[英]Undoable Text Area in Java
I'm just approaching the programming in java.... I'd like to create a small Text Editor (Windows Notepad clone...). 我正在使用Java进行编程。...我想创建一个小的文本编辑器(Windows记事本克隆...)。
I'm searching for a Class that extend the JTextArea implementing the undo & redo actions. 我正在寻找一个扩展JTextArea的类,该类实现了撤消和重做操作。 I found a code that match my needs, and I tried to adapt it to my purposes.
我找到了满足自己需求的代码,并尝试使其适应我的目的。
Here's the code: 这是代码:
import java.awt.Toolkit;
import java.awt.event.FocusEvent;
import java.awt.event.FocusListener;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import javax.swing.JTextArea;
import javax.swing.event.UndoableEditEvent;
import javax.swing.event.UndoableEditListener;
import javax.swing.undo.CannotRedoException;
import javax.swing.undo.CannotUndoException;
import javax.swing.undo.UndoManager;
class UndoableTextArea extends JTextArea implements UndoableEditListener, FocusListener, KeyListener
{
private static final long serialVersionUID = 1L;
private UndoManager m_undoManager;
public UndoableTextArea() {
this(new String());
}
public UndoableTextArea(String text) {
super(text);
getDocument().addUndoableEditListener(this);
this.addKeyListener(this);
this.addFocusListener(this);
}
private void createUndoMananger() {
m_undoManager = new UndoManager();
m_undoManager.setLimit(50);
}
private void removeUndoMananger() {
m_undoManager.end();
}
public void focusGained(FocusEvent fe) {
createUndoMananger();
}
public void focusLost(FocusEvent fe) {
removeUndoMananger();
}
public void undo()
{
try {
m_undoManager.undo();
} catch (CannotUndoException cue) {
Toolkit.getDefaultToolkit().beep();
}
}
public void redo()
{
try {
m_undoManager.redo();
} catch (CannotRedoException cue) {
Toolkit.getDefaultToolkit().beep();
}
}
public void undoableEditHappened(UndoableEditEvent e) {
m_undoManager.addEdit(e.getEdit());
}
public void keyPressed(KeyEvent e) {
if ((e.getKeyCode() == KeyEvent.VK_Z) && (e.isControlDown())) {
try {
m_undoManager.undo();
} catch (CannotUndoException cue) {
Toolkit.getDefaultToolkit().beep();
}
}
if ((e.getKeyCode() == KeyEvent.VK_Y) && (e.isControlDown())) {
try {
m_undoManager.redo();
} catch (CannotRedoException cue) {
Toolkit.getDefaultToolkit().beep();
}
}
}
public void keyReleased(KeyEvent e) {
}
public void keyTyped(KeyEvent e) {
}
}
Using Accellerators Key CTRL + Z , CTRL + Y while typing in the object, there's no problem.... but methods undo()
and redo()
added by me for use this actions from menuItem objetcs, don't work... 在键入对象时使用Accellerators键CTRL + Z , CTRL + Y没问题....但是我添加的方法
undo()
和redo()
用于在menuItem objetcs中使用此操作,所以不起作用...
(...)
menuItem15 = new JMenuItem("Undo");
menuItem16 = new JMenuItem("Redo");
(...)
public void actionPerformed(ActionEvent e)
{
//Undo
if (e.getSource() == menuItem15)
{
textArea1.undo();
}
//Redo
if (e.getSource() == menuItem16)
{
textArea1.redo();
}
}
Any suggestions? 有什么建议么? Sorry for my bad english...
对不起,我的英语不好...
Thanks! 谢谢!
The problem is likely due to the code adding and removing the UndoManager upon focusGained and focusLost events: 该问题可能是由于代码在focusGained和focusLost事件上添加和删除了UndoManager导致的:
public void focusGained(FocusEvent fe) {
createUndoMananger();
}
public void focusLost(FocusEvent fe) {
removeUndoMananger();
}
When you click on the menu, the text area temporarily loses the focus, whereupon the UndoManager is discarded and then a new instance is created. 当您单击菜单上时,文本区域会暂时失去焦点,随后将放弃UndoManager,然后创建一个新实例。 The new instance doesn't know about previous undoable edit events, and thus undo and redo do not work.
新实例不知道以前的可撤消编辑事件,因此撤消和重做不起作用。
I suggest creating the UndoManager once and keeping it attached to the document until the GUI is disposed (ie until the dialog / window is closed). 我建议一次创建UndoManager并将其附加在文档上,直到释放GUI(即关闭对话框/窗口)为止。
Solved! 解决了! I realized that the creation of the UndoManager was linked to the event of focusGained() of my JTextArea extended object.
我意识到UndoManager的创建与JTextArea扩展对象的focusGained()事件相关联。 So, when I was selecting action by menuItem, I lose the focus and the UndoManager destroyed.
因此,当我通过menuItem选择操作时,我失去了焦点,UndoManager被破坏了。
I changed the method createUndoMananger from private to public, and Invoked outside the class... 我将createUndoMananger方法从私有更改为公共,并在课程外调用了...
(..)
public void createUndoMananger() {
m_undoManager = new UndoManager();
m_undoManager.setLimit(50);
}
public void removeUndoMananger() {
m_undoManager.end();
}
public void focusGained(FocusEvent fe) {
//createUndoMananger();
//System.out.println("focusGained()");
}
public void focusLost(FocusEvent fe) {
//removeUndoMananger();
//System.out.println("focusLost()");
}
(...) (...)
Thanks anyway!!! 不管怎么说,还是要谢谢你!!!
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