undoabletoggleapp3.java

来自「java swing 开发代码」· Java 代码 · 共 112 行

// UndoableToggleApp3.java
// A sample app showing the use of UndoManager.
//
package	jswing.ch18;

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

public class UndoableToggleApp3 extends JFrame {

  private UndoManager manager = new UndoManager();
  private JButton undoButton;
  private JButton redoButton;

  // Create the main frame and everything in it.
  public UndoableToggleApp3() {

    // Create some toggle buttons.
    UndoableJToggleButton tog1 = new UndoableJToggleButton("One");
    UndoableJToggleButton tog2 = new UndoableJToggleButton("Two");
    UndoableJToggleButton tog3 = new UndoableJToggleButton("Three");
    
    // Add our listener to each toggle button.
    SimpleUEListener sl = new SimpleUEListener();
    tog1.addUndoableEditListener(sl);
    tog2.addUndoableEditListener(sl);
    tog3.addUndoableEditListener(sl);

    // Lay out the buttons.
    Box buttonBox = new Box(BoxLayout.Y_AXIS);
    buttonBox.add(tog1);
    buttonBox.add(tog2);
    buttonBox.add(tog3);

    // Create undo and redo buttons (initially disabled).
    undoButton = new JButton("Undo");
    redoButton = new JButton("Redo");
    undoButton.setEnabled(false);
    redoButton.setEnabled(false);

    // Add a listener to the undo button. It attempts to call undo() on the
    // UndoManager, then enables/disables the undo/redo buttons as appropriate.
    undoButton.addActionListener(new ActionListener() {
      public void actionPerformed(ActionEvent ev) {
        try {
          manager.undo();
        } catch (CannotUndoException ex) { ex.printStackTrace(); }
        finally {
          updateButtons();
        }
      }
    });

    // Add a redo listener: just like the undo listener.
    redoButton.addActionListener(new ActionListener() {
      public void actionPerformed(ActionEvent ev) {
        try {
          manager.redo();
        } catch (CannotRedoException ex) { ex.printStackTrace(); }
        finally {
          updateButtons();
        }
      }
    });

    // Lay out the undo/redo buttons.
    Box undoRedoBox = new Box(BoxLayout.X_AXIS);
    undoRedoBox.add(Box.createGlue());
    undoRedoBox.add(undoButton);
    undoRedoBox.add(Box.createHorizontalStrut(2));
    undoRedoBox.add(redoButton);
    undoRedoBox.add(Box.createGlue());

    // Lay out the main frame.
    getContentPane().setLayout(new BorderLayout());
    getContentPane().add(buttonBox, BorderLayout.CENTER);
    getContentPane().add(undoRedoBox, BorderLayout.SOUTH);
    setSize(400, 150);
  }

  public class SimpleUEListener implements UndoableEditListener {
    // When an UndoableEditEvent is generated (each time one of the buttons
    // is pressed), we add it to the UndoManager and then get the manager's
    // undo/redo names and set the undo/redo button labels. Finally, we
    // enable/disable these buttons by asking the manager what we are
    // allowed to do.
    public void undoableEditHappened(UndoableEditEvent ev) {
      manager.addEdit(ev.getEdit());
      updateButtons();
    }
  }

  // Method to set the text and state of the undo/redo buttons.
  protected void updateButtons() {
    undoButton.setText(manager.getUndoPresentationName());
    redoButton.setText(manager.getRedoPresentationName());
    undoButton.getParent().validate();
    undoButton.setEnabled(manager.canUndo());
    redoButton.setEnabled(manager.canRedo());
  }

  // Main program just creates the frame and displays it.
  public static void main(String[] args) {
    JFrame f = new UndoableToggleApp3();
    f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    f.setVisible(true);
  }
}