Develop Reference

Adapter pattern with Buttons, adaptor class has to know which button was pressed

This is an actionPerformed in a Swing panel with custom buttons from a framework which scrambles their classes so all methods are a():String or b():void and there is no way to make out what it actually is.
I got a compiler error becaus when I inherit this button class the compiler find a():void an a():String which is not allowed in Java. My solution was to use the adapter pattern like this:
public abstract class FactoryButton {
private CustomButton button;
public FactoryButton(int width, int height) {
button = new DynButton();
button.setSize(width, height);
}
public DynButton getButton() {
return button;
}
}
So my FactoryButton has the CustomButton class as a private member. The FactoryButton is the parent of another Button class named FactorySelectionButton
which has an action performed where I used to be able to get the source of the event:
#Override
public void actionPerformed(ActionEvent arg0) {
if (arg0.getSource() instanceof FactorySelectionButton) {
// User selected a factory
selectedItem = ((FactorySelectionButton) arg0.getSource()).getFactory();
// Close the screen, so control returns back to the parent window
cancel();
} else {
// other buttons implementation
}
}
But now since I solved one problem with the adapter pattern I have another the arg0.getSource() no longer gives me the FactorySelectionButton but it now gives a CustomButton which gives me no way to know which custom button is pressed.
The reason for not throwing away the custom button is that I am bound to the framework, I have to use it and the amount of factories can grow so I don't want hardcoded buttons.
So anyone have an idea on how I can fix this?

I found a way around it by looping over all my components and checking whether they have the button I need and they double checking whether it's really an instance of the class I want.
#Override
public void actionPerformed(ActionEvent arg0) {
for (FactoryButton component : components) {
if(component.getButton().equals(arg0.getSource()) && component instanceof FactorySelectionButton)
selectedItem = ((FactorySelectionButton) component).getFactory();
return;
}
//other buttons implementation
}

Allow parent to handle mouse event

I added a JPanel to a JRadioButton - so that I may display whatever I want in the radio button.
This all worked as expected. But to allow for text wrapping, I used a JTextArea and added it to the JPanel contained within the radio button.
Now I have an issue where, if the user clicks on the JTextArea, then the JTextArea consumes the mouseEvent and as a result there is no response from the radio button (it doesn't 'select').
Is there a way get the JTextArea to ignore the mouse click, so that the parent may handle it instead?
I tried add the JTextArea's listeners to the radioButton instead.
I also tried to remove its listeners completely, but both these attempts failed.
Anyone have any suggestions?

Strong beware
Most JSomething are not meant to be used as containers even though it's possible - the outcome of doing it anyway is more or less visually and behaviourally undetermined!
That said, did it recently, to implement something similar to a Windows task dialog. If the requirement includes keeping the button clickable (and why else would you mis-use it as a container :-) the main problem (layout apart) is to make all added components completely mouse-transparent. Which is more difficult than can be expected. The minimum is to not allow adding of mouseListeners and disable the acceptance of mouseEvents:
final JTextArea area = new JTextArea("replacement ..") {
#Override
public synchronized void addMouseListener(MouseListener l) {
LOG.info("adding here ...?");
}
#Override
public synchronized void addMouseMotionListener(
MouseMotionListener l) {
}
#Override
public synchronized void addMouseWheelListener(
MouseWheelListener l) {
}
#Override
public void addNotify() {
disableEvents(AWTEvent.MOUSE_EVENT_MASK |
AWTEvent.MOUSE_MOTION_EVENT_MASK |
AWTEvent.MOUSE_WHEEL_EVENT_MASK);
super.addNotify();
}
};
Plus make sure it's not focusable
area.setEditable(false);
area.setFocusable(false);
area.setRequestFocusEnabled(false);
Plus unregister dragging and tooltips
ToolTipManager.sharedInstance().unregisterComponent(area);
area.setDragEnabled(false);
Nevertheless, there might still be surprises ahead, f.i. call the following twice (that is disable and enable again), which will internally re-enable mouseEvent:
area.setAutoscrolls(!area.getAutoscrolls());
So at the end of the day, we might get away with it - but never be entirely certain that we succeeded.

What about this? Create and add your own MouseListener to TextArea
JPanel p = new JPanel();
JTextArea t = new JTextArea("line \n line");
t.addMouseListener(new MyMouseListener());
p.add(t);
jRadioButton1.add(p);
jRadioButton1.addMouseListener(new MyRadioButtonMouseListener());
And in the MyMouseListener Dispatch event
private class MyMouseListener implements MouseListener {
#Override
public void mouseClicked(MouseEvent e) {
Component source = (Component) e.getSource();
source.getParent().getParent().dispatchEvent(e); // 2x getParent() because JTextArea->JPanel->JRadio
}
.
.
.
}
And finally RadioButtonMouseListener
private class MyRadioButtonMouseListener implements MouseListener {
#Override
public void mouseClicked(MouseEvent e) {
System.out.println("CLICK ON RADIOBUTTON !!");
}
.
.
.
}

