I have a JComboBox whose values are retrieved across the net.
I'm looking for a way to indicate that fact to the user, when the user wants to see the list, expands the drop down, and only then the data is being retrieved.
The basic requirements include:
JComboBox's drop-down shouldn't lock the EDT, but the combo's action should not work until there are values.
User should know when all data has been retrieved.
The size (UI real-estate) of the indication should be as small as possible.
Note that the data isn't retrieved until the user wants to see the combo's values (i.e. expands the drop-down list).
The solution i've used:
I've used a SwingWorker to keep the UI responsive. The combo box was overlayed using JIDE's Overlayable with JIDE's InfiniteProgressPanel that listens to the worker.
To avoid locking the EDT, your data retrieval should be done in a background thread. I would use a SwingWorker to find and load the values since this makes available a background thread with other goodies that make it very Swing-friendly. I would make the JComboBox enabled property false until all values have been loaded, and then enable it via setEnabled(true). You will know the SwingWorker is done either through its done() method (by overriding it), or by adding a PropertyChangeListener to the SwingWorker and being notified when its state is SwingWorker.StateValue.DONE.
One way for the user to know that the process is complete is that they will see when the combo box has been re-enabled. If you want a more obvious indicator, you could display a JProgressBar or a ProgressMonitor. This could be displayed in a dialog if you wish to leave the GUI appearance mostly unchanged.
I implemented it by adding "Loading..." item and a special border around the JComboBox. On click separate thread is started adding new items via SwingUtilities.invokeAndWait. When loading is completed the "Loading..." last item is removed.
to not force my users to wait until the data is loaded, combine the answers by eel and stan :-)
start off with the model containing zero or one real value plus the dummy entry "loading"
register a PopupMenuListener and start a SwingWorker loading the data (into a separate datastructure, might be a new model) in its very first menuWillBecomeVisible
while loading, select the dummy entry (and/or whatever else is appropriate to inform the user what's happening), the action has to be aware of "nothing-to-do-yet" as well
listen to the worker, when receiving the DONE replace/fill the data into the combo's model
Related
I'm dealing with a WebApp (Vaadin19) and stuck now in the question, how to share an object-state change from one component to another. There is one object instance in two or more components. After changing an attribute of the object in one component and going back to another component, I want to see the changed attribute.
Let me explain, what I mean:
There is a grid with some lines of data. The grid shows only a subset of the data to respect the clarity.
A click on the grid opens a detailed view in "read mode". The data is structured (contains sub-objects itself).
A click on the "read mode"-view opens then a dialog with tabs. The activated tab depends on the sub-object, that was clicked before.
After changing an element in the sub-object and closing the dialog, I want that the UI will reload/revalidate it's content. I think it's clear, that I use there the same object-instance.
Is there an event I have to submit to the UI?
Or:
What is the best approach for this?
The actual refresh is easy: theGrid.getDataProvider().refreshAll(), or refreshItem instead if you have access to the item that has been changed and it has a good implementation of equals and hashCode.
How to hook things up so that the dialog notifies the grid is then really depending on your architecture.
If they are already close to each other in the code, then you could e.g. store a reference to the Grid in an instance field and just reference that in the dialog handler.
If you want to decouple, then you need some kind of event bus. You can use the regular Spring event mechanisms as long as you ensure that the event stays within the UI scope. Alternatively, you can use ComponentUtil::addListener and ComponentUtil::fireEvent to use e.g. UI.getCurrent as a simple event bus.
In SWT, I can find plenty of events that fire when text is typed into the combo, the user makes a selection, etc.
Are there any triggers for when the combo list gets updated, though?
E.g., if I the list is
['apple', 'banana']
and it becomes
['apple', 'banana', 'shoe']
is there any trigger for that, and if not, can I create one?
SWT does not send an event if the list of items of a Combo or CComb changes.
If you use a JFace ComboViewer, its IContentProvider gets informed when the viewer's input changes through its inputChanged() method.
