Because want to work in a TabHost in one of the tabs below to add a TabHost, went on the Internet to find relevant posts imitation result in "Did you forget to call the 'public voidsetup (LocalActivityManager activityGroup)?" Such a mistake, says inherit ActivityGroup online, or TabActivity rather than the activity

Join activitytabHost. Setup (enclosing getLocalActivityManager ()); Is ok, but this changed after teacher_tab. Setup (enclosing getLocalActivityManager ()); It will report null pointer error "Java. Lang. NullPointerException: Attempt to invoke virtual method 'void android. Widget. The TabHost. Setup (android. App. LocalActivityManager)' on a null object reference",
Below is a Java code

 
Public class TeacherActivity extends ActivityGroup {

Private Context Context=TeacherActivity. This; 
Private List ListMyCourses=new ArrayList<> (a); 
Void getMyCourses () {
List Mycourses=CMSClient. GetMyCourses (SystemConfig. Username); 
ListMyCourses. The clear (); 
C: for (CourseSummary mycourses) {
ListMyCourses. Add (c); 
} 
} 

@ Override 
Protected void onCreate (Bundle savedInstanceState) {
Super. OnCreate (savedInstanceState); 
TabHost teacher_tab=the findViewById (R.i which abhost_teacher); 
Teacher_tab. Setup (enclosing getLocalActivityManager ()); 
//TabHost teacher_tab=getTabHost (); 
//LayoutInflater. The from (this). Inflate (R.l ayout. Activity_teacher_main, teacher_tab. GetTabContentView (), true); 

Teacher_tab. AddTab (teacher_tab newTabSpec (" taba "). SetIndicator (" my course "). SetContent (R.i which eacher_mycourses)); 
Teacher_tab. AddTab (teacher_tab newTabSpec (" firm "). SetIndicator (" course maintenance "). SetContent (new Intent (this, TeacherActivity_courserepair. Class))); 
Teacher_tab. AddTab (teacher_tab newTabSpec (" tabc "). SetIndicator (" schedule view "). SetContent (R.i which eacher_coursetable)); 

//I of course TAB 
ListView listview_mycourses=the findViewById (R.i d.l ist_view_teacher_course); 
GetMyCourses (); 
for(int i=0; i Log i. (" cmstag, "listMyCourses. Get (I). CourseName); 
} 
MyCoursesAdapter MDP=new MyCoursesAdapter (context, R.l ayout. Listview_sub_mycourse, listMyCourses); 
Listview_mycourses. SetAdapter (MDP); 
Listview_mycourses. SetOnItemClickListener (new AdapterView. OnItemClickListener () {
@ Override 
Public void onItemClick (AdapterView<?> The parent, View View, int position, long id) {
CourseSummary myCourse=listMyCourses. Get (position); 
Intent Intent=new Intent (context, CourseDetailsActivity. Class); 
Intent. PutExtra (" course_id "myCourse. CourseId); 
The context. StartActivity (intent); 
} 
}); 

//label switching event handling, setOnTabChangedListener 
Teacher_tab. SetOnTabChangedListener (new TabHost. OnTabChangeListener () {
@ Override 
Public void onTabChanged (String tabId) {
If (tabId. Equals (" taba ")) {//the first tag 

} 
If (tabId. Equals (" firm ")) {//course maintenance 

} 
If (tabId. Equals (" tabc ")) {//schedule to see 

} 
} 
}); 
} 
} 

Here is the error message

 
E/AndroidRuntime: FATAL EXCEPTION: the main 
Process: cn.edu.njrts.cms, PID: 8947 
Java. Lang. RuntimeException: Unable to start the activity ComponentInfo {cn.edu.njrts.cms/cn.edu.njrts.cms.TeacherActivity} : Java. Lang. NullPointerException: Attempt to invoke virtual method 'void android. Widget. The TabHost. Setup (android. App. LocalActivityManager)' on a null object reference 
. An android app. ActivityThread. PerformLaunchActivity (ActivityThread. Java: 2665) 
. An android app. ActivityThread. HandleLaunchActivity (ActivityThread. Java: 2726) 
. An android app. ActivityThread. - wrap12 (ActivityThread. Java) 
An android. App. ActivityThread $H.h andleMessage (ActivityThread. Java: 1477) 
An android. OS. Handler. DispatchMessage (Handler. Java: 102) 
. An android OS. Stars. Loop (154). Which Java: 
. An android app. ActivityThread. Main (6119) ActivityThread. Java: 
The at Java. Lang. Reflect. Method. Invoke (Native Method) 
At com. Android. Internal. OS. $MethodAndArgsCaller ZygoteInit. Run (ZygoteInit. Java: 886) 
At com. Android. Internal. OS. ZygoteInit. Main (ZygoteInit. Java: 776) 
Under Caused by: Java. Lang. NullPointerException: Attempt to invoke virtual method 'void android. Widget. The TabHost. Setup (android. App. LocalActivityManager)' on a null object reference 
The at cn.edu.njrts.cms.TeacherActivity.onCreate (TeacherActivity. Java: 38) 
. An android app. Activity. PerformCreate (6679) Activity. Java: 
. An android app. Instrumentation. CallActivityOnCreate (1118) Instrumentation. Java: 
. An android app. ActivityThread. PerformLaunchActivity (ActivityThread. Java: 2618) 
. An android app. ActivityThread. HandleLaunchActivity (ActivityThread. Java: 2726) 
. An android app. ActivityThread. - wrap12 (ActivityThread. Java) 
An android. App. ActivityThread $H.h andleMessage (ActivityThread. Java: 1477) 
An android. OS. Handler. DispatchMessage (Handler. Java: 102) 
. An android OS. Stars. Loop (154). Which Java: 
. An android app. ActivityThread. Main (6119) ActivityThread. Java: 
The at Java. Lang. Reflect. Method. Invoke (Native Method) 
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