activity_preference.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:padding="16dp"
    android:orientation="vertical">
    
    <EditText
        android:id="@+id/editName"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="Name"/>
    
    <Button
        android:id="@+id/buttonSend"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="send"/>

</LinearLayout>

SharedPreference.java

public class PreferenceActivity extends AppCompatActivity {

    private static final String KEY_NAME = "name";
    private static final String KEY_ID = "id";
    private static final String KEY_AGE = "age";

    private static final String PREFERENCES_NAME = "mcu";

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_preferences);
        // define shared preferences
        final SharedPreferences sharedPreferences =  getSharedPreferences(PREFERENCES_NAME, Context.MODE_PRIVATE);

        final EditText editName = (EditText) findViewById(R.id.editName);
        // get name data
        String name = sharedPreferences.getString(KEY_NAME, "default value");
        editName.setText(name);

        Button buttonSend = (Button) findViewById(R.id.buttonSend);
        buttonSend.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                // click event
                // shared preferences support type String int boolean float long String Set
                // saved name data
                sharedPreferences
                        .edit()
                        //key, value
                        .putString(KEY_NAME, editName.getText().toString())
                        .apply();
            }
        });
    }
}