Integrating MIDP into the Device

Underlying the decisions about how to implement app management tasks is the larger question of how to integrate MIDP into the device.

MIDP Implementors

Recommend: Integrate MIDP app management into the device's native app-management functionality. Have the device treat a MIDlet like a native app. Don't require users to start the Java platform on the device and then manage their MIDlets.

Although MIDP implementors might want to advertise their use of Java technology by having users launch the Java platform to manage MIDlets, using native app-management functionality provides more predictability. Users already know how to manage native apps, so there is no extra training required and fewer support issues. Because of the importance of predictability, using the native app-management functionality is more likely to be successful in the long run. Sun's MIDP for Palm OS uses the native app-management functionality to manage MIDlets. As Screenshot shows, MIDP for Palm OS places icons for MIDlet suites on the app launcher with native apps. Tapping the icon runs the app, whether the app is native or a MIDlet suite. Other management tasks, such as installing and removing apps, are also the same for native apps and MIDlet suites.

Screenshot MIDlet and Native app Icons on the Launcher

Icons

Many devices include icons in their app Management screens. The icons help remind users what an app does. A MIDlet's icons can be supplied by either the MIDP implementor or the app developer.

MIDP Implementors

Consider: Use the MIDlet suite's icons if they are present. If a MIDlet suite has an icon that is too large, consider top- and left-justifying it, then clipping it; if an icon is too small, consider centering it on a background of the correct size.

Recommend: Have generic icons for MIDlet suites and MIDlets. Use the generic icons if the MIDlet suite does not include icons, or includes icons that you cannot use. For example, the icon associated with SmartTicket, shown in Screenshot, is a generic icon for MIDlet suites that have only one MIDlet.

app Developers

Consider: Provide 12-by-12 pixel, color icons in PNG format that devices can show to users. The icons should also look good displayed in grayscale. A MIDlet suite can contain one icon for the suite and one icon for each MIDlet.

app developers provide icons by putting the PNG files into the MIDlet suite's JAR file, and by setting the values of the corresponding MIDlet-Icon and MIDlet-n-Icon properties. The properties can be in the MIDlet suite's JAD file or its JAR file's manifest. (See "Getting Information on MIDlet Suites" on page 194 for more information on the properties and values that can be in a MIDlet suite's JAD and JAR files.)

Recommend: If you provide an icon for a MIDlet suite that contains multiple MIDlets, the icon should graphically indicate it. For example, the Games MIDlet suite has multiple MIDlets. The icon for the Games MIDlet suite, shown in Screenshot, indicates this by having multiple items (such as the ball) that are meant to represent games.

Personal Storage for MIDlet Suites

Some operators give their users a personal storage area, which holds data that the user can download to their device. For example, some operators allow their users to use the area to store wallpaper or games that they have bought.

MIDP Implementors

Consider: Integrate MIDlet suites into the personal storage area, if the operator you are working with offers that service to its users. This would enable you to charge users only once for a particular version of a MIDlet suite, even if they have to reinstall it later. (That is, if they install it from their personal storage area, they would not be charged.) Users might have to download a MIDlet and install it a second time if, for example, the MIDlet became corrupted or they deleted it by mistake.