undoablejtogglebutton.java

java swing 开发代码

// UndoableJToggleButton.java
// Sample undoable toggle button class. Supports only a single listener to
// simplify the code.
//
package	jswing.ch18;

import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;

public class UndoableJToggleButton extends JToggleButton {
  private UndoableEditListener listener;

  // For this example, we'll just provide one constructor . . .
  public UndoableJToggleButton(String txt) {
    super(txt);
  }

  // Set the UndoableEditListener.
  public void addUndoableEditListener(UndoableEditListener l) {
    listener = l; // Should ideally throw an exception if listener != null
  }

  // Remove the UndoableEditListener.
  public void removeUndoableEditListener(UndoableEditListener l) {
    listener = null;
  }

  // We override this method to call the super implementation first (to fire the
  // action event) and then fire a new UndoableEditEvent to our listener.
  protected void fireActionPerformed(ActionEvent ev) {

    // Fire the ActionEvent as usual.
    super.fireActionPerformed(ev);

    if (listener != null) {
      listener.undoableEditHappened(new UndoableEditEvent(this,
        new UndoableToggleEdit(this)));
    }
  }
}