Java by API/javax.swing.undo/StateEdit
StateEdit: canRedo()
<source lang="java">
import java.awt.BorderLayout; import java.awt.Container; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import java.util.Hashtable; import javax.swing.Box; import javax.swing.BoxLayout; import javax.swing.JButton; import javax.swing.JCheckBox; import javax.swing.JFrame; import javax.swing.JRadioButton; import javax.swing.JToggleButton; import javax.swing.undo.CannotRedoException; import javax.swing.undo.CannotUndoException; import javax.swing.undo.StateEdit; import javax.swing.undo.StateEditable; public class UndoableToggleApp4 extends JFrame implements StateEditable {
private JToggleButton tog = new JToggleButton("ToggleButton");
private JCheckBox cb = new JCheckBox("CheckBox");
private JRadioButton radio = new JRadioButton("RadioButton");
private JButton undoButton = new JButton("Undo");
private JButton redoButton = new JButton("Redo");
private JButton startButton = new JButton("Start");
private JButton endButton = new JButton("End");
private StateEdit edit;
public UndoableToggleApp4() {
SimpleListener sl = new SimpleListener();
tog.addActionListener(sl);
cb.addActionListener(sl);
radio.addActionListener(sl);
Box buttonBox = new Box(BoxLayout.Y_AXIS);
buttonBox.add(tog);
buttonBox.add(cb);
buttonBox.add(radio);
startButton.setEnabled(true);
endButton.setEnabled(false);
undoButton.setEnabled(false);
redoButton.setEnabled(false);
startButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent ev) {
edit = new StateEdit(UndoableToggleApp4.this);
startButton.setEnabled(false);
endButton.setEnabled(true);
// undoButton.setEnabled(edit.canUndo());
//
// NOTE: We really don"t want to be able to undo until end() is pressed,
// but StateEdit does not enforce this for us!
undoButton.setEnabled(false);
redoButton.setEnabled(edit.canRedo());
}
});
endButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent ev) {
edit.end();
startButton.setEnabled(true);
endButton.setEnabled(false);
undoButton.setEnabled(edit.canUndo());
redoButton.setEnabled(edit.canRedo());
}
});
// Add a listener to the undo button. It attempts to call undo() on the
// current edit, then enables/disables the undo/redo buttons as appropriate.
undoButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent ev) {
try {
edit.undo();
} catch (CannotUndoException ex) {
ex.printStackTrace();
} finally {
undoButton.setEnabled(edit.canUndo());
redoButton.setEnabled(edit.canRedo());
}
}
});
redoButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent ev) {
try {
edit.redo();
} catch (CannotRedoException ex) {
ex.printStackTrace();
} finally {
undoButton.setEnabled(edit.canUndo());
redoButton.setEnabled(edit.canRedo());
}
}
});
// Lay out the state/end and undo/redo buttons.
Box undoRedoBox = new Box(BoxLayout.X_AXIS);
undoRedoBox.add(Box.createGlue());
undoRedoBox.add(startButton);
undoRedoBox.add(Box.createHorizontalStrut(2));
undoRedoBox.add(endButton);
undoRedoBox.add(Box.createHorizontalStrut(2));
undoRedoBox.add(undoButton);
undoRedoBox.add(Box.createHorizontalStrut(2));
undoRedoBox.add(redoButton);
undoRedoBox.add(Box.createGlue());
// Lay out the main frame.
Container content = getContentPane();
content.setLayout(new BorderLayout());
content.add(buttonBox, BorderLayout.CENTER);
content.add(undoRedoBox, BorderLayout.SOUTH);
setSize(400, 150);
}
public class SimpleListener implements ActionListener {
// When any toggle button is clicked, we turn off the undo and redo
// buttons, reflecting the fact that we can only undo/redo the last
// set of state changes as long as no additional changes have been made.
public void actionPerformed(ActionEvent ev) {
undoButton.setEnabled(false);
redoButton.setEnabled(false);
}
}
// Save the state of the app by storing the current state of the three
// buttons. We"ll use the buttons themselves as keys and their selected
// state as values.
public void storeState(Hashtable ht) {
ht.put(tog, new Boolean(tog.isSelected()));
ht.put(cb, new Boolean(cb.isSelected()));
ht.put(radio, new Boolean(radio.isSelected()));
}
// Restore state based on the values we saved when storeState() was called.
