Android wifimanager getSystemContext返回null

我正在尝试访问Wifi并将其打开和关闭。 这里是logcat：

03-09 20:30:45.601: I/Process(28690): Sending signal. PID: 28690 SIG: 9
03-09 20:30:45.932: D/AbsListView(28891): Get MotionRecognitionManager
03-09 20:30:45.982: D/AbsListView(28891): unregisterIRListener() is called 
03-09 20:30:46.002: D/libEGL(28891): loaded /vendor/lib/egl/libEGL_adreno.so
03-09 20:30:46.002: D/libEGL(28891): loaded /vendor/lib/egl/libGLESv1_CM_adreno.so
03-09 20:30:46.012: D/libEGL(28891): loaded /vendor/lib/egl/libGLESv2_adreno.so
03-09 20:30:46.012: I/Adreno-EGL(28891): <qeglDrvAPI_eglInitialize:316>: EGL 1.4 QUALCOMM build:  (CL4169980)
03-09 20:30:46.012: I/Adreno-EGL(28891): OpenGL ES Shader Compiler Version: 17.01.10.SPL
03-09 20:30:46.012: I/Adreno-EGL(28891): Build Date: 09/26/13 Thu
03-09 20:30:46.012: I/Adreno-EGL(28891): Local Branch: 
03-09 20:30:46.012: I/Adreno-EGL(28891): Remote Branch: 
03-09 20:30:46.012: I/Adreno-EGL(28891): Local Patches: 
03-09 20:30:46.012: I/Adreno-EGL(28891): Reconstruct Branch: 
03-09 20:30:46.052: D/OpenGLRenderer(28891): Enabling debug mode 0
03-09 20:30:46.052: D/AbsListView(28891): unregisterIRListener() is called 
03-09 20:30:46.122: D/AbsListView(28891): unregisterIRListener() is called 
03-09 20:30:46.142: D/AbsListView(28891): unregisterIRListener() is called 
03-09 20:30:48.724: E/InputEventReceiver(28891): Exception dispatching input event.
03-09 20:30:48.724: D/AndroidRuntime(28891): Shutting down VM
03-09 20:30:48.724: W/dalvikvm(28891): threadid=1: thread exiting with uncaught exception (group=0x41d34898)
03-09 20:30:48.764: E/AndroidRuntime(28891): FATAL EXCEPTION: main
03-09 20:30:48.764: E/AndroidRuntime(28891): java.lang.NullPointerException
03-09 20:30:48.764: E/AndroidRuntime(28891):    at com.AliTooq.locationtasklauncer.ActionManager.wifiOff(ActionManager.java:158)
03-09 20:30:48.764: E/AndroidRuntime(28891):    at com.AliTooq.locationtasklauncer.ActionManager.activate(ActionManager.java:43)
03-09 20:30:48.764: E/AndroidRuntime(28891):    at com.AliTooq.locationtasklauncer.Profile.activate(Profile.java:126)
03-09 20:30:48.764: E/AndroidRuntime(28891):    at com.AliTooq.locationtasklauncer.ProfileFragment$1.onItemClick(ProfileFragment.java:39)
03-09 20:30:48.764: E/AndroidRuntime(28891):    at android.widget.AdapterView.performItemClick(AdapterView.java:301)
03-09 20:30:48.764: E/AndroidRuntime(28891):    at android.widget.AbsListView.performItemClick(AbsListView.java:1507)
03-09 20:30:48.764: E/AndroidRuntime(28891):    at android.widget.AbsListView$PerformClick.run(AbsListView.java:3336)
03-09 20:30:48.764: E/AndroidRuntime(28891):    at android.widget.AbsListView.onTouchEvent(AbsListView.java:4632)
03-09 20:30:48.764: E/AndroidRuntime(28891):    at android.view.View.dispatchTouchEvent(View.java:7817)
03-09 20:30:48.764: E/AndroidRuntime(28891):    at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2435)
03-09 20:30:48.764: E/AndroidRuntime(28891):    at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2159)
03-09 20:30:48.764: E/AndroidRuntime(28891):    at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2441)
03-09 20:30:48.764: E/AndroidRuntime(28891):    at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2174)
03-09 20:30:48.764: E/AndroidRuntime(28891):    at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2441)
03-09 20:30:48.764: E/AndroidRuntime(28891):    at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2174)
03-09 20:30:48.764: E/AndroidRuntime(28891):    at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2441)
03-09 20:30:48.764: E/AndroidRuntime(28891):    at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2174)
03-09 20:30:48.764: E/AndroidRuntime(28891):    at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2441)
03-09 20:30:48.764: E/AndroidRuntime(28891):    at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2174)
03-09 20:30:48.764: E/AndroidRuntime(28891):    at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2441)
03-09 20:30:48.764: E/AndroidRuntime(28891):    at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2174)
03-09 20:30:48.764: E/AndroidRuntime(28891):    at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2441)
03-09 20:30:48.764: E/AndroidRuntime(28891):    at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2174)
