The JavaTM Tutorial

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Trail: Creating a GUI with JFC/Swing
Lesson: Laying Out Components Within a Container

## How to Use BorderLayout

> Here's a snapshot of an application that uses a `BorderLayout`.

> You can run BorderLayoutDemo using JavaTM Web Start. Its code is in `BorderLayoutDemo.java`.

> As the preceding picture shows, a `BorderLayout` has five areas. These areas are specified by the `BorderLayout` constants `PAGE_START`, `PAGE_END`, `LINE_START`, `LINE_END`, and `CENTER`.

> > Version note: Before 1.4, the preferred names for the various areas were different, ranging from points of the compass (for example, `BorderLayout.NORTH` for the top area) to wordier versions of the constants we use in our examples. The constants our examples use are preferred because they are standard and enable programs to adjust to languages that have different orientations.

> If you enlarge the window, 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` — just the center, or center and bottom, for example.

> The following code adds components to a frame's content pane. Because content panes use `BorderLayout` by default, the code doesn't need to set the layout manager. You can find the whole program in `BorderLayoutDemo.java`.

> >     ...//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);

> We strongly recommend that you specify the component's location (for example, `BorderLayout.LINE_END`) as one of the arguments to the `add` method. If you leave it out, the component will be added to the center, but your code will be much less clear. If you find that a component is missing from a container controlled by a `BorderLayout`, make sure that you specified the component's location and that you didn't put another component in the same location.

> All our examples that use `BorderLayout` specify the component as the first argument to the `add` method. For example:

> >     add(component, BorderLayout.CENTER)  //preferred

> However, you might see code in other programs that specifies the component second. 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

> `BorderLayout` defines a couple of constructors and some methods for adding space between components.

> [PENDING: The following will be converted to be in the Tutorial's standard API table format.]

> By default, a `BorderLayout` puts no gap between the components it manages. In the preceding applet, any apparent gaps are the result of the buttons reserving extra space around their apparent display area. You can specify gaps (in pixels) using the following constructor:

> >     BorderLayout(int horizontalGap, int verticalGap)

> You can also use the following methods to set the horizontal and vertical gaps, respectively:

> >     void setHgap(int)
> >     void setVgap(int)

### Examples that Use BorderLayout

> Here are a few of the many examples that use `BorderLayout`.

> Example | Where Described | Notes
> --- | --- | ---
> `BorderLayoutDemo` | This page | Puts a component in each of the five possible locations.
> `TabbedPaneDemo` | How to Use Tabbed Panes | One of many examples that puts a single component in the center of a content pane, so that the component is as large as possible.
> `CheckBoxDemo` | How to Use Check Boxes | Creates a `JPanel` that uses a `BorderLayout`. Puts components into the left (actually, `LINE_START`) and center locations.

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