If that's not what you want, then you are free to write application code that notifies interested observers about content changes.
I want to get my event listener called when the component is repainted (JComponent). I read about different Event Listeners but none seems to be the correct one for Invalidate or Repaints. Any way to do this?
Why I want this: I'm trying to get notified when there is some change in a control, in order to fire the method that tracks the changes (as in the file has changed, "do you want to save changes?").
Another use for this is for manually invoking the custom layout manager of a non-added-to-the-container-but-drawn component (this one is kind of complex, it's for a GUI editor program).
Why I want this: I'm trying to get notified when there is some change in a control, in order to fire the method that tracks the changes (as in the file has changed, "do you want to save changes?").
Normally, you track changes to an edited file in the GUI model class. Every time your model adds or removes a character, you set a dirty flag in the model that you check later.
Another use for this is for manually invoking the custom layout manager of a non-added-to-the-container-but-drawn component (this one is kind of complex, it's for a GUI editor program).
Your understanding of Swing appears to be backwards. The components don't drive the layout. The layout arranges the components.
Here's one example of a Swing character based text editor.
Here's a Stack Overflow question about a GUI builder editor.
I have a JTree, a JTable and a JList which displays the same set of objects, but in different order and with different information. If an item is selected from one of the Component, I want to select the same object on the other two Components (meaning they should be highlighted). Naturally I monitor the selection events with a Listener. Here is the problem, when a Component retrieves the selected object, I'll have to make sure the object is selected on the other Components by calling selection methods on them. This, will then notify the selection listeners on the other two components. But each of those events will in turn call selection events on components other than itself, causing an infinite loop going among the three Components.
I see one solution is to use a boolean flag, and make the listeners not propagate the selection if the flag is set. However, this seems cumbersome and not elegant. Is there a way to simply tell JTree, JTable and JList to make the selection but not fire any events (as oppose to fire an event and then catching and stopping it with a boolean flag)?
Take a look at SharedModelDemo. I think it does what you're looking for.
I would use a flag indicating whether it's user changes or internal changes but yu can also remove listeners before selection call and add them after to prevent events firing.
First, let it be known that I'm new to java and it's quirks. I'm a seasoned programmer with various languages, which may be why I'm stuck...
I have an application that, possibly due to poor design, spawns new JFrames through the users' work-flow. My question is, if there is an event in a spawned JFrame, is it able to contact and pass data or an event to it's parent?
I have read that using a JDialog seems to be the way to design, but let's assume that's not an option. Essentially, JFrame1 contains a JTable with a list of data. An action spawns JFrame2 and a user "does something" that impacts the data in the list in JFrame1. Upon closing JFrame2, is there a way to control the JTable based on JFrame2's close event?
It's a pretty basic concept, I just can't seem to find the mechanism that would allow such an action.
Thanks!
You can use "listeners" to listen for various events.
It sounds like you might want to start with How to Write a Window Listener.
I have read that using a JDialog seems to be the way to design, but let's assume that's not an option.
Why? The code is the same and JDialogs where designed for this purpose. What is the specific requirement that says you need to use a JFrame?
An action spawns JFrame2 and a user "does something" that impacts the data in the list in JFrame1. Upon closing JFrame2, is there a way to control the JTable based on JFrame2's close event?
This is a common design. The user selects a row to change or update and a model dialog is created to display all the data so it can be changed. When the dialog is saved the data in the table is updated. If this is your requirement, then you can just pass in the TableModel to the dialog. Then when the dialog is closed you update the TableModel and the table will be repainted automatically.
You would have to capture the window closing event using a window listener. The window listener would also need a reference to the data that needs to be changed.
In addition to using Window.addWindowListener() on either a JFrame or a JDialog, consider using a model-view approach. Have the close event modify the table's data, rather than the table itself. Use AbstractTableModel as the model for the table, and listen for changes to the data.