ui_ex19.java

J2ME 无线通信技术应用开发源代码

// 程序名UI_Ex19.java
// 测试Form中的ItemStateListener
import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;

public class UI_Ex19 extends MIDlet implements CommandListener {
  private Display display; // 引用MIDlet的Display 对象
  private Form form; // 声明一个Form对象
  private Command cmdExit; // 设定按钮用于退出MIDlet
  Item[] items; //Form中要添加的Item

  public UI_Ex19() {
    display = Display.getDisplay(this);// 获取一个Display实例，它是唯一的
    cmdExit = new Command("Exit", Command.SCREEN, 1);
    items = new Item[] {
      new TextField("INPUT:","",50,0),
      new StringItem("OUTPUT:","________"),
    }; //构造一个Item数组
    form = new Form("Reverse",items);
    form.append("NOTE:\nIt's a demo only.");
    form.addCommand(cmdExit);// 为Displayable对象添加一个Command对象
    form.setCommandListener(this);// 为Displayable对象添加事件监听器
    
    ItemStateListener listener = new ItemStateListener() {
      public void itemStateChanged(Item item) {
        if (item == items[0]) {
          int len = ((TextField)items[0]).size();
          if (len == 0) {
            items[1].setLabel("OUTPUT:");
            ((StringItem)items[1]).setText("________");
          } else {
            char[] charArray1 = new char[len];
            char[] charArray2 = new char[len];
            ((TextField)items[0]).getChars(charArray1);
            for (int i=0;i<len;i++) {
              charArray2[i] = charArray1[len-i-1];
            }
            items[1].setLabel("Word Reversed:");
            ((StringItem)items[1]).setText("\n"+new String(charArray2));
          }
        }
      }
    }; 
    
    form.setItemStateListener(listener);
  }

  public void startApp() {
    display.setCurrent(form);// 把form设置为当前屏幕或当前Displayable对象
    //form.append(new StringItem(null,"Hello!"));
    //((StringItem)form.get(form.size()-1)).setText("Hello J2ME!");
  }

  public void pauseApp() {
  }

  public void destroyApp(boolean unconditional) {
  }

  public void commandAction(Command c, Displayable d) {
    if (c == cmdExit) {
      destroyApp(false);
      notifyDestroyed();
    }
  }
}