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Trail: Creating a GUI with JFC/Swing
Lesson: Using Swing Components
Using Swing Components
Using Top-Level Containers
The JComponent Class
Using Text Components
Text Component Features
The Text Component API
How to Use Various Components
How to Make Applets
How to Use Buttons, Check Boxes, and Radio Buttons
How to Use the ButtonGroup Component
How to Use Color Choosers
How to Use Combo Boxes
How to Make Dialogs
How to Use Editor Panes and Text Panes
How to Use File Choosers
How to Use Formatted Text Fields
How to Make Frames (Main Windows)
How to Use Internal Frames
How to Use Labels
How to Use Layered Panes
How to Use Lists
How to Use Menus
How to Use Panels
How to Use Password Fields
How to Use Progress Bars
How to Use Root Panes
How to Use Scroll Panes
How to Use Separators
How to Use Sliders
How to Use Spinners
How to Use Split Panes
How to Use Tabbed Panes
How to Use Tables
How to Use Text Areas
How to Use Text Fields
How to Use Tool Bars
How to Use Tool Tips
How to Use Trees
How to Use HTML in Swing Components
How to Use Models
How to Use Icons
How to Use Borders
Solving Common Component Problems
Home Page > Creating a GUI with JFC/Swing > Using Swing Components
Solving Common Component Problems

> This section discusses problems that you might encounter while using components. If you don't find your problem in this section, consult the following sections:
> - Solving Common Problems Using Other Swing Features
> - Solving Common Layout Problems
> - Solving Common Event-Handling Problems
> - Solving Common Painting Problems

> Problem: I'm having trouble implementing a model (or some other code that's similar to something already in Java SE Platform, Standard Edition).

> - Look at the Java SE source code. It's distributed with the JDK, and it's a great resource for finding code examples of implementing models, firing events, and the like.
> Problem: Whenever the text in my text field updates, the text field's size changes.
> - You should specify the preferred width of the text field by specifying the number of columns it should have room to display. To do this, you can use either an `int` argument to the `JTextField` constructor or the `setColumns` method.
> Problem: Certain areas of the content pane look weird when they're repainted.
> - If you set the content pane, make sure it's opaque. You can do this by invoking `setOpaque(true)` on your content pane. Note that although `JPanel`s are opaque in most look and feels, that's not true in the GTK+ look and feel. See Adding Components to the Content Pane for details.
> - If one or more of your components performs custom painting, make sure you implemented it correctly. See Solving Common Painting Problems for help.
> - You might have a thread safety problem. See the next entry.

> Problem: My program is exhibiting weird symptoms that sometimes seem to be related to timing.

> - Make sure your code is thread-safe. See Concurrency in Swing for details.

> Problem: My modal dialog gets lost behind other windows.

> - If the dialog has a null parent component, try setting it to a valid frame or component when you create it.
> - This bug was fixed in the 6.0 release. For more information, see 4255200.

> Problem: The scroll bar policies don't seem to be working as advertised.

> - Some Swing releases contain bugs in the implementations for the `VERTICAL_SCROLLBAR_AS_NEEDED` and the `HORIZONTAL_SCROLLBAR_AS_NEEDED` policies. If feasible for your project, use the most recent release of Swing.
> - If the scroll pane's client can change size dynamically, the program should set the client's preferred size and then call `revalidate` on the client.
> - Make sure you specified the policy you intended for the orientation you intended.
> Problem: My scroll pane has no scroll bars.
> - If you want a scroll bar to appear all the time, specify either `VERTICAL_SCROLLBAR_ALWAYS` or `HORIZONTAL_SCROLLBAR_ALWAYS` for the scroll bar policy as appropriate.
> - If you want the scroll bars to appear as needed, and you want to force the scroll bars to be needed when the scroll pane is created, you have two choices: either set the preferred size of scroll pane or its container, or implement a scroll-savvy class and return a value smaller than the component's standard preferred size from the `getPreferredScrollableViewportSize` method. Refer to Sizing a Scroll Pane for information.
> Problem: The divider in my split pane don't move!
> - You need to set the minimum size of at least one of the components in the split pane. Refer to Positioning the Divider and Restricting Its Range for information.
> Problem: The `setDividerLocation` method of `JSplitPane` doesn't work.
> - The `setDividerLocation(double)` method has no effect if the split pane has no size (typically true if it isn't onscreen yet). You can either use `setDividerLocation(int)` or specify the preferred sizes of the split pane's contained components and the split pane's resize weight instead. Refer to Positioning the Divider and Restricting Its Range for information.
> Problem: The borders on nested split panes look too wide.
> - If you nest split panes, the borders accumulate — the border of the inner split panes display next to the border of the outer split pane causing borders that look extra wide. The problem is particularly noticeable when nesting many split panes. The workaround is to set the border to null on any split pane that is placed within another split pane. For information, see bug # 4131528 in the Bug Database at the Sun Developer Network (SDN).
> Problem: The buttons in my tool bar are too big.
> - Try reducing the margin for the buttons. For example:

>   >     button.setMargin(new Insets(0,0,0,0));

> Problem: The components in my layered pane aren't layered correctly. In fact, the layers seem to be inversed — the lower the depth the higher the component.
> - This can happen if you use an `int` instead of an `Integer` when adding components to a layered pane. To see what happens, make the following change to `LayeredPaneDemo`:

>   Change this... | to this...
>   --- | ---
>   `layeredPane.add(label, new Integer(i));` | `layeredPane.add(label, i);`

> Problem: The method call `colorChooser.setPreviewPanel(null)` does not remove the color chooser's preview panel as expected.

> - A `null` argument specifies the default preview panel. To remove the preview panel, specify a standard panel with no size, like this: `colorChooser.setPreviewPanel(new JPanel());`

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