j2me程序代码请求解答

[anne]

请帮忙解答下面程序的功能是什么.另有5处需要添加代码.请帮忙添加.
import javax.microedition.lcdui.*;
import javax.microedition.midlet.MIDlet;

public class HelloWorld extends MIDlet implements CommandListener{
private Display display;
private TextBox[] myScreen;
private Command cmdExit;
private Command cmdNext;
private Command cmdPrev;
static int MaxScreen = 4;
int currentPos;

public HelloWorld(){
currentPos = 0;
display = Display.getDisplay(this);
cmdExit = new Command ("退出",Command.SCREEN,1);
cmdPrev = new Command ("上一页","点击转至上一页",Command.SCREEN,2);
cmdNext = new Command ("下一页","点击转至下一页",Command.SCREEN,3);
myScreen = new TextBox[MaxScreen];
myScreen[0] = createScreen("屏幕一","床前明月光");
myScreen[0] = createScreen("屏幕二","疑是地上霜");
myScreen[0] = createScreen("屏幕三","举头望明月");
myScreen[0] = createScreen("屏幕四","低头思故乡");
}
private TextBox createScreen(String screenTitle,String screenContent){
TextBox tmpScreen = new TextBox(screenTitle,screenContent,50,0);
if(!screenTitletrim().equals("屏幕一")){
此处需要添加代码 1)
}
if (!screenTitle.trim().equals("屏幕四")){
此处需要添加代码 2)
}
此处需要添加代码 3)
return tmpScreen;
}
public void startApp()
{
gotoScreen(0);
}
private void gotoScreen(int num){
此处需要添加代码 4)
}
public void pauseApp()
{

}
public void destroyApp(boolean unconditional){

}
public void commandAction(Command c,Displayable d){
if(c == cmdPrev){
if (currentPos > 0){
currentPos--;
gotoScreen(currenPos);

}
}
if(c == cmdNext){
if(currentPos < 3) {
currentPos++;
}
gotoScreen(currentPos);
}
if(c==cmdExit){
此处需要添加代码 5)
notifyDestroyed();
}
}

}

[Moon0Light]

public HelloWorld(){
currentPos = 0;
display = Display.getDisplay(this);
cmdExit = new Command ("退出",Command.SCREEN,1);
cmdPrev = new Command ("上一页","点击转至上一页",Command.SCREEN,2);
cmdNext = new Command ("下一页","点击转至下一页",Command.SCREEN,3);
myScreen = new TextBox[MaxScreen];
myScreen[0] = createScreen("屏幕一","床前明月光");
myScreen[0] = createScreen("屏幕二","疑是地上霜");//这里的index似乎应该是1
myScreen[0] = createScreen("屏幕三","举头望明月");//……2
myScreen[0] = createScreen("屏幕四","低头思故乡");//……3
}
private TextBox createScreen(String screenTitle,String screenContent){
TextBox tmpScreen = new TextBox(screenTitle,screenContent,50,0);
if(!screenTitle.trim().equals("屏幕一")){//!or not
tmpScreen=myScreen[0]; //此处需要添加代码 1)
}
if (!screenTitle.trim().equals("屏幕四")){//! or not
tmpScreen=myScreen[3]; //此处需要添加代码 2)
}
//此处需要添加代码 3)?
return tmpScreen;
}
public void startApp()
{
gotoScreen(0);
}
private void gotoScreen(int num){
//此处需要添加代码 4)
switch(num){
case 0:
createScreen("屏幕一","……");
break;
case 1:
createScreen("屏幕二","……");
break;
case 2:
createScreen("屏幕三","……");
break;
case 3:
createScreen("屏幕四","……");
break;
}
}
public void pauseApp()
{

}
public void destroyApp(boolean unconditional){

}
public void commandAction(Command c,Displayable d){
if(c == cmdPrev){
if (currentPos > 0){
currentPos--;
gotoScreen(currenPos);

}
}
if(c == cmdNext){
if(currentPos < 3) {
currentPos++;
}
gotoScreen(currentPos);
}
if(c==cmdExit){
destroyApp(false);//此处需要添加代码 5)
notifyDestroyed();
}
}

没仔细猜测代码的实现功能，大概是用command和textbox来控制显示四屏文本。
代码我没编译，直接写的，要是有错，不要见笑！（第一次发出现网络错误，郁闷！！！）