10-07 21:05:32.704 22810-22810/com.seedxyx.noteinfingers E/AndroidRuntime﹕ FATAL EXCEPTION: main

java.lang.NullPointerException at android.view.ViewGroup.dispatchVisibilityChanged(ViewGroup.java:1029) at android.view.ViewGroup.dispatchVisibilityChanged(ViewGroup.java:1029) at android.view.ViewGroup.dispatchVisibilityChanged(ViewGroup.java:1029) at android.view.ViewGroup.dispatchVisibilityChanged(ViewGroup.java:1029) at android.view.ViewGroup.dispatchVisibilityChanged(ViewGroup.java:1029) at android.view.ViewGroup.dispatchVisibilityChanged(ViewGroup.java:1029) at android.view.ViewGroup.dispatchVisibilityChanged(ViewGroup.java:1029) at android.view.View.setFlags(View.java:8370) at android.view.View.setVisibility(View.java:5512) at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:2638) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2097) at android.app.ActivityThread.access$600(ActivityThread.java:133) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1203) at android.os.Handler.dispatchMessage(Handler.java:99) at android.os.Looper.loop(Looper.java:137) at android.app.ActivityThread.main(ActivityThread.java:4794) at java.lang.reflect.Method.invokeNative(Native Method) at java.lang.reflect.Method.invoke(Method.java:511) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:789) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:556) at dalvik.system.NativeStart.main(Native Method) app突然就刚进去就崩溃了，这是个什么错误？