如何使用 BorderLayout

If you are interested in using JavaFX to create your GUI, see Working With Layouts in JavaFX.

The following figure represents a snapshot of an application that uses the BorderLayout class.

Click the Launch button to run BorderLayoutDemo using Java™ Web Start (download JDK 7 or later). Alternatively, to compile and run the example yourself, consult the example index.

The complete code of this demo is in the BorderLayoutDemo.java file.

As the preceding picture shows, a BorderLayout object has five areas. These areas are specified by the BorderLayout constants:

• PAGE_START
• PAGE_END
• LINE_START
• LINE_END
• CENTER

If the window is enlarged, the center area gets as much of the available space as possible. The other areas expand only as much as necessary to fill all available space. Often a container uses only one or two of the areas of the BorderLayout object — just the center, or the center and the bottom.

The following code adds components to a frame's content pane. Because content panes use the BorderLayout class by default, the code does not need to set the layout manager. The complete program is in the BorderLayoutDemo.java file.

...//Container pane = aFrame.getContentPane()...
JButton button = new JButton("Button 1 (PAGE_START)");
pane.add(button, BorderLayout.PAGE_START);

//Make the center component big, since that's the
//typical usage of BorderLayout.
button = new JButton("Button 2 (CENTER)");
button.setPreferredSize(new Dimension(200, 100));
pane.add(button, BorderLayout.CENTER);

button = new JButton("Button 3 (LINE_START)");
pane.add(button, BorderLayout.LINE_START);

button = new JButton("Long-Named Button 4 (PAGE_END)");
pane.add(button, BorderLayout.PAGE_END);

button = new JButton("5 (LINE_END)");
pane.add(button, BorderLayout.LINE_END);

Specify the component's location (for example, BorderLayout.LINE_END) as one of the arguments to the add method. If this component is missing from a container controlled by a BorderLayout object, make sure that the component's location was specified and no another component was placed in the same location.

All tutorial examples that use the BorderLayout class specify the component as the first argument to the add method. 例如：

add(component, BorderLayout.CENTER)  //preferred

However, the code in other programs specifies the component as the second argument. For example, here are alternate ways of writing the preceding code:

add(BorderLayout.CENTER, component)  //valid but old fashioned
    or
add("Center", component)             //valid but error prone

The BorderLayout API

The following table lists constructors and methods to specify gaps (in pixels).

Examples that Use BorderLayout

The following table lists code examples that use the BorderLayout class and provides links to related sections.