I was trying to implement Tab Activity but I am getting the exception shown below in log cat file

Question

I have made 5 class file. 3 fragment activity 1 main activity and 1 adapter class.

logcat

 05-06 12:17:17.213    1398-1398/com.example.neeraj.tabac E/AndroidRuntime﹕ 
    FATAL EXCEPTION: main
    java.lang.RuntimeException: Unable to start activity       ComponentInfo{com.example.neeraj.tabac/com.example.neeraj.tabac.ActivityMain}:                      java.lang.NullPointerException
             android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2211)
           android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2261)
            android.app.ActivityThread.access$600(ActivityThread.java:141)
             android.app.ActivityThread$H.handleMessage(ActivityThread.java:1256)
             android.os.Handler.dispatchMessage(Handler.java:99)
             android.os.Looper.loop(Looper.java:137)
             android.app.ActivityThread.main(ActivityThread.java:5103)
             java.lang.reflect.Method.invokeNative(Native Method)
             java.lang.reflect.Method.invoke(Method.java:525)
             com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
             com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
             dalvik.system.NativeStart.main(Native Method)
     Caused by: java.lang.NullPointerException
             com.example.neeraj.tabac.ActivityMain.onCreate(ActivityMain.java:60)
             android.app.Activity.performCreate(Activity.java:5133)
             android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
             android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2175)
             android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2261)
             android.app.ActivityThread.access$600(ActivityThread.java:141)
             android.app.ActivityThread$H.handleMessage(ActivityThread.java:1256)
             android.os.Handler.dispatchMessage(Handler.java:99)
             android.os.Looper.loop(Looper.java:137)
             android.app.ActivityThread.main(ActivityThread.java:5103)
             java.lang.reflect.Method.invokeNative(Native Method)
             java.lang.reflect.Method.invoke(Method.java:525)
             com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
             com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
             dalvik.system.NativeStart.main(Native Method)

This is the main activity file:

 public class ActivityMain extends FragmentActivity {
        ViewPager Tab;
        TabFragment TabAdapter;
        ActionBar actionBar;


    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.a_main);

        TabAdapter = new TabFragment(getSupportFragmentManager());

        Tab = (ViewPager)findViewById(R.id.pager);
        Tab.setOnPageChangeListener(
                new ViewPager.SimpleOnPageChangeListener() {
                    @Override
                    public void onPageSelected(int position) {

                        actionBar = getActionBar();
                        actionBar.setSelectedNavigationItem(position);                    }
                });
        Tab.setAdapter(TabAdapter);

        actionBar = getActionBar();
        //Enable Tabs on Action Bar
        actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
        ActionBar.TabListener tabListener = new ActionBar.TabListener(){

            @Override
            public void onTabReselected(ActionBar.Tab tab,
                                        FragmentTransaction ft) {
                // TODO Auto-generated method stub

            }

            @Override
            public void onTabSelected(ActionBar.Tab tab, FragmentTransaction ft) {

                Tab.setCurrentItem(tab.getPosition());
            }

            @Override
            public void onTabUnselected(ActionBar.Tab tab,
                                        FragmentTransaction ft) {
                // TODO Auto-generated method stub

            }};
        //Add New Tab
        actionBar.addTab(actionBar.newTab().setText("Android").setTabListener(tabListener));
        actionBar.addTab(actionBar.newTab().setText("iOS").setTabListener(tabListener));
            actionBar.addTab(actionBar.newTab().setText("Windows").setTabListener(tabListener));

    }
    }

Please help me as its for my project and I'm new to Android Studio. Even the strikes comes in main activity which I don't know why.

actionBar.addTab(actionBar.newTab().setText("Android").setTabListener(tabListener)); actionBar.addTab(actionBar.newTab().setText("iOS").setTabListener(tabListener)); actionBar.addTab(actionBar.newTab().setText("Windows").setTabListener(tabListener)); — kr16, May 06 '15 at 16:41
its seems your actionBar value is null if this line is your line 60 .. — Abdul Momen Khan, May 06 '15 at 16:42

score 0 · Answer 1 · answered May 06 '15 at 16:43

0

It seems like your ActionBar is null, try using. This happens when you use AppCompat

actionBar = getSupportActionBar();

You also need to use android.support.v7.app.ActionBar actionBar when defining it.

answered May 06 '15 at 16:43

Bojan Kseneman

15,488
2
54
59

actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS); – kr16 May 06 '15 at 16:59
Yes, I know. Your actionbar is null – Bojan Kseneman May 06 '15 at 17:01
what can i do ? the above method is not wroking. – kr16 May 06 '15 at 17:06

score 0 · Answer 2 · answered May 06 '15 at 16:49

0

Or you can try to add this line before setContentView

getWindow().requestFeature(Window.FEATURE_ACTION_BAR);

answered May 06 '15 at 16:49

Nik Myers

1,843
19
28

I was trying to implement Tab Activity but I am getting the exception shown below in log cat file

2 Answers2