H/W Login

Main_Activity============================================

package com.example.user.sharedpreferences;

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 MainActivity extends Activity {

    EditText txtUserName;
    EditText txtPassword;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        // Getting information form user name and password fields
        txtUserName=(EditText)findViewById(R.id.txtUserName);
        txtPassword=(EditText)findViewById(R.id.txtPassword);
        // If user exist go automatically to Logged

        if(CheckUser())
        {
            SharedPreferences pref=getApplicationContext().getSharedPreferences("myPref",MODE_PRIVATE);
            Intent loggedIntent=new Intent(this,Logged.class);
            // Send  user name to Logged screen
            loggedIntent.putExtra("userPut", pref.getString("Logged", "Error"));
            // Go to logged screen
            this.startActivity(loggedIntent);
        }

    }
    // Checking if user exist

    private boolean CheckUser()
    {
        SharedPreferences pref=getApplicationContext().getSharedPreferences("users", MODE_PRIVATE);
        String userName = pref.getString("Logged","Error");
        // If user not exist return false
        return (!userName.equals("Error"));
    }


    public void btnNext(View v)
    {
        SharedPreferences pref = getApplicationContext().getSharedPreferences("users", MODE_PRIVATE);
        String logUserName=txtUserName.getText().toString().toLowerCase();
        String logPassword=txtPassword.getText().toString();
        String logPasswordConf=pref.getString(logUserName, "Error");
        // If any field is empty
        if(logUserName.isEmpty() || logPassword.isEmpty())
        {
            Toast.makeText(this,"One of more fields is empty",Toast.LENGTH_SHORT).show();
            return;
        }
        // if user name or password doesn't exist in "users" file
        else if(!pref.contains(logUserName) || !logPassword.equals(logPasswordConf))
        {
            Toast.makeText(this,"Invalid user name or password ",Toast.LENGTH_SHORT).show();
            return;
        }
        // if proper data
        else
        {
            SharedPreferences.Editor editor=pref.edit();
            editor.putString("Logged",logUserName).commit();
            Toast.makeText(this,"You have successfuly logged",Toast.LENGTH_SHORT).show();
            Intent loggedIntent = new Intent(this, Logged.class);
            // Send  user name to Logged screen
            loggedIntent.putExtra("userPut", pref.getString("Logged", "Error"));
            // Go to logged screen
            this.startActivity(loggedIntent);
        }

    }
    // Go to registration screen
    public void btnRegister(View v)
    {
        Intent registerIntent=new Intent(this,Register.class);
        // Go to registration screen
        this.startActivity(registerIntent);
    }
}


Register=======================================================

package com.example.user.sharedpreferences;

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



public class Register extends Activity {

    EditText txtUserName,txtPassword1,txtPassword2;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.register);
        // Pointers
        txtUserName=(EditText)findViewById(R.id.regUserName);
        txtPassword1=(EditText)findViewById(R.id.regPassword1);
        txtPassword2=(EditText)findViewById(R.id.regPassword2);

    }
    public void btnCancel(View v)
    {
        Intent cancelIntent=new Intent(this,MainActivity.class);
        // Go to login screen
        this.startActivity(cancelIntent);
    }



    // Registration
    public void btnRegister(View v)
        {
            SharedPreferences pref=getApplicationContext().getSharedPreferences("users", MODE_PRIVATE);
            SharedPreferences.Editor editor=pref.edit();

            String regUserName=txtUserName.getText().toString().toLowerCase();
            String regPassword1=txtPassword1.getText().toString();
            String regPassword2=txtPassword2.getText().toString();

