My task - Version 1.1 / Oorya

//==========================================MainActivity
package com.example.com.myshared;

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 txtUser;
    EditText txtPass;

    @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 (checkUser())
        {
            //if key found , start the second activity.
            SharedPreferences pref=getApplicationContext().getSharedPreferences("myPref",MODE_PRIVATE);
            Intent iEntry = new Intent(this,Entry.class);
            iEntry.putExtra("putUser", pref.getString("userLogged", "error"));
            this.startActivity(iEntry);
            finish();
        }
    }


    private boolean checkUser()
    {
        //declaration of shared preferences
        SharedPreferences pref=getApplicationContext().getSharedPreferences("myPref",MODE_PRIVATE);
        //getting value of key "user"
        String userName = pref.getString("userLogged","error");
        //return false if key "user" not exists
        return (!userName.equals("error"));
    }

    public void btnLogin(View v)
    {
        SharedPreferences pref = getApplicationContext().getSharedPreferences("myPref",MODE_PRIVATE);

        String userName=txtUser.getText().toString().toLowerCase();
        String password= txtPass.getText().toString();
        String passDB=pref.getString(userName,"ErrorP");

        if(userName.equals("") || password.equals("")) {
            Toast.makeText(this, "Please type username and password", Toast.LENGTH_LONG).show();
            return;
        }
            else if(!pref.contains(userName)) {
                Toast.makeText(this, "Please register", Toast.LENGTH_LONG).show();
                return;
            }
                else if(password.equals(passDB)) {
                    Toast.makeText(this, "Good to see you", Toast.LENGTH_SHORT).show();
                }
                    else
                    {
                        Toast.makeText(this, "Wrong user name or password", Toast.LENGTH_LONG).show();
                        return;
                    }

        //declaration of editor to edit shared preferences
        SharedPreferences.Editor editor=pref.edit();
        //create key "user" with value of userName, if key exists, it will be overwritten
        editor.putString("userLogged",userName);
        //commit the changes
        editor.commit();

        Intent iEntry = new Intent(this,Entry.class);
        iEntry.putExtra("putUser", pref.getString("userLogged","error"));
        this.startActivity(iEntry);
        finish();
    }

    public void btnReg(View v)
    {
        Intent regIntent = new Intent(this, Register.class);
        this.startActivity(regIntent);
    }
}

//======================================REGISTER CLASS
package com.example.com.myshared;

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, txtPass1, txtPass2;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.register);
        setPointer();
    }

    public void setPointer()
    {
        txtUser=(EditText)findViewById(R.id.user);
        txtPass1=(EditText)findViewById(R.id.pass1);
        txtPass2=(EditText)findViewById(R.id.pass2);
    }


    public void btnRegister(View v)
    {
        SharedPreferences pref=getApplicationContext().getSharedPreferences("myPref", MODE_PRIVATE);
        //declaration of editor to edit shared preferences
        SharedPreferences.Editor editor=pref.edit();
        //insert into string value from EditText
        String userName=txtUser.getText().toString().toLowerCase();
        String password1=txtPass1.getText().toString();
        String password2=txtPass2.getText().toString();

        if(userName.equals("")||password1.equals("")){
            Toast.makeText(this, "Please type username and password", Toast.LENGTH_LONG).show();
            return;
        }
            else if(pref.contains(userName)) {
                Toast.makeText(this, "The username exist, please type another username", Toast.LENGTH_LONG).show();
            return;
            }
                else if(!password1.equals(password2)){
                    Toast.makeText(this, "The password must be equals", Toast.LENGTH_LONG).show();
                    return;
                }
        //create key "user name" with value of your password
        editor.putString(userName, password1);

        //commit the changes
        editor.commit();

        Intent iLogin = new Intent(this, MainActivity.class);
        this.startActivity(iLogin);
        finish();
    }

    public void btnCancel(View v)
    {
        finish();
    }
}

//===========================================ENTRY CLASS
package com.example.com.myshared;

import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.view.View;
import android.widget.ListView;
import android.widget.TextView;
import java.util.Map;


public class Entry extends Activity {

    TextView txt;
    ListView myList;
    Context context = this;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.entry);
        txt=(TextView)findViewById(R.id.text);
        myList=(ListView)findViewById(R.id.myListV);
        String myUser = getIntent().getStringExtra("putUser");
        txt.setText("Hello " + myUser);
        SharedPreferences pref=getApplicationContext().getSharedPreferences(myUser, MODE_PRIVATE);

