如何找到生成 DocumentEvent 的源组件 [英] how to find source component that generated a DocumentEvent

问题描述

是否可以发现哪个对象生成了 DocumentEvent?像我可以用 ActionListener 做的事情:

Is it possible to discover which oject generated a DocumentEvent? Something like i can do with ActionListener:

JTextField field = new JTextField("");
field.addActionListener(actionListener);

//inside ActionListener
public void actionPerformed(ActionEvent arg0) {
  if (arg0.getSource() instanceof JTextField) //true

}

我想对 DocumentEvent 做同样的事情，但似乎不一样:

I would like to do the same with DocumentEvent but seems not to work the same way:

JTextField field = new JTextField("");
field.getDocument.addDocumentListener(documentListener);
//inside documentListener
public void insertUpdate(DocumentEvent){
  if (arg0.getSource() instanceof JTextField) //false: class is javax.swing.text.PlainDocument
  if (arg0.getSource() instanceof MyComponent){
      MyComponent comp = (MyComponent)arg0.getSource();
      comp.callSpecificMethodUponMyComp(); 
  }
}

回答者应考虑以下几点:

The answser should take in consideration the following points:

1. 就我而言，仅了解生成事件的对象类型是不够的，但我需要在运行时引用它.
2. 通常，事件是从 Swing 对象的扩展(myComp 公共 JTextField)生成的.这些对象存储应在运行时在侦听器方法(如 insertUpdate)中检索的附加信息
3. DocumentListener 是从不知道生成事件的字段的类中实现的.可以在运行时将不同类型的不同字段附加到侦听器.

推荐答案

可以在文档中设置一个属性来告诉你文档属于哪个文本组件:

You can set a property in the document to tell you which textcomponent the document belongs to:

例如:

final JTextField field = new JTextField("");
field.getDocument().putProperty("owner", field); //set the owner

final JTextField field2 = new JTextField("");
field2.getDocument().putProperty("owner", field2); //set the owner

DocumentListener documentListener = new DocumentListener() {

     public void changedUpdate(DocumentEvent documentEvent) {}

     public void insertUpdate(DocumentEvent documentEvent) {

         //get the owner of this document
         Object owner = documentEvent.getDocument().getProperty("owner");
         if(owner != null){
             //owner is the jtextfield
             System.out.println(owner);
         }
     }

     public void removeUpdate(DocumentEvent documentEvent) {}

     private void updateValue(DocumentEvent documentEvent) {}
};

field.getDocument().addDocumentListener(documentListener);
field2.getDocument().addDocumentListener(documentListener);

或者:

获取引发事件的文档并将其与文本字段的文档进行比较.

Get the document that sourced the event and compare it to the document of the textfield.

示例:

public void insertUpdate(DocumentEvent documentEvent) {
    if (documentEvent.getDocument()== field.getDocument()){
        System.out.println("event caused by field");
    }
    else if (documentEvent.getDocument()== field2.getDocument()){
        System.out.println("event caused by field2");
    }
}

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