Question

I’m developing a small j2me game and i want to create a menu for this application. I imagine the menu as a vertical list of items with a cursor on the left or right side that i can move from item to item, something like this menu example but as a main menu.
What elements should i use to obtains such effects? I need only advices or links, i will develope it myself.

Thanks in advance!

import java.util.Vector;

import javax.microedition.lcdui.Canvas;
import javax.microedition.lcdui.Font;
import javax.microedition.lcdui.Graphics;
import javax.microedition.lcdui.Image;

Answer 1

What you plan looks doable. Can’t give much links because don’t recall any that could help on stuff like you’re doing. Actually, most useful link for you will probably be MIDP (JSR 118) API reference – your part is going to be mostly lcdui package, and especially Graphics API.

As for advice, no problem. First thing to note is that there will be more coding and more (much more) testing/debugging than it was in your prior experiment with implicit list. If you can think of some possible deadline / timing requirements that may become a problem – just keep in mind that prior design with implicit list as a fallback. It won’t look as fancy but it’ll work work safe and correct.

Another important thing is to decide what kind devices you are going to target. For menu like one you are going to develop, it may be rather difficult to get consistent look and feel both at 160×200 basic phone with ITU-T keypad and on 400×600 touchscreen smartphone. Below I am going to assume you’ll try to target as wide variety of devices as possible – note the narrower you can get it, the easier it will be to code and test.

When targeting lots of different devices it is helpful to use an emulator that can be configured to simulate various display sizes and resolution, presense or absence of touchscreen input etc. Keep in mind though that emulator alone won’t fully simulate real device. To keep your feets on the ground, consider also some regular smoke testing of your application with real device, preferable using over-the-air (OTA) installation.

Here are some particular API tips that I can think of now.

• Use Canvas.getGameAction to handle pressed key code – that is likely the most reliable/portable way to figure up/down and select actions for menu.
• Use Canvas.hasPointerEvents to figure if there’s touch screen support. Users with touch screen devices may get disappointed if it turns out that your fancy menu can’t react when they tap on screen.
• Use Font.getHeight and Font.stringWidth to figure how much space is occupied by menu item text.
• Use Image.getGraphics if you want to draw something over the image object.

As I mentioned, you most likely will do a lot of stuff using lcdui.Graphics API. It’s mostly rather simple, but you will probably need to understand somewhat tricky stuff about clipping. Good luck.