加载活动时，根据情况将开关设置为关闭

Question

I have a switch on my actionbar (or anywhere in the activity page) which I like to set to either On or Off depending on the wifi status.
If phone's wifi is on, I'd like to have the switch set to On and if it's off then to Off.

I tried placing the code below to onCreate, onStart - but the it causes the app to crash.

switchWifiToggle.setChecked(Wifi.Enabled());

I am new to android/java otherwise I'd share the stack trace.
There are ton's and ton's of information on the logcat, so I'm not sure what exactly to share here (I am a .NET guy).

Registering to BroadcastReceiver will not help, as I want the switch to set to the right state while the app is loading (or done loading).

The image here uses the switch as a Master Switch - I want to set the state of this switch once the app is loaded somewhere, similar to onCreate or onStart or...

Thanks

Update: Stack trace added

02-06 09:15:39.943     632-1066/? E/LocSvc_IzatApiV02﹕ W/virtual int izat_core::IzatApiV02::injectLocation(GpsExtLocation):665]: error! inject position failed
02-06 09:15:39.963     632-1066/? E/LocSvc_ApiV02﹕ W/virtual loc_api_adapter_err LocApiV02::injectPosition(double, double, float):492]: error! status = eLOC_CLIENT_FAILURE_INVALID_PARAMETER, inject_pos_ind.status = UNKNOWN
02-06 09:15:40.063  16882-16882/com.learn.wifitwo E/WiFiMainActivity﹕ +++ ON CREATE +++
02-06 09:15:40.113  16882-16882/com.learn.wifitwo E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.learn.wifitwo, PID: 16882
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.learn.wifitwo/com.learn.wifitwo.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'boolean com.learn.wifitwo.WiFi.IsEnabled()' on a null object reference
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
        at android.app.ActivityThread.access$800(ActivityThread.java:135)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
        at android.os.Handler.dispatchMessage(Handler.java:102)
        at android.os.Looper.loop(Looper.java:136)
        at android.app.ActivityThread.main(ActivityThread.java:5017)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
 Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'boolean com.learn.wifitwo.WiFi.IsEnabled()' on a null object reference
        at com.learn.wifitwo.MainActivity.onCreate(MainActivity.java:99)
        at android.app.Activity.performCreate(Activity.java:5231)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
        at android.app.ActivityThread.access$800(ActivityThread.java:135)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
        at android.os.Handler.dispatchMessage(Handler.java:102)
        at android.os.Looper.loop(Looper.java:136)
        at android.app.ActivityThread.main(ActivityThread.java:5017)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)

Answer 1

'boolean com.learn.wifitwo.WiFi.IsEnabled()' I am guessing that you have null WiFi null object. Before you invoke IsEnabled method you should initialize your Object :) I dont know what is the name of object but I can presume it might be that

 protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);

         WiFi wifiObject = new WiFi();
        switchWifiToggle.setChecked(wifiObject.isEnabled());

     } 

or made Enabled method in class WiFi a static one then you can use it like that

 protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);

        switchWifiToggle.setChecked(WiFI.isEnabled());

     }