显示java.lang.NullPointerException
所以在过去的几个小时里，我一直在为此苦苦挣扎，并且在找不到解决我的问题的方法之前进行搜索。 基本上我试图在Fragment扩展中使用Context，它给了我错误，我在这个要点中粘贴了完整的代码
在此处输入链接描述
从我在SO上发现的情况来看，这听起来像是在Context有null时发生的，但我不明白如何解决这个问题。
logcat的：
> 06-18 10:20:08.972 5718-5718/com.aparosecurity.kblock W/dalvikvm﹕ > threadid=1: thread exiting with uncaught exception (group=0x41625898) > 06-18 10:20:08.992 5718-5718/com.aparosecurity.kblock > E/AndroidRuntime﹕ FATAL EXCEPTION: main > java.lang.NullPointerException > at com.aparosecurity.kblock.ImageFragment.onCreate(ImageFragment.java:77) > at android.support.v4.app.Fragment.performCreate(Fragment.java:1477) > at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:904) > at android.support.v4.app.FragmentManagerImpl.performPendingDeferredStart(FragmentManager.java:834) > at android.support.v4.app.Fragment.setUserVisibleHint(Fragment.java:841) > at android.support.v4.app.FragmentPagerAdapter.setPrimaryItem(FragmentPagerAdapter.java:130) > at android.support.v4.view.ViewPager.populate(ViewPager.java:1066) > at android.support.v4.view.ViewPager.populate(ViewPager.java:914) > at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1436) > at android.view.View.measure(View.java:15848) > at android.widget.LinearLayout.measureVertical(LinearLayout.java:847) > at android.widget.LinearLayout.onMeasure(LinearLayout.java:588) > at android.view.View.measure(View.java:15848) > at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5012) > at android.widget.FrameLayout.onMeasure(FrameLayout.java:310) > at android.view.View.measure(View.java:15848) > at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5012) > at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1404) > at android.widget.LinearLayout.measureVertical(LinearLayout.java:695) > at android.widget.LinearLayout.onMeasure(LinearLayout.java:588) > at android.view.View.measure(View.java:15848) > at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5012) > at android.widget.FrameLayout.onMeasure(FrameLayout.java:310) > at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2189) > at android.view.View.measure(View.java:15848) > at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:1905) > at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1104) > at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1284) > at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1004) > at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5481) > at android.view.Choreographer$CallbackRecord.run(Choreographer.java:749) > at android.view.Choreographer.doCallbacks(Choreographer.java:562) > at android.view.Choreographer.doFrame(Choreographer.java:532) > at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:735) > at android.os.Handler.handleCallback(Handler.java:730) > at android.os.Handler.dispatchMessage(Handler.java:92) > at android.os.Looper.loop(Looper.java:137) > at android.app.ActivityThread.main(ActivityThread.java:5136) > at java.lang.reflect.Method.invokeNative(Native Method) > at java.lang.reflect.Method.invoke(Method.java:525) > at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737) > at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553) > at dalvik.system.NativeStart.main(Native Method)
任何帮助表示赞赏。
特定行失败，使用mContext时发生错误。
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
fragVal = getArguments() != null ? getArguments().getInt("val") : 1;
mHandler = new Handler();
// Initializes a Bluetooth adapter. For API level 18 and above, get a reference to
// BluetoothAdapter through BluetoothManager.
final BluetoothManager bluetoothManager =
(BluetoothManager) mContext.getSystemService(Context.BLUETOOTH_SERVICE);
mBluetoothAdapter = bluetoothManager.getAdapter();
}
你还没有初始化mContext ，它是空的。 在空引用上调用方法会导致NPE。
在片段中，使用getActivity()获取对可用作Context的托管活动的引用。 （警告：只有当附加到活动工程在onCreate()其配备后onAttach()
所以，更换
mContext.getSystemService()
同
getActivity().getSystemService()