Java: JScrollPane disable scrolling when ctrl is pressed

I want to disable scrolling with the mousewheel in my JScrollPane while ctrl is pressed.
When you press ctrl and move the wheel you will zoom in/out AND also scroll the panel, which is not what I wanted.
Here's the working code:
scroller = new JScrollPane(view);
scroller.removeMouseWheelListener(scroller
.getMouseWheelListeners()[0]);
scroller.addMouseWheelListener(new MouseWheelListener() {
public void mouseWheelMoved(final MouseWheelEvent e) {
if (e.isControlDown()) {
if (e.getWheelRotation() < 0) {
// Zoom +
} else {
// Zoom -
}
} else if (e.isShiftDown()) {
// Horizontal scrolling
Adjustable adj = getScroller().getHorizontalScrollBar();
int scroll = e.getUnitsToScroll() * adj.getBlockIncrement();
adj.setValue(adj.getValue() + scroll);
} else {
// Vertical scrolling
Adjustable adj = getScroller().getVerticalScrollBar();
int scroll = e.getUnitsToScroll() * adj.getBlockIncrement();
adj.setValue(adj.getValue() + scroll);
}
}
});
Edited my question and resolved it myself.
If you have any tweaks go ahead and tell me!

Take a look at Mouse Wheel Controller. You won't be able to use the exact code but you should be able to use the concept of the class.
The code replaces the default MouseWheelListener with a custom listener. Then it recreates the event with one different parameter in redispatches the event to the default listeners.
In your case you won't need to create a new event you will just need to prevent any event with a Control modifier from being redispatched to the default listeners and instead you invoke the code you posted in your question.

In order to temporarily disable scrolling you could manipulate the scrollbar's unit increment value and, respectively, restore it again.
Just add a key listener to the view port panel and react to Ctrl key pressed:
editorPane.addKeyListener(new KeyAdapter(){
#Override
public void keyPressed(KeyEvent e) {
if ((e.getModifiersEx() & InputEvent.CTRL_DOWN_MASK) != 0)
getVerticalScrollBar().setUnitIncrement(0);
else
getVerticalScrollBar().setUnitIncrement(15);
}
#Override
public void keyReleased(KeyEvent e) {
if ((e.getModifiersEx() & InputEvent.CTRL_DOWN_MASK) != 0)
getVerticalScrollBar().setUnitIncrement(0);
else
getVerticalScrollBar().setUnitIncrement(15);
}
});

Setting caret position in JTextArea

I have a JTextArea. I have a function that selects some amount of text when some combination is called. It's done properly. The thing is, I want to move caret to the selection beginning when some text is selected and VK_LEFT is pressed. KeyListener is implemented properly, I tested it in other way. The thing is, that when I write following code:
#Override public void keyPressed( KeyEvent e) {
if(e.getKeyChar()==KeyEvent.VK_LEFT)
if(mainarea.getSelectedText()!=null)
mainarea.setCaretPosition(mainarea.getSelectionStart());
}
and add an instance of this listener to mainarea, select some text (using my function) and press left arrow key, the caret position is set to the end of selection... And I wont it to be in the beginning... What's the matter? :S

Here's a code snippet
Action moveToSelectionStart = new AbstractAction("moveCaret") {
#Override
public void actionPerformed(ActionEvent e) {
int selectionStart = textComponent.getSelectionStart();
int selectionEnd = textComponent.getSelectionEnd();
if (selectionStart != selectionEnd) {
textComponent.setCaretPosition(selectionEnd);
textComponent.moveCaretPosition(selectionStart);
}
}
public boolean isEnabled() {
return textComponent.getSelectedText() != null;
}
};
Object actionMapKey = "caret-to-start";
textComponent.getInputMap().put(KeyStroke.getKeyStroke("LEFT"), actionMapKey);
textComponent.getActionMap().put(actionMapKey, moveToSelectionStart);
Note: it's not recommended to re-define typically installed keybindings like f.i. any of the arrow keys, users might get really annoyed ;-) Better look for some that's not already bound.

JComboBox actions

Is there a way to distinguish between a JComboBox's index being changed programatically using setSelectedBoundValue and by clicking on the JComboBox?

This is ugly and truly a hack, but works!
The ActionEvent contains a field modifiers which in this case is the mouse button id. So using that may help you distinguish between setSelectedIndex or setSelectedValue and mouse clicks (by the way setSelectedBoundValue is not a method on JComboBox):
box.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
if (e.getModifiers() != 0) {
// ~ mouse button pressed ;)
}
}
});

setSelectedBoundValue
Never heard of that method?
Is there a way to distinguish between a JComboBox's index being changed programatically
Not really. You can remove the listener:
comboBox.removeActionListener(...);
comboBox.setSelectedItem(...);
comboBox.addActionListener(...);
You can set your own class variable.
manualSelection = true;
comboBox.setSelectedIndex(...);
manualSelection = false;