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Layouts

Textbook: Section 12.6

There are several categories of GUI classes of which you should be aware:

We've covered all but the last. Now we're covering the last, composed of classes that implement the LayoutManager interface.

The layout classes tell a container class how it should lay out the components it contains. What we can do is to set the layout of a container, telling it to change its approach for handling components. Each container has such a method, called setLayout().

void setLayout(LayoutManager manager)
Changes the layout technique for the container.

Each container also has two methods for putting components into the container.
void add(Component what)
Inserts what into the panel, using the default placement.
void add(Component what, Object info)
Inserts what into the panel, using info as information about where the object should be placed.

BorderLayout

We've actually already seen the BorderLayout class: It's the default layout for a JFrame's container. Creating a BorderLayout is simple:

BorderLayout()
Creates a BorderLayout object.
When you add something to a container that's using the BorderLayout, you will generally use the add() method that takes an info parameter, and you will pass something like BorderLayout.NORTH saying on which border to place the component (or BorderLayout.CENTER to place the component in the middle).

FlowLayout

The FlowLayout class is even simpler: It places the components in left-to-right order. Each component gets sized to its preferred size. When the components fill the row, they start being placed in the next row.

FlowLayout()
Creates a FlowLayout object.
With a container using FlowLayout, you'll generally use the add() that doesn't take an info parameter.

FlowLayout is the default layout for a JPanel.

GridLayout

In the GridLayout class, components are placed left-right, top-down in a strict grid. Each component is resized to fill its grid space.

GridLayout(int rows, int columns)
Creates a GridLayout object, represent the layout strategy with rows rows and columns columns.

Next: Case study: Temperature conversion. Up: Composing GUIs. Previous: The JPanel class.