Undo Text using Ctrl Z in Java

[luan45]

This tutorial will teach you how to create a program that can undo a text using a shortcut key of ctrl+z in java.

So, now let's start this tutorial!

1. Open JCreator or NetBeans and make a java program with a file name of undoCtrlZ.java.

2. Import the following package library:

1. import
   
   java.awt.event.*
   
   ;
   
   //used to access ActionEvent class
   
2. import
   
   javax.swing.*
   
   ;
   
   //used to access AbstractAction,JFrame, JScrollPane, JTextArea, and KeyStroke class
   
3. import
   
   javax.swing.event.*
   
   ;
   
   // used to access UndoableEditEvent and UndoableEditListener class
   
4. import
   
   javax.swing.text.*
   
   ;
   
   // used to access the Document and JTextComponent class
   
5. import
   
   javax.swing.undo.*
   
   ;
   
   // used to access CannotUndoException and UndoManager class
   

3. We will initialize variables in our Main, variable frame as JFrame, txtArea for JTextArea, undo as UndoManager and declare it as final because we will create an inner class on it, variable doc for the Document class.

1. JFrame
   
   frame =
   
   new
   
   JFrame
   
   (
   
   )
   
   ;
   
   //instantiate frame
   
2. JTextArea
   
   txtArea =
   
   new
   
   JTextArea
   
   (
   
   )
   
   ;
   
   //instantiate textArea
   
3. final
   
   UndoManager
   
   undo =
   
   new
   
   UndoManager
   
   (
   
   )
   
   ;
   
   //instantiate an UndoManager
   
4. Document
   
   doc =
   
   txtArea.getDocument
   
   (
   
   )
   
   ;
   
   //instantiate a Document class of the txtArea
   

4. Create an inner class for the UndoableEditEvent of the doc in our textArea. This will trigger that the textArea can be editable.

1. doc.addUndoableEditListener
   
   (
   
   new
   
   UndoableEditListener
   
   (
   
   )
   
   {
   
2. public
   
   void
   
   undoableEditHappened(
   
   UndoableEditEvent
   
   evt)
   
   {
   
3. undo.addEdit
   
   (
   
   evt.getEdit
   
   (
   
   )
   
   )
   
   ;
   
4. }
   
5. }
   
   )
   
   ;
   

5. Create also an inner class that will have an undo event on the textArea. This will use the getActionMap method.

1. txtArea.getActionMap
   
   (
   
   )
   
   .put
   
   (
   
   "Undo"
   
   , new
   
   AbstractAction
   
   (
   
   "Undo"
   
   )
   
   {
   
2. public
   
   void
   
   actionPerformed(
   
   ActionEvent
   
   evt)
   
   {
   
3. try
   
   {
   
4. if
   
   (
   
   undo.canUndo
   
   (
   
   )
   
   )
   
   {
   
5. undo.undo
   
   (
   
   )
   
   ;
   
6. }
   
7. }
   
   catch
   
   (
   
   CannotUndoException
   
   e)
   
   {
   
8. }
   
9. }
   
10. }
    
    )
    
    ;
    

To have a ctrl z shortcut for the undo. Have this code below:

1. txtArea.getInputMap
   
   (
   
   )
   
   .put
   
   (
   
   KeyStroke
   
   .getKeyStroke
   
   (
   
   "control Z"
   
   )
   
   , "Undo"
   
   )
   
   ;
   

6. Lastly, add the components, set the size and visibility to true, and close its operation.

1. txtArea.getInputMap
   
   (
   
   )
   
   .put
   
   (
   
   KeyStroke
   
   .getKeyStroke
   
   (
   
   "control Z"
   
   )
   
   , "Undo"
   
   )
   
   ;
   
2. 
   
