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Downloading images in J2ME

John Muchow, Freelance Technical Writer

John Muchow, a freelance technical writer and recruiter, is the author of Core J2ME Technology and MIDP. Visit Core J2ME for additional source code, articles, and developer resources. Send John e-mail for additional information about writing projects or technical recruiting.

Summary: This tutorial demonstrates how to download and display images with J2ME (Java 2 Micro Edition) and the Mobile Information Device Profile (MIDP).

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Date: 07 Oct 2003
Level: Introductory
PDF: A4 and Letter (582 KB | 38 pages)Get Adobe® Reader®

Activity: 3547 views
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Before you start

About this tutorial

This tutorial demonstrates how to download and display images with J2ME (Java 2 Micro Edition) and the Mobile Information Device Profile (MIDP).

I'll walk through creating two J2ME applications, each showing how to open a network connection to a remote server, and download and display an image. The first application is bare-bones, with no frills. I'll build upon this application in the second example to add support for downloading of images in a background thread and providing consistent messages to the user to indicate the current status of the application.

By the end of this tutorial you see just how easy it is to begin writing network-aware applications with J2ME.

Prerequisites

You'll need two software tools to complete this tutorial:

The Java Development Kit (JDK): The JDK provides the Java source code compiler and a utility to create Java Archive (JAR) files. When working with version 2.0 of the Wireless Toolkit (as I will be here), you'll need to download JDK version 1.4 or greater. Download JDK version 1.4.1.
The Wireless Toolkit (WTK): The Sun Microsystems Wireless Toolkit (WTK) is an integrated development environment (IDE) for creating Java 2 Platform, Micro Edition (J2ME) MIDlets. The WTK download contains an IDE, as well as the libraries required for creating MIDlets. Download J2ME Wireless Toolkit 2.0.

Install the software

The Java Development Kit (JDK)
Use the JDK documentation to install the JDK. You can choose either the default directory or specify another directory. If you choose to specify a directory, make a note of where you install the JDK. During the installation process for the Wireless Toolkit, the software attempts to locate the Java Virtual Machine (JVM); if it cannot locate the JVM, you are prompted for the JDK installation path.

The Wireless Toolkit (WTK)
This tutorial builds on an earlier developerWorks tutorial "MIDlet Development with the Wireless Toolkit" (see Resources), which explains the basics of creating MIDlets with the toolkit. This tutorial is an excellent starting point if you are new to the Wireless Toolkit.

The Wireless Toolkit is contained within a single executable file. Run this file to begin the installation process. It is recommended that you use the default installation directory. However, if you do not use the default directory, make sure the path you select does not include any spaces.

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