循序渐进学J2Me，第三步

最新推荐文章于 2025-06-08 13:52:17 发布

原创最新推荐文章于 2025-06-08 13:52:17 发布 · 413 阅读

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CC 4.0 BY-SA版权

文章标签：

#j2me #command #null #import #class

本文介绍了一个简单的Java ME应用示例，展示了如何创建MIDlet、设置界面元素并响应用户命令，包括退出和导航到下一个屏幕的功能。

这一步很简单，增加一个NextCommand。
import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;

/**
* @author netscaner
*/
public class Midlet extends MIDlet implements CommandListener {
    private Form showForm;
    private StringItem stringItem;
    private Command exitCommand;
    private Command NextCommand;

    public StringItem getStringItem() {
        if (stringItem == null) {
            stringItem = new StringItem("Hello", "Hello, World!");
        }
        return stringItem;
    }

public Form getForm() {
        if (showForm == null) {
            showForm = new Form("Welcome", new Item[] { getStringItem() });
            showForm.addCommand(getExitCommand());
            showForm.addCommand(getNextCommand());
            showForm.setCommandListener(this);
        }
        return showForm;
    }

    public void startMIDlet() {
        switchDisplayable(null, getForm());
    }

    public void exitMIDlet() {
        switchDisplayable (null, null);
        destroyApp(true);
        notifyDestroyed();
    }

    public void switchDisplayable(Alert alert, Displayable nextDisplayable) {
        Display display = getDisplay();
        if (alert == null) {
            display.setCurrent(nextDisplayable);
        } else {
            display.setCurrent(alert, nextDisplayable);
        }
    }

        public Display getDisplay () {
        return Display.getDisplay(this);
    }

    public Command getExitCommand() {
        if (exitCommand == null) {
            exitCommand = new Command("Exit", Command.EXIT, 0);
        }
        return exitCommand;
    }

    public Command getNextCommand() {
        if (NextCommand == null) {
            NextCommand = new Command("Next", Command.SCREEN, 0);
        }
        return NextCommand;
    }

    public void commandAction(Command command, Displayable displayable) {
        if (displayable == showForm) {
            if (command == exitCommand) {
                exitMIDlet();
            }
            if (command == NextCommand) {

            }
        }
    }

    public void startApp() throws MIDletStateChangeException {
            startMIDlet ();
    }

public void pauseApp() {
}

public void destroyApp(boolean unconditional) {
}
}