DisconnectDevice crashes app

[Yenthe666]

Hi guys,

First of all, great project! It works pretty good but I'm now having a problem when I want to disconnect my BLE device.

        public DeviceList (IAdapter adapter)
        {
            InitializeComponent ();
            StartUpJobs(adapter);
            MessagingCenter.Subscribe<CharacteristicDetail_TISensor>(this, "DisconnectDeviceAndRefreshDevices", (sender) =>
            {
                //This prints the name of the device I'm connected with.
                DisplayAlert("Props", "Name: " + currentDevice.Name, "ok");
                //Disconnect it
                adapter.DisconnectDevice(currentDevice);
                StartUpJobs(adapter);
            });
        }

The variable currentDevice gets filled in another method:

 void ServiceList(IAdapter adapter, IDevice device)
        {
this.serviceListadapter = adapter;
            this.serviceListdevice = device;
            this.services = new ObservableCollection<IService>();
            //listView.ItemsSource = services;

            if (services.Count == 0)
            {
                Debug.WriteLine("No services, attempting to connect to device");
                // start looking for the device
                adapter.ConnectToDevice(device);
                currentDevice = device;
            }
         }

When the user clicks on a device he goes to a detailpage. When the user then presses the back button I use the MessageCenter to notify my page to do something:
CharacteristicDetail_TISensor.xaml.cs:

        protected override bool OnBackButtonPressed()
        {
            base.OnBackButtonPressed();
            Xamarin.Forms.MessagingCenter.Send<CharacteristicDetail_TISensor>(this, "DisconnectDeviceAndRefreshDevices");
            Navigation.PopModalAsync();
            return false;
        }

When I execute my app it will crash on this line:

adapter.DisconnectDevice(currentDevice);

Error log:

