Class 14: Lab: Java's Abstract Windowing Toolkit

Held Tuesday, February 15, 2000

Overview

Today we consider how to build simple graphical applications in Java. We will consider some basics, including windows, buttons, text fields, and events.

Notes

• This Thursday's convocation is Mathematics 4,000 Years Ago and will be given by Noyce Visiting Professor Richard Guy. I expect that it will be a lot of fun.
• On Thursday afternoon, Pete Broadwell will be giving a talk about his internship at IBM. I also expect that this talk will be a lot of fun.
• A few of you have asked about my grading policies on exams. They are not the same as for homeworks. On exams, you start with 100 and I take off for incorrect parts of your answers. (I also give a few points of extra credit here and there when I see something particularly nice.)
• Even though I worked until 11 p.m. last night, I was not able to get your homeworks graded. I hope to return them tomorrow morning.
• Don't forget to turn in project teams tomorrow.
• I'd appreciate it if you'd indicate the amount of time you spend on each problem (or subproblem) of the exam.
• Are there other questions on exam 1?

Contents

• GUIs in Java
• First GUI Lab

Summary

• GUI basics
• Java's Abstract Windowing Toolkit (AWT)
• Primary components: Frames, TextFields, etc.
• Event handling
• Lab G2: Java's Abstract Windowing Toolkit
• Due:
  • Preparatory reading of Lab G2

GUIs in Java

• Although many of the programs we've been writing are text-based, most modern programs use a graphical user interface (GUI).
• Java's included toolkits for building GUIs since the early versions.
  • Unfortunately, these toolkits have changed substantially as Java evolved from 1.0 to 1.1 and from 1.1 to 1.2.
  • We'll focus on the Abstract Windowing Toolkit (AWT) because it is supported in Java 1.1 and Java 1.2.
  • Java 1.2 add Swing, but Swing is not yet fully supported on our HP/UX workstations. (It's also not supported on some other platforms, which makes the AWT appropriate for many programs.)
• GUIs use an event-driven programming model. We might also call this a reactive model.
  • Rather than using an imperative model in which your program says step-by-step what do do, reactive programs have event handlers which basically say ``when this happens, do this''.
  • You'll still need a main method to create the objects which supply these event handlers.
• As you might guess, GUIs have a number of components (menus, buttons, text labels, etc.). In Java, each component is an object.
• We put components into windows and frames using the add method.
  • A layout determines how/where the components appear.
• Each component can have one or more listeners that respond to the events that pertain to the object. (You should have read something about this in chapter 1 of Java Plus Data Structures.)
• The rest of the details are in the lab.
• You will find that there are many different techniques for designing GUI applications. I'll probably use a few different ones throughout the term.

First GUI Lab

Do as much of G2.1 through G2.4 as you can.

You should try to finish up the rest in the evening, although I will understand if you cannot because of the amount of time you're devoting to the exam.