Wireless Java Developing

Securing Network Data Let's look at something a little more complicated. Suppose you wish to conceal the data you are sending over the network. The protected password example showed one way for a client to authenticate itself to the server, but ... [full story]

Protecting Passwords with a Message Digest Having installed the Bouncy Castle cryptography package, let's try a simple example involving authentication. Computer systems often use passwords instead of digital signatures (or certificates) because they're so much easier. A password is a shared ... [full story]

HTTPS is Almost Everything You Could Want The Generic Connection Framework has always been flexible enough to allow MIDP implementations to include support for HTTPS, which is HTTP over a secure connection like TLS or SSL. Starting with MIDP 2.0, support ... [full story]

Using Parsers in the J2ME Wireless Toolkit Incorporating a parser into your MIDlet suite is surprisingly easy. If a compiled JAR or ZIP file of classes is available, you can drop it into the lib directory of your project. For example, ... [full story]

Porting Techniques If you do decide to port one of the parsers that doesn't build in MIDP out of the box, there are several techniques you may wish to consider: Dump features you don't need. If the parser code is modularized well, ... [full story]

Using kXML 1.21 Currently, kXML 1.21 is the most complete and well-supported parser. Originally developed at the Universität Dortmund in Germany, it is now part of the Enhydra web site. It is based on Common XML (http://simonstl.com/articles/cxmlspec.txt), which is a set ... [full story]

MIDP XML Parser Roundup Table 14-1 lists small, open-source XML parsers that can be used with the MIDP platform. Each of these parsers is released under some type of open-source software license as listed in the License column. The Size column ... [full story]

MIDP XML Parser Roundup Table 14-1 lists small, open-source XML parsers that can be used with the MIDP platform. Each of these parsers is released under some type of open-source software license as listed in the License column. The Size column ... [full story]

Optimizing Application Deployment One last area of optimization has to do with the actual deployment of your application. As you may remember from Chapter 3, MIDlets are packaged in MIDlet suites, which are really just fancy JAR files. One way to ... [full story]

Coding for Speed Small devices have small, relatively slow processors. Part of your task as a developer is ensuring that your application runs fast enough that users won't reject it. Optimize Loops One simple optimization has to do with looping. A typical loop ... [full story]

Optimizing Memory Use It's easy for J2SE programmers to be blasé about memory usage. After all, having a garbage collector means that you don't have to worry about explicitly freeing memory—objects that are no longer in use will be magically harvested ... [full story]

Diagnostic Tools in the J2ME Wireless Toolkit Starting with version 1.0.4, the J2ME Wireless Toolkit contains three tools you can use to understand your application's performance. The first tool is a memory monitor. You can see a graph of memory usage in ... [full story]

Benchmarking In the J2SE world, there are many tools for examining the performance of code, the location of bottlenecks, and memory usage. Unfortunately, little of this is available in the J2ME world. For the most part, you'll have to perform benchmarking ... [full story]

The Mobile Media API MIDP 2.0's audio support is a subset of the full power of the Mobile Media API. If you're using the J2ME Wireless Toolkit, its emulators support the full MMAPI by default. This means that you have other ... [full story]

Tones and Tone Sequences You've already seen how easy it is to play single tones using Manager. There's a somewhat more sophisticated tone sequence player lurking in the MIDP 2.0 media APIs. It's implemented within the Player and Control architecture, which ... [full story]

Listening for Player Events Player includes methods for adding and removing listeners that will be notified about various milestones in the Player's life: public void addPlayerListener(PlayerListener playerListener) public void removePlayerListener(PlayerListener playerListener) PlayerListener defines a single method that is called with a variety of informational ... [full story]

Controlling Players A Player's media time is its current position in the audio playback. For example, a Player that is halfway through a 4-second audio clip would have a media time of 2,000,000 microseconds. If you want to jump to a ... [full story]

Player Life Cycle Because playing audio may use scarce resources on a MIDP device, and because sampled audio files are relatively large, Player has a detailed life cycle that allows its behavior to be closely controlled. The life cycle is described ... [full story]

Supported Content Types and Protocols One of the least understood aspects of the ABB is its supported content types. MIDP 2.0 is very flexible about the content types and protocols an implementation may support. All the specification says is that if ... [full story]

MIDP 2.0 Media Concepts Audio data comes in a variety of content types. A content type is really just a file format, a specification that tells how each bit in the data contributes to the resulting sound. Common audio content types ... [full story]

Quick Start You can play tones by calling this method in javax.microedition.media.Manager: public static void playTone(int note, int duration, int volume) In this method, note is specified just like a MIDI note, where each integer corresponds to a single key on a piano ... [full story]

Special Effects Although they are not strictly contained in the Game API, two other methods in the Display class are closely related: public boolean flashBacklight(int duration) public boolean vibrate(int duration) Both methods accept a duration in milliseconds that specifies how long the backlight should ... [full story]

Using Sprites While a TiledLayer uses a palette of tiles to fill a large area, a Sprite uses a palette of tiles to animate a layer that is the same size as a single tile. Usually a sprite represents one of ... [full story]

Using Tiled Layers A tiled layer is made from a palette of tiles, just as you might assemble decorative tiles to create a pretty design next to your bathtub. The tiles come from a single image that is divided into equal-sized ... [full story]

Understanding Layers The rest of the Game API is devoted to layers. Layers are graphic elements that can be combined to create a complete scene. You might, for example, have a background of mountains, another background of city buildings, and several ... [full story]

Polling for Key States GameCanvas offers an alternate method for responding to key presses, which are expected to be the way for the user to control the game. Instead of passively waiting for the key event callbacks defined in Canvas, GameCanvas ... [full story]

Driving Animation with GameCanvas GameCanvas extends javax.microedition.lcdui.Canvas with methods for animation and key state polling. GameCanvas is used differently than Canvas: To use Canvas, you subclass it and define the paint() method. Inside paint(), you use a Graphics to render graphics on ... [full story]

Multithreading and Animation As with any graphic-interface toolkit, threading with the MIDP user-interface classes is a little tricky. The user-interface implementation has its own thread that handles both user-interface methods and screen painting. For example, when the user presses a key ... [full story]

Double Buffering Double buffering is a well-known technique for reducing flicker in drawing and animations. Imagine you are implementing an animation that clears and redraws the entire screen for each frame of the animation. Without double buffering, the animation will flicker ... [full story]

Game Actions Key codes may be useful in certain situations, but they're fairly specific to a device. MIDP offers a simple abstraction called a game action that makes it easier to map user key events to events that will be useful ... [full story]

Key Events Canvas handles events at a lower level than the other Displayable subclasses. Although you can add Commands and respond to them, Canvas also includes a set of methods that handle interaction with the individual keys of a device. The following ... [full story]

Drawing Shapes, Text, and Images The Graphics class contains methods for drawing shapes, text, and images on a Canvas. It also maintains some state, like the current pen color and line style. MIDP's Graphics class is similar to the Graphics and ... [full story]