[MonoDroid] UNHANDLED EXCEPTION:
[MonoDroid] System.NullReferenceException: Object reference not set to an instance of an object
[MonoDroid] at Robotics.Mobile.Core.Bluetooth.LE.Device.Disconnect () <0x00018>
[MonoDroid] at Robotics.Mobile.Core.Bluetooth.LE.Adapter.DisconnectDevice (Robotics.Mobile.Core.Bluetooth.LE.IDevice) <0x0004b>
[MonoDroid] at Robotics.Mobile.BtLEExplorer.DeviceList/<>c__DisplayClass0.<.ctor>b__1 (Robotics.Mobile.BtLEExplorer.CharacteristicDetail_TISensor) <0x0007f>
[MonoDroid] at Xamarin.Forms.MessagingCenter/<>c__DisplayClass4`1<Robotics.Mobile.BtLEExplorer.CharacteristicDetail_TISensor>.<Subscribe>b__3 (object,object) <0x00097>
[MonoDroid] at Xamarin.Forms.MessagingCenter.InnerSend (string,System.Type,System.Type,object,object) <0x0013b>
[MonoDroid] at Xamarin.Forms.MessagingCenter.Send<Robotics.Mobile.BtLEExplorer.CharacteristicDetail_TISensor> (Robotics.Mobile.BtLEExplorer.CharacteristicDetail_TISensor,string) <0x00047>
[MonoDroid] at Robotics.Mobile.BtLEExplorer.CharacteristicDetail_TISensor.OnBackButtonPressed () <0x0002b>
[MonoDroid] at Xamarin.Forms.Page.SendBackButtonPressed () <0x0001f>
[MonoDroid] at Xamarin.Forms.NavigationPage.OnBackButtonPressed () <0x0001f>
[MonoDroid] at Xamarin.Forms.Page.SendBackButtonPressed () <0x0001f>
[MonoDroid] at Xamarin.Forms.Platform.Android.Platform.HandleBackPressed (object,System.EventArgs) <0x0005f>
[MonoDroid] at Xamarin.Forms.Platform.Android.FormsApplicationActivity.OnBackPressed () <0x0004b>
[MonoDroid] at Android.App.Activity.n_OnBackPressed (intptr,intptr) <0x00037>
[MonoDroid] at (wrapper dynamic-method) object.9a29b4dc-78cd-4d75-abb3-df0633e117be (intptr,intptr) <0x0003b>
[art] JNI RegisterNativeMethods: attempt to register 0 native methods for md52ce486a14f4bcd95899665e9d932190b.JavaProxyThrowable
[InputEventSender] Exception dispatching finished signal.
[MessageQueue-JNI] Exception in MessageQueue callback: handleReceiveCallback
[MessageQueue-JNI] md52ce486a14f4bcd95899665e9d932190b.JavaProxyThrowable: System.NullReferenceException: Object reference not set to an instance of an object
[MessageQueue-JNI] at Robotics.Mobile.Core.Bluetooth.LE.Device.Disconnect () <0x00018>
[MessageQueue-JNI] at Robotics.Mobile.Core.Bluetooth.LE.Adapter.DisconnectDevice (Robotics.Mobile.Core.Bluetooth.LE.IDevice) <0x0004b>
[MessageQueue-JNI] at Robotics.Mobile.BtLEExplorer.DeviceList/<>c__DisplayClass0.<.ctor>b__1 (Robotics.Mobile.BtLEExplorer.CharacteristicDetail_TISensor) <0x0007f>
[MessageQueue-JNI] at Xamarin.Forms.MessagingCenter/<>c__DisplayClass4`1<Robotics.Mobile.BtLEExplorer.CharacteristicDetail_TISensor>.<Subscribe>b__3 (object,object) <0x00097>
[MessageQueue-JNI] at Xamarin.Forms.MessagingCenter.InnerSend (string,System.Type,System.Type,object,object) <0x0013b>
[MessageQueue-JNI] at Xamarin.Forms.MessagingCenter.Send<Robotics.Mobile.BtLEExplorer.CharacteristicDetail_TISensor> (Robotics.Mobile.BtLEExplorer.CharacteristicDetail_TISensor,string) <0x00047>
[MessageQueue-JNI] at Robotics.Mobile.BtLEExplorer.CharacteristicDetail_TISensor.OnBackButtonPressed () <0x0002b>
[MessageQueue-JNI] at Xamarin.Forms.Page.SendBackButtonPressed () <0x0001f>
[MessageQueue-JNI] at Xamarin.Forms.NavigationPage.OnBackButtonPressed () <0x0001f>
[MessageQueue-JNI] at Xamarin.Forms.Page.SendBackButtonPressed () <0x0001f>
[MessageQueue-JNI] at Xamarin.Forms.Platform.Android.Platform.HandleBackPressed (object,System.EventArgs) <0x0005f>
[MessageQueue-JNI] at Xamarin.Forms.Platform.Android.FormsApplicationActivity.OnBackPressed () <0x0004b>
[MessageQueue-JNI] at Android.App.Activity.n_OnBackPressed (intptr,intptr) <0x00037>
[MessageQueue-JNI] at (wrapper dynamic-method) object.9a29b4dc-78cd-4d75-abb3-df0633e117be (intptr,intptr) <0x0003b>
[MessageQueue-JNI] 
[MessageQueue-JNI]  at md5530bd51e982e6e7b340b73e88efe666e.FormsApplicationActivity.n_onBackPressed(Native Method)
[MessageQueue-JNI]  at md5530bd51e982e6e7b340b73e88efe666e.FormsApplicationActivity.onBackPressed(FormsApplicationActivity.java:94)
[MessageQueue-JNI]  at android.app.Activity.onKeyUp(Activity.java:2456)
[MessageQueue-JNI]  at android.view.KeyEvent.dispatch(KeyEvent.java:2643)
