AWT Layout Managers Chapter 10 Java Certification Study















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AWT Layout Managers (Chapter 10) Java Certification Study Group January 21, 1999 Mark Roth

Layout Managers Grid. Layout Border. Layout Flow. Layout. Manager

Layout Managers • Removes repetitious need to lay out components precisely. • Insulates developer from the fact that components have different sizes when instantiated on different platforms. • All implement java. awt. Layout. Manager interface.

Containers vs. Components • Container extends Component • Components are things like Button and Checkbox. • Containers contain Components

Hierarchy Sample (from Roberts, Figure 10. 4) Frame Panel Label Text Field Scrollbar Button Panel

Defaults • Panel = Flow. Layout • Applet = Flow. Layout • Frame = Border. Layout

Constructing a Panel • Construct the panel (new Panel()). • Give the panel a layout manager (set. Layout()) • Populate the panel (add()) • Add the panel to its own container (add()).

Component Size and Position • Sizes and positions are merely suggestions, overridden by the Layout. Manager. • Each Component has a preferred size, which is “just big enough” to display the component.

Flow. Layout Manager • Default type for Panels and Applets. • A lot like a word processor: – Arranges components in horizontal rows. – Components “wrap” to the next line if they don’t fit across. • Honors a component’s preferred size. • Specify in constructor: – Flow. Layout. LEFT, Flow. Layout. CENTER, Flow. Layout. RIGHT

Grid. Layout Manager • Grid. Layout( rows, columns ) • Forces a size on a component equal to the size of the cell. • add( component ) - Adds from left to right.

Border. Layout Manager “North” “West” “Center” “South” “East”

Border. Layout Manager • North and South – Honors preferred height – Forces width to width of container • East and West – Honors preferred width – Forces height to height of container. • Remainder of space given to center. • add( component, String )

“Find the Layout Manager” • Refer to 10. 4 and find the following Layout Managers: – (1) Border. Layout – (4) Grid. Layout – (1) Flow. Layout

Other Layout Managers • • Grid. Bag Layour Manager Card Layout Manager No Layout Manager Create Your Own Layout Manager

References • All Material in this Presentation is heavily based on: Roberts, Simon and Heller, Philip, Java 1. 1 Certification Study Guide, 1997: SYBEX™. ISBN: 0 -7821 -2069 -5 • Selected portions from JDK 1. 1. 6 Java. Doc HTML pages.