我在设置一个属于另一个 bean 的 bean 并使其正确更新时遇到问题。更具体地说，我有:
public class MyForm extends javax.swing.JFrame {
MyBean aBean;
JTextField aTextField;
....
public MyBean getABean() { return aBean; }
public void setABean(MyBean newBean) {
MyBean oldBean = aBean;
aBean = newBean;
propertyChangeSupport.firePropertyChange(PROP_MYBEAN, oldBean, aBean);
}
...
binding = Bindings.createAutoBinding(
AutoBinding.UpdateStrategy.READ_WRITE,
aBean,
ELProperty.create("${file.name}"),
aTextField,
BeanProperty.create("text")
);
bindingGroup.addBinding(binding);
...
}
其中 MyBean 有一个 File 成员，该成员具有适当的 getters 和 setters。我想做的是拥有它，以便我可以使用 setter 更改 aBean 并更新绑定(bind)到它的任何内容以反射(reflect)新 aBean 的值。
我可以看到这个问题；原来的aBean被绑定(bind)到TextField，当分配新的aBean时，没有“交换”。然而，看到问题并不意味着我有解决方案!
我当前的解决方法涉及中间人类。我有 MyForm 有 MyMiddleMan 和 MyMiddleMan 有 MyBean。每当我想要更改 MyBean 时，MyMiddleMan 中的 setter 就会被调用，并触发 MyForm 可以看到的适当事件。 MyForm 的成员永远不会改变，因此它“有效”。
我的解决方法在很多层面上都很糟糕。有没有更好、最佳实践的方法？我承认我不是 Beans 专家，可能会遗漏一些明显的东西。我正在使用 NetBeans IDE 8.0(如果相关的话)，并且希望使用该构建器生成我的 GUI。显然，我的真实代码比这个示例大得多，所以如果我每次都必须开始添加额外的代码，它可能会变得很麻烦。
我下面有一个工作示例来演示我的问题。由于Bean需要公开，所以一共有三个文件； MyBean.java、MyMiddleMan.java 和 MyForm.java。它应该生成四个绑定(bind)文本字段。第一个演示我可以毫无问题地更改成员的内容。第二个显示了我的问题(我知道为什么它不起作用，只是不知道如何修复它)，第三个是无关紧要的，取自教程作为“健全性检查”，第四个是使用我的“MyMiddleMan” “解决方法。
MyBean.java
package testpackage;
import java.beans.PropertyChangeListener;
import java.beans.PropertyChangeSupport;
import java.io.File;
public class MyBean {
private File file;
public static final String PROP_FILE = "file";
public MyBean() {
}
public MyBean(File file) {
this.file = file;
}
public File getFile() {
return file;
}
public void setFile(File file) {
File oldFile = this.file;
this.file = file;
propertyChangeSupport.firePropertyChange(PROP_FILE, oldFile, file);
}
private transient final PropertyChangeSupport propertyChangeSupport = new PropertyChangeSupport(this);
public void addPropertyChangeListener(PropertyChangeListener listener) {
propertyChangeSupport.addPropertyChangeListener(listener);
}
public void removePropertyChangeListener(PropertyChangeListener listener) {
propertyChangeSupport.removePropertyChangeListener(listener);
}
@Override
public String toString() {
return "MyBean{" + "file=" + file.getName() + '}';
}
}
MyMiddleMan.java
package testpackage;
import java.beans.PropertyChangeListener;
import java.beans.PropertyChangeSupport;
public class MyMiddleMan {
private MyBean myBean;
public static final String PROP_MYBEAN = "myBean";
/**
* Get the value of myBean
*
* @return the value of myBean
*/
public MyBean getMyBean() {
return myBean;
}
/**
* Set the value of myBean
*
* @param myBean new value of myBean
*/
public void setMyBean(MyBean myBean) {
MyBean oldMyBean = this.myBean;
this.myBean = myBean;
propertyChangeSupport.firePropertyChange(PROP_MYBEAN, oldMyBean, myBean);
}
private transient final PropertyChangeSupport propertyChangeSupport = new PropertyChangeSupport(this);
/**
* Add PropertyChangeListener.