[MessageQueue-JNI]  at android.app.Activity.dispatchKeyEvent(Activity.java:2707)
[MessageQueue-JNI]  at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchKeyEvent(PhoneWindow.java:2276)
[MessageQueue-JNI]  at android.view.ViewRootImpl$ViewPostImeInputStage.processKeyEvent(ViewRootImpl.java:4020)
[MessageQueue-JNI]  at android.view.ViewRootImpl$ViewPostImeInputStage.onProcess(ViewRootImpl.java:3982)
[MessageQueue-JNI]  at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3544)
[MessageQueue-JNI]  at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:3597)
[MessageQueue-JNI]  at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:3563)
[MessageQueue-JNI]  at android.view.ViewRootImpl$AsyncInputStage.forward(ViewRootImpl.java:3680)
[MessageQueue-JNI]  at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:3571)
[MessageQueue-JNI]  at android.view.ViewRootImpl$AsyncInputStage.apply(ViewRootImpl.java:3737)
[MessageQueue-JNI]  at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3544)
[MessageQueue-JNI]  at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:3597)
[MessageQueue-JNI]  at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:3563)
[MessageQueue-JNI]  at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:3571)
[MessageQueue-JNI]  at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3544)
[MessageQueue-JNI]  at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:3597)
[MessageQueue-JNI]  at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:3563)
[MessageQueue-JNI]  at android.view.ViewRootImpl$AsyncInputStage.forward(ViewRootImpl.java:3713)
[MessageQueue-JNI]  at android.view.ViewRootImpl$ImeInputStage.onFinishedInputEvent(ViewRootImpl.java:3874)
[MessageQueue-JNI]  at android.view.inputmethod.InputMethodManager$PendingEvent.run(InputMethodManager.java:2208)
[MessageQueue-JNI]  at android.view.inputmethod.InputMethodManager.invokeFinishedInputEventCallback(InputMethodManager.java:1849)
[MessageQueue-JNI]  at android.view.inputmethod.InputMethodManager.finishedInputEvent(InputMethodManager.java:1840)
[MessageQueue-JNI]  at android.view.inputmethod.InputMethodManager$ImeInputEventSender.onInputEventFinished(InputMethodManager.java:2185)
[MessageQueue-JNI]  at android.view.InputEventSender.dispatchInputEventFinished(InputEventSender.java:141)
[MessageQueue-JNI]  at android.os.MessageQueue.nativePollOnce(Native Method)
[MessageQueue-JNI]  at android.os.MessageQueue.next(MessageQueue.java:143)
[MessageQueue-JNI]  at android.os.Looper.loop(Looper.java:122)
[MessageQueue-JNI]  at android.app.ActivityThread.main(ActivityThread.java:5254)
[MessageQueue-JNI]  at 
[AndroidRuntime] Shutting down VM
[AndroidRuntime] FATAL EXCEPTION: main
[AndroidRuntime] Process: Robotics.Mobile.BtLEExplorer.Droid, PID: 18171
[AndroidRuntime] java.lang.RuntimeException: java.lang.reflect.InvocationTargetException
[AndroidRuntime]    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
[AndroidRuntime] Caused by: java.lang.reflect.InvocationTargetException
[AndroidRuntime]    at java.lang.reflect.Method.invoke(Native Method)
[AndroidRuntime]    at java.lang.reflect.Method.invoke(Method.java:372)
[AndroidRuntime]    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
[AndroidRuntime]    ... 1 more
[AndroidRuntime] Caused by: md52ce486a14f4bcd95899665e9d932190b.JavaProxyThrowable: System.NullReferenceException: Object reference not set to an instance of an object
[AndroidRuntime] at Robotics.Mobile.Core.Bluetooth.LE.Device.Disconnect () <0x00018>
[AndroidRuntime] at Robotics.Mobile.Core.Bluetooth.LE.Adapter.DisconnectDevice (Robotics.Mobile.Core.Bluetooth.LE.IDevice) <0x0004b>
[AndroidRuntime] at Robotics.Mobile.BtLEExplorer.DeviceList/<>c__DisplayClass0.<.ctor>b__1 (Robotics.Mobile.BtLEExplorer.CharacteristicDetail_TISensor) <0x0007f>
[AndroidRuntime] at Xamarin.Forms.MessagingCenter/<>c__DisplayClass4`1<Robotics.Mobile.BtLEExplorer.CharacteristicDetail_TISensor>.<Subscribe>b__3 (object,object) <0x00097>
...

[Yenthe666]

Well, turns out this was partially my issue. You cannot disconnect on the adapter from the DeviceList etc but only when you're in ServiceList. But still, this should be fixed I assume.