Lab7 SharedPreference Example (Part1)

 

Storing data to Shared Preferences 

1.    Create a new Android Project called SharedPrefExample with package mdad.localdata and Activity name: SharedPrefExample.

2.    Copy/replace activity_main.xml file with the code below:

<?xml version="1.0" encoding="utf-8"?>

<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

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


        <TextView
            android:id="@+id/tvPw"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Password"
            android:layout_marginLeft="100dp" />
        <EditText
            android:id="@+id/etPw"
            android:inputType="textPassword"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginLeft="100dp"
            android:ems="10" />
        <Button
            android:id="@+id/btnLogin"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginLeft="100dp"
            android:text="Login" />
    </LinearLayout>

</androidx.constraintlayout.widget.ConstraintLayout>

3.    Create 2 more activities called  setPassword  and DetailsActivity 

       Use the codes below to create the Layout for activity_set_password.xml

<?xml version="1.0" encoding="utf-8"?>

<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".setPassword">

    <LinearLayout
        android:id="@+id/linearLayout"
        android:layout_width="0dp"
        android:layout_height="0dp"
        android:orientation="vertical"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent">

        <TextView
            android:id="@+id/tvName"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginLeft="100dp"
            android:layout_marginTop="150dp"
            android:text="Your Name" />

        <EditText
            android:id="@+id/etName"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginLeft="100dp"
            android:ems="10" />

        <TextView
            android:id="@+id/tvPwd1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginLeft="100dp"
            android:text="Password" />

        <EditText
            android:id="@+id/etPwd1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginLeft="100dp"
            android:ems="10" />

        <TextView
            android:id="@+id/tvPwd2"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginLeft="100dp"
            android:text="Confirm Password" />

        <EditText
            android:id="@+id/etPwd2"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginLeft="100dp"
            android:ems="10"
            android:inputType="textPassword" />

        <Button
            android:id="@+id/btnSet"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginLeft="100dp"
            android:text="Set Password" />

    </LinearLayout>


</androidx.constraintlayout.widget.ConstraintLayout>

Use the codes below to create the Layout for activity_details.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".DetailsActivity">


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

    <TextView
        android:id="@+id/tvWelcome"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="horizontal">

        <Button
            android:id="@+id/btnLogOut"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center"
            android:layout_marginTop="20dp"
            android:text="Log Out" />

        <Button
            android:id="@+id/btnClearPassword"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center"
            android:layout_marginTop="20dp"
            android:text="Clear Password" />

    </LinearLayout>

</LinearLayout>
</androidx.constraintlayout.widget.ConstraintLayout>

3.    Edit MainActivity.java

Declare class variables

EditText pwd;
Button loginBtn;
SharedPreferences prf;
String sPassword;

    

inside the onCreate method, 

Do the binding

pwd = (EditText)findViewById(R.id.etPw);
loginBtn = (Button)findViewById(R.id.btnLogin);
    

inside the onCreate method, 

we read the data from sharedPreference loginDetails. 

check if the pw is null, if it is null we launch the activity setPassword

prf = getSharedPreferences("loginDetails",MODE_PRIVATE);// open from sharedPref

//if pw (password) is null means it has not been set or 
//it is the 1st time the user use the app and has not set the password yet
if  (prf.getString("pw",null) ==null)
{
    Toast.makeText(getApplicationContext(),"Empty",Toast.LENGTH_LONG).show();
    Intent nextPage = new Intent(MainActivity.this, setPassword.class);
    startActivity(nextPage);
    finish();
}
else{
    sPassword=prf.getString("pw",null); 
    //if not null , we read and store the pw in sPassword
}

    

Create a Login Button listener

if the user enter the password (password) is equal to the password from SharedPref (sPassword)

then we launch the DetailsActivity 

else

we just simply Toast a message (Credentials are not valid)

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

        String password = pwd.getText().toString(); //get text from user

        if( password.equals(sPassword) ){

            Toast.makeText(getApplicationContext(), "Login Successful",Toast.LENGTH_SHORT).show();
            Intent intent = new Intent(MainActivity.this,DetailsActivity.class);
            startActivity(intent);
            finish();
        }
        else
        {
            Toast.makeText(getApplicationContext(),"Credentials are not valid",Toast.LENGTH_SHORT).show();
        }
    }
});
    

Test it out

4.    Edit setPassword.java

Declare class variables

SharedPreferences pref;

EditText pwd1, pwd2, etName;
Button btnSetPW;  

inside the onCreate method, 

Do the binding

etName = (EditText)findViewById(R.id.etName);
pwd1 = (EditText)findViewById(R.id.etPwd1);
pwd2 = (EditText)findViewById(R.id.etPwd2);
btnSetPW= (Button)findViewById(R.id.btnSet);

Create a Button listener for SetPw button

btnSetPW.setOnClickListener(new View.OnClickListener() {

    @Override
    public void onClick(View view) {

      
    }
});

    

inside the onClick method, we set the values in SharedPreference

String name = etName.getText().toString(); //getText from user
String pw1 = pwd1.getText().toString();//getText from user
String pw2 = pwd2.getText().toString();//getText from user

if (pw1.equals(pw2)) {  //check if both pw1 and pw2 are the same

    pref = getSharedPreferences("loginDetails", MODE_PRIVATE); //Open sharedPreference
 
    SharedPreferences.Editor editor = pref.edit(); //set Editor mode
    editor.putString("sname", name);  
    editor.putString("pw", pw1);
    editor.commit();

    Intent nextPage = new Intent(setPassword.this, MainActivity.class);//goto next Activity
    startActivity(nextPage);
    finish();  //finish the current activity
}
else
{
    Toast.makeText(getApplicationContext(), "Your password & confirmation password do not match", Toast.LENGTH_LONG).show();
}

Test it out

5.    Edit DetailsActivity.java

Declare class variables

SharedPreferences prf;    

inside the onCreate method, 

Do the binding

TextView result = (TextView)findViewById(R.id.tvWelcome);
Button btnLogOut = (Button)findViewById(R.id.btnLogOut);
Button btnClearPw = (Button)findViewById(R.id.btnClearPassword);

read the data from sharedPreferences , loginDetails

prf = getSharedPreferences("loginDetails",MODE_PRIVATE);

result.setText("Hello, "+prf.getString("sname",null));

Create a Button listener for btnClearPw button

btnClearPw.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View v) {
        SharedPreferences.Editor editor = prf.edit(); //set edit mode
        editor.clear();
        editor.commit();

        Intent intent = new Intent(DetailsActivity.this,MainActivity.class);
        startActivity(intent);
    }
});

    

Create a Button listener for btnLogOut button

btnLogOut.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View v) {
       finish(); //finish the current activity

        Intent intent = new Intent(DetailsActivity.this,MainActivity.class);
        startActivity(intent);
    }
});
    

Test it out