displaydemo.java~12~

J2ME高级用户界面的学习代码

//DisplayDemo.java

import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;

public class DisplayDemo extends MIDlet implements CommandListener
{
  private Display display;
  private TextBox scrHelp;
  private TextBox scrJump;
  private TextBox[] myScreen;

  private Command cmdBack = new Command("Back",Command.BACK,1);
  private Command cmdForw = new Command("Forward",Command.SCREEN,1);
  private Command cmdJump = new Command("Goto",Command.SCREEN,2);
  private Command cmdExit = new Command("Exit",Command.SCREEN,2);
  private Command cmdHelp = new Command("Help",Command.HELP,1);
  private Command cmdCanc = new Command("Cancel",Command.CANCEL,1);
  private Command cmdConf = new Command("OK",Command.OK,1);

  static int MaxHistory = 8;
  static int MaxScreen = 4;
  int[] history;
  int currentPos;
  int historyLen;

  public DisplayDemo()
  {
    display = Display.getDisplay(this);

    String helpStr = new String("This is a Demo of Multi-Screens");
    scrHelp = new TextBox("Help",helpStr,100,TextField.ANY);
    scrHelp.addCommand(cmdCanc);
    scrHelp.setCommandListener(this);

    scrJump = new TextBox("Goto","This Screen is designed for GOTO command.",70,TextField.ANY);
    scrJump.addCommand(cmdConf);
    scrJump.addCommand(cmdCanc);
    scrJump.setCommandListener(this);

    myScreen = new TextBox[MaxScreen];
    myScreen[0] = createScreen("Screen 1","This is Screen 1");
    myScreen[1] = createScreen("Screen 2","This is Screen 2");
    myScreen[2] = createScreen("Screen 3","This is Screen 3");
    myScreen[3] = createScreen("Screen 4","This is Screen 4");

    history = new int[MaxHistory];
    currentPos = -1;
    historyLen = 0;
  }

  public void startApp()
  {
    gotoScreen(0);
    addHistory(0);
  }
  public void pauseApp(){}
  public void destroyApp(boolean unconditional){}

  private TextBox createScreen(String screenTitle,String screenContent)
  {
    TextBox tempScreen = new TextBox(screenTitle,screenContent,50,0);
    tempScreen.addCommand(cmdForw);
    tempScreen.addCommand(cmdBack);
    tempScreen.addCommand(cmdJump);
    tempScreen.addCommand(cmdHelp);
    tempScreen.addCommand(cmdExit);
    tempScreen.setCommandListener(this);
    return tempScreen;
  }

  private void addHistory(int num)
  {
    if(historyLen < MaxHistory)
    {
      historyLen++;
      history[historyLen] = num;
      currentPos++;
    }
    else
    {
      for(int i = 0;i < MaxHistory;i++)
      {
        history[i] = history[i + 1];
      }
      history[MaxHistory] = num;
      currentPos = historyLen - 1;
    }
  }

  void gotoScreen(int num)
  {
    display.setCurrent(myScreen[num]);
  }

  public void commandAction(Command c,Displayable d)
  {
    if(cmdBack == c)
    {
      if(currentPos > 0)
      {
        currentPos--;
        gotoScreen(history[currentPos]);
      }
      return;
    }
    if(cmdForw == c)
    {
      if(currentPos < historyLen)
      {
          currentPos++;
          gotoScreen(history[currentPos]);
      }
      return;
    }

    if(cmdJump ==  c)
    {
      display.setCurrent(scrJump);
      return;
    }

    if(cmdCanc == c)
    {
      gotoScreen(history[currentPos]);
      return;
    }

    if(cmdConf == c)
    {
      int next = Integer.parseInt(scrJump.getString());
      if((next > 0)&&(next <= MaxScreen))
      {
        display.setCurrent(myScreen[next - 1]);
        addHistory(next - 1);
      }
      return;
    }
    if(cmdExit == c)
    {
      destroyApp(false);
      notifyDestroyed();
    }
  }
}