package com.example.myfirstapp;

import android.content.Intent;
import android.content.SharedPreferences;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup;
import android.widget.CompoundButton;
import android.widget.CompoundButton.OnCheckedChangeListener;
import android.widget.ToggleButton;
import android.widget.TextView;
import static com.example.myfirstapp.R.id.toggle_text;
import static com.example.myfirstapp.R.string.change_font;


public class ShowAnOption extends AppCompatActivity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_show_an_option);
    SharedPreferences sharedPrefs = getSharedPreferences("com.example.xyz", MODE_PRIVATE);
    toggle.setChecked(sharedPrefs.getBoolean("NameOfThingToSave", true));
}

public void change_font(View v) {

    int fssize;

    if (toggle.isChecked())
    {
        SharedPreferences.Editor editor = getSharedPreferences("com.example.xyz", MODE_PRIVATE).edit();
        editor.putBoolean("NameOfThingToSave", true);
        editor.commit();
        fssize=20;
    }
    else
    {
        SharedPreferences.Editor editor = getSharedPreferences("com.example.xyz", MODE_PRIVATE).edit();
        editor.putBoolean("NameOfThingToSave", false);
        editor.commit();
        fssize=40;
    }

    Intent intent1 = new Intent (getBaseContext(), DisplayMessageActivity.class);
    intent1.putExtra("Font_Size", fssize);

}

}

package com.example.myfirstapp;

import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.ViewGroup;
import android.widget.TextView;

public class DisplayMessageActivity extends AppCompatActivity {

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

    Intent intent = getIntent();
    Intent intent1 = getIntent();
    String message = intent.getStringExtra(MainActivity.EXTRA_MESSAGE);
    int Font_Size = intent1.getIntExtra("Font_Size",50);
    TextView textView = new TextView(this);
    textView.setTextSize(Font_Size);
    textView.setText(message);

    ViewGroup layout = (ViewGroup) findViewById(R.id.activity_display_message);
    layout.addView(textView);
}
}

setOnCheckedChangeListener();
private void setOnCheckedChangeListener() {
    swAll.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
        public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
            if (isChecked) {
                Toast.makeText(MainActivity.this, "Switch On", Toast.LENGTH_SHORT).show();
                Intent intentSP = new Intent(MainActivity.this, SwitchActivity.class );
                Bundle extras = new Bundle();
                extras.putString("FONT","true" );
                intentSP.putExtras(extras);
                startActivity( intentSP );
            } else {
                Toast.makeText(MainActivity.this, "Switch Off", Toast.LENGTH_SHORT).show();
            }
        }
    });
}

Intent intentSP = getIntent();
    Bundle bundle = intentSP.getExtras();
    tORf = bundle.getString("FONT");
    doWhat(null);

public void doWhat(View view){
    if(tORf.equals("true")){
        chkBoxOne.setChecked(true);
    }else {
Toast.makeText( SwitchActivity.this, "NOT TRUE", Toast.LENGTH_LONG ).show();
    }
}