Android：getSupportActionBar（）始终在ActionBarSherlock库中返回null

Question

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) {
    }
}

Answer 1

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">

Answer 2

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.

Answer 3

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.

Answer 4

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);

Answer 5

这是一个有趣的：不要将主题设置为 -

    android:theme="@style/Theme.NoActionbar"

Answer 6

您可能从getSupportActionBar()获取null的另一个原因是在Honeycomb +上的TabHost中使用该活动。

Answer 7

Depending how your write out code. ensure that you did set the toolbar first before calling it.

  mToolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(mToolbar);
        getSupportActionBar().setDisplayShowHomeEnabled(true);

Answer 8

I just changed in Manifest

android:theme="@style/AppTheme.NoActionBar"

to:

  android:theme="@style/AppTheme"

and the error gone

Answer 9

whenever we set customview using sherlock library. just remove this requestWindowFeature(Window.FEATURE_NO_TITLE); like this we make customview using sherlock bar library..

            getSupportActionBar().setDisplayHomeAsUpEnabled(true);
    getSupportActionBar().setDisplayOptions(ActionBar.DISPLAY_SHOW_CUSTOM); 
    getSupportActionBar().setCustomView(R.layout.header_sherlock_xmllayout);
    header_tvleft = (TextView) findViewById(R.id.header_tvleft);
    header_tvleft.setText("Back");

Answer 10

在（ super.onCreate() ）忘记调用super.onCreate()之后我遇到了这个问题

Answer 11

you are declared Theme.Sherlock or Theme.Sherlock.Light as your activity or application theme in the manifest Or using a custom theme that inherits from one of these two

Example:-

<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/Theme.Sherlock.Light" >

also u can use dark theme:-

android:theme="@style/Theme.Sherlock"

Answer 12

I ran into this after adding a library to my project. The remedy was to look in the library and remove any styles name "AppTheme" if you are using this same theme name in your manifest. There wasn't a conflict on my Galaxy S4, Jelly Bean, while there was a conflict on my Galaxy Tab.

Answer 13

I added android:theme="@android:style/Theme.Dialog" to my activity in the Android Manifest file in an attempt to make it a dialogue activity. This too will remove the action bar hence a null pointer. Remove it or don't call getSupportActioBar

Answer 14

I make this mistake because i add the toobar in the fragment xml file. The code to find the toolbar in fragment is this:getActivity().findViewByid(id...),but my toolbar is in fragment xml file,so that there was no toolbar found and no toolbar beeing setSipprotActionBar() and also nothing get when getSupportActionBar(). So remember : Do not put the toolbar in your fragment`s xml file.