Android 片段中的Null变量和Null视图

我正在使用NavigationDrawer和Fragments。我有上面写的片段，里面有一个开关。我需要知道开关是激活的还是不使用它作为方法的参数，但是当我在声明开关后调用它时，变量会给我null以及视图

编辑：问题是片段在OnCreateView中创建了视图，并在屏幕上正确显示了所有内容，但是当我试图在修改switchP的方法中访问rootview时，它会给我null，我不知道为什么

Switch switchP;

@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
    rootview = inflater.inflate(R.layout.valor_unico, container, false);

    switchP = (Switch) rootview.findViewById(R.id.switchP);

    return rootview;
}


public String processProp(String prop) {
    switch ( calc.controlarSintaxis(prop)){
        case 0:
            return calc.resultadoValUnico(prop, switchP.isActivated());
        case 1:
            return "Error";
        case -1:
            return "Other error";
        default: return null;
    }
}

以下是错误日志：

`04-10 14:26:24.142  15494-15494/com.hernan.calculadorlogicov31 E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.hernan.calculadorlogicov31, PID: 15494
java.lang.IllegalStateException: Could not execute method of the activity
        at android.view.View$1.onClick(View.java:3827)
        at android.view.View.performClick(View.java:4442)
        at android.view.View$PerformClick.run(View.java:18473)
        at android.os.Handler.handleCallback(Handler.java:733)
        at android.os.Handler.dispatchMessage(Handler.java:95)
        at android.os.Looper.loop(Looper.java:136)
        at android.app.ActivityThread.main(ActivityThread.java:5105)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:515)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:792)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:608)
        at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.reflect.InvocationTargetException
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:515)
        at android.view.View$1.onClick(View.java:3822)
        at android.view.View.performClick(View.java:4442)
        at android.view.View$PerformClick.run(View.java:18473)
        at android.os.Handler.handleCallback(Handler.java:733)
        at android.os.Handler.dispatchMessage(Handler.java:95)
        at android.os.Looper.loop(Looper.java:136)
        at android.app.ActivityThread.main(ActivityThread.java:5105)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:515)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:792)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:608)
        dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
        at com.hernan.calculadorlogicov31.vista.ValorUnico.processProp(ValorUnico.java:40)
        at com.hernan.calculadorlogicov31.vista.Main.mostrarResultado(Main.java:101)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:515)
        at android.view.View$1.onClick(View.java:3822)
        at android.view.View.performClick(View.java:4442)
        at android.view.View$PerformClick.run(View.java:18473)
        at android.os.Handler.handleCallback(Handler.java:733)
        at android.os.Handler.dispatchMessage(Handler.java:95)
        at android.os.Looper.loop(Looper.java:136)
        at android.app.ActivityThread.main(ActivityThread.java:5105)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:515)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:792)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:608)
        at dalvik.system.NativeStart.main(Native Method)`

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检查在onCreateViewpost logcat之前是否使用了switchP和rootview，其中它将变为null？在onCreateView之前，这些变量未被使用，如果我在调试期间观察switchP，它将成功创建、分配，但当片段最终激活时，它将变为null，并且片段的视图也将变为null