E/AndroidRuntime：致命异常：主。 ExpadableListView Isses

Question

当我尝试运行我的应用程序我碰到下面的错误，我只得到了这些错误一旦实施和expandablelistview：

7686/com.example.admin.n0499049 E/AndroidRuntime: FATAL EXCEPTION: main 
Process: com.example.admin.n0499049, PID: 7686 
java.lang.RuntimeException: Unable to start activity ComponentInfo { com.example.admin.n0499049/com.example.admin.n0499049.MainActivity }: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ExpandableListView.setAdapter(android.widget.ExpandableListAdapter)' 
on a null object reference 
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java: 2665) 
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java: 2726) 
at android.app.ActivityThread. - wrap12(ActivityThread.java) 
at android.app.ActivityThread$H.handleMessage(ActivityThread.java: 1477) 
at android.os.Handler.dispatchMessage(Handler.java: 102) 
at android.os.Looper.loop(Looper.java: 154) 
at android.app.ActivityThread.main(ActivityThread.java: 6119) 
at java.lang.reflect.Method.invoke(Native Method) 
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java: 886) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java: 776) 
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ExpandableListView.setAdapter(android.widget.ExpandableListAdapter)' 
on a null object reference 
at com.example.admin.n0499049.MainActivity.onCreate(MainActivity.java: 34) 
at android.app.Activity.performCreate(Activity.java: 6679) 
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java: 1118) 
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java: 2618) 
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java: 2726)  
at android.app.ActivityThread. - wrap12(ActivityThread.java)  
at android.app.ActivityThread$H.handleMessage(ActivityThread.java: 1477)  
at android.os.Handler.dispatchMessage(Handler.java: 102)  
at android.os.Looper.loop(Looper.java: 154)  
at android.app.ActivityThread.main(ActivityThread.java: 6119)  
at java.lang.reflect.Method.invoke(Native Method)  
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java: 886)  
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java: 776)  

Answer 1

你ExpandableListView为空时，一定要正确地启动它。 ü之前调用ExpandableListView.setAdapter(...)