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rey,
October 11, 2008 at 11:36 AM

Creating Midlet Application For Login in J2ME

This example show to create the Midlet application for user login . All Midlet applications for the MIDP ( Mobile Information Device Profile) derived from Midlet class and it play a role as a mediator between the application and the environment in which the application runs. The Midlet life cycle manage the flow of application. It is in the javax.microedition.midlet package, so import this package in your application. The javax.microedition.icdui package is used for following classes:

Alert
AlertType
Canvas
ChoiceGroup
Command
DateField
Display
Displayable
Font
Form
Gauge
Graphics
Image
ImageItem
Item
List
Screen
StringItem
TextBox
TextField
Ticker
In this example we will create a Midlet (LoginExample), that will show following output display look like below:

Click on 'Launch' Button then the login page display like below:

Give Your LoginID 'sandeep' and Password 'sandeep' then it call the commandAction where if condition will be executed and it calls a function (validateUser()) which checks whether name and password is equal to 'sandeep' or not if it equal to 'sandeep' then it executed the showMsg() function which show a congratulation message but if name and password is not equal to 'sandeep' then it call tryAgain() function which show the error page like figure below and it return on login page with refresh value.

Source Code Of LoginExample.java

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

public class LoginExample extends MIDlet implements CommandListener{
private Display display;
private TextField userName,password;
public Form form;
private Command login,cancel;
private Image img, imge, img2;

public LoginExample() {
form = new Form("Sign in");
userName = new TextField("LoginID:", "", 30, TextField.ANY);
password = new TextField("Password:", "", 30, TextField.PASSWORD);
cancel = new Command("Cancel", Command.CANCEL, 2);
login = new Command("Login", Command.OK, 2);
try{
img = Image.createImage("/logo.png");
imge = Image.createImage("/front_left1_bad.png");
img2 = Image.createImage("/Congratulations-1.png");
}catch(Exception e){
System.out.println(e.getMessage());
}
}

public void startApp() {
display = Display.getDisplay(this);
try{form.append(img);}catch(Exception e){}
form.append(userName);
form.append(password);
form.addCommand(cancel);
form.addCommand(login);
form.setCommandListener(this);
display.setCurrent(form);
}

public void pauseApp() {}

public void destroyApp(boolean unconditional) {
notifyDestroyed();
}

public void validateUser(String name, String password) {
if (name.equals("sandeep") && password.equals("sandeep")) {
showMsg();
} else {
tryAgain();
}
}

public void showMsg() {
Alert success = new Alert("Login Successfully", "Your Login Process is completed!",
img2, AlertType.INFO);
success.setImage(img2);
userName.setString("");
password.setString("");
display.setCurrent(success, form);
}

public void tryAgain() {
Alert error = new Alert("Login Incorrect", "Please try again", imge, AlertType.ERROR);
error.setTimeout(900);
error.setImage(imge);
userName.setString("");
password.setString("");
display.setCurrent(error, form);
}

public void commandAction(Command c, Displayable d) {
String label = c.getLabel();
if(label.equals("Cancel")) {
destroyApp(true);
} else if(label.equals("Login")) {
validateUser(userName.getString(), password.getString());
}
}
}

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