点击打开悬浮窗直接崩溃，系统是5.1

[ChloeDimen]

01-21 18:33:05.663 4217-4217/? E/AndroidRuntime: FATAL EXCEPTION: main
Process: xzr.perfmon, PID: 4217
java.lang.RuntimeException: Unable to create service xzr.perfmon.FloatingWindow: java.lang.NullPointerException: Attempt to invoke interface method 'float android.content.SharedPreferences.getFloat(java.lang.String, float)' on a null object reference
at android.app.ActivityThread.handleCreateService(ActivityThread.java:2791)
at android.app.ActivityThread.access$1800(ActivityThread.java:151)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1402)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5280)
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:963)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:758)
Caused by: java.lang.NullPointerException: Attempt to invoke interface method 'float android.content.SharedPreferences.getFloat(java.lang.String, float)' on a null object reference
at xzr.perfmon.FloatingWindow.init(FloatingWindow.java:66)
at xzr.perfmon.FloatingWindow.onCreate(FloatingWindow.java:290)
at android.app.ActivityThread.handleCreateService(ActivityThread.java:2781)