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Android: getSupportActionBar() always returns null in ActionBarSherlock library

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By User


I'm trying to use the ActionBarSherlock library to provide backwards compatible ActionBar support with tabs in my Android app, so I downloaded the latest build, built the demo, and ran it.



If you go to Action Bar, then select Tab Navigation it crashes every time. Here's the stack trace:




09-03 02:34:47.940: ERROR/AndroidRuntime(3078): FATAL EXCEPTION: main 09-03 02:34:47.940: ERROR/AndroidRuntime(3078): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.actionbarsherlock.sample.demos/com.actionbarsherlock.sample.demos.app.ActionBarTabNavigation}: java.lang.NullPointerException 09-03 02:34:47.940: ERROR/AndroidRuntime(3078): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1748) 09-03 02:34:47.940: ERROR/AndroidRuntime(3078): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1764) 09-03 02:34:47.940: ERROR/AndroidRuntime(3078): at android.app.ActivityThread.access$1500(ActivityThread.java:122) 09-03 02:34:47.940: ERROR/AndroidRuntime(3078): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1002) 09-03 02:34:47.940: ERROR/AndroidRuntime(3078): at android.os.Handler.dispatchMessage(Handler.java:99) 09-03 02:34:47.940: ERROR/AndroidRuntime(3078): at android.os.Looper.loop(Looper.java:132) 09-03 02:34:47.940: ERROR/AndroidRuntime(3078): at android.app.ActivityThread.main(ActivityThread.java:4025) 09-03 02:34:47.940: ERROR/AndroidRuntime(3078): at java.lang.reflect.Method.invokeNative(Native Method) 09-03 02:34:47.940: ERROR/AndroidRuntime(3078): at java.lang.reflect.Method.invoke(Method.java:491) 09-03 02:34:47.940: ERROR/AndroidRuntime(3078): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:841) 09-03 02:34:47.940: ERROR/AndroidRuntime(3078): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:599) 09-03 02:34:47.940: ERROR/AndroidRuntime(3078): at dalvik.system.NativeStart.main(Native Method) 09-03 02:34:47.940: ERROR/AndroidRuntime(3078): Caused by: java.lang.NullPointerException 09-03 02:34:47.940: ERROR/AndroidRuntime(3078): at com.actionbarsherlock.sample.demos.app.ActionBarTabNavigation.onCreate(ActionBarTabNavigation.java:19) 09-03 02:34:47.940: ERROR/AndroidRuntime(3078): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1048) 09-03 02:34:47.940: ERROR/AndroidRuntime(3078): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1712) 09-03 02:34:47.940: ERROR/AndroidRuntime(3078): ... 11 more




I can't move forward with my app until this is fixed. I wrote a bunch of code, set up the action bar in my app, and tried to run it, and it crashes with an NPE because of the null return value on the getSupportActionBar() call.



The relevant code is actually in the demo for the library: 





public class ActionBarTabNavigation extends FragmentActivity implements ActionBar.TabListener {

    @Override

    public void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);



        getSupportFragmentManager()

            .beginTransaction()

            .add(android.R.id.content, FragmentStackSupport.CountingFragment.newInstance(0))

            .commit();



        getSupportActionBar().setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);

        for (int i = 0; i < 3; i++) {

            ActionBar.Tab tab = getSupportActionBar().newTab();

            tab.setText("Tab " + i);

            tab.setTabListener(this);

            getSupportActionBar().addTab(tab);

        }

    }



    @Override

    public void onTabReselected(Tab tab, FragmentTransaction ft) {

    }



    @Override

    public void onTabSelected(Tab tab, FragmentTransaction ft) {

        getSupportFragmentManager()

            .beginTransaction()

            .replace(android.R.id.content, FragmentStackSupport.CountingFragment.newInstance(tab.getPosition()))

            .commit();

    }



    @Override

    public void onTabUnselected(Tab tab, FragmentTransaction ft) {

    }

}

Source: Tips4all, CCNA FINAL EXAM
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Comments

  1. UserMay 14, 2012 at 9:09 AM

    You should add the Sherlock theme to your application

    <application android:icon="@drawable/icon" android:label="@string/app_name"
    android:debuggable="false" android:theme="@style/Theme.Sherlock">

    ReplyDelete
  2. UserMay 14, 2012 at 9:09 AM

    Another reason this will happen (on honeycomb +) devices is because the windowNoTitle attribute is set in your style. Get rid of that as ActionBarSherlock will automatically remove it in pre-honeycomb devices for you.

    ReplyDelete
  3. UserMay 14, 2012 at 9:09 AM

    Another reason you might get null from getSupportActionBar() is trying to call it before setContentView(R.layout.main) or in your example adding a fragment.

    I refactored oncreate and mistakenly put getSupportActionBar().setNavigationMode(ActionBar.NAVIGATION_MODE_TABS); after super.onCreate(savedInstanceState);

    ReplyDelete
  4. UserMay 14, 2012 at 9:09 AM

    I had the same problem on the Android ICS 4.0.4. I was using requestWindowFeature(Window.FEATURE_NO_TITLE); on the FragmentActivity, but this was hiding the ActionBar on ICS+ devices that caused the getSupportActionBar() to be null.

    Simply removed the:
    requestWindowFeature(Window.FEATURE_NO_TITLE);

    And it worked like a charm.

    Hope it helps someone.

    ReplyDelete

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