1. Tim McKenna Seneca@York
Layout Mangers in Java
Tim McKenna

2. Layout Managers
A container (JPanel) has a layout manager.
A layout manager is an object that manages the size and location of the components inside a container.

3. Layout Managers
A top-level container (JFrame) has a "content pane" which can be set to a container (JPanel).
This container can contain other containers.
Containers can be associated with different layout managers.

4. Containment Hierarchy
a logical hierarchy of containers
nest containers inside other containers JPanel (inside JPanel …) inside JFrame
advantages
a more organized, cleaner GUI layout
new components can be added to one container without affecting the other containers
programming technique: use of panels inside panels, each with different layouts

5. Use of Panels
Components are grouped into different containers, i.e. JPanels
Each container uses its own layout manager to position components.
Another container uses its layout manager to position the panels.

6. Three Common Layout Managers
java.awt.FlowLayout
java.awt.BorderLayout
java.awt.GridLayout

7. FlowLayout Manager default for panels and applets
multiple components placed from left to right, from top to bottom
alignment and spacing can be adj.
Example: FlowLayoutManager.java
Exercise: Resize the window and see how the components flow.

8. BorderLayout Manager default for JFrame window objects
locations marked by 5 areas: NORTH, SOUTH, EAST, WEST, CENTER
each area can contain only ONE object, usually a JPanel object
sizing of the areas: NORTH, SOUTH: horizontal expansion EAST, WEST: vertical expansion CENTER: flows
Example: BorderLayoutManager.java

9. GridLayout Manager locations: a grid of rows and columns
size of the components: equal size
Example: GridLayoutManager.java

10. Layout Managers Flow/Border/Grid Layouts all have limited use.
GridBagLayout is much more flexible and much harder to use.
bobjects package JPanelGrid combines GridLayout ease of use and GridBagLayout power.
see JFrameJPanelGrid.java