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我在設置一個屬於另一個bean的成員並且正確更新的bean時遇到問題。更具體地講，我有：在另一個JavaBean中設置一個綁定的JavaBean
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有適當的getter廣告setter方法File成員。我正在嘗試做的是讓它可以使用setter更改aBean，並且有任何綁定的更新以反映新的aBean的值。
我可以看到這個問題;原始的aBean被綁定到TextField，並且當一個新的aBean被分配時，沒有「交換」。但是，看到問題並不意味着我有解決方案！
我目前的解決方法涉及中間人類。我有MyForm有MyMiddleMan和MyMiddleMan有MyBean。無論何時我想更改MyBean，調用者MyMiddleMan都會被調用並觸發MyForm所看到的適當事件。 MyForm的成員從不改變，因此它「工作」。
我的解決方法在許多層面上都很糟糕。有沒有更好的，最佳實踐的方式？我承認我不是豆類專家，可能會錯過一些明顯的東西。如果相關，我正在使用NetBeans IDE 8.0，並且想要使用構建器生成我的GUI。顯然，我的真實代碼比這個例子大得多，所以如果我不得不每次都添加額外的代碼，它可能會很麻煩。
我有一個下面的工作示例，演示了我的問題。由於豆類需要公開，有三個文件; MyBean.java，MyMiddleMan.java和MyForm.java。它應該產生四個綁定的文本字段。第一個演示可以改變一個成員的內容而沒有問題。第二個顯示了我的問題（我知道爲什麼它不起作用，而不是如何解決它），第三個是無關緊要的，從教程中作爲一個「理智檢查」，第四個是使用我的「MyMiddleMan 「解決方法。
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 這在很大程度上是自動的NetBeans生成。
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
}