Data Storage Schemes in Android-Shared preferences (Setting Font Size)

To Setting Dynamic Fonts Size in Android Activity Use “Shared Preferences”

1. Create a project SharedPreference and add the bellow code

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    >

    <SeekBar
        android:id="@+id/SeekBar01"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content" />

    <TextView
        android:id="@+id/TextView01"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="@string/hello" />

    <EditText
        android:id="@+id/EditText01"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content" />

    <Button
        android:id="@+id/btnSave"
        android:text="Save"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />

</LinearLayout>

package com.jetbrain.nazim.sharedpreferences;
//[changeable as your project package]

import android.app.Activity;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.SeekBar;
import android.widget.SeekBar.OnSeekBarChangeListener;
import android.widget.Toast;

public class SharedPreferencesActivity extends Activity {

    private SharedPreferences prefs;
    private String prefName = "MyPref";
    private EditText editText;
    private SeekBar seekBar;
    private Button btn;

    private static final String FONT_SIZE_KEY = "fontsize";
    private static final String TEXT_VALUE_KEY = "textvalue";

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_shared_preferences);

        editText = (EditText) findViewById(R.id.EditText01);
        seekBar = (SeekBar) findViewById(R.id.SeekBar01);
        btn = (Button) findViewById(R.id.btnSave);

        btn.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {

                //---get the SharedPreferences object---
                //prefs = getSharedPreferences(prefName, MODE_PRIVATE);
                prefs = getPreferences(MODE_PRIVATE);

                SharedPreferences.Editor editor = prefs.edit();

                //---save the values in the EditText view to preferences---
                editor.putFloat(FONT_SIZE_KEY, editText.getTextSize());
                editor.putString(TEXT_VALUE_KEY, editText.getText().toString());

                //---saves the values---
                editor.commit();

                //---display file saved message---
                Toast.makeText(getBaseContext(),
                        "Font size saved successfully!"+editText.getTextSize(),
                        Toast.LENGTH_SHORT).show();
            }
        });

        //---load the SharedPreferences object---
        //SharedPreferences prefs = getSharedPreferences(prefName, MODE_PRIVATE);
        prefs = getPreferences(MODE_PRIVATE);

        //---set the TextView font size to the previously saved values---
        float fontSize = prefs.getFloat(FONT_SIZE_KEY, 12);

        //---init the SeekBar and EditText---
        seekBar.setProgress((int) fontSize);
        editText.setText(prefs.getString(TEXT_VALUE_KEY, ""));
        editText.setTextSize(seekBar.getProgress());

        seekBar.setOnSeekBarChangeListener(new OnSeekBarChangeListener() {
            @Override
            public void onStopTrackingTouch(SeekBar seekBar) {
            }

            @Override
            public void onStartTrackingTouch(SeekBar seekBar) {
            }

            @Override
            public void onProgressChanged(SeekBar seekBar, int progress,
                                          boolean fromUser) {
                //---change the font size of the EditText---
                editText.setTextSize(progress);
            }
        });
    }
}

now run your project