Solving Common Component Problems解决常见组件问题

This section discusses problems that you might encounter while using components. 本节讨论使用组件时可能遇到的问题。If you do not find your problem in this section, consult the following sections:如果您在本节中没有找到问题，请参阅以下部分：

• Solving Common Problems Using Other Swing Features使用其他回转特征解决常见问题
• Solving Common Layout Problems解决常见布局问题
• Solving Common Event-Handling Problems解决常见事件处理问题
• Solving Common Painting Problems解决常见涂装问题

Problem: I am having trouble implementing a model (or some other code that is similar to something already in Java SE Platform, Standard Edition).我在实现模型（或与JavaSE平台标准版中已有的代码类似的其他代码）时遇到了问题。

• Look at the Java SE source code. It is distributed with the JDK, and it is a great resource for finding code examples of implementing models, firing events, and the like.查看JavaSE源代码。它与JDK一起发布，是查找实现模型、触发事件等代码示例的一个很好的资源。

Problem: Whenever the text in my text field updates, the text field's size changes.每当文本字段中的文本更新时，文本字段的大小就会改变。

• You should specify the preferred width of the text field by specifying the number of columns it should have room to display. 您应该通过指定文本字段应有显示空间的列数来指定文本字段的首选宽度。To do this, you can use either an int argument to the JTextField constructor or the setColumns method.为此，可以对JTextField构造函数或setColumns方法使用int参数。

Problem: Certain areas of the content pane look weird when they are repainted.内容窗格的某些区域重新绘制时看起来很奇怪。

• If you set the content pane, make sure it is opaque. 如果设置了内容窗格，请确保它是不透明的。You can do this by invoking setOpaque(true) on your content pane. 您可以通过调用内容窗格上的setOpaque(true)来实现这一点。Note that although JPanels are opaque in most look and feels, that is not true in the GTK+ look and feel. 请注意，尽管JPanel在大多数外观中是不透明的，但在GTK+外观中则不是这样。See Adding Components to the Content Pane for details.有关详细信息，请参阅将组件添加到内容窗格。
• If one or more of your components performs custom painting, make sure you implemented it correctly. 如果一个或多个组件执行自定义绘制，请确保正确实现它。See Solving Common Painting Problems for help.请参见解决常见的绘制问题以获取帮助。
• You might have a thread safety problem. 您可能有线程安全问题。See the next entry.请参阅下一项。

Problem: My program is exhibiting weird symptoms that sometimes seem to be related to timing.我的程序显示出奇怪的症状，有时似乎与时间有关。

• Make sure your code is thread-safe. 确保代码是线程安全的。See Concurrency in Swing for details.有关详细信息，请参阅Swing中的并发。

Problem: My modal dialog gets lost behind other windows.我的模态对话框在其他窗口后面丢失。

• If the dialog has a null parent component, try setting it to a valid frame or component when you create it.如果对话框的父组件为空，请在创建时尝试将其设置为有效的框架或组件。
• This bug was fixed in the 6.0 release. 这个bug在6.0版本中得到了修复。For more information, see 4255200.有关更多信息，请参阅4255200。

Problem: The scroll bar policies do not seem to be working as advertised.滚动条策略似乎并不像广告所说的那样有效。

• Some Swing releases contain bugs in the implementations for the VERTICAL_SCROLLBAR_AS_NEEDED and the HORIZONTAL_SCROLLBAR_AS_NEEDED policies. 一些Swing发行版在VERTICAL_SCROLLBAR_AS_NEEDED和HORIZONTAL_SCROLELBAR_AS-NEEDED策略的实现中包含bug。If feasible for your project, use the most recent release of Swing.如果对您的项目可行，请使用Swing的最新版本。
• 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.如果滚动窗格的客户端可以动态更改大小，程序应该设置客户端的首选大小，然后在客户端上调用revalidate。
• Make sure you specified the policy you intended for the orientation you intended.确保您指定了您打算用于培训的政策。

Problem: My scroll pane has no scroll bars.我的滚动窗格没有滚动条。

• 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.如果希望滚动条始终显示，请根据需要为滚动条策略指定VERTICAL_SCROLLBAR_ALWAYS或HORIZONTAL_SCROLELBAR_ALWAYS。
• 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. 如果希望滚动条根据需要显示，并且希望在创建滚动窗格时强制使用滚动条，则有两种选择：要么设置滚动窗格或其容器的首选大小，要么实现一个滚动类，并从getPreferredScrollableViewportSize方法返回一个小于组件标准首选大小的值。Refer to Sizing a Scroll Pane for information.有关信息，请参阅调整滚动窗格的大小。

Problem: The divider in my split pane does not move!拆分窗格中的分隔线不移动！

• You need to set the minimum size of at least one of the components in the split pane. 您需要设置拆分窗格中至少一个组件的最小大小。Refer to Positioning the Divider and Restricting Its Range for information.有关信息，请参阅定位分流器和限制其范围。

Problem: The setDividerLocation method of JSplitPane does not work.JSplitPane的setDividerLocation方法不起作用。

• The setDividerLocation(double) method has no effect if the split pane has no size (typically true if it is not onscreen yet). 如果拆分窗格没有大小，则setDividerLocation(double)方法无效（如果尚未在屏幕上显示，则通常为true）。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. 您可以使用setDividerLocation(int)或指定拆分窗格所包含组件的首选大小以及拆分窗格的调整大小权重。Refer to Positioning the Divider and Restricting Its Range for information.有关信息，请参阅定位分流器和限制其范围。

Problem: The borders on nested split panes look too wide.嵌套拆分窗格上的边框看起来太宽。

• 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. 如果嵌套拆分窗格，边框将累积—内部拆分窗格的边框显示在外部拆分窗格边框的旁边，导致边框看起来特别宽。The problem is particularly noticeable when nesting many split panes. 当嵌套许多拆分窗格时，问题尤其明显。The workaround is to set the border to null on any split pane that is placed within another split pane. 解决方法是将放置在另一个拆分窗格中的任何拆分窗格的边框设置为空。For information, see bug # 4131528 in the Java Bug Database.有关信息，请参阅Java bug数据库中的bug#4131528。

Problem: The buttons in my tool bar are too big.我工具栏中的按钮太大了。

• Try reducing the margin for the buttons. 尝试减少按钮的边距。For example:例如：

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

Problem: The components in my layered pane are not layered correctly. 分层窗格中的组件分层不正确。In fact, the layers seem to be inversed — the lower the depth the higher the component.事实上，这些层似乎是相反的—深度越低，组件越高。

• This can happen if you use an int instead of an Integer when adding components to a layered pane. 如果在向分层窗格添加组件时使用int而不是Integer，则可能发生这种情况。To see what happens, in the LayeredPaneDemo class, change layeredPane.add(label, new Integer(i)); to layeredPane.add(label, i);要查看发生了什么，请在LayeredPaneDemo类中将layeredPane.add(label, new Integer(i));更改为layeredPane.add(label, i);.

Problem: The method call colorChooser.setPreviewPanel(null) does not remove the color chooser's preview panel as expected.调用colorChooser.setPreviewPanel(null)的方法没有按预期移除颜色选择器的预览面板。

• A null argument specifies the default preview panel. null参数指定默认预览面板。To remove the preview panel, specify a standard panel with no size, like this: 要删除预览面板，请指定无尺寸的标准面板，如下所示：colorChooser.setPreviewPanel(new JPanel());