Encryption Wrapper for Android SharedPreferences

/*
 * Copyright (C) 2013, Daniel Abraham
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.example.securepreferences;

import android.content.SharedPreferences;
import android.content.SharedPreferences.Editor;
import android.os.Bundle;
import android.preference.CheckBoxPreference;
import android.preference.EditTextPreference;
import android.preference.ListPreference;
import android.preference.PreferenceActivity;
import android.preference.PreferenceManager;

import java.util.Map.Entry;

public class OldPreferenceActivity extends PreferenceActivity {

    private SharedPreferences mInsecurePrefs;
    private SharedPreferences mSecurePrefs;

    private CheckBoxPreference mCheckBox;
    private EditTextPreference mText;
    private ListPreference mList;

    @Override
    @SuppressWarnings("deprecation")
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        addPreferencesFromResource(R.xml.preferences);

        mInsecurePrefs = PreferenceManager.getDefaultSharedPreferences(this);
        mSecurePrefs = new SecurePreferences(this);

        mCheckBox = (CheckBoxPreference) findPreference(getString(R.string.checkbox_key));
        mText = (EditTextPreference) findPreference(getString(R.string.text_key));
        mList = (ListPreference) findPreference(getString(R.string.list_key));
    }

    @Override
    public void onStart() {
        super.onStart();

        // Decrypt relevant key/value pairs, if they exist
        for (Entry<String, ?> entry : mSecurePrefs.getAll().entrySet()) {
            final String key = entry.getKey();
            if (key == null) {
                continue;
            } else if (key.equals(getString(R.string.checkbox_key))) {
                mCheckBox.setChecked(mSecurePrefs.getBoolean(key, false));
            } else if (key.equals(getString(R.string.text_key))) {
                mText.setText(mSecurePrefs.getString(key, null));
            } else if (key.equals(getString(R.string.list_key))) {
                final int value = Integer.parseInt(mSecurePrefs.getString(key, null));
                mList.setValueIndex(value - 1); // Zero based index = selection value - 1
            }
        }
    }

    @Override
    public void onStop() {
        super.onStop();

        // Replace unencrypted key/value pairs with encrypted ones
        final Editor insecureEditor = mInsecurePrefs.edit();
        final Editor secureEditor = mSecurePrefs.edit();
        String key = getString(R.string.checkbox_key);
        if (mInsecurePrefs.contains(key)) {
            secureEditor.putBoolean(key, mInsecurePrefs.getBoolean(key, false));
            insecureEditor.remove(key);
        }
        key = getString(R.string.text_key);
        if (mInsecurePrefs.contains(key)) {
            secureEditor.putString(key, mInsecurePrefs.getString(key, null));
            insecureEditor.remove(key);
        }
        key = getString(R.string.list_key);
        if (mInsecurePrefs.contains(key)) {
            secureEditor.putString(key, mInsecurePrefs.getString(key, null));
            insecureEditor.remove(key);
        }
        insecureEditor.commit();
        secureEditor.commit();
    }
}