        String[] taskArr = new String[pref.getAll().size()];
        int cnt=0;
        Map<String, ?> allTask = pref.getAll();

        for (Map.Entry<String, ?> singleTask : allTask.entrySet())
        {
            taskArr[cnt] = singleTask.getKey();
            cnt++;
        }

        TaskAdapter myTask = new TaskAdapter(context,taskArr,myUser);
        myList.setAdapter(myTask);
    }

    public void btnLogout(View v)
    {
        //declaration of shared preferences
        SharedPreferences pref=getApplicationContext().getSharedPreferences("myPref",MODE_PRIVATE);
        //declaration of editor
        SharedPreferences.Editor editor=pref.edit();
        //remove key user and pass
        editor.remove("userLogged");
        //commit changes
        editor.commit();
        //start another window - main window
        Intent iMain = new Intent(this,MainActivity.class);
        this.startActivity(iMain);
        finish();
    }

    public void btnAddTask(View view)
    {
        Intent iAddTask = new Intent(this, AddTask.class);
        iAddTask.putExtra("putUserTask", getIntent().getStringExtra("putUser"));
        this.startActivity(iAddTask);
        finish();
    }
}

//=========================================ADD TASK CLASS
package com.example.com.myshared;

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

public class AddTask extends Activity {

    EditText txtTask;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.add_task);
        txtTask = (EditText)findViewById(R.id.task_type);
    }

    public void btnConfirm(View view)
    {
        String myUser = getIntent().getStringExtra("putUserTask");
        SharedPreferences pref=getApplicationContext().getSharedPreferences(myUser, MODE_PRIVATE);
        SharedPreferences.Editor editor = pref.edit();

        String task = txtTask.getText().toString();
        editor.putString(task, "0");
        editor.commit();

        Intent iEntry = new Intent(this, Entry.class);
        iEntry.putExtra("putUser", myUser);
        this.startActivity(iEntry);
        finish();
    }


    public void btnCancelTask(View view)
    {
        SharedPreferences pref=getApplicationContext().getSharedPreferences("myPref",MODE_PRIVATE);
        Intent iEntry = new Intent(this, Entry.class);
        iEntry.putExtra("putUser", pref.getString("userLogged", "error"));
        this.startActivity(iEntry);
        finish();
    }
}

//============================================TASK ADAPTER CLASS
package com.example.com.myshared;

import android.content.Context;
import android.content.SharedPreferences;
import android.graphics.Color;
import android.view.Gravity;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.LinearLayout;
import android.widget.TextView;
import android.widget.Toast;


public class TaskAdapter extends BaseAdapter
{
    Context context;
    String myTask[];
    String myUser;

    public TaskAdapter(Context context,String myTask[], String myUser)
    {
        this.context=context;
        this.myTask=myTask;
        this.myUser=myUser;
    }
    @Override
    public int getCount() {
        return myTask.length;
    }

    @Override
    public Object getItem(int position) {
        return myTask[position];
    }

    @Override
    public long getItemId(int position) {
        return position;
    }

    @Override
    public View getView(final int position, View convertView, ViewGroup parent)
    {
        final SharedPreferences pref=context.getApplicationContext().getSharedPreferences(myUser, context.MODE_PRIVATE);
        final SharedPreferences.Editor editor = pref.edit();

        LinearLayout myLayout = new LinearLayout(context);
        myLayout.setOrientation(LinearLayout.VERTICAL);

        final TextView task = new TextView(context);
        task.setText(myTask[position]);
        task.setTextSize(32);
        task.setGravity(Gravity.CENTER_HORIZONTAL);
        task.setWidth(myLayout.getWidth() / 2);

        if(pref.getString(myTask[position], "error").equals("1"))
            task.setBackgroundColor(Color.GREEN);
        else
            task.setBackgroundColor(Color.RED);

        task.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                if(pref.getString(myTask[position], "error").equals("0")) {
                    editor.putString(myTask[position], "1");
                    editor.commit();
                    task.setBackgroundColor(Color.GREEN);
                    Toast.makeText(context, "The mission was successful ", Toast.LENGTH_SHORT).show();
                }
                else
                {
                    editor.putString(myTask[position], "0");
                    editor.commit();
                    task.setBackgroundColor(Color.RED);
                    Toast.makeText(context, "The mission not successful ", Toast.LENGTH_SHORT).show();
                }
            }
        });
        myLayout.addView(task);
        return myLayout;
    }
}
}