Crash: NullPointerException in NetworkService.java line 99

[vickychijwani]

java.lang.RuntimeException: Unable to start activity ComponentInfo{me.vickychijwani.spectre/me.vickychijwani.spectre.view.PostListActivity}: java.lang.RuntimeException: Could not dispatch event: class me.vickychijwani.spectre.event.LoadUserEvent to handler [EventHandler public void me.vickychijwani.spectre.network.NetworkService.onLoadUserEvent(me.vickychijwani.spectre.event.LoadUserEvent)]: Attempt to invoke interface method 'void me.vickychijwani.spectre.network.GhostApiService.getCurrentUser(retrofit.Callback)' on a null object reference
       at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2298)
       at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
       at android.app.ActivityThread.access$800(ActivityThread.java:144)
       at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
       at android.os.Handler.dispatchMessage(Handler.java:102)
       at android.os.Looper.loop(Looper.java:135)
       at android.app.ActivityThread.main(ActivityThread.java:5221)
       at java.lang.reflect.Method.invoke(Method.java)
       at java.lang.reflect.Method.invoke(Method.java:372)
       at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
       at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
Caused by: java.lang.RuntimeException: Could not dispatch event: class me.vickychijwani.spectre.event.LoadUserEvent to handler [EventHandler public void me.vickychijwani.spectre.network.NetworkService.onLoadUserEvent(me.vickychijwani.spectre.event.LoadUserEvent)]: Attempt to invoke interface method 'void me.vickychijwani.spectre.network.GhostApiService.getCurrentUser(retrofit.Callback)' on a null object reference
       at com.squareup.otto.Bus.throwRuntimeException(Bus.java:458)
       at com.squareup.otto.Bus.dispatch(Bus.java:388)
       at com.squareup.otto.Bus.dispatchQueuedEvents(Bus.java:369)
       at com.squareup.otto.Bus.post(Bus.java:338)
       at me.vickychijwani.spectre.view.PostListActivity.onCreate(PostListActivity.java:82)
       at android.app.Activity.performCreate(Activity.java:5933)
       at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1105)
       at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2251)
       at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
       at android.app.ActivityThread.access$800(ActivityThread.java:144)
       at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
       at android.os.Handler.dispatchMessage(Handler.java:102)
       at android.os.Looper.loop(Looper.java:135)
       at android.app.ActivityThread.main(ActivityThread.java:5221)
       at java.lang.reflect.Method.invoke(Method.java)
       at java.lang.reflect.Method.invoke(Method.java:372)
       at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
       at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
Caused by: java.lang.NullPointerException: Attempt to invoke interface method 'void me.vickychijwani.spectre.network.GhostApiService.getCurrentUser(retrofit.Callback)' on a null object reference
       at me.vickychijwani.spectre.network.NetworkService.onLoadUserEvent(NetworkService.java:99)
       at java.lang.reflect.Method.invoke(Method.java)
       at java.lang.reflect.Method.invoke(Method.java:372)
       at com.squareup.otto.EventHandler.handleEvent(EventHandler.java:89)
       at com.squareup.otto.Bus.dispatch(Bus.java:386)
       at com.squareup.otto.Bus.dispatchQueuedEvents(Bus.java:369)
       at com.squareup.otto.Bus.post(Bus.java:338)
       at me.vickychijwani.spectre.view.PostListActivity.onCreate(PostListActivity.java:82)
       at android.app.Activity.performCreate(Activity.java:5933)
       at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1105)
       at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2251)
       at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
       at android.app.ActivityThread.access$800(ActivityThread.java:144)
       at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
       at android.os.Handler.dispatchMessage(Handler.java:102)
       at android.os.Looper.loop(Looper.java:135)
       at android.app.ActivityThread.main(ActivityThread.java:5221)
       at java.lang.reflect.Method.invoke(Method.java)
       at java.lang.reflect.Method.invoke(Method.java:372)
       at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
       at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)

Crashlytics issue

[vickychijwani]

This occurs in the following scenario: when the app is in the background, the entire process may get killed, but activity back stack is maintained. So when the app is re-opened, Application#onCreate() is called again, which re-initializes the NetworkService, which sets mApi (and mAuthToken!) to null, which causes the NPE above.

See http://stackoverflow.com/a/14376919/504611 for more info. To reproduce, follow these steps: http://stackoverflow.com/a/18695974/504611, or: minimize the app and launch a few other apps, then lock the phone, unlock it after a minute and open the app again.

The obvious solution is to recreate mApi correctly on application startup, using the following algorithm:

1. When user logs in, record the fact in a persistent boolean flag
2. In Application#onCreate:
   • Construct and start the NetworkService
   • Now if we have a valid access token and the user was logged in, then recreate mApi using the access token
   • Else if we have the user's credentials and the user was logged in, then fire a LoginStartEvent
   • Else do nothing