In windows it is possible to show a grayed out JCheckbox, to show that the collection of data which it represents not all items have the same value.
Is this even possible with a JCheckBox? How do i go about this? (Hoping there's a way to not override it)
Thanks
It's possible with some of work.
I have this code from some years ago. Is based in some examples I found in internet, but I cannot find any reference to the original creator, so I apologize
import javax.swing.*;
import javax.swing.event.ChangeListener;
import javax.swing.plaf.ActionMapUIResource;
import java.awt.event.*;
/**
* Maintenance tip - There were some tricks to getting this code
* working:
*
* 1. You have to overwite addMouseListener() to do nothing
* 2. You have to add a mouse event on mousePressed by calling
* super.addMouseListener()
* 3. You have to replace the UIActionMap for the keyboard event
* "pressed" with your own one.
* 4. You have to remove the UIActionMap for the keyboard event
* "released".
* 5. You have to grab focus when the next state is entered,
* otherwise clicking on the component won't get the focus.
* 6. You have to make a TristateDecorator as a button model that
* wraps the original button model and does state management.
*/
public class TristateCheckBox extends JCheckBox {
/** This is a type-safe enumerated type */
public static class State { private State() { } }
public static final State NOT_SELECTED = new State();
public static final State SELECTED = new State();
public static final State DONT_CARE = new State();
private final TristateDecorator model;
public TristateCheckBox(String text, Icon icon, State initial){
super(text, icon);
// Add a listener for when the mouse is pressed
super.addMouseListener(new MouseAdapter() {
public void mousePressed(MouseEvent e) {
grabFocus();
model.nextState();
}
});
// Reset the keyboard action map
ActionMap map = new ActionMapUIResource();
map.put("pressed", new AbstractAction() {
public void actionPerformed(ActionEvent e) {
grabFocus();
model.nextState();
}
});
map.put("released", null);
SwingUtilities.replaceUIActionMap(this, map);
// set the model to the adapted model
model = new TristateDecorator(getModel());
setModel(model);
setState(initial);
}
public TristateCheckBox(String text, State initial) {
this(text, null, initial);
}
public TristateCheckBox(String text) {
this(text, DONT_CARE);
}
public TristateCheckBox() {
this(null);
}
/** No one may add mouse listeners, not even Swing! */
public void addMouseListener(MouseListener l) { }
/**
* Set the new state to either SELECTED, NOT_SELECTED or
* DONT_CARE. If state == null, it is treated as DONT_CARE.
*/
public void setState(State state) { model.setState(state); }
/** Return the current state, which is determined by the
* selection status of the model. */
public State getState() { return model.getState(); }
public void setSelected(boolean b) {
if (b) {
setState(SELECTED);
} else {
setState(NOT_SELECTED);
}
}
/**
* Exactly which Design Pattern is this? Is it an Adapter,
* a Proxy or a Decorator? In this case, my vote lies with the
* Decorator, because we are extending functionality and
* "decorating" the original model with a more powerful model.
*/
private class TristateDecorator implements ButtonModel {
private final ButtonModel other;
private TristateDecorator(ButtonModel other) {
this.other = other;
}
private void setState(State state) {
if (state == NOT_SELECTED) {
other.setArmed(false);
setPressed(false);
setSelected(false);
} else if (state == SELECTED) {
other.setArmed(false);
setPressed(false);
setSelected(true);
} else { // either "null" or DONT_CARE
other.setArmed(true);
setPressed(true);
setSelected(true);
}
}
/**
* The current state is embedded in the selection / armed
* state of the model.
*
* We return the SELECTED state when the checkbox is selected
* but not armed, DONT_CARE state when the checkbox is
* selected and armed (grey) and NOT_SELECTED when the
* checkbox is deselected.
*/
private State getState() {
if (isSelected() && !isArmed()) {
// normal black tick
return SELECTED;
} else if (isSelected() && isArmed()) {
// don't care grey tick
return DONT_CARE;
} else {
// normal deselected
return NOT_SELECTED;
}
}
/** We rotate between NOT_SELECTED, SELECTED and DONT_CARE.*/
private void nextState() {
State current = getState();
if (current == NOT_SELECTED) {
setState(SELECTED);
} else if (current == SELECTED) {
setState(DONT_CARE);
} else if (current == DONT_CARE) {
setState(NOT_SELECTED);
}
}
/** Filter: No one may change the armed status except us. */
public void setArmed(boolean b) {
}
/** We disable focusing on the component when it is not
* enabled. */
public void setEnabled(boolean b) {
setFocusable(b);
other.setEnabled(b);
}
/** All these methods simply delegate to the "other" model
* that is being decorated. */
public boolean isArmed() { return other.isArmed(); }
public boolean isSelected() { return other.isSelected(); }
public boolean isEnabled() { return other.isEnabled(); }
public boolean isPressed() { return other.isPressed(); }
public boolean isRollover() { return other.isRollover(); }
public void setSelected(boolean b) { other.setSelected(b); }
public void setPressed(boolean b) { other.setPressed(b); }
public void setRollover(boolean b) { other.setRollover(b); }
public void setMnemonic(int key) { other.setMnemonic(key); }
public int getMnemonic() { return other.getMnemonic(); }
public void setActionCommand(String s) {
other.setActionCommand(s);
}
public String getActionCommand() {
return other.getActionCommand();
}
public void setGroup(ButtonGroup group) {
other.setGroup(group);
}
public void addActionListener(ActionListener l) {
other.addActionListener(l);
}
public void removeActionListener(ActionListener l) {
other.removeActionListener(l);
}
public void addItemListener(ItemListener l) {
other.addItemListener(l);
}
public void removeItemListener(ItemListener l) {
other.removeItemListener(l);
}
public void addChangeListener(ChangeListener l) {
other.addChangeListener(l);
}
public void removeChangeListener(ChangeListener l) {
other.removeChangeListener(l);
}
public Object[] getSelectedObjects() {
return other.getSelectedObjects();
}
}
}
My colleague who this question came from thought of this;
++ No overridden JCheckBox
-- not a real tri-state Combo
I think he's satisfied. Thanks for the help