Develop Reference

SWT Keylistener is not triggered

I have a SWT GUI, containing different elements (Text, Buttons, Labels...) which are themselves in different Composites.
I would like to make the navigation easier using some keybindings such as "Alt+c" to call the Cancel Button, "Alt+f" to call the finish button etc... When using a KeyListener on a specific component, the listener is triggered, but it implies that the component has the focus (and this is not very convenient !).
So I tried to register the listener on the shell itself, but the result is the same and nothing is triggered.
How should I proceed in order to get my listener triggered no matters what element is currently focused ?
Any hint would be appreciated.
Thanks for reading.
Edit
Regarding the comments, I tried to add the keylistener recursively to all the composites of the GUI, and it's working. However, I guess there is probably a "clever" way to do it.

You can use the Display addFilter or addListener methods to add a listener which is always called.
Display.getDefault().addListener(SWT.KeyDown, new Listener() {
#Override
public void handleEvent(final Event event) {
// TODO handle event
}
});
These listeners use the lower level Listener interface rather than KeyListener.
addFilter is similar to addListener but is called earlier and can change the event.

The easiest way is to add a event filter to the display:
Here is an example I use to activate a search field when a user types command-F in our main application window.
Display.getCurrent().addFilter(SWT.KeyDown, event -> {
// Only respond to key events for our shell.
if (getShell().equals(Display.getCurrent().getActiveShell())) {
// Activate the focus for our search widget when user types 'f'
// (control-f, command-f, or just f)
if (event.keyCode == 'f') {
if (!searchField.isFocusControl()) {
searchField.setFocus();
}
}
}
});

How to check if and which mouse button is pressed in Swing

How can I check if currently any mouse button is pressed and if so, which one it is?
The thing is that I need to use this kind of information in MouseListener.mouseEntered(). I checked MouseEvent but I could not find the method which would help me.
The getButton() method seems to only return value if there has been change in buttons' state.
Is there a way to find this out without manually keeping track of this somehow vie MouseListener.mousePressed()/mouseReleased() methods.

How can I check if currently any mouse button is pressed and if so, which one it is?
Presumably you want to invoke specific code depending on the button pressed so you can do something like:
if (SwingUtilities.isLeftMouseButton(...))
// do something

You could start by looking at How to write a Mouse Listener and the JavaDocs for MouseEvent in particular, the getButton method.
However, there are cross platform considerations that need to taken into consideration, which are overed by SwingUtilities.isLeftMouseButton and equivalent methods...

This will solve your problem
long eventMask = AWTEvent.MOUSE_MOTION_EVENT_MASK + AWTEvent.MOUSE_EVENT_MASK;
Toolkit.getDefaultToolkit().addAWTEventListener(new AWTEventListener() {
public void eventDispatched(AWTEvent e) {
System.out.println(e.paramString()+"-"+e.getSource());
}
}, eventMask);
This is a Global Event Listeners.
Get the source and button from AWTEvent and do whatever you want to perform.

Mouse event handling in Swing

I was wondering, how does a Swing component know where the mouse is and when it is clicked, and how could I use that in my own class, without having to add a new mouse listener every time i want to add an object to a new panel?
EDIT:
Im extending JComponent and I want to get an event method called when the mouse moves
EDIT2:
Got it working now thanks everyone!

Add an actionlistener to your JButton and it will tell you when its been clicked like so:
someButton.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent e) {
//the button was pressed and do your stuff here.
}
}

how does the JButton know where the mouse is and when it clicked
thats what for Listeners are - it listens for a corresponding type of event
just implement ActionListener and register it to its listener by doing this:
jbutton.addActionListener(this);
now when you click the button it will generate an event which will b handled in this part
public void actionPerformed(ActionEvent e){
... // handle event
}

From the comments of the other post, you want to register a MouseListener to you custom component using Component#addMouseListener
You may like to have a read through How to write a mouse listener for more info

How to detect mouse moving while left button down?

I would like to detect mouse moving, while the left button is pressed.
I simply create a drawing application. I can detect the mouse move without any mouse pressed. But I want to detect WITH left mouse pressed.
I think there is not any listener for this. So, what is the idea to do that?

component.addmouseMotionListener(new MouseAdapter() {
public void mouseDragged(MouseEvent evt) {
if ( SwingUtilities.isLeftMouseButton(evt)) {
// do your stuff here
}
}
});

there is mouseDragged method in MouseMotionListener...check this out for more details...

In your MouseMotionListener you can check for this using:
SwingUtilities.isLeftMouseButton(me.getPoint())
and you would listen for the mouseDragged event.

I think there might be some sort of mouse drag listener, but if not...
Capture the mouse button down and up events. In those events, set a boolean such as leftButtonIsDown = true (unless there's already some easy way to query that) and then in the mouse movement events use a block like if (leftButtonIsDown)

