GridBagLayout

GridBagLayout is a flexible layout manager in Java that is used with AWT and Swing. It arranges components in a grid of rows and columns and allows components to span multiple cells. The layout's behavior is controlled by GridBagConstraints, which encode the position, size, and resizing behavior of each component.

Key concepts include gridx and gridy, which specify the component's cell coordinates, and gridwidth and gridheight, which allow a component to span several cells. The fill property controls how a component uses available space, with NONE, HORIZONTAL, VERTICAL, or BOTH. Weightx and weighty determine how extra horizontal and vertical space is distributed among components when the container is resized. Insets provide external padding, and ipadx and ipady add internal padding. The anchor defines alignment when a component does not fill its cell.

GridBagLayout computes the sizes of columns and rows from the components' preferred and minimum sizes, adjusted by insets and padding, and then distributes any extra space to components with positive weight values. Because components can span multiple cells and have different weights, layouts can be highly adaptive but require careful configuration to avoid gaps or unexpected resizing.

This layout is particularly useful for complex, responsive user interfaces where nesting multiple panels would be cumbersome. It is part of the standard Java library (java.awt.GridBagLayout and java.awt.GridBagConstraints) and is commonly used in Swing applications that require fine-grained control over component placement.