AWT Canvas cannot gain focus in the presence of another focusable component - java

I have a simple GUI with a JTextField and an AWT Canvas (to prevent the counter-question as to why I'm using an AWT Canvas: I need to have a window handle).
The Canvas is to process input events, that means it must be focusable. I assure this by using setFocusable(true) in its constructor, later checks using isFocusable() confirm that it is indeed focusable.
Now, the JTextField gains the focus by default when the GUI opens. That's fine by me so far. However, there is no way to get the focus away from that JTextField.
The article "The AWT Focus Subsystem" clearly states that if a focusable component is being clicked on, it will gain the focus. This does not happen, in fact, I receive zero focus change events whatsoever, only if the window gets deactivated and activated again, but then the focus is right back to the JTextField.
Explicit invocations of requestFocus() and requestFocusInWindow() do not help either, the latter always returns false.
I have gotten the same results with any focusable component if I replace the JTextField. If the Canvas is the only focusable container, everything works fine because it will always have the focus.
Am I missing something here? Is there any way I can make my Canvas gain focus in the presence of another focusable component, preferably without making that one unfocusable?

basically in swing focus gained 1st. left(ToRight) JComponents on the top
in most completed GUI, and if there (together with creating JComponents) are added Listeners to the JComponents, then these Listeners (f.e. Document) can take focus...
but works for me on startUp:
last lines in something class about JComponets ..
myFrame.pack();
myFrame.setVisible(true);
Runnable doRun = new Runnable() {
public void run() {
myComponent.grabFocus();
myComponent.requestFocus();//or requestFocusInWindow
}
};
SwingUtilities.invokeLater(doRun);

Sorry for leaving some info out that turned out to be the root of the problem.
As mentioned, I'm using a heavyweight component so I have a window handle. I need one because it is passed to an OpenGL application in a native library, the AWT canvas is then used as a rendering canvas.
In Windows, Java uses the GWLP_USERDATA window field to store a pointer to an AWTComponent object. However, said OpenGL application overrides that field to store its own Window object pointer, which will of course break all AWT related functionality.
I solved this problem by creating a custom window message handler that delegates incoming messages to both the OpenGL application and Java's AWT part.

Related

Java keyListener with multiple JPanel

I'm having a problem with Java KeyListener when adding adding another JPanel with 5 JLabels, I've searched around this website, and most solutions to this problem involve switching from KeyListener to KeyBindings. This wont work for me because I need to know exactly when a key is pressed, released and held down. To my knowledge, KeyBindings does not provide all those.
I've tried to use
this.requestFocus();
after creating the new JPanel, but it didn't work, however when I use the same line inside the paintComponent(), it works. Which brings me to my questions: How does this reflect on performance? My paintComponent() is called about 60 times/sec. Is there a way to call it once and still have this working? I see that requestDefaultFocus() from the type JComponent is deprecated...
I've also tried adding same KeyListener to the second JPanel, but that didn't help. Im guessing one of the JLabels is the one that gets focus?
This wont work for me because I need to know exactly when a key is pressed, released and held down. To my knowledge, KeyBindings does not provide all those.
Yes it does. You have an Action for "pressed" and "released". There is no such Action as "held down" (even for a KeyListener), you just get multiple events generated.
this.requestFocus();
That is not the proper method to use for requestion focus on a component. Read the API for that method and it will tell you the proper method to use.
however when I use the same line inside the paintComponent(), it works.
This is because you can't request focus on a component until the frame has been realized, which means you've invoked pack() or setVisible() on the frame.
Is there a way to call it once and still have this working?
See the RequestFocusListener class in Dialog Focus.
The proper solution is to use Key Bindings so you don't need to use these work arounds.

