Fix switch to VPN button in Snackbar

mobile/src/main/scala/com/github/shadowsocks/GlobalConfigFragment.scala

@@ -20,13 +20,16 @@
 
 package com.github.shadowsocks
 
+import android.content.SharedPreferences
+import android.content.SharedPreferences.OnSharedPreferenceChangeListener
 import android.os.Bundle
 import android.support.design.widget.Snackbar
 import android.support.v14.preference.SwitchPreference
 import be.mygod.preference.PreferenceFragment
 import com.github.shadowsocks.utils.{Key, TcpFastOpen}
+import com.github.shadowsocks.ShadowsocksApplication.app
 
-class GlobalConfigFragment extends PreferenceFragment {
+class GlobalConfigFragment extends PreferenceFragment with OnSharedPreferenceChangeListener {
   override def onCreatePreferences(bundle: Bundle, key: String) {
     addPreferencesFromResource(R.xml.pref_global)
     val switch = findPreference(Key.isAutoConnect).asInstanceOf[SwitchPreference]
@@ -53,5 +56,16 @@ class GlobalConfigFragment extends PreferenceFragment {
       tfo.setEnabled(false)
       tfo.setSummary(getString(R.string.tcp_fastopen_summary_unsupported, java.lang.System.getProperty("os.version")))
     }
+    app.settings.registerOnSharedPreferenceChangeListener(this)
+  }
+
+  override def onDestroy() {
+    app.settings.unregisterOnSharedPreferenceChangeListener(this)
+    super.onDestroy()
+  }
+
+  def onSharedPreferenceChanged(pref: SharedPreferences, key: String): Unit = key match {
+    case Key.isNAT => findPreference(key).asInstanceOf[SwitchPreference].setChecked(pref.getBoolean(key, false))
+    case _ =>
   }
 }

mobile/src/main/scala/com/github/shadowsocks/MainActivity.scala

@@ -170,7 +170,7 @@ class MainActivity extends Activity with ServiceBoundContext with Drawer.OnDrawe
   override def onServiceDisconnected(): Unit = changeState(State.IDLE)
 
   private def addDisableNatToSnackbar(snackbar: Snackbar) = snackbar.setAction(R.string.switch_to_vpn, (_ =>
-    if (state == State.STOPPED) app.editor.putBoolean(Key.isNAT, false)): View.OnClickListener)
+    if (state == State.STOPPED) app.editor.putBoolean(Key.isNAT, false).apply()): View.OnClickListener)
 
   override def binderDied() {
     detachService()