findViewById返回null TextView

Question

This one is driving me and my team completely crazy.

We can't reproduce as it works well on all our test devices but we are getting thousands of crash reports complaining of java.lang.NullPointerException for a TextView which is obtained by findViewById in onCreate (after calling setContentView and with the correct id and layout file)

java.lang.RuntimeException: Unable to start activity ComponentInfo{xxxxxxxxxxxxx.activities.PremiumActivity}: java.lang.NullPointerException
       at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2097)
       at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2122)
       at android.app.ActivityThread.access$600(ActivityThread.java:140)
       at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1228)
       at android.os.Handler.dispatchMessage(Handler.java:99)
       at android.os.Looper.loop(Looper.java:137)
       at android.app.ActivityThread.main(ActivityThread.java:4895)
       at java.lang.reflect.Method.invokeNative(Method.java)
       at java.lang.reflect.Method.invoke(Method.java:511)
       at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:994)
       at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:761)
       at dalvik.system.NativeStart.main(NativeStart.java)
Caused by: java.lang.NullPointerException
       at xxxxxxxxx.activities.PremiumActivity.onCreate(PremiumActivity.java:258)
       at android.app.Activity.performCreate(Activity.java:5163)
       at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1094)
       at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2061)
       at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2122)
       at android.app.ActivityThread.access$600(ActivityThread.java:140)
       at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1228)
       at android.os.Handler.dispatchMessage(Handler.java:99)
       at android.os.Looper.loop(Looper.java:137)
       at android.app.ActivityThread.main(ActivityThread.java:4895)
       at java.lang.reflect.Method.invokeNative(Method.java)
       at java.lang.reflect.Method.invoke(Method.java:511)
       at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:994)
       at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:761)
       at dalvik.system.NativeStart.main(NativeStart.java)

Here is the onCreate method:

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.premium_activity_layout);
    premiumInfoHeaderTextView = (TextView) findViewById(R.id.premiumHeaderTextView);
    int themeColor = MPThemeManager.getSharedInstance(this).themeColor();
    premiumInfoHeaderTextView.setTextColor(themeColor);

That last line is the one causing the nullPointerException (line 258)

Not sure if it can be related but the activity extends SherlockFragmentActivity

And of course premiumInfoHeaderTextView is declared as a TextView outside the onCreate method as we also use it elsewhere.

Answer 1

A crazy fix to a crazy bug!!

As expected in my earlier comment, the bug comes from the fact the an old layout xml file for tablets (under /res/layout-large) has beed removed in our latest version (we now use a single layout file under /res/layout).

Remember the line causing the Null Exception:

premiumInfoHeaderTextView = (TextView) findViewById(R.id.premiumHeaderTextView);

This is due to the fact that our former version layout did not have any view with id = premiumHeaderTextView and that on some tablets for users who upgraded from the previous to the new version, the old layout file has not been deleted and the system is therefore looking for id in the old /res/layout-large/premium_activity_layout.xml rather than in the new (common to all devices) /res/layout/premium_activity_layout.xml

Using crashlytics to understand that all crashes were happening on tablet devices was key to identify this "bug" which seems like a system bug on some tablets as they should not keep old resource files when the apk is upgrade.

So in summary, I copied the /res/layout/premium_activity_layout.xml to /res/layout-large in order to force tablet users to use the new layout and not an old "cached" version. That has completely fixed the bug