Android Sharedpreferences Complete Guide

Step 1: Set Up Your Android Project

First, create a new project in Android Studio.

1. Open Android Studio and choose "Start a new Android Studio project."
2. Choose "Empty Activity" and click "Next."
3. Enter your project name, package name, and save location.
4. Choose the language (Java/Kotlin) and select a minimum API level.
5. Click "Finish" to create your project.

Step 2: Create Your Layout

Next, we'll design a simple layout to use in our example. Open res/layout/activity_main.xml and modify it as shown below:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:padding="16dp">

    <EditText
        android:id="@+id/editTextName"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="Enter your name"
        android:inputType="textPersonName"/>

    <Button
        android:id="@+id/buttonSave"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Save"
        android:layout_below="@id/editTextName"
        android:layout_marginTop="16dp"/>

    <TextView
        android:id="@+id/textViewName"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Your Name:"
        android:layout_below="@id/buttonSave"
        android:layout_marginTop="16dp"/>

</RelativeLayout>

Step 3: Implement SharedPreferences in MainActivity

Now we will use SharedPreferences to save and retrieve the name from the EditText field.

Using Java:

package com.example.sharedpreferencesexample;

import androidx.appcompat.app.AppCompatActivity;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {

    private EditText editTextName;
    private Button buttonSave;
    private TextView textViewName;

    // Name of the SharedPreferences file
    private static final String PREFS_NAME = "MyPrefsFile";

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

        editTextName = findViewById(R.id.editTextName);
        buttonSave = findViewById(R.id.buttonSave);
        textViewName = findViewById(R.id.textViewName);

        // Load the name from SharedPreferences
        SharedPreferences settings = getSharedPreferences(PREFS_NAME, MODE_PRIVATE);
        String name = settings.getString("Name", "No name entered");
        textViewName.append(" " + name);

        buttonSave.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String name = editTextName.getText().toString();
                // Save the name to SharedPreferences
                SharedPreferences settings = getSharedPreferences(PREFS_NAME, MODE_PRIVATE);
                SharedPreferences.Editor editor = settings.edit();
                editor.putString("Name", name);
                editor.apply(); // or editor.commit();

                // Update the TextView
                textViewName.setText("Your Name: " + name);
            }
        });
    }
}

Using Kotlin:

package com.example.sharedpreferencesexample

import android.content.SharedPreferences
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import kotlinx.android.synthetic.main.activity_main.*

class MainActivity : AppCompatActivity() {

    // Name of the SharedPreferences file
    private val PREFS_NAME = "MyPrefsFile"

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        // Load the name from SharedPreferences
        val settings: SharedPreferences = getSharedPreferences(PREFS_NAME, MODE_PRIVATE)
        val name: String = settings.getString("Name", "No name entered") ?: "No name entered"
        textViewName.text = "Your Name: $name"

        buttonSave.setOnClickListener {
            val name: String = editTextName.text.toString()
            // Save the name to SharedPreferences
            val settings: SharedPreferences = getSharedPreferences(PREFS_NAME, MODE_PRIVATE)
            val editor: SharedPreferences.Editor = settings.edit()
            editor.putString("Name", name)
            editor.apply() // or editor.commit()

            // Update the TextView
            textViewName.text = "Your Name: $name"
        }
    }
}

Step 4: Run Your Application

Run the application on an emulator or a physical device.

1. Connect your device or start an emulator.
2. Click the "Run" button in Android Studio.
3. Enter your name in the EditText field.
4. Click the "Save" button.
5. The name should be displayed in the TextView.
6. Close the app and reopen it. The saved name should still be displayed, demonstrating that SharedPreferences has stored the data.

Summary

You have just implemented SharedPreferences in your Android application, allowing you to save and retrieve small amounts of data even when the app is closed and reopened. SharedPreferences is ideal for scenarios where you need to persist user preferences or settings. You can expand on this by saving other types of data, such as Boolean values, integers, floats, longs, or sets of strings.