3. frame.setDefaultCloseOperation
   
   (
   
   JFrame
   
   .EXIT_ON_CLOSE
   
   )
   
   ;
   
4. frame.getContentPane
   
   (
   
   )
   
   .add
   
   (
   
   new
   
   JScrollPane
   
   (
   
   txtArea)
   
   )
   
   ;
   
5. frame.setSize
   
   (
   
   380
   
   , 320
   
   )
   
   ;
   
6. frame.setLocationRelativeTo
   
   (
   
   null
   
   )
   
   ;
   
7. frame.setVisible
   
   (
   
   true
   
   )
   
   ;
   

Output:

Here's the full code of this tutorial:

1. import
   
   java.awt.event.*
   
   ;
   
   //used to access ActionEvent class
   
2. import
   
   javax.swing.*
   
   ;
   
   //used to access AbstractAction,JFrame, JScrollPane, JTextArea, and KeyStroke class
   
3. import
   
   javax.swing.event.*
   
   ;
   
   // used to access UndoableEditEvent and UndoableEditListener class
   
4. import
   
   javax.swing.text.*
   
   ;
   
   // used to access the Document and JTextComponent class
   
5. import
   
   javax.swing.undo.*
   
   ;
   
   // used to access CannotUndoException and UndoManager class
   
6. 
   
7. 
   
8. public
   
   class
   
   undoCtrlZ {
   
9. public
   
   static
   
   void
   
   main(
   
   String
   
   [
   
   ]
   
   args)
   
   {
   
10. JFrame
    
    frame =
    
    new
    
    JFrame
    
    (
    
    "Ctrl+Z Undo"
    
    )
    
    ;
    
    //instantiate frame
    
11. JTextArea
    
    txtArea =
    
    new
    
    JTextArea
    
    (
    
    )
    
    ;
    
    //instantiate textArea
    
12. final
    
    UndoManager
    
    undo =
    
    new
    
    UndoManager
    
    (
    
    )
    
    ;
    
    //instantiate an UndoManager
    
13. Document
    
    doc =
    
    txtArea.getDocument
    
    (
    
    )
    
    ;
    
    //instantiate a Document class of the txtArea
    
14. 
    
15. doc.addUndoableEditListener
    
    (
    
    new
    
    UndoableEditListener
    
    (
    
    )
    
    {
    
16. public
    
    void
    
    undoableEditHappened(
    
    UndoableEditEvent
    
    evt)
    
    {
    
17. undo.addEdit
    
    (
    
    evt.getEdit
    
    (
    
    )
    
    )
    
    ;
    
18. }
    
19. }
    
    )
    
    ;
    
20. 
    
21. txtArea.getActionMap
    
    (
    
    )
    
    .put
    
    (
    
    "Undo"
    
    , new
    
    AbstractAction
    
    (
    
    "Undo"
    
    )
    
    {
    
22. public
    
    void
    
    actionPerformed(
    
    ActionEvent
    
    evt)
    
    {
    
23. try
    
    {
    
24. if
    
    (
    
    undo.canUndo
    
    (
    
    )
    
    )
    
    {
    
25. undo.undo
    
    (
    
    )
    
    ;
    
26. }
    
27. }
    
    catch
    
    (
    
    CannotUndoException
    
    e)
    
    {
    
28. }
    
29. }
    
30. }
    
    )
    
    ;
    
31. 
    
32. txtArea.getInputMap
    
    (
    
    )
    
    .put
    
    (
    
    KeyStroke
    
    .getKeyStroke
    
    (
    
    "control Z"
    
    )
    
    , "Undo"
    
    )
    
    ;
    
33. 
    
34. frame.setDefaultCloseOperation
    
    (
    
    JFrame
    
    .EXIT_ON_CLOSE
    
    )
    
    ;
    
35. frame.getContentPane
    
    (
    
    )
    
    .add
    
    (
    
    new
    
    JScrollPane
    
    (
    
    txtArea)
    
    )
    
    ;
    
36. frame.setSize
    
    (
    
    380
    
    , 320
    
    )
    
    ;
    
37. frame.setLocationRelativeTo
    
    (
    
    null
    
    )
    
    ;
    
38. frame.setVisible
    
    (
    
    true
    
    )
    
    ;
    
39. }
    
40. }
    

For more inquiries and need programmer for your thesis systems in any kind of programming languages, just contact my number below.

Best Regards,

Engr. Lyndon Bermoy
IT Instructor/System Developer/Android Developer/Freelance Programmer
Mobile: 09488225971
Landline: 826-9296
E-mail:[email protected]

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