*
* @param listener
*/
public void addPropertyChangeListener(PropertyChangeListener listener) {
propertyChangeSupport.addPropertyChangeListener(listener);
}
/**
* Remove PropertyChangeListener.
*
* @param listener
*/
public void removePropertyChangeListener(PropertyChangeListener listener) {
propertyChangeSupport.removePropertyChangeListener(listener);
}
}
MyForm.java 其中大部分是由 NetBeans 自动生成的。
package testpackage;
import java.beans.PropertyChangeListener;
import java.beans.PropertyChangeSupport;
import java.io.File;
public class MyForm extends javax.swing.JFrame {
private static final long serialVersionUID = -9151817428068627139L;
public MyForm() {
initComponents();
myBean1.setFile(new File("test.txt"));
setMyBean2(new MyBean(new File("test.txt")));
myMiddleMan1.setMyBean(new MyBean(new File("test.txt")));
System.out.println("MyBean1: " + myBean1);
System.out.println("MyBean2: " + myBean2);
System.out.println("MyMiddleMan.myBean: " + myMiddleMan1.getMyBean());
}
public static final String PROP_MYBEAN2 = "myBean2";
/**
* Get the value of myBean2
*
* @return the value of myBean2
*/
public MyBean getMyBean2() {
return myBean2;
}
/**
* Set the value of myBean2
*
* @param myBean2 new value of myBean2
*/
public void setMyBean2(MyBean myBean2) {
MyBean oldMyBean2 = this.myBean2;
this.myBean2 = myBean2;
propertyChangeSupport.firePropertyChange(PROP_MYBEAN2, oldMyBean2, myBean2);
}
private transient final PropertyChangeSupport propertyChangeSupport = new PropertyChangeSupport(this);
/**
* Add PropertyChangeListener.
*
* @param listener
*/
public void addPropertyChangeListener(PropertyChangeListener listener) {
propertyChangeSupport.addPropertyChangeListener(listener);
}
/**
* Remove PropertyChangeListener.
*
* @param listener
*/
public void removePropertyChangeListener(PropertyChangeListener listener) {
propertyChangeSupport.removePropertyChangeListener(listener);
}
/**
* This method is called from within the constructor to initialize the form.
* WARNING: Do NOT modify this code. The content of this method is always
* regenerated by the Form Editor.
*/
@SuppressWarnings("unchecked")
// <editor-fold defaultstate="collapsed" desc="Generated Code">
private void initComponents() {
bindingGroup = new org.jdesktop.beansbinding.BindingGroup();
myBean1 = new testpackage.MyBean();
myBean2 = new testpackage.MyBean();
myMiddleMan1 = new testpackage.MyMiddleMan();
jTextField1 = new javax.swing.JTextField();
jTextField2 = new javax.swing.JTextField();
jSlider1 = new javax.swing.JSlider();
jTextField3 = new javax.swing.JTextField();
jTextField4 = new javax.swing.JTextField();
jLabel1 = new javax.swing.JLabel();
jLabel2 = new javax.swing.JLabel();
jLabel3 = new javax.swing.JLabel();
jLabel4 = new javax.swing.JLabel();
setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
org.jdesktop.beansbinding.Binding binding = org.jdesktop.beansbinding.Bindings.createAutoBinding(org.jdesktop.beansbinding.AutoBinding.UpdateStrategy.READ_WRITE, myBean1, org.jdesktop.beansbinding.ELProperty.create("${file.name}"), jTextField1, org.jdesktop.beansbinding.BeanProperty.create("text"));
bindingGroup.addBinding(binding);
binding = org.jdesktop.beansbinding.Bindings.createAutoBinding(org.jdesktop.beansbinding.AutoBinding.UpdateStrategy.READ, jSlider1, org.jdesktop.beansbinding.ELProperty.create("${value}"), jTextField2, org.jdesktop.beansbinding.BeanProperty.create("text"));
bindingGroup.addBinding(binding);
binding = org.jdesktop.beansbinding.Bindings.createAutoBinding(org.jdesktop.beansbinding.AutoBinding.UpdateStrategy.READ_WRITE, myBean2, org.jdesktop.beansbinding.ELProperty.create("${file.name}"), jTextField3, org.jdesktop.beansbinding.BeanProperty.create("text"));
bindingGroup.addBinding(binding);
binding = org.jdesktop.beansbinding.Bindings.createAutoBinding(org.jdesktop.beansbinding.AutoBinding.UpdateStrategy.READ_WRITE, myMiddleMan1, org.jdesktop.beansbinding.ELProperty.create("${myBean.file.name}"), jTextField4, org.jdesktop.beansbinding.BeanProperty.create("text"));
