我正在寫一個文本編輯器。在這里我遇到了一個問題。我需要為 JTextArea 實作 UNDO 和 Redo 功能。為此，我使用 UndoManager。但是，如果我取消或回傳，則操作將被取消或一次回傳一個字符。如何使動作被取消或回傳，而不是按字符，而是按單詞。
這就是我的代碼的樣子：
jta.getDocument().addUndoableEditListener( new UndoableEditListener() {
public void undoableEditHappened(UndoableEditEvent e) {
undoManager.addEdit(e.getEdit());
}
});
public static void undo() {
if (undoManager.canUndo())
try {
undoManager.undo();
} catch (CannotRedoException cre) {
cre.printStackTrace();
}
}
public static void redo() {
if (undoManager.canRedo())
try {
undoManager.redo();
} catch (CannotRedoException cre) {
cre.printStackTrace();
}
}
不幸的是，這個解決方案不起作用。我不明白如何使用它，因為我沒有足夠的編程經驗：
import java.awt.BorderLayout;
import java.awt.EventQueue;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.ArrayList;
import java.util.List;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.JToolBar;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;
import javax.swing.event.UndoableEditEvent;
import javax.swing.event.UndoableEditListener;
import javax.swing.text.AbstractDocument;
import javax.swing.text.BadLocationException;
import javax.swing.undo.AbstractUndoableEdit;
import javax.swing.undo.CannotUndoException;
import javax.swing.undo.CompoundEdit;
import javax.swing.undo.UndoableEdit;
public class Main {
public static void main(String[] args) {
new Main();
}
public Main() {
EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
JButton btnUndo = new JButton("Undo");
JButton btnRedo = new JButton("Redo");
UndoManager undoManager = new UndoManager();
undoManager.addChangeListener(new ChangeListener() {
@Override
public void stateChanged(ChangeEvent e) {
btnUndo.setEnabled(undoManager.canUndo());
btnRedo.setEnabled(undoManager.canRedo());
}
});
EditorPane editorPane = new EditorPane(undoManager);
JToolBar tb = new JToolBar();
btnUndo.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
undoManager.undo();
}
});
tb.add(btnUndo);
btnRedo.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
undoManager.redo();
}
});
tb.add(btnRedo);
JFrame frame = new JFrame();
frame.add(tb, BorderLayout.NORTH);
frame.add(new JScrollPane(editorPane));
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class EditorPane extends JPanel {
private UndoManager undoManager;
public EditorPane(UndoManager undoManager) {
setLayout(new BorderLayout());
this.undoManager = undoManager;
JTextArea textArea = new JTextArea(20, 40);
textArea.getDocument().addUndoableEditListener(undoManager);
add(new JScrollPane(textArea));
}
}
public class UndoManager extends AbstractUndoableEdit implements UndoableEditListener {
private String lastEditName = null;
private List<MergeComponentEdit> edits = new ArrayList<MergeComponentEdit>(32);
private MergeComponentEdit current;
private int pointer = -1;
private List<ChangeListener> changeListeners = new ArrayList<>(8);
public void addChangeListener(ChangeListener changeListener) {
changeListeners.add(changeListener);
}
public void removeChangeListener(ChangeListener changeListener) {
changeListeners.remove(changeListener);
}
public void undoableEditHappened(UndoableEditEvent e) {
UndoableEdit edit = e.getEdit();
if (edit instanceof AbstractDocument.DefaultDocumentEvent) {
try {
AbstractDocument.DefaultDocumentEvent event = (AbstractDocument.DefaultDocumentEvent) edit;
int start = event.getOffset();
int len = event.getLength();
if (start len > event.getDocument().getLength()) {
createCompoundEdit();
current.addEdit(edit);
lastEditName = edit.getPresentationName();
} else {
String text = event.getDocument().getText(start, len);
boolean isNeedStart = false;
if (current == null) {
isNeedStart = true;
} else if (text.contains(" ")) {
isNeedStart = true;
} else if (lastEditName == null || !lastEditName.equals(edit.getPresentationName())) {
isNeedStart = true;
}
while (pointer < edits.size() - 1) {
edits.remove(edits.size() - 1);
isNeedStart = true;
}
if (isNeedStart) {
createCompoundEdit();
}
current.addEdit(edit);
lastEditName = edit.getPresentationName();
}
fireStateChanged();
} catch (BadLocationException e1) {
e1.printStackTrace();
}
}
}
public void createCompoundEdit() {
if (current == null) {
current = new MergeComponentEdit();
} else if (current.getLength() > 0) {
current = new MergeComponentEdit();
}
edits.add(current);
pointer ;
}
public void undo() throws CannotUndoException {
if (!canUndo()) {
throw new CannotUndoException();
}
MergeComponentEdit u = edits.get(pointer);
u.undo();
pointer--;
fireStateChanged();
}
public void redo() throws CannotUndoException {
if (!canRedo()) {
throw new CannotUndoException();
}
pointer ;
MergeComponentEdit u = edits.get(pointer);
u.redo();
fireStateChanged();
}
public boolean canUndo() {
return pointer >= 0;
}
public boolean canRedo() {
return edits.size() > 0 && pointer < edits.size() - 1;
}
protected void fireStateChanged() {
if (changeListeners.isEmpty()) {
return;
}
ChangeEvent evt = new ChangeEvent(this);
for (ChangeListener listener : changeListeners) {
listener.stateChanged(evt);
}
}
protected class MergeComponentEdit extends CompoundEdit {
boolean isUnDone = false;
public int getLength() {
return edits.size();
}
public void undo() throws CannotUndoException {
super.undo();
isUnDone = true;
}
public void redo() throws CannotUndoException {
super.redo();
isUnDone = false;
}
public boolean canUndo() {
return edits.size() > 0 && !isUnDone;
}
public boolean canRedo() {
return edits.size() > 0 && isUnDone;
}
}
}
}
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