yanivJava

//============================MainActivity
package com.example.y.login;

import android.app.Activity;
import android.content.Intent;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.EditText;
import android.widget.Toast;

public class MainActivity extends Activity
{
    EditText txtUser;
    EditText txtPass;
    String userNameLogged;

    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        txtUser = (EditText) findViewById(R.id.user);
        txtPass = (EditText) findViewById(R.id.pass);
        if (userLogged())
        {
            Intent myLogged = new Intent(this, Hello.class);
            myLogged.putExtra("userName", userNameLogged);
            this.startActivity(myLogged);
        }
    }

    private boolean userLogged()
    {
        SharedPreferences myPref = getApplication().getSharedPreferences("myPref", MODE_PRIVATE);
        userNameLogged = myPref.getString("logged", "error");
        if (userNameLogged.equals("error"))
            return false;
        else
            return true;
    }

    public void btnLogin(View v)
    {
        if (checkUser())
        {
            Intent helloIntent = new Intent(this, Hello.class);
            this.startActivity(helloIntent);
        } else
            Toast.makeText(this, "Wrong user name or password!", Toast.LENGTH_LONG).show();
    }
    private boolean checkUser()
    {
        SharedPreferences myPref=getApplication().getSharedPreferences("myPref",MODE_PRIVATE);
        String userName=myPref.getString("userName", "error");
        String userPass=myPref.getString("userPass","error");
        if (userName.equals(txtUser.getText().toString())&&userPass.equals(txtPass.getText().toString()))
            return true;
        else
            return false;
    }
    public void btnReg(View v)
    {
        Intent registerIntent=new Intent(this, Register.class);
        this.startActivity(registerIntent);   }
}
//=============================================Hello
package com.example.y.login;


import android.app.Activity;
import android.content.Intent;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.view.View;
import android.widget.TextView;

public class Hello extends Activity
{
    String userName;
    TextView myTxt;
    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.hello);
        myTxt=(TextView)findViewById(R.id.user);
        myTxt.setText("Hello"+getUserName());
    }

    private String getUserName()
    {
        SharedPreferences myPref=getApplicationContext().getSharedPreferences("myPref",MODE_PRIVATE);
        userName=myPref.getString("user","error");
        return userName;
    }

    public void btnLogout (View v)
    {
        SharedPreferences myPref=getApplicationContext().getSharedPreferences("myPref",MODE_PRIVATE);
        SharedPreferences.Editor editor=myPref.edit();
        editor.remove("user");
        editor.commit();
        Intent mainIntent=new Intent(this,MainActivity.class);
        this.startActivity(mainIntent);
    }
}
/=============================================Register
package com.example.y.login;

import android.app.Activity;
import android.content.Intent;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.view.View;
import android.widget.EditText;
import android.widget.Toast;

public class Register extends Activity
{
    EditText txtUser;
    EditText txtPass1;
    EditText txtPass2;

    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.regis);
        setPointer();
    }
    public void setPointer()
    {
        txtUser=(EditText)findViewById(R.id.user);
        txtPass1=(EditText)findViewById(R.id.passReg1);
        txtPass2=(EditText)findViewById(R.id.passReg2);
    }
    public void btnRegister (View v)
    {
        SharedPreferences myPref=getApplicationContext().getSharedPreferences("myPref",MODE_PRIVATE);
        SharedPreferences.Editor editor=myPref.edit();
        String userName=txtUser.getText().toString();
        String password1=txtPass1.getText().toString();
        String password2=txtPass2.getText().toString();
        String userDB=myPref.getString("userNameLogged","error");
        if (userName.equals(userDB))
        {
            Toast.makeText(this,"The user name exist, please type another user name", Toast.LENGTH_LONG).show();
            return;
        }
        else if (!password1.equals(password2))
        {
            Toast.makeText(this,"The password must be equls",Toast.LENGTH_LONG).show();
            return;
        }
        editor.putString("userNameLogged", userName);
        editor.putString("userNameLogged", password1);
        editor.commit();
        Intent myLogin=new Intent(this, MainActivity.class);
        this.startActivity(myLogin);
    }
    public void btnCancle (View v)
    {
        Intent myLog=new Intent(this,MainActivity.class);
        this.startActivity(myLog);
    }
}