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

    <!--Edit text for getting user input-->
    <EditText
        android:id="@+id/idEdtMessage"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginStart="10dp"
        android:layout_marginTop="50dp"
        android:layout_marginEnd="10dp"
        android:hint="Enter your message" />

    <!--button for saving data-->
    <Button
        android:id="@+id/idBtnSaveData"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginStart="10dp"
        android:layout_marginTop="40dp"
        android:layout_marginEnd="10dp"
        android:text="Save Data"
        android:textAllCaps="false" />

</LinearLayout>

package com.example.gfgpagination;

import android.content.Context;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.text.TextUtils;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

import androidx.appcompat.app.AppCompatActivity;

public class MainActivity extends AppCompatActivity {
    // creating constant keys for shared preferences.
    public static final String SHARED_PREFS = "shared_prefs";
    // key for storing email.
    public static final String MESSAGE_KEY = "message_key";
    // variable for shared preferences.
    SharedPreferences sharedpreferences;
    // creating variables for our edit text and button.
    private EditText messageEdt;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        // getting the data which is stored in shared preferences.
        sharedpreferences = getSharedPreferences(SHARED_PREFS, Context.MODE_PRIVATE);
        // initializing our variables.
        messageEdt = findViewById(R.id.idEdtMessage);
        Button saveBtn = findViewById(R.id.idBtnSaveData);
        // adding on click listener for our button.
        saveBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                // inside on click we are checking if the entered data
                // by user is empty or not.
                String msg = messageEdt.getText().toString();
                if (TextUtils.isEmpty(msg)) {
                    // if the input is empty we are displaying a toast message.
                    Toast.makeText(MainActivity.this, "Please enter your message", Toast.LENGTH_SHORT).show();
                } else {
                    // if the input is not empty we are calling a method to save
                    // data to shared prefs.
                    saveMessage(msg);
                }
            }
        });
    }

    private void saveMessage(String msg) {
        SharedPreferences.Editor editor = sharedpreferences.edit();
        // below lines will put values for
        // message in shared preferences.
        editor.putString(MESSAGE_KEY, msg);
        // to save our data with key and value.
        editor.apply();
        // on below line we are displaying a toast message after adding data to shared prefs.
        Toast.makeText(this, "Message saved to Shared Preferences", Toast.LENGTH_SHORT).show();
        // after that we are setting our edit text to empty
        messageEdt.setText("");
    }
}