03-09 20:30:48.764: E/AndroidRuntime(28891):    at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchTouchEvent(PhoneWindow.java:2326)
03-09 20:30:48.764: E/AndroidRuntime(28891):    at com.android.internal.policy.impl.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1612)
03-09 20:30:48.764: E/AndroidRuntime(28891):    at android.app.Activity.dispatchTouchEvent(Activity.java:2494)
03-09 20:30:48.764: E/AndroidRuntime(28891):    at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:2274)
03-09 20:30:48.764: E/AndroidRuntime(28891):    at android.view.View.dispatchPointerEvent(View.java:8025)
03-09 20:30:48.764: E/AndroidRuntime(28891):    at android.view.ViewRootImpl$ViewPostImeInputStage.processPointerEvent(ViewRootImpl.java:4659)
03-09 20:30:48.764: E/AndroidRuntime(28891):    at android.view.ViewRootImpl$ViewPostImeInputStage.onProcess(ViewRootImpl.java:4547)
03-09 20:30:48.764: E/AndroidRuntime(28891):    at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:4148)
03-09 20:30:48.764: E/AndroidRuntime(28891):    at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:4198)
03-09 20:30:48.764: E/AndroidRuntime(28891):    at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:4167)
03-09 20:30:48.764: E/AndroidRuntime(28891):    at android.view.ViewRootImpl$AsyncInputStage.forward(ViewRootImpl.java:4252)
03-09 20:30:48.764: E/AndroidRuntime(28891):    at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:4175)
03-09 20:30:48.764: E/AndroidRuntime(28891):    at android.view.ViewRootImpl$AsyncInputStage.apply(ViewRootImpl.java:4309)
03-09 20:30:48.764: E/AndroidRuntime(28891):    at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:4148)
03-09 20:30:48.764: E/AndroidRuntime(28891):    at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:4198)
03-09 20:30:48.764: E/AndroidRuntime(28891):    at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:4167)
03-09 20:30:48.764: E/AndroidRuntime(28891):    at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:4175)
03-09 20:30:48.764: E/AndroidRuntime(28891):    at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:4148)
03-09 20:30:48.764: E/AndroidRuntime(28891):    at android.view.ViewRootImpl.deliverInputEvent(ViewRootImpl.java:6293)
03-09 20:30:48.764: E/AndroidRuntime(28891):    at android.view.ViewRootImpl.doProcessInputEvents(ViewRootImpl.java:6231)
03-09 20:30:48.764: E/AndroidRuntime(28891):    at android.view.ViewRootImpl.enqueueInputEvent(ViewRootImpl.java:6202)
03-09 20:30:48.764: E/AndroidRuntime(28891):    at android.view.ViewRootImpl$WindowInputEventReceiver.onInputEvent(ViewRootImpl.java:6373)
03-09 20:30:48.764: E/AndroidRuntime(28891):    at android.view.InputEventReceiver.dispatchInputEvent(InputEventReceiver.java:188)
03-09 20:30:48.764: E/AndroidRuntime(28891):    at android.view.InputEventReceiver.nativeConsumeBatchedInputEvents(Native Method)
03-09 20:30:48.764: E/AndroidRuntime(28891):    at android.view.InputEventReceiver.consumeBatchedInputEvents(InputEventReceiver.java:177)
03-09 20:30:48.764: E/AndroidRuntime(28891):    at android.view.ViewRootImpl.doConsumeBatchedInput(ViewRootImpl.java:6346)
03-09 20:30:48.764: E/AndroidRuntime(28891):    at android.view.ViewRootImpl$ConsumeBatchedInputRunnable.run(ViewRootImpl.java:6392)
03-09 20:30:48.764: E/AndroidRuntime(28891):    at android.view.Choreographer$CallbackRecord.run(Choreographer.java:791)
03-09 20:30:48.764: E/AndroidRuntime(28891):    at android.view.Choreographer.doCallbacks(Choreographer.java:591)
03-09 20:30:48.764: E/AndroidRuntime(28891):    at android.view.Choreogra
03-09 20:30:50.576: I/Process(28891): 9Sending signal. PID: 28891 SIG: 9

我不知道问题的原因是什么。我已将该类更改为active，但它仍然会收到相同的错误

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另外，我确信我在Mainfest文件中的权限。

您可能忘了添加权限。不确定是否需要所有这些，但前两个是肯定的

<uses-permission android:name="android.permission.ACCESS_WIFI_STATE"/>
<uses-permission android:name="android.permission.CHANGE_WIFI_STATE"/>
<uses-permission android:name="android.permission.CHANGE_NETWORK_STATE"/>
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>

<uses-permission android:name="android.permission.ACCESS_WIFI_STATE"/>
<uses-permission android:name="android.permission.CHANGE_WIFI_STATE"/>
<uses-permission android:name="android.permission.CHANGE_NETWORK_STATE"/>
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>