swing focus issue, lost focus, focusgain not invoked

I have a complex and heavy swing client application which contains many modal compponents, jdialogs, internal frames etc. on some cases, a problem occurs and it is impossible to focus on swing textfields anymore. You may click on some jbuttons, jcheckboxes but it is impossible to focus and edit values on editable jtextfields anymore. The gainfocus events of editable textfields are not triggered anymore, only the requestfocus methods are invoked when you perform click on textfields.
I found a way(hack) so resolve the problematic case, when the trouble case occurs, and you show some joptionpane message or modal jdialog and close it by clicking or disposing, the problem goes away any you may click onto the textfields and edit them.
As a solution, i do some check, if you try focusing on a component, i start a timer thread in the requestfocus event of clicked textfield and keep the instance as focusrequesting component. After some time i check the last focused component by
KeyboardManager.getCurrentKeyboardFocusManager().getPermanentFocusOwner()
If no problem occured, and the textfield gained the focus, the returned object (retur value of getPermanentFocusOwner) is the same instance as the focusrequesting component. But if the problematic case occured, the returned object is different from the focus requesting one and i open my temporarily jdialog by:
JDialog dialog=new OptionPane().createDialog(KeyboardFocusManager.getCurrentFocusManager().getActiveWindow(), "");
dialog.setModal(true);
// MUST be modal to fix the lost focus case
// start closing thread, which closes the dialog after some few time by dialog.dispose
new Closer(dialog).start();
dialog.setVisible(true);
This mechanism works, i now it is not very stable. And on some cases,the dialog.dispose() does not work, the temporarily windows remains always on the screen, not closeable, and because it is modal, client can not do any actions anymore. The dialog MUST be modal to solve the focus problem, because non-modal dialogs does not resolve the focus problem declared above. The dispose method of jdialog has many synchronized blocks, mutex objects etc, I think there occurs some deadlocks.
Any better mechanism suggestions, ideas? I know the best solution is to check the current application, analyse it or rewrite it. But it is very complex, heavy and model and view is not well properly organised. I have short time because the client is waiting, need some temporarily solutions, tricks or hacks.
You may click on some jbuttons, jcheckboxes but it is impossible to
focus and edit values on editable jtextfields anymore.
this is issue (quite common) with JTextField in JWindow without parent (JFrame), use undecorated JDialog instead
I saw here some issue with Focus, FocusSubsystem on Linux OS with last Java version, but never caused to block users input to JTextField
the best workaround for a.m. issue is RequestFocusListener by #camickr
dialog.setVisible(true); should be wrapped in invokeLater(), more see in Initial Thread (valid for all Top-Level Containers created on runtime too)
nothing clear from your question without posting an SSCCE, short, runnable, compilable, demonstraded, caused with a.m. issue

Focus problems with JDK7 and native components

We have a swing application which embeds a IE ocx component via JNIWrapper.
After switching from jdk6 to jdk7 we start noticing focus problems. When the embedded IE shows a web page with text fields (e.g. the google search page) than the trouble starts:
The Browser 'catches' the focus, so u can start typing in the search text field. Every key typed goes to the IE ocx. But swing seems to ignore this focus change. Even if i change the focus to a swing text field (and swing shows the blinking input cursor), all typed keys goes to the IE ocx
The only way to 'fix' the focus is to deacitvate and activate the main frame. after that the focus seems to be consistent. But if i click in the google search text field again, the focus is broken again.
It seems there is a big change to focus handling in jdk7. From the link:
On the Windows platform, a concept of “synthetic focus” has been implemented. It means that a focus owner component only emulates its focusable state whereas real native focus is set to a “focus proxy” component. This component receives key and input method native messages and dispatches them to a focus owner. Prior to JDK7 a focus proxy component was a dedicated hidden child component inside a frame/dialog. In JDK7 a frame/dialog itself serves as a focus proxy. Now it proxies focus not only for components in an owned window but for all child components as well. A simple window never receives native focus and relies on focus proxy of its owner. This mechanism is transparent for a user but should be taken into account when debugging.
Anyone has an idea to 'fix' the behavior?
EDIT: Here some code to reproduce the problem with JxBrowser
public static void main(String[] args) {
Browser browser = BrowserFactory.createBrowser(BrowserType.IE);
JFrame frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(browser.getComponent(), BorderLayout.CENTER);
JPanel panel = new JPanel();
frame.getContentPane().add(panel, BorderLayout.NORTH);
textField = new JTextField();
panel.add(textField);
textField.setColumns(10);
frame.setSize(700, 500);
frame.setLocationRelativeTo(null);
frame.setVisible(true);
browser.navigate("http://www.google.com");
}
All - We just experienced this problem with another browser component (DjProject Native Swing). Everything works fine under Java 1.6 but under Java-7 we started seeing weird problems where you can type into an input box but if you select backwards to fix a typo you could not type after making the mouse click. To recover you had to select out of the input field and then back in to continue your edit.
See http://docs.oracle.com/javase/7/docs/webnotes/tsg/TSG-Desktop/html/awt.html#gdcqp
Particularly the part here about sythentic focus and focus proxies.
Anyway to cut a long story short - in our case I was able to find a work-around by attaching a mouse listener to the JWebBrowser.getNativeComponent(). Then on mousePressed execute a browser.requestFocus() followed by a browser.getNativeComponent().requestFocusInWindow();
Hope this helps anyone else that comes across this.
Try looking at FocusListener and WindowFocusListener to implement the listeners for either the Swing components themselves or the JFrame. Whenever a call is made to focusLost(..) it you can use requestFocus() on the Window or Component to force the focus to return.
I finally found a working workaround. During figuring out what was causing this it was noticed that clicking on another component (i.e. a JLabel) and clicking back on the text field worked fine. So I replicated that behavior using AWT Robot class. See more details in Replicating Mouse behavior in Code.
Try the latest jdk of Java 1.7. It worked for me.
Earlier, I was not able to enter any input in the text fields. After upgrading, I do not face that problem.
http://bugs.sun.com/view_bug.do?bug_id=8018672