Java JTree valueChanged Event before MouseEvent

Here's the situation, I have a jFrame with a tabbed pane and within the tabs I have a couple of jTables and a jTree. I want to be able to chain the selections between the tables and the tree based on whether a user uses a ctrl/shift + click versus a regular click. (If you hold ctrl and click in the first table/tree, it adds to the overall selection, if you use a regular click it clears the selections in the other tables/tree). Currently I'm having an issue with Java's jTree component. I have added a TreeSelectionListener and a MouseListener with a class that implements both interfaces, call it MyBigListener;
i.e.
MyBigListener listener = new MyBigListener();
jTree1.addMouseListener( listener );
jTree1.addTreeSelectionListener( listener );
MyBigListener implements TreeSelectionListener, MouseListener {
private boolean chained = false;
public synchronized setChained(boolean ch){
chained = ch;
}
public synchronized boolean isChained(){
return chained
}
public void valueChanged(TreeSelectionEvent e){
if(isChained()){ blah... }
}
public void mousePressed(MouseEvent e){
setChained(e.isControlDown() || e.isShiftDown());
}
}
My plan was to set a boolean flag if the user uses a ctrl/shift + click that I could check during the valueChanged(TreeSelectionEvent e) implemented by the tree selection listener.
I want to be able to process the mouse events before the valueChanged TreeSelectionEvents, but the problem is that I receive the mouse events after the valueChanged treeSelection event. This seems weird to me that I receive the selection change before the mouse pressed event fires, when the selection change is actually initiated by the mouse pressed. (I've already synchronized the boolean flag setting, which ironically helped to highlight the mis-order of events.)
I've already tried alternatives like adding a keyListener, but this doesn't work when the focus is on a separate frame, which goofs me up when a user holds ctrl and then clicks into the jTree causing it to receive both the focus and fire any valueChanged selection events.
Any help would be appreciated, thanks!
--EDIT-- #akf
I have separate jTables and jTrees in a tabbed Pane that serve as a summary/control panel for data in a nodal-graph. I'm using these components in the tabbed Pane to do coordinated selection to a graph displayed in a separate jFrame. Individually each table works just fine for its selection as does the jTree. It's coordinating between the panes that's tricky. This works fine so far with jTable components because I fire the new selections as the result of a MouseEvent where I can tell if the shift/ctrl button was down, formulate my new selection, and pass it to the parent frame which coordinates selections between all panes and sends the final selection to the graph. However, the parent needs to know if it needs to chain a selection between panes, or squash the others. With the jTables it's fine again, because I fire selection changes as the result of a mouse click. The jTree is more of a problem because I'm doing some forced selections. If you click on a branch, it forces all leaves into the selection. I needed to implement a TreeSelectionListener to do that, but only get a valueChanged(TreeSelectionEvent) to realized changes. I added a mouseListener to listen for ctrl+clicks and shift+clicks, but apparently the events don't always happen in the same order.. at least so far I receive the valueChanged event before the mousePressed event, so checking to if a ctrl+click happened posts after the selection has already been modified.
Right now, I'm posting a pending selection change and then have the MouseListener grab that and send it up the chain, but if these events aren't guaranteed to happen in the same order, at some point it's going to fail. Implementing a delayer also rubs me the wrong way.
Thanks for the help so far.
--EDIT2-- #ykaganovich
I think overriding the fireValueChanged method is closer to the right way to go about things. Depending on my definition of what actions should cause a "chained" selection to the other components, I'd need to gather some context on what's going on before the valuedChanged method fires. This basically means calling it myself in all cases where I can define what it means by who triggers it. I.e. If a mouse event causes it and ctrl is down then set what I need to set (interpret) then fire. If it's going to change due to a keyboard event, again, set what I need to set, then fire. I don't think the TreeSelectionModel is the way to go, because I still won't know what the circumstances were when the event fired. I think this means I'll need to rewrite parts of the jTree to do this but I guess I'll see how it goes. Thanks.

Don't do it that way, override JTree.fireValueChanged instead.
Try something like this (untested):
class ChainedSelectionEvent extends TreeSelectionEvent {
ChainedSelectionEvent(TreeSelectionEvent e) {
super(e.newSource, e.paths, e.areNew, e.oldLeadSelectionPath, e.newLeadSelectionPath);
}
}
protected void fireValueChanged(TreeSelectionEvent e) {
if(chained) { // figure out separately
super.fireValueChanged(new ChainedSelectionEvent(e));
} else {
super.fireValueChanged(e);
}
}
Then check instanceof ChainedSelectionEvent in your listener
EDIT
Actually, I think the right way to do this is to implement your own TreeSelectionModel, and override fireValueChanged there instead. Assuming setSelectionPath(s) methods imply a new selection, and add/removeSelectionPath(s) imply chaining, you could distinguish between the two cleanly. I don't like listening to either keyboard or mouse events explicitly, because there's more than one way to change a selection (e.g. if someone is holding down SHIFT and hitting a down-arrow, you won't get a mouse event).

You may get the mouse event before or after the tree selection event. Best not to rely on such orders. The reason is that the tree selection event is caused in response to the mouse event. Is that mouse event listener called before or after your listener? Could be either.
This sort of thing is closely involved with the implementation of the PL&F.

the key here is to understand that a JTree is delivered with a BasicTreeUI.MouseHandler, see javax.swing.plaf.basic.BasicTreeUI.
to answer the central question, "what fires fireValueChanged", the answer is "this mouse handler"... which turns out to be the only mouse listener returned when you go tree.getMouseListeners().
So you have to replace this default mouse listener with your own version ... which is a little tricky. I use Jython, which everyone needs to discover. This code shouldn't be too difficult to translate into Java however:
from javax.swing.plaf.basic import BasicTreeUI
def makeMouseHandlerClass():
class MouseHandlerClass( BasicTreeUI.MouseHandler ):
def mousePressed( self, mouseEvent ):
genLog.info( "mouse handler MOUSE PRESSED!" )
nTFSelf.mousePressedStatus = True
BasicTreeUI.MouseHandler.mousePressed( self, mouseEvent )
nTFSelf.mousePressedStatus = False
return MouseHandlerClass
suppliedMouseHandler = nTFSelf.taskTree.mouseListeners[ 0 ]
nTFSelf.taskTree.removeMouseListener( suppliedMouseHandler )
nTFSelf.taskTree.addMouseListener( makeMouseHandlerClass()( nTFSelf.taskTree.getUI() ))
... basically the equivalent Java here would be to extend BasicTreeUI.MouseHandler as MyMouseHandler, and then in the last line replace with new MyMouseHandler( tree.getUI() )... "nTFSelf" here is merely a reference to the "this" object of the code where all this is being written...