// Note that StateEdit discards any state info that did not change from
// between the start state and the end state, so we can"t assume that the
// state for all 3 buttons is in the Hashtable.
public void restoreState(Hashtable ht) {
Boolean b1 = (Boolean) ht.get(tog);
if (b1 != null)
tog.setSelected(b1.booleanValue());
Boolean b2 = (Boolean) ht.get(cb);
if (b2 != null)
cb.setSelected(b2.booleanValue());
Boolean b3 = (Boolean) ht.get(radio);
if (b3 != null)
radio.setSelected(b3.booleanValue());
}
// Main program just creates the frame and displays it.
public static void main(String[] args) {
JFrame f = new UndoableToggleApp4();
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.setVisible(true);
}
}
</source>
StateEdit: canUndo()
<source lang="java">
import java.awt.BorderLayout; import java.awt.Container; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import java.util.Hashtable; import javax.swing.Box; import javax.swing.BoxLayout; import javax.swing.JButton; import javax.swing.JCheckBox; import javax.swing.JFrame; import javax.swing.JRadioButton; import javax.swing.JToggleButton; import javax.swing.undo.CannotRedoException; import javax.swing.undo.CannotUndoException; import javax.swing.undo.StateEdit; import javax.swing.undo.StateEditable; public class UndoableToggleApp4 extends JFrame implements StateEditable {
private JToggleButton tog = new JToggleButton("ToggleButton");
private JCheckBox cb = new JCheckBox("CheckBox");
private JRadioButton radio = new JRadioButton("RadioButton");
private JButton undoButton = new JButton("Undo");
private JButton redoButton = new JButton("Redo");
private JButton startButton = new JButton("Start");
private JButton endButton = new JButton("End");
private StateEdit edit;
public UndoableToggleApp4() {
SimpleListener sl = new SimpleListener();
tog.addActionListener(sl);
cb.addActionListener(sl);
radio.addActionListener(sl);
Box buttonBox = new Box(BoxLayout.Y_AXIS);
buttonBox.add(tog);
buttonBox.add(cb);
buttonBox.add(radio);
startButton.setEnabled(true);
endButton.setEnabled(false);
undoButton.setEnabled(false);
redoButton.setEnabled(false);
startButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent ev) {
edit = new StateEdit(UndoableToggleApp4.this);
startButton.setEnabled(false);
endButton.setEnabled(true);
// undoButton.setEnabled(edit.canUndo());
//
// NOTE: We really don"t want to be able to undo until end() is pressed,
// but StateEdit does not enforce this for us!
undoButton.setEnabled(false);
redoButton.setEnabled(edit.canRedo());
}
});
endButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent ev) {
edit.end();
startButton.setEnabled(true);
endButton.setEnabled(false);
undoButton.setEnabled(edit.canUndo());
redoButton.setEnabled(edit.canRedo());
}
});
// Add a listener to the undo button. It attempts to call undo() on the
// current edit, then enables/disables the undo/redo buttons as appropriate.
undoButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent ev) {
try {
edit.undo();
} catch (CannotUndoException ex) {
ex.printStackTrace();
} finally {
undoButton.setEnabled(edit.canUndo());
redoButton.setEnabled(edit.canRedo());
}
}
});
redoButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent ev) {
try {
edit.redo();
} catch (CannotRedoException ex) {
ex.printStackTrace();
} finally {
undoButton.setEnabled(edit.canUndo());
redoButton.setEnabled(edit.canRedo());
}
}
});
// Lay out the state/end and undo/redo buttons.
Box undoRedoBox = new Box(BoxLayout.X_AXIS);
undoRedoBox.add(Box.createGlue());
undoRedoBox.add(startButton);
undoRedoBox.add(Box.createHorizontalStrut(2));
undoRedoBox.add(endButton);
undoRedoBox.add(Box.createHorizontalStrut(2));
undoRedoBox.add(undoButton);
undoRedoBox.add(Box.createHorizontalStrut(2));
undoRedoBox.add(redoButton);
undoRedoBox.add(Box.createGlue());
// Lay out the main frame.
Container content = getContentPane();
content.setLayout(new BorderLayout());
content.add(buttonBox, BorderLayout.CENTER);
content.add(undoRedoBox, BorderLayout.SOUTH);
setSize(400, 150);
}
public class SimpleListener implements ActionListener {
// When any toggle button is clicked, we turn off the undo and redo
// buttons, reflecting the fact that we can only undo/redo the last
// set of state changes as long as no additional changes have been made.
public void actionPerformed(ActionEvent ev) {
undoButton.setEnabled(false);
redoButton.setEnabled(false);
}
}
// Save the state of the app by storing the current state of the three
// buttons. We"ll use the buttons themselves as keys and their selected
// state as values.
public void storeState(Hashtable ht) {
ht.put(tog, new Boolean(tog.isSelected()));
ht.put(cb, new Boolean(cb.isSelected()));
ht.put(radio, new Boolean(radio.isSelected()));
}
// Restore state based on the values we saved when storeState() was called.
