如何为我的应用程序创建设置

Question

我正在开发一款可让用户打开/关闭某些特定功能的应用，例如Wi-Fi，蓝牙等。但我似乎无法做到这一点，首选项屏幕上的切换按钮没有响应我的设置java代码。这是我尝试过的事情

SettingsFragment.java

import android.content.Context;
import android.content.SharedPreferences;
import android.net.wifi.WifiManager;
import android.os.Bundle;
import android.preference.PreferenceFragment;


public class SettingsFragment extends PreferenceFragment implements SharedPreferences
        .OnSharedPreferenceChangeListener{
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        // Loads the XML preferences file.
        addPreferencesFromResource(R.xml.preferences);
    }

    public void onSharedPreferenceChanged(SharedPreferences preferences, String key) {

        if(key.equals(getString(R.string.wifi))){

            WifiManager wifiManager = (WifiManager)getActivity().getSystemService(Context.WIFI_SERVICE);
            wifiManager.setWifiEnabled(true);
        }
    }


}

preference.xml

<?xml version="1.0" encoding="utf-8"?>
<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android">
<PreferenceCategory android:title="Battery Saver Mode">
    <SwitchPreference
        android:defaultValue="true"
        android:key="battery_tone"
        android:title="@string/pref_title_new_message_notifications"/>

    <SwitchPreference
        android:defaultValue="true"
        android:title="@string/pref_bluetooth"
        android:key="@string/bluetooth"/>

    <SwitchPreference
        android:defaultValue="true"
        android:title="@string/pref_mobile_data"
        android:key="mobile_data"/>
    <SwitchPreference
        android:defaultValue="true"
        android:title="@string/pref_vibrate"
        android:key="vibrate"/>
    <SwitchPreference
        android:defaultValue="true"
        android:title="@string/pref_sync"
        android:key="sync"/>
    <SwitchPreference
        android:defaultValue="true"
        android:title="@string/pref_wifi"
        android:key="@string/wifi"/>
    <SwitchPreference
        android:defaultValue="true"
        android:title="@string/pref_airplane_mode"
        android:key="airmode"/>
</PreferenceCategory>
</PreferenceScreen>