Java swing Jlist创建

Question

Hello I want to create a Jlist in java swing but I cannot understand where I can show it. All the tutorials I've seen so far create the list in a new window which is not what I want. I want to use a tool or something to give specific coordinates and site at the frame I am currently in. I am new to java swing so I could use some help. I use windows builder pro as a plug-in for eclipse. Is there any tool I could use to "draw" where the list will be presented?

Thx in advance

I tried this but it won't work.

JPanel panel = new JPanel();
panel.setBounds(36, 109, 619, 202);
MainFrame.getContentPane().add(panel);

final JScrollPane scrollPane = new JScrollPane();
panel.add(scrollPane);


/*on a click listener of a button*/
    scrollPane.setLayout( new BorderLayout() );
                getContentPane().add( scrollPane );

                // Create some items to add to the list
                String  listData[] =
                {
                    "Item 1",
                    "Item 2",
                    "Item 3",
                    "Item 4"
                };
                JList listbox = new JList( listData );
                scrollPane.add( listbox, BorderLayout.CENTER );

but when I run the program I get an error like this:

Exception in thread "AWT-EventQueue-0" java.lang.ClassCastException: layout of JScrollPane must be a ScrollPaneLayout at javax.swing.JScrollPane.setLayout(Unknown Source) at Main$3.mouseClicked(Main.java:122) at java.awt.AWTEventMulticaster.mouseClicked(Unknown Source) at java.awt.Component.processMouseEvent(Unknown Source) at javax.swing.JComponent.processMouseEvent(Unknown Source) at java.awt.Component.processEvent(Unknown Source) at java.awt.Container.processEvent(Unknown Source) at java.awt.Component.dispatchEventImpl(Unknown Source) at java.awt.Container.dispatchEventImpl(Unknown Source) at java.awt.Component.dispatchEvent(Unknown Source) at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source) at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source) at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source) at java.awt.Container.dispatchEventImpl(Unknown Source) at java.awt.Window.dispatchEventImpl(Unknown Source) at java.awt.Component.dispatchEvent(Un known Source) at java.awt.EventQueue.dispatchEventImpl(Unknown Source) at java.awt.EventQueue.access$200(Unknown Source) at java.awt.EventQueue$3.run(Unknown Source) at java.awt.EventQueue$3.run(Unknown Source) at java.security.AccessController.doPrivileged(Native Method) at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source) at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source) at java.awt.EventQueue$4.run(Unknown Source) at java.awt.EventQueue$4.run(Unknown Source) at java.security.AccessController.doPrivileged(Native Method) at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source) at java.awt.EventQueue.dispatchEvent(Unknown Source) at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source) at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source) at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source) at java.awt.EventDispatchThread.pumpEvents(Unknown Source) at java.awt.EventDispatch Thread.pumpEvents(Unknown Source) at java.awt.EventDispatchThread.run(Unknown Source)

Answer 1

What you want to do is essentially place a component (here a JList that is held by a JScrollPane -- and trust me, you want it inside of a JScrollPane) into a Container (usually a JPanel), and there are three general ways to do this:

1. Give the JPanel a null layout, and then set the size and position of any and all components that you add to it, including the JScrollPane-holding JPanel via the setBounds(...) method, or...
2. Use a GUI builder to place components for you in an absolute fashion, or with the assistance of layout managers, or...
3. Create your GUI using nested JPanels, each one using its own layout manager, add your JList-containing JScrollPane to one of the JPanels in an intelligent way (which depends on the layout manager) and let your layouts and the components preferred sizes set all the appropriate sizes.

In the very short term the first path is the quickest and easiest, but in the medium to long term, it has serious problems because it makes for very inflexible GUI's that while they might look good on one platform look terrible on most other platforms or screen resolutions and that are very difficult to update and maintain. Instead you will want to study and learn the layout managers and then nest JPanels, each using its own layout manager to create pleasing and complex GUI's that look good on all OS's.

The second path will allow you to create quick and easy GUI's, but if you're not familiar with the Swing library yet and reasonably adept at using the layout managers, you can get hamstrung if you need to modify your code at a later time, since you'll be rigidly tied to the code-generation utility. Don't get me wrong though, this is a viable solution if you are pretty good with Swing coding, as long as the GUI builder software doesn't go defunct (which has happened in the past).

The best answer to your question in my opinion is to learn how to use the layout managers, and then use them. And to learn them, please have a look here: The Layout Manager Tutorial .

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Edit
Regarding your edited question and the code you've posted:

• Never set the layout of the JScrollPane as this will prevent the JScrollPane from functioning.
• Instead and again, place your JList inside of a JScrollPane (in its viewport actually, but if you pass the JList into the JScrollPane's constructor, you'll be doing this).
• Then add the JScrollPane into a container, a JPanel, using appropriate layouts.
• Don't use setBounds(...)
• Nest your JPanels each using its own layout, each containing other components and JPanels.
• Pack your GUI after adding all components via the pack() method, and then call setVisible(true) on the top-level window.

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Edit 2
You state in commment:

Can you provide me with a brief tutorial? I will edit the question right away to show you the problem

I stated that I did.

I meant for the Jpanel not for the layouts!

Please understand that our only source of understanding of your problems is what you specifically tell us. The more pertinent information in your questions, the better we can understand them and the better we can help Here is a great link that will get you to the most important Swing tutorials. You can find this link in the swing tag that you use with your question:

• Swing Info