bindingGroup.addBinding(binding);
jLabel1.setText("Altering aBean");
jLabel2.setText("Setting new aBean");
jLabel3.setText("Slider (irrelevant)");
jLabel4.setText("Using MyMiddleMan");
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)
.addGroup(layout.createSequentialGroup()
.addComponent(jLabel1)
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
.addComponent(jTextField1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
.addGroup(layout.createSequentialGroup()
.addComponent(jLabel2)
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
.addComponent(jTextField3, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
.addGroup(layout.createSequentialGroup()
.addComponent(jLabel4)
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
.addComponent(jTextField4, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
.addGroup(layout.createSequentialGroup()
.addComponent(jLabel3)
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
.addComponent(jTextField2, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
.addComponent(jSlider1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)))
.addContainerGap(79, Short.MAX_VALUE))
);
layout.setVerticalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addContainerGap()
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
.addComponent(jLabel1)
.addComponent(jTextField1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
.addComponent(jLabel2)
.addComponent(jTextField3, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
.addComponent(jLabel3)
.addComponent(jTextField2, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
.addComponent(jSlider1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
.addComponent(jLabel4)
.addComponent(jTextField4, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
.addContainerGap(190, Short.MAX_VALUE))
);
bindingGroup.bind();
pack();
}// </editor-fold>
/**
* @param args the command line arguments
*/
public static void main(String args[]) {
/* Set the Nimbus look and feel */
//<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
/* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
* For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html
*/
try {
for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
if ("Nimbus".equals(info.getName())) {
javax.swing.UIManager.setLookAndFeel(info.getClassName());
break;
}
}
} catch (ClassNotFoundException ex) {
java.util.logging.Logger.getLogger(MyForm.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (InstantiationException ex) {
java.util.logging.Logger.getLogger(MyForm.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (IllegalAccessException ex) {
java.util.logging.Logger.getLogger(MyForm.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (javax.swing.UnsupportedLookAndFeelException ex) {
java.util.logging.Logger.getLogger(MyForm.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
}
//</editor-fold>
/* Create and display the form */
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
new MyForm().setVisible(true);
}
});
}
// Variables declaration - do not modify
private javax.swing.JLabel jLabel1;
private javax.swing.JLabel jLabel2;
private javax.swing.JLabel jLabel3;
private javax.swing.JLabel jLabel4;
private javax.swing.JSlider jSlider1;
private javax.swing.JTextField jTextField1;
private javax.swing.JTextField jTextField2;
private javax.swing.JTextField jTextField3;
private javax.swing.JTextField jTextField4;
private testpackage.MyBean myBean1;
private testpackage.MyBean myBean2;
private testpackage.MyMiddleMan myMiddleMan1;
private org.jdesktop.beansbinding.BindingGroup bindingGroup;
// End of variables declaration
}
最佳答案
我已经解决了。
我选择 myBean 作为源并绑定(bind)到 ${file.name}。
有效的方法是选择 Form 作为源并绑定(bind)到 ${myBean.file.name}。
关于java - 在另一个 JavaBean 中设置绑定(bind)的 JavaBean，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/22778776/