Questions tagged [layout-manager]

LayoutManager is the Java interface for classes that know how to layout the contents of Container. The typical containers include JPanel for Swing and Panel for AWT but many others (like Window) are possible.

The layout manager lays out container components following rules that are different for each implementation. For instance, GridLayout arranges components in a table-like way while BorderLayout places one into center and up to four others at each edge.

While layout managers often call getPreferredSize on the component to know how much space it would need, the size hints are also regularly ignored. E.G. in GridLayout all components become the size of the largest width and height, in BorderLayout the CENTER component will be stretched to the available space, the top/bottom will be stretched in width and the line start/end will be stretched in height).

Layouts are typically combined in order to achieve complex GUIs. E.G. as seen in the Nested Layout Example.

If the layout manager of some particular component is set to null, components can be positioned in arbitrary way by setting they bounds manually. This causes many problems, & the first step in fixing those problems is typically to 'set a layout'.

Existing Layout Managers

AWT

• BorderLayout. Provides a CENTER & 4 borders in which to place components.
• CardLayout good for swapping many components or views in a single parent container.
• FlowLayout easiest to use, puts components one after another, left-right, top-to-bottom. Typically only suited to single rows of components.
• GridBagLayout can do some simple tasks easily (like 'center at preferred size') yet also allows complex layouts.
• GridLayout provides a WxH grid of component spaces, each the same size.

Swing

• BoxLayout provides a 'box' like construct for adding components in a row or column.
• GroupLayout is powerful, allowing alignment across components and component groups, but is generally considered to be a layout for use by an IDE.
• OverlayLayout allows components to be stacked.
• ScrollPaneLayout Used internally by other Swing components.
• SpringLayout is a way of layoun out components with white space allowing alignment along component edges.
• ViewportLayout Used internally by other Swing components.

3rd party

• MigLayout is highly regarded.
• FormLayout part of the JGoodies Forms
• TableLayout - An Alternative to GridBagLayout

Relevant tutorials:

• Using Layout Managers
• A Visual Guide to Layout Managers