java - Android - Activity constructor

Question

I noticed that using the shortcut Alt + Insert and selecting the builders, it tries to create a constructor with each private property (e.g. cManager and mTextView). I remember I already created projects without it and worked correctly.

The error happens when I run the application, following the full logcat and the Activity constructor:

Constructor with private property:

private ConnectivityManager cManager;
private TextView mTextView;

public SplashScreenActivity() {
    this.cManager = (ConnectivityManager) this.getSystemService(Context.CONNECTIVITY_SERVICE);
    this.mTextView = (TextView)this.findViewById(R.id.mProgressText);
}

Logcat:

02-20 18:20:56.155    1591-1591/com.universo91.towersrock I/art﹕ Not late-enabling -Xcheck:jni (already on)
02-20 18:20:58.355    1591-1591/com.universo91.towersrock D/AndroidRuntime﹕ Shutting down VM
    --------- beginning of crash
02-20 18:20:58.361    1591-1591/com.universo91.towersrock E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: com.universo91.towersrock, PID: 1591
    java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.universo91.towersrock/com.universo91.towersrock.Pages.SplashScreenActivity}: java.lang.InstantiationException: class com.universo91.towersrock.Pages.SplashScreenActivity has no zero argument constructor
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2209)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
            at android.app.ActivityThread.access$800(ActivityThread.java:144)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5221)
            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:899)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
     Caused by: java.lang.InstantiationException: class com.universo91.towersrock.Pages.SplashScreenActivity has no zero argument constructor
            at java.lang.Class.newInstance(Class.java:1563)
            at android.app.Instrumentation.newActivity(Instrumentation.java:1065)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2199)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
            at android.app.ActivityThread.access$800(ActivityThread.java:144)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5221)
            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:899)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
     Caused by: java.lang.NoSuchMethodException: <init> []
            at java.lang.Class.getConstructor(Class.java:531)
            at java.lang.Class.getDeclaredConstructor(Class.java:510)
            at java.lang.Class.newInstance(Class.java:1561)
            at android.app.Instrumentation.newActivity(Instrumentation.java:1065)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2199)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
            at android.app.ActivityThread.access$800(ActivityThread.java:144)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5221)
            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:899)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
02-20 18:20:58.772    1591-1603/com.universo91.towersrock I/art﹕ Background sticky concurrent mark sweep GC freed 1747(114KB) AllocSpace objects, 0(0B) LOS objects, 37% free, 391KB/623KB, paused 825us total 382.655ms
02-20 18:21:29.824    1690-1690/com.universo91.towersrock D/AndroidRuntime﹕ Shutting down VM
02-20 18:21:29.829    1690-1690/com.universo91.towersrock E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: com.universo91.towersrock, PID: 1690
    java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.universo91.towersrock/com.universo91.towersrock.Pages.SplashScreenActivity}: java.lang.InstantiationException: class com.universo91.towersrock.Pages.SplashScreenActivity has no zero argument constructor
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2209)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
            at android.app.ActivityThread.access$800(ActivityThread.java:144)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5221)
            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:899)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
     Caused by: java.lang.InstantiationException: class com.universo91.towersrock.Pages.SplashScreenActivity has no zero argument constructor
            at java.lang.Class.newInstance(Class.java:1563)
            at android.app.Instrumentation.newActivity(Instrumentation.java:1065)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2199)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
            at android.app.ActivityThread.access$800(ActivityThread.java:144)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5221)
            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:899)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
     Caused by: java.lang.NoSuchMethodException: <init> []
            at java.lang.Class.getConstructor(Class.java:531)
            at java.lang.Class.getDeclaredConstructor(Class.java:510)
            at java.lang.Class.newInstance(Class.java:1561)
            at android.app.Instrumentation.newActivity(Instrumentation.java:1065)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2199)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
            at android.app.ActivityThread.access$800(ActivityThread.java:144)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5221)
            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:899)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
02-20 18:21:30.168    1690-1702/com.universo91.towersrock I/art﹕ Background sticky concurrent mark sweep GC freed 1749(114KB) AllocSpace objects, 0(0B) LOS objects, 37% free, 391KB/623KB, paused 856us total 166.355ms
02-20 18:21:53.341    1690-1690/com.universo91.towersrock I/Process﹕ Sending signal. PID: 1690 SIG: 9
02-20 18:26:00.878    1754-1754/com.universo91.towersrock D/AndroidRuntime﹕ Shutting down VM
02-20 18:26:00.903    1754-1754/com.universo91.towersrock E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: com.universo91.towersrock, PID: 1754
    java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.universo91.towersrock/com.universo91.towersrock.Pages.SplashScreenActivity}: java.lang.IllegalStateException: System services not available to Activities before onCreate()
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2209)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
            at android.app.ActivityThread.access$800(ActivityThread.java:144)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5221)
            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:899)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
     Caused by: java.lang.IllegalStateException: System services not available to Activities before onCreate()
            at android.app.Activity.getSystemService(Activity.java:4989)
            at com.universo91.towersrock.Pages.SplashScreenActivity.<init>(SplashScreenActivity.java:24)
            at java.lang.reflect.Constructor.newInstance(Native Method)
            at java.lang.Class.newInstance(Class.java:1572)
            at android.app.Instrumentation.newActivity(Instrