J2ME从零开始（学习笔记4）

★ List组件
List是选择列表组件，为用户提供多种选择项，List有两种构造函数
List（String title , int listType）;
List( String title , int listType , String [ ] stringElements, Image[ ] imageElements);
第三个参数有三种，Choice.EXCLUSIVE, Choice.MULTIPLE, Choice.IMPLICIT，这里涉及到Choice这个接口，实际上List实现了Choice这个接口。
当然List和其他组件也有很多自己的方法，大家可以参见API
以下是些简单的List代码：

package J2ME001;

import javax.microedition.lcdui.Choice;
import javax.microedition.lcdui.Command;
import javax.microedition.lcdui.CommandListener;
import javax.microedition.lcdui.Display;
import javax.microedition.lcdui.Displayable;
import javax.microedition.lcdui.List;
import javax.microedition.midlet.MIDlet;
import javax.microedition.midlet.MIDletStateChangeException;

public class ListMIDlet extends MIDlet implements CommandListener {

private List excList;
private List mulList;
private List impList;

private final Command cmdExcList = new Command("Exclusive", Command.ITEM, 1);
private final Command cmdMulList = new Command("Multiple", Command.ITEM, 1);
private final Command cmdImpList = new Command("Implicit", Command.ITEM, 1);

private final Command cmdExit = new Command("Exit", Command.ITEM, 1);
private Display display;

public ListMIDlet() {

excList = new List("EXCLUSIVE", Choice.EXCLUSIVE, new String[] {
"Element1", "Element2", "Element3" }, null);
mulList = new List("MULTIPLE", Choice.MULTIPLE, new String[] {
"Element1", "Element2", "Element3" }, null);
impList = new List("IMPLICIT", Choice.IMPLICIT, new String[] {
"Element1", "Element2", "Element3" }, null);

excList.addCommand(cmdMulList);
excList.addCommand(cmdImpList);
excList.addCommand(cmdExit);
excList.setCommandListener(this);
mulList.addCommand(cmdExcList);
mulList.addCommand(cmdImpList);
mulList.addCommand(cmdExit);
mulList.setCommandListener(this);
impList.addCommand(cmdExcList);
impList.addCommand(cmdMulList);
impList.addCommand(cmdExit);
impList.setCommandListener(this);

}

protected void destroyApp(boolean arg0) {
// TODO Auto-generated method stub

}

protected void pauseApp() {
// TODO Auto-generated method stub

}

protected void startApp() throws MIDletStateChangeException {
display = Display.getDisplay(this);
display.setCurrent(excList);
}

public void commandAction(Command command, Displayable displayable) {
if (command.equals(cmdExcList)) {
display.setCurrent(excList);
} else if (command.equals(cmdImpList)) {
display.setCurrent(impList);
} else if (command.equals(cmdMulList)) {
display.setCurrent(mulList);
} else if (command.equals(cmdExit)) {
this.notifyDestroyed();
this.destroyApp(true);
}
}

}