FATAL EXCEPTION：main Process java.lang.RuntimeException：无法启动活动ComponentInfo

Question

我想问一些问题。 当我与其他项目分开运行此代码时，它运行完美。但是当我与其他代码结合时，它会崩溃。这是我收到的错误消息。

---------崩溃的开始

05-23 23:53:50.898 20269-20269/inducesmile.com.androidquizapplication E/AndroidRuntime: 
FATAL EXCEPTION: main
Process: inducesmile.com.androidquizapplication, PID: 20269
java.lang.RuntimeException: Unable to start activity ComponentInfo{inducesmile.com.androidquizapplication/com.example.lututkopak.ccbtsa.tips}: 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:2434)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2494)
    at android.app.ActivityThread.access$900(ActivityThread.java:153)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1347)
    at android.os.Handler.dispatchMessage(Handler.java:102)
    at android.os.Looper.loop(Looper.java:148)
    at android.app.ActivityThread.main(ActivityThread.java:5477)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
 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.lututkopak.ccbtsa.tips.onCreate(tips.java:38)
    at android.app.Activity.performCreate(Activity.java:6323)
    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1108)
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2387)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2494) 
    at android.app.ActivityThread.access$900(ActivityThread.java:153) 
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1347) 
    at android.os.Handler.dispatchMessage(Handler.java:102) 
    at android.os.Looper.loop(Looper.java:148) 
    at android.app.ActivityThread.main(ActivityThread.java:5477) 
    at java.lang.reflect.Method.invoke(Native Method) 
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) 
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616) 
05-23 23:54:00.885 20269-20275/inducesmile.com.androidquizapplication W/art: Suspending all threads took: 5.415ms
05-23 23:58:20.835 20269-20269/inducesmile.com.androidquizapplication I/Process: Sending signal. PID: 20269 SIG: 9