Android NullPointerException in ItemDetail Fragment when setting title

Question

I don't know why but I get reports that many of my users get a NullPointerException in This line: appBarLayout.setTitle("אזעקה (" + mItem.datetime + ")");

I've tried many things to catch this exception but I just can't figure out how it reaches this line and gets a NullPointerException.

First I made sure that appBarLayout isn't null. Then I checked that my mItem.datetime does contain the datetime that it should.

Here is my code:

    mItem = AlertsDetails.items_map.get(getArguments().getString(ARG_ITEM_ID));

    Activity activity = this.getActivity();

    if (mItem == null || mItem.datetime == null)
    {
        activity.finish();
    }

    CollapsingToolbarLayout appBarLayout = (CollapsingToolbarLayout) activity.findViewById(R.id.toolbar_layout);
    if (appBarLayout != null) {
        appBarLayout.setTitle("אזעקה (" + mItem.datetime + ")");
        appBarLayout.setBackgroundResource(R.mipmap.alert_background);
    }

What did I miss here? How is that possible that both appBarLayout and mItem.datetime aren't null but yet the setTitle method creates a NullPointerException?

These are the error logs I get:

java.lang.RuntimeException: 
  at android.app.ActivityThread.performLaunchActivity (ActivityThread.java:2955)
  at android.app.ActivityThread.handleLaunchActivity (ActivityThread.java:3030)
  at android.app.ActivityThread.-wrap11 (Unknown Source)
  at android.app.ActivityThread$H.handleMessage (ActivityThread.java:1696)
  at android.os.Handler.dispatchMessage (Handler.java:105)
  at android.os.Looper.loop (Looper.java:164)
  at android.app.ActivityThread.main (ActivityThread.java:6938)
  at java.lang.reflect.Method.invoke (Native Method)
  at com.android.internal.os.Zygote$MethodAndArgsCaller.run (Zygote.java:327)
  at com.android.internal.os.ZygoteInit.main (ZygoteInit.java:1374)
Caused by: java.lang.NullPointerException: 
  at com.morha.cumtaalerts.fragments.ItemDetailFragment.onCreate (ItemDetailFragment.java:63)
  at android.support.v4.app.Fragment.performCreate (Fragment.java:2328)
  at android.support.v4.app.FragmentManagerImpl.moveToState (FragmentManager.java:1379)
  at android.support.v4.app.FragmentTransition.addToFirstInLastOut (FragmentTransition.java:1188)
  at android.support.v4.app.FragmentTransition.calculateFragments (FragmentTransition.java:1071)
  at android.support.v4.app.FragmentTransition.startTransitions (FragmentTransition.java:115)
  at android.support.v4.app.FragmentManagerImpl.executeOpsTogether (FragmentManager.java:2379)
  at android.support.v4.app.FragmentManagerImpl.removeRedundantOperationsAndExecute (FragmentManager.java:2337)
  at android.support.v4.app.FragmentManagerImpl.execPendingActions (FragmentManager.java:2244)
  at android.support.v4.app.FragmentManagerImpl.dispatchStateChange (FragmentManager.java:3255)
  at android.support.v4.app.FragmentManagerImpl.dispatchActivityCreated (FragmentManager.java:3205)
  at android.support.v4.app.FragmentController.dispatchActivityCreated (FragmentController.java:195)
  at android.support.v4.app.FragmentActivity.onStart (FragmentActivity.java:597)
  at android.support.v7.app.AppCompatActivity.onStart (AppCompatActivity.java:177)
  at android.app.Instrumentation.callActivityOnStart (Instrumentation.java:1340)
  at android.app.Activity.performStart (Activity.java:7191)
  at android.app.ActivityThread.performLaunchActivity (ActivityThread.java:2918)

Thank you!

Possible duplicate of [What is a NullPointerException, and how do I fix it?](https://stackoverflow.com/questions/218384/what-is-a-nullpointerexception-and-how-do-i-fix-it) — ADM, Jun 06 '18 at 14:35

score 1 · Accepted Answer · answered Jun 06 '18 at 13:36

1

Add return; after you finish the Activity:

if (mItem == null || mItem.datetime == null)
{
    activity.finish();
    return;
}

answered Jun 06 '18 at 13:36

HedeH

2,869
16
25

That's my best guess. You should always add `return;` after you call `finish()` on an `Activity`, because the code after this line might still run and you'll get crashes like this. – HedeH Jun 06 '18 at 13:42

Android NullPointerException in ItemDetail Fragment when setting title

1 Answers1