How do you refresh a JPanel on the panel change from container CardLayout?
Use the show() method. From the Java API:
Flips to the component that was added to this layout with the specified name, using addLayoutComponent. If no such component exists, then nothing happens.
CardLayout#first(), next(), and previous() do something similar.
Sometimes, when I've made a panel swap like this (though not that I can remember on CardLayout, but it's been a while since I used it), I've also needed to pack the frame again. If that doesn't work, you can call revalidate(), which lets Swing know that the component needs to be redrawn.
You may also want to consider using a tabbed pane, as it does a lot of this for you; I started out a project trying to use CardLayout and decided to use a the tabbed pane instead. Depends on what you want to do, of course.
Is there an actionlistener or something that I can have it reload/refresh my data on that screen?
Assuming you have a model that supplies data to your view (panel), two approaches are common:
Arrange for your model to extend Observable and your view to register as an Observer.
Arrange for your model to manage an EventListenerList, in effect creating you own analog of ActionEvent.
In either approach, use the listener of the control that switches views tell the model to update its registered observers/listeners. The example in How to Use CardLayout uses a JComboBox and itemStateChanged(). There's additional discussion here.
Is there an actionlistener or
something that I can have it
reload/refresh my data on that screen?
You can use an AncestorListener. It fires when a component is added to a Container. So when you swap cards the event is fired. You would need to add the listener to each panel you add to the CardLayout:
Another problem with the CardLayout is that the panel doesn't gain focus when it is swapped. I use this approach to set focus on the panel. Check out Card Layout Focus.
panel.addAncestorListener(...);
The show() method does the trick of switching panels, but it doesn't "refresh" the data. Is there an actionlistener or something that I can have it reload/refresh my data on that screen?
Related
I am now writing code simple GUI that's for start the game window. I only need Do you want to start game message and start button on the window. But I have a confusing concepts for the JFrame and JPanel. Actually, I thought I need to add JPanel to JFrame to add the other components such as JLabel, JButton,...etc. But I realized I don't actually need JPanel. I can just add the components simply use add(button), add(label) to JFrame. So why I need JPanel. And I think JFrame doesn't need JPanel but JPanel need JFrame. Am I understand correctly?
No, not always. A simple graphical user interface may be implemented by just adding components "directly" to a JFrame. But in order to get more flexibility, you would always use JPanels. For example, to employ different layouts in different parts of the GUI, to group certain components together, etc.
A JFrame is backed by a JRootPane, a part of which is a contentPane.
(image from Oracle Javadoc)
When you add components to a JFrame, you are really adding them to the content pane, e.g.: frame.getContentPane().add(Component).
A JFrame is a common starting scene of a Swing GUI application, while a JPanel is intended to be put in another scene (container). Since both content pane and a JPanel inherit from the same class (Container) you may use them in a similar manner, as far as adding components to them goes.
Do I need JPanel always?
No. Well, unless you need a Swing GUI. Then yes.
Another answer replied words to the effect. "No, you can add components direct to a frame" What they missed was that components added to a JFrame are added to the content pane (automatically). The content pane is a JPanel.
Having said that:
I (and many others) would recommend designing an app based around a main content panel, then adding that panel to a top-level container as needed. The top level container might be a JFrame, JWindow, JDialog, JOptionPane ..
What prompted the question? A JPanel is a very 'light weight' container (in more ways than one). A GUI can contain 1000s and not be burdened by doing so. Of course, that's a rare requirement, but just saying .. use panels as needed and don't worry about it.
I currently have build an application where I use multiple frames.
But it would be nice if I could use the frames I used all in just 1 frame.
Like in the image below.
So if you press the left button "Speler Overzicht" that it will show the users in the right panel and I still have my buttons in the left panel.
Generally speaking, it's a very bad idea to base you UI classes on JFrame, as it locks you into a single use case, meaning you can't add the UI component (frame) to other containers.
I better solution is to base your UI components on JPanels, which then allows you to add them to where ever you need them. It also makes life easier to extend them, but that's another story.
To allow the user to move between multiple views, you can use either a CardLayout or JTabbedPane depending on your needs
See How to Use CardLayout and How to Use Tabbed Panes for more details
Use JPanels instead.
buttonPanel=new JPanel();
overzichtPanel=new JPanel();
buttonPanel.add(button);// do this for every button
overzichtPanel.add(componentsYouWantToAdd);// replace with your variables of course
frame.add(buttonPanel, BorderLayout.WEST)
frame.add(overzichtPanel, BorderLayout.CENTER)
You cannot put one JFrame inside another. You have a some design choices here. You can change your JFrames to JPanels. This is probably the easiest change. On the other hand, you can look at using Internal Frames instead.
I wonder whether there is a possiblity to change the visibility of more than one item (textbox, button, chart ...) in a JFrame in one simple(?) command.
Thanks for answers and ideas!
(Hiding the whole JFrame is no option ;))
You could use a CardLayout, as shown here.
Obviously, one of the two panels shown in the demo would have no components.
Place all into a panel and hide/show the panel. That should propagate to all child components as well
Place components into Collection, then you can use simple iteration to set/clear any flags. You need to create a Collection and add objects to it, but this allows to separate visibility control from the component layout.
My main JFrame content panel which is card layout and I have added many (say panel1, panel2) panel as card. I would like to update UI panel1 when something changes in panel2.
How to update child (panel) of CardLayout in Swing?
The observer pattern, discussed here, is the key to this. In particular, both panels could listen to a common model, which would fire events to update each listening panel. Examples using PropertyChangeListener may be found here and here.
Maintain a reference to the target of what you want to change, and use some kind of callback function to detect the changes. Use the stored reference in the callback function. How you specifically implement this should be whatever makes most sense for your code... but what you are trying to do is a simple task.
I have several JPanels that contain buttons, labels, etc. that I want to switch between from a main JFrame. Currently I am trying to use the this.add(JPanelname); method and this.remove(JPanelname); with the validate(); and repaint(); methods
The problem is it will add the panel to the JFrame but it will not remove it. I am not sure how exactly to go about this.
Maybe you should be using a Card Layout.
Or maybe you should be using modal JDialogs. So whenever you click on the "widjet" a new window is displayed. Then when you close the dialog you are back on your main frame.
If you are constantly switching between JPanels, then a JTabbedPane may be the right thing to use. It should not be necessary to call "validate" or "repaint" when you add or remove a JPanel. Do you have a layout manager installed? Do you make sure to call add/remove only within the UI event thread? Also, typically one does not call "validate()" but rather "invalidate()" to invalidate the container for updates.