ui_ex25.java

J2ME 无线通信技术应用开发源代码

// 程序名UI_Ex25.java
// 测试ImageItem对象
import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;

public class UI_Ex25 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
  private Command cmdChange; // 设定按钮用于退出MIDlet
  private ImageItem imageItem; //设置一个ImageItem对象
  private Image[] images;
  private static int NumOfImage = 4;//表示图象数组元素个数
  private int index;

  public UI_Ex25() {
    index = 0;
    display = Display.getDisplay(this);// 获取一个Display实例，它是唯一的
    form = new Form("Test ImageItem");
    try {
      images = new Image[] {
        Image.createImage("/Duke2.png"),
        Image.createImage("/Duke1.png"),
        Image.createImage("/Duke3.png"),
        Image.createImage("/Duke1.png")
      }; //数组元素的数目应该与NumOfImage相等
    } catch (java.io.IOException e) {
    }
    imageItem = new ImageItem("Animation",images[NumOfImage-1],0x303,"a image exceeds display's capacity");
    form.append(imageItem);
    cmdExit = new Command("Exit", Command.SCREEN, 1);
    cmdChange = new Command("Change", Command.SCREEN, 1);
    form.addCommand(cmdExit);// 为Displayable对象添加一个Command对象
    form.addCommand(cmdChange);// 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
  }

  public void startApp() {
    display.setCurrent(form);// 把form设置为当前屏幕或当前Displayable对象
  }

  public void pauseApp() {
  }

  public void destroyApp(boolean unconditional) {
  }

  public void commandAction(Command c, Displayable d) {
    if (c == cmdChange) {
      imageItem.setImage(images[index++]);
      if (index == NumOfImage) {
        index = 0;
      }
      return;
    }

    if (c == cmdExit) {
      destroyApp(false);
      notifyDestroyed();
    }
  }
}