How to create component that does't give focus to the Window

I have JTextField with FocusListener that call textfield.grabFocus() every time when textfield lose focus. But unfortunetly, it allow parent Window to react on user action. Is there any way to don't give the focus to the Window using only JTextField methods?
If I'm understanding you correctly, you don't want any other controls on your program to be usable while this field requires focus. The problem is, each object is likely to have at least one event listener waiting for some action to occur, and stealing your focus away from you.
You can make all objects not focusable by setting setFocusable(false) for each object, but that will still allow events to be captured.
I'd override/replace (or possibly completely remove, if really necessary) the event listeners on all the other objects to only perform actions when the proper conditions are met (when your object doesn't require focus, if that would ever occur). If overridden/replaced, each listener could then return focus to the JTextField if those conditions are not met.
Also, it is better to use requestFocus() or requestFocusInWindow() instead of grabFocus(). See JComponent grabFocus() and JComponent requestFocus() for more information.

Swing: Adding listener to a component and ALL its decoration?

Can I add a listener (let's say MouseAdapter) to a Swing component
and all it's internal decoration components?
So that when a JInternalFrame is moved by the mouse
(by dragging its window title bar), it would give me following events:
mousePressed event,
mouseDragged event,
mouseReleased event.
Currently, I receive none of the above events when dragging
JInternalFrame.
I hope there is some standardized solution, but I couldn't find any.
EDIT:
Some people suggest using ComponentListener, but that wouldn't do for
me. I need to know, when the user stops dragging (mouseReleasedEvent),
not when the component moves.
Yes, you can add a listener to all a container's components. getComponents and add the listener. You should be able to manage to do this recursively. You can also use ContainerListener to check for adding and removing components.
However, MouseListener and MouseMotionListener behave strangely in that the event normally bubbles up to the parent, but does not do so if a listener is present (how is that for hopeless design?).
Your choices are:
Recursively adding listeners (bad, see above)
Adding listeners to specific components (fragile)
Adding a "glass pane" (a messy hack)
Adding an AWTEventListener to Toolkit (requires permissions)
Pushing an EventQueue and checking through events (doesn't work of Opera and Safari apparently; stops system copy-and-paste and applet dragging from working)
Use ComponentListener?
I found out how it could be done, but something tells me, it's a dirty hack ;)
Well, it works, but who can give me the guarantee that it works everywhere?
// ctor goes here {
InternalFrameUI thisUI = getUI();
((BasicInternalFrameUI) thisUI).getNorthPane()
.addMouseMotionListener(new MyMouseListener());
// }
NorthPane turns out to be the window title bar.
You should probably use a MouseMotionListener instead of a MouseListener.
In the JInternalFrame API documentation, it says:
Generally, you add JInternalFrames to
a JDesktopPane. The UI delegates the
look-and-feel-specific actions to the
DesktopManager object maintained by
the JDesktopPane.
Maybe you should add your listener to the JDesktopPane.
MouseListener/MouseMotionListener wont detect when dragging a JInternalFrame. Your best bet here to detect movement is using a ComponentListener on the JInternalFrame itself.

Categories