PHP-Fusion Powered Website - Articles: 053 Java Android Program to Demonstrate Creating and Saving Shared Preferences

Here is source code of the Program to Demonstrate Creating and Saving Shared Preferences in Android. The program is successfully compiled and run on a Windows system using Eclipse Ide. The program output is also shown below.

Shared Preferences are a simple, lightweight name/value pair (NVP) mechanism for saving primitive application data, most commonly a user’s application preferences.

Creating And Saving Shared Preferences
Using the SharedPreferences class, you can create named maps of name/value pairs that can be persisted across sessions and shared among application components running within the same application sandbox.
To create or modify a Shared Preference, call getSharedPreferences on the current Context, passing in the name of the Shared Preference to change.

SharedPreferences mySharedPreferences = getSharedPreferences(MY_PREFS,
Activity.MODE_PRIVATE);

Shared Preferences are stored within the application’s sandbox, so they can be shared between an application’s components but aren’t available to other applications.
To modify a Shared Preference, use the SharedPreferences.Editor class. Get the Editor object by calling edit on the Shared Preferences object you want to change.

SharedPreferences.Editor editor = mySharedPreferences.edit();

Use the put methods to insert or update the values associated with the specified name:

// Store new primitive types in the shared preferences object.
editor.putBoolean(“isTrue”, true);
editor.putFloat(“lastFloat”, 1f);
editor.putInt(“wholeNumber”, 2);
editor.putLong(“aNumber”, 3l);
editor.putString(“textEntryValue”, “Not Empty”);

To save edits, call apply or commit on the Editor object to save the changes asynchronously or synchronously,
respectively.

// Commit the changes.
editor.apply();

Accessing Shared Prefernces
Accessing Shared Preferences, like editing and saving them, is done using the getSharedPreferences method
.
Use the type-safe get methods to extract saved values. Each getter takes a key and a default
value (used when no value has yet been saved for that key.)

// Retrieve the saved values.
boolean isTrue = mySharedPreferences.getBoolean(“isTrue”, false);
float lastFloat = mySharedPreferences.getFloat(“lastFloat”, 0f);
int wholeNumber = mySharedPreferences.getInt(“wholeNumber”, 1);
long aNumber = mySharedPreferences.getLong(“aNumber”, 0);
String stringPreference =
mySharedPreferences.getString(“textEntryValue”, “”);

You can return a map of all the available Shared Preferences keys values by calling getAll, and
check for the existence of a particular key by calling the contains method.

Map<String, ?> allPreferences = mySharedPreferences.getAll();
boolean containsLastFloat = mySharedPreferences.contains(“lastFloat”);

In this tutorial we create an application which stores a User name and email-id, using Shared-Preferences we save the data and retrieve the saved data ,as an example the user-name and user-password is hard-coded as test.

Main Activity

 
package com.example.sharedpreferences;
 
import java.util.HashMap;
 
import android.app.Activity;
import android.os.Bundle;
import android.text.Html;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;
 
public class MainActivity extends Activity {
 
    AlertDialogCreator alert = new AlertDialogCreator();
    SessionCreator session;
    Button Logout;
 
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        session = new SessionCreator(getApplicationContext());
 
        TextView lblName = (TextView) findViewById(R.id.lblName);
        TextView lblEmail = (TextView) findViewById(R.id.lblEmail);
 
        Logout = (Button) findViewById(R.id.Logout);
 
        Toast.makeText(getApplicationContext(),
                "User Login Status: " + session.isLoggedIn(), Toast.LENGTH_LONG)
                .show();
 
        session.checkLogin();
 
        HashMap<String, String> user = session.getUserDetails();
        String name = user.get(SessionCreator.KEY_NAME);
        String email = user.get(SessionCreator.KEY_EMAIL);
        lblName.setText(Html.fromHtml("Name: <b>" + name + "</b>"));
        lblEmail.setText(Html.fromHtml("Email: <b>" + email + "</b>"));
        Logout.setOnClickListener(new View.OnClickListener() {
 
            @Override
            public void onClick(View arg0) {
                session.logoutUser();
            }
        });
    }
}

AlertDialogCreator.java

 
package com.example.sharedpreferences;
 
import android.app.AlertDialog;
import android.content.Context;
import android.content.DialogInterface;
 
public class AlertDialogCreator {
 
    public void showAlertDialog(Context context, String title, String message,
            Boolean status) {
        AlertDialog alertDialog = new AlertDialog.Builder(context).create();
        alertDialog.setTitle(title);
        alertDialog.setMessage(message);
 
        if (status != null) {
            alertDialog
                    .setIcon((status) ? R.drawable.success : R.drawable.fail);
        }
        alertDialog.setButton("OK", new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog, int which) {
            }
        });
        alertDialog.show();
    }
}

SessionCreator.java

 
package com.example.sharedpreferences;
 
import java.util.HashMap;
 
import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.content.SharedPreferences;
import android.content.SharedPreferences.Editor;
 
public class SessionCreator {
    SharedPreferences pref;
    Editor editor;
    // an editor is used to edit your preferences
    Context context;
 
    // Shared Preference file name
    private static final String PREF_NAME = "Pref";
 