            // If any field is empty
            if(regUserName.isEmpty() || regPassword1.isEmpty() || regPassword2.isEmpty())
            {
                Toast.makeText(this,"One of more fields is empty",Toast.LENGTH_SHORT).show();
                return;
            }
            // if user name exist
            else if(pref.contains(regUserName))
            {
                Toast.makeText(this,"User name is exists",Toast.LENGTH_SHORT).show();
                return;
            }
            // if passwords match
            else if(!regPassword1.equals(regPassword2))
            {
                Toast.makeText(this,"Passwords don't match",Toast.LENGTH_SHORT).show();
                return;
            }
            // if proper data
            Toast.makeText(this,"Registration was successful",Toast.LENGTH_SHORT).show();
            // Adding a new user
            editor.putString(regUserName, regPassword1).commit();
            Intent registeredIntent = new Intent(this, MainActivity.class);
            // Go to login screen
            this.startActivity(registeredIntent);

        }



    }

Logged=======================================================

package com.example.user.sharedpreferences;


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 Logged extends Activity{

    TextView txtUserName;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.logged);
        // Pointer to text view
        txtUserName=(TextView)findViewById(R.id.textView);
        // Print "Hello "+ user name from main activity
        txtUserName.setText("Hello "+getIntent().getStringExtra("userPut"));
    }
    // Go back to main activity and remove the user name and password
    public void btnLogout(View v)
    {
        SharedPreferences pref=getApplicationContext().getSharedPreferences("users",MODE_PRIVATE);
        SharedPreferences.Editor editor=pref.edit();
        // Remove last logged user
        editor.remove("Logged").commit();
        Intent logoutIntent=new Intent(this,MainActivity.class);
        // Go to login screen
        this.startActivity(logoutIntent);
    }
}

main_Activity xml =================================================

<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    xmlns:android="http://schemas.android.com/apk/res/android">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical"
        android:background="@color/white">


        <ImageView
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:src="@drawable/user_login"/>
        <TextView
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="User Login"
            android:textSize="25sp"
            android:gravity="center" />

        <EditText
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:hint="User name"
            android:textSize="20sp"
            android:id="@+id/txtUserName"
            android:inputType="text" />

        <EditText
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:hint="Password"
            android:textSize="20sp"
            android:id="@+id/txtPassword"
            android:inputType="textPassword" />

        <Button
            android:layout_width="150sp"
            android:layout_height="wrap_content"
            android:text="Login"
            android:textSize="20sp"
            android:onClick="btnNext"
            android:layout_gravity="center" />
        <Button
            android:layout_width="150sp"
            android:layout_height="wrap_content"
            android:text="Register"
            android:textSize="20sp"
            android:onClick="btnRegister"
            android:layout_gravity="center"/>

    </LinearLayout>

</LinearLayout>


register xml =====================================================

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical" android:layout_width="match_parent"
    android:layout_height="match_parent">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical"
        android:background="@color/white">

        <ImageView
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:src="@drawable/new_user"/>

        <TextView
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="Create a new user"
            android:textSize="25sp"
            android:gravity="center"/>

        <EditText
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:hint="User name"
            android:textSize="20sp"
            android:id="@+id/regUserName"
            android:inputType="text"/>
        <EditText
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:hint="Password"
            android:textSize="20sp"
            android:id="@+id/regPassword1"
            android:inputType="textPassword"/>
        <EditText
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:hint="Confirm password"
            android:textSize="20sp"
            android:id="@+id/regPassword2"
            android:inputType="textPassword"/>
        <Button
            android:layout_width="150sp"
            android:layout_height="wrap_content"
            android:text="Register"
            android:textSize="20sp"
            android:onClick="btnRegister"
            android:layout_gravity="center"/>
        <Button
            android:layout_width="150sp"
            android:layout_height="wrap_content"
            android:text="Cancel"
            android:textSize="20sp"
            android:onClick="btnCancel"
            android:layout_gravity="center"/>

    </LinearLayout>

</LinearLayout>

logged xml=====================================================

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical"
        android:background="@color/white">
        <ImageView
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:src="@drawable/logged2"/>



        <TextView
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:textSize="25sp"
            android:gravity="center"
            android:id="@+id/textView"/>

        <Button
            android:layout_width="150sp"
            android:layout_height="wrap_content"
            android:text="Logout"
            android:textSize="20sp"
            android:onClick="btnLogout"
            android:layout_gravity="center"/>
    </LinearLayout>


</LinearLayout>