照着《第一行代码》第2版写的Service崩溃了，请问什么原因？

照着书上写的，也就在3个覆写方法里打印下日志，运行时直接崩溃了

不过Android Studio自动生成的onStartCommand()方法见下图，我把红线部分删掉了

AndroidRuntime: FATAL EXCEPTION: main

Process: com.example.h.servicetest, PID: 3583

java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.h.servicetest/com.example.h.servicetest.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.Window$Callback android.view.Window.getCallback()' on a null object reference

at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2327)

at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)

at android.app.ActivityThread.-wrap11(ActivityThread.java)

at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)

at android.os.Handler.dispatchMessage(Handler.java:102)

at android.os.Looper.loop(Looper.java:148)

at android.app.ActivityThread.main(ActivityThread.java:5417)

at java.lang.reflect.Method.invoke(Native Method)

at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)

at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)

Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.Window$Callback android.view.Window.getCallback()' on a null object reference

at android.support.v7.app.AppCompatDelegateImplBase.<init>(AppCompatDelegateImplBase.java:120)

at android.support.v7.app.AppCompatDelegateImplV9.<init>(AppCompatDelegateImplV9.java:155)

at android.support.v7.app.AppCompatDelegateImplV11.<init>(AppCompatDelegateImplV11.java:31)

at android.support.v7.app.AppCompatDelegateImplV14.<init>(AppCompatDelegateImplV14.java:55)

at android.support.v7.app.AppCompatDelegateImplV23.<init>(AppCompatDelegateImplV23.java:33)

at android.support.v7.app.AppCompatDelegate.create(AppCompatDelegate.java:203)

at android.support.v7.app.AppCompatDelegate.create(AppCompatDelegate.java:185)

at android.support.v7.app.AppCompatActivity.getDelegate(AppCompatActivity.java:519)

at android.support.v7.app.AppCompatActivity.findViewById(AppCompatActivity.java:190)

at com.example.h.servicetest.MainActivity.<init>(MainActivity.java:11)

at java.lang.Class.newInstance(Native Method)

at android.app.Instrumentation.newActivity(Instrumentation.java:1067)

at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2317)