캘린더 만들기를 했고요 캘린더 한페이지만 했을떄는 오류가없고 실행도 잘됐습니다
근데 버튼하나만 추가해서 엑티비티 두개로 만들어줬는데 오류는 안뜨는데 앱실행시 언폴츈 뜨면서 앱이 꺼집니다 ㅠㅠ
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.samplecalendar, PID: 7908
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.samplecalendar/com.example.samplecalendar.Main2Activity}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.widget.GridView.findViewById(int)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2325)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387)
at android.app.ActivityThread.access$800(ActivityThread.java:151)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5254)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.widget.GridView.findViewById(int)' on a null object reference
at com.example.samplecalendar.Main2Activity.onCreate(Main2Activity.java:82)
at android.app.Activity.performCreate(Activity.java:5990)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2278)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387)
at android.app.ActivityThread.access$800(ActivityThread.java:151)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5254)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
오류 링크를 클릭하면 밑에 tv_Date 부분이 선택이됩니다
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
tvDate = (TextView)findViewById(R.id.tv_date);
gridView = (GridView)findViewById(R.id.gridview);