// Note that StateEdit discards any state info that did not change from
// between the start state and the end state, so we can"t assume that the
// state for all 3 buttons is in the Hashtable.
public void restoreState(Hashtable ht) {
Boolean b1 = (Boolean) ht.get(tog);
if (b1 != null)
tog.setSelected(b1.booleanValue());
Boolean b2 = (Boolean) ht.get(cb);
if (b2 != null)
cb.setSelected(b2.booleanValue());
Boolean b3 = (Boolean) ht.get(radio);
if (b3 != null)
radio.setSelected(b3.booleanValue());
}
// Main program just creates the frame and displays it.
public static void main(String[] args) {
JFrame f = new UndoableToggleApp4();
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.setVisible(true);
}
}
</source>
StateEdit: end()
<source lang="java">
import java.awt.BorderLayout; import java.awt.Container; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import java.util.Hashtable; import javax.swing.Box; import javax.swing.BoxLayout; import javax.swing.JButton; import javax.swing.JCheckBox; import javax.swing.JFrame; import javax.swing.JRadioButton; import javax.swing.JToggleButton; import javax.swing.undo.CannotRedoException; import javax.swing.undo.CannotUndoException; import javax.swing.undo.StateEdit; import javax.swing.undo.StateEditable; public class UndoableToggleApp4 extends JFrame implements StateEditable {
private JToggleButton tog = new JToggleButton("ToggleButton");
private JCheckBox cb = new JCheckBox("CheckBox");
private JRadioButton radio = new JRadioButton("RadioButton");
private JButton undoButton = new JButton("Undo");
private JButton redoButton = new JButton("Redo");
private JButton startButton = new JButton("Start");
private JButton endButton = new JButton("End");
private StateEdit edit;
public UndoableToggleApp4() {
SimpleListener sl = new SimpleListener();
tog.addActionListener(sl);
cb.addActionListener(sl);
radio.addActionListener(sl);
Box buttonBox = new Box(BoxLayout.Y_AXIS);
buttonBox.add(tog);
buttonBox.add(cb);
buttonBox.add(radio);
startButton.setEnabled(true);
endButton.setEnabled(false);
undoButton.setEnabled(false);
redoButton.setEnabled(false);
startButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent ev) {
edit = new StateEdit(UndoableToggleApp4.this);
startButton.setEnabled(false);
endButton.setEnabled(true);
// undoButton.setEnabled(edit.canUndo());
//
// NOTE: We really don"t want to be able to undo until end() is pressed,
// but StateEdit does not enforce this for us!
undoButton.setEnabled(false);
redoButton.setEnabled(edit.canRedo());
}
});
endButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent ev) {
edit.end();
startButton.setEnabled(true);
endButton.setEnabled(false);
undoButton.setEnabled(edit.canUndo());
redoButton.setEnabled(edit.canRedo());
}
});
// Add a listener to the undo button. It attempts to call undo() on the
// current edit, then enables/disables the undo/redo buttons as appropriate.
undoButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent ev) {
try {
edit.undo();
} catch (CannotUndoException ex) {
ex.printStackTrace();
} finally {
undoButton.setEnabled(edit.canUndo());
redoButton.setEnabled(edit.canRedo());
}
}
});
redoButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent ev) {
try {
edit.redo();
} catch (CannotRedoException ex) {
ex.printStackTrace();
} finally {
undoButton.setEnabled(edit.canUndo());
redoButton.setEnabled(edit.canRedo());
}
}
});
// Lay out the state/end and undo/redo buttons.
Box undoRedoBox = new Box(BoxLayout.X_AXIS);
undoRedoBox.add(Box.createGlue());
undoRedoBox.add(startButton);
undoRedoBox.add(Box.createHorizontalStrut(2));
undoRedoBox.add(endButton);
undoRedoBox.add(Box.createHorizontalStrut(2));
undoRedoBox.add(undoButton);
undoRedoBox.add(Box.createHorizontalStrut(2));
undoRedoBox.add(redoButton);
undoRedoBox.add(Box.createGlue());
// Lay out the main frame.
Container content = getContentPane();
content.setLayout(new BorderLayout());
content.add(buttonBox, BorderLayout.CENTER);
content.add(undoRedoBox, BorderLayout.SOUTH);
setSize(400, 150);
}
public class SimpleListener implements ActionListener {
// When any toggle button is clicked, we turn off the undo and redo
// buttons, reflecting the fact that we can only undo/redo the last
// set of state changes as long as no additional changes have been made.
public void actionPerformed(ActionEvent ev) {
undoButton.setEnabled(false);
redoButton.setEnabled(false);
}
}
// Save the state of the app by storing the current state of the three
// buttons. We"ll use the buttons themselves as keys and their selected
// state as values.
public void storeState(Hashtable ht) {
ht.put(tog, new Boolean(tog.isSelected()));
ht.put(cb, new Boolean(cb.isSelected()));
ht.put(radio, new Boolean(radio.isSelected()));
}
// Restore state based on the values we saved when storeState() was called.
// Note that StateEdit discards any state info that did not change from
// between the start state and the end state, so we can"t assume that the
// state for all 3 buttons is in the Hashtable.
public void restoreState(Hashtable ht) {
Boolean b1 = (Boolean) ht.get(tog);
if (b1 != null)
tog.setSelected(b1.booleanValue());
Boolean b2 = (Boolean) ht.get(cb);
if (b2 != null)
cb.setSelected(b2.booleanValue());
Boolean b3 = (Boolean) ht.get(radio);
if (b3 != null)
radio.setSelected(b3.booleanValue());
}
// Main program just creates the frame and displays it.
public static void main(String[] args) {
JFrame f = new UndoableToggleApp4();
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.setVisible(true);
}
}
</source>