    // Shared Preferences Key
    private static final String IS_LOGIN = "IsLoggedIn";
 
    public static final String KEY_NAME = "name";
    public static final String KEY_EMAIL = "email";
 
    public SessionCreator(Context context) {
        this.context = context;
        /*
         * Setting the mode as Private so that the preferences should only be
         * used in this application and not by any other application
         * also the preferences can be Shared Globally by using -
         *Activity.MODE_WORLD_READABLE - to read Application components data
         *globally and,
         *Activity.MODE_WORLD_WRITEABLE -file can be written globally by any
         *other application. 
         */
 
 
        pref = context.getSharedPreferences(PREF_NAME, Activity.MODE_PRIVATE);
        /*
         * the same pref mode can be set to private by using 0 as a flag instead
         * of Acticity.MODE_PRIVATE
         */
        editor = pref.edit();
    }
 
    // Creating a login session
    public void createLoginSession(String name, String email) {
        editor.putBoolean(IS_LOGIN, true);
        editor.putString(KEY_NAME, name);
        editor.putString(KEY_EMAIL, email);
        editor.commit();
    }
 
    public void checkLogin() {
        // Check login status
        if (!this.isLoggedIn()) {
            // user is not logged in redirect to Login Activity
            Intent i = new Intent(context, Login.class);
            // Closing all the Activities
            i.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
 
            i.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
 
            context.startActivity(i);
        }
 
    }
 
    // Getting stored session data of user and returing this data as a HASH MAP
    public HashMap<String, String> getUserDetails() {
        HashMap<String, String> user = new HashMap<String, String>();
        // user name
        user.put(KEY_NAME, pref.getString(KEY_NAME, null));
 
        // user email id
        user.put(KEY_EMAIL, pref.getString(KEY_EMAIL, null));
        return user;
    }
 
    // Clearing a session data
    public void logoutUser() {
        editor.clear();
        editor.commit();
 
        Intent i = new Intent(context, Login.class);
        // Closing all the Activities
        i.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
 
        // Add new Flag to start new Activity
        i.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
 
        context.startActivity(i);
    }
 
    // Get Login State
    public boolean isLoggedIn() {
        return pref.getBoolean(IS_LOGIN, false);
    }
}

Login.java

package com.example.sharedpreferences;
 
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
 
public class Login extends Activity {
 
    EditText txtUsername, txtPassword;
    Button btnLogin;
 
    AlertDialogCreator alert = new AlertDialogCreator();
    SessionCreator session;
 
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);
        setContentView(R.layout.login);
        session = new SessionCreator(getApplicationContext());
 
        txtUsername = (EditText) findViewById(R.id.Username);
        txtPassword = (EditText) findViewById(R.id.Password);
 
        Toast.makeText(getApplicationContext(),
                "User Login Status: " + session.isLoggedIn(), Toast.LENGTH_LONG)
                .show();
 
        btnLogin = (Button) findViewById(R.id.Loginbutton);
 
        btnLogin.setOnClickListener(new View.OnClickListener() {
 
            @Override
            public void onClick(View arg0) {
                String username = txtUsername.getText().toString();
                String password = txtPassword.getText().toString();
 
                if (username.trim().length() > 0
                        && password.trim().length() > 0) {
                    if (username.equals("test") && password.equals("test")) {
                        session.createLoginSession("SanFoundry",
                                "sanfoundry@gmail.com");
                        Intent i = new Intent(getApplicationContext(),
                                MainActivity.class);
                        startActivity(i);
                        finish();
 
                    } else {
                        alert.showAlertDialog(Login.this, "Login failed",
                                "Username/Password is incorrect", false);
                    }
                } else {
                    alert.showAlertDialog(Login.this, "Login failed",
                            "Please enter username and password", false);
                }
 
            }
        });
    }
 
}

ActivityMain.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".MainActivity"
    android:orientation="vertical" >
 
    <TextView
        android:id="@+id/lblName"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_marginBottom="10dip"
        android:layout_marginTop="40dip"
        android:singleLine="true" />
 
    <TextView
        android:id="@+id/lblEmail"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_marginBottom="40dip"
        android:singleLine="true" />
 
    <Button
        android:id="@+id/Logout"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/lblName"
        android:layout_alignParentBottom="true"
        android:layout_marginBottom="95dp"
        android:text="Logout" />
 
</LinearLayout>

Login.xml

 
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >
 
    <TextView
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_marginBottom="5dip"
        android:singleLine="true"
        android:text="Username" />
 
    <EditText
        android:id="@+id/Username"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_marginBottom="10dip" />
 
    <TextView
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_marginBottom="5dip"
        android:text="Password" />
 
    <EditText
        android:id="@+id/Password"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_marginBottom="20dip"
        android:password="true"
        android:singleLine="true" />
 
    <Button
        android:id="@+id/Loginbutton"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="Login" />
 
</LinearLayout>

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.sharedpreferences"
    android:versionCode="1"
    android:versionName="1.0" >
 
    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="17" />
 
    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="com.example.sharedpreferences.MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
 
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity
            android:name="com.example.sharedpreferences.Login"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.Login" />
 
                <category android:name="android.intent.category.DEFAULT" />
            </intent-filter>
        </activity>
    </application>
 
</manifest>

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053 Java Android Program to Demonstrate Creating and Saving Shared Preferences

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