeController {
private PropertyChangeModel model;
public PropertyChangeController() {
model = new PropertyChangeModel();
}
public int getCounter() {
return model.getCounter();
}
public void setCounter(int i) {
model.setCounter(i);
}
}
class PropertyChangeModel {
public static final String CHANGED = "property change model updated";
private int counter;
private SwingPropertyChangeSupport pcs;
public PropertyChangeModel() {
counter = 0;
pcs = new SwingPropertyChangeSupport(this);
}
public int getCounter() {
return counter;
}
public void setCounter(int i) {
int oldValue = counter;
int newValue = i;
counter = newValue;
pcs.firePropertyChange(CHANGED, oldValue, newValue);
System.out.println("setCounter finished with oldValue=" + oldValue + ", newValue=" + newValue);
}
}
我没有运行您的程序,但我发现有一件事不正常:
public void setCounter(int i) {
int oldValue = counter;
int newValue = i;
pcs.firePropertyChange(CHANGED, oldValue, newValue);
counter = newValue;
System.out.println("setCounter finished with oldValue=" + oldValue + ", newValue=" + newValue);
}
应该是:
public void setCounter(int i) {
int oldValue = counter;
int newValue = i;
counter = newValue;
pcs.firePropertyChange(CHANGED, oldValue, newValue);
System.out.println("setCounter finished with oldValue=" + oldValue + ", newValue=" + newValue);
}
您应该仅在更新模型值后发出通知
不过,您的主要问题是没有向模型添加PropertyChangeListener
e、 g
谢谢,我已经更新了代码示例,以便在触发通知之前放置
计数器=newValue
。至于PropertyChangeListener,我在视图中添加了一个,因为我希望得到通知。这不对吗?(我想这一定是因为我的程序不工作了!)@user1002119:这是倒过来的。您将侦听器添加到正在侦听的项中,以获取对模型的更改。然后,您的侦听器将通知视图。请查看上面对代码的更改。@user1002119:虽然我会在一个单独的类中创建单个控件/模型和视图,并将它们连接起来,但是为了回答的速度(我必须去工作),我还没有对您的代码做这么大的更改。感谢您花时间帮助我!那么您将侦听器添加到触发属性更改通知的同一个对象?您更新的示例确实很有帮助,我能够在我的实际项目中实现这一点。再次感谢!
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;
import javax.swing.event.SwingPropertyChangeSupport;
public class Main extends JFrame {
public Main() {
PropertyChangeView theGui = new PropertyChangeView();
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setResizable(true);
add(theGui);
pack();
setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
new Main();
}
});
}
}
class PropertyChangeView extends JPanel {
private JButton button;
private JTextField textfield;
private GridBagConstraints gbc;
private PropertyChangeController controller;
public PropertyChangeView() {
super(new GridBagLayout());
PropertyChangeModel model = new PropertyChangeModel();
controller = new PropertyChangeController(model);
button = new JButton("Click me to increment the count");
textfield = new JTextField(10);
button.addActionListener(new ButtonListener());
model.addPropertyChangeListener(new MyPropertyChangeListener());
gbc = new GridBagConstraints();
gbc.gridheight = 1;
gbc.gridwidth = 1;
gbc.anchor = GridBagConstraints.LINE_START;
gbc.fill = GridBagConstraints.BOTH;
gbc.gridx = 0;
gbc.gridy = 0;
add(button, gbc);
gbc.gridx = 1;
gbc.gridy = 0;
add(textfield, gbc);
}
private class MyPropertyChangeListener implements PropertyChangeListener {
@Override
public void propertyChange(PropertyChangeEvent evt) {
System.out.println("Event received " + evt);
if (evt.getPropertyName().equals(PropertyChangeModel.CHANGED)) {
textfield.setText(evt.getNewValue().toString());
}
}
}
private class ButtonListener implements ActionListener {
@Override
public void actionPerformed(ActionEvent e) {
controller.setCounter(controller.getCounter() + 1);
System.out.println("counter now = " + controller.getCounter());
}
}
}
class PropertyChangeController {
private PropertyChangeModel model;
// public PropertyChangeController() {
// model = new PropertyChangeModel();
// }
public PropertyChangeController(PropertyChangeModel model) {
this.model = model;
}
public int getCounter() {
return model.getCounter();
}
public void setCounter(int i) {
model.setCounter(i);
}
}
class PropertyChangeModel {
public static final String CHANGED = "property change model updated";
private int counter;
private SwingPropertyChangeSupport pcs;
public PropertyChangeModel() {
counter = 0;
pcs = new SwingPropertyChangeSupport(this);
}
public void addPropertyChangeListener(
PropertyChangeListener l) {
pcs.addPropertyChangeListener(l);
}
public int getCounter() {
return counter;
}
public void setCounter(int i) {
int oldValue = counter;
int newValue = i;
counter = newValue;
pcs.firePropertyChange(CHANGED, oldValue, newValue);
System.out.println("setCounter finished with oldValue=" + oldValue
+ ", newValue=" + newValue);
}
}