May 6, 1998CS102-02Lecture 6-2 Cross-Platform Programming CS Lecture 6-2 Making everyone happy

May 6, 1998CS102-02Lecture 6-2 Agenda Two kinds of inheritance Interfaces in Java The End of OO

May 6, 1998CS102-02Lecture 6-2 Web vs. Java Design Web designers are used to testing their sites and pages on –Multiple platforms –Screen resolutions –Color ranges –Browsers Can't just create Web sites on and for their own high-powered, million-color development machines

May 6, 1998CS102-02Lecture 6-2 Graphics across Platforms Different computers almost agree on text, but strongly disagree on graphics –Screen resolutions –Colors: 8-bit grey, 16-bit and 24-bit –Fonts: Not everybody has Times New Roman Narrow –User interface: Keyboards, mouse button count and accessibility

May 6, 1998CS102-02Lecture 6-2 Cross-Platform Fonts Different platforms have different fonts –Different names for similar fonts Java has a set of logical fonts –Monospaced, Dialog, Serif and Sans Serif –Font attributes (size, style,...)

May 6, 1998CS102-02Lecture 6-2 The Abstract Windowing Toolkit Abstract away the details of building graphical user interfaces (GUIs)

May 6, 1998CS102-02Lecture 6-2 The AWT Hierarchy

May 6, 1998CS102-02Lecture 6-2 The Need for Abstraction

May 6, 1998CS102-02Lecture 6-2 Arranging Things Java uses layout managers to control how components appear on-screen –Achieve different effects by using different layout managers –Going without Grid layout Flow layout

May 6, 1998CS102-02Lecture 6-2 Laying It All Out

May 6, 1998CS102-02Lecture 6-2 Picking a Layout Manager I Need to display a component in as much space as it can get. –Consider using BorderLayoutBorderLayout put the space-hungry component in the center –GridBagLayoutGridBagLayout Set the constraints for the component so that fill=GridBagConstraints.BOTH From The Java Tutorial

May 6, 1998CS102-02Lecture 6-2 Picking a Layout Manager II Need to display a few components in a compact row at their natural size. –Use a Panel to hold the components –Use Panel's default FlowLayout managerFlowLayout Need to display a few same-sized components in rows and/or columns. –GridLayout fits the billGridLayout From The Java Tutorial

May 6, 1998CS102-02Lecture 6-2 The AWT Works for You Abstraction is all well and good, but Java programs still need to run on actual machines Just one API for buttons (provided by the Button class) –Looks different on a Macintosh than on a PC running Windows 95. Peer classes link the AWT components you see to the underlying platform

May 6, 1998CS102-02Lecture 6-2 Behind the Scenes

May 6, 1998CS102-02Lecture 6-2 Swingin' with Java Swing components are lightweight Use a different architecture than AWT

May 6, 1998CS102-02Lecture 6-2 Swing Look-and-Feel Metal (Java) Early Mac MotifWindows Organic (Santa Fe) Organic (Vancouver)

May 6, 1998CS102-02Lecture 6-2 Beans JavaBeans is a portable, platform- independent software component model written in Java Enables developers to write reusable components once and run them anywhere

May 6, 1998CS102-02Lecture 6-2 Going Cross-Platform with Java Graphics –GUI components –Fonts –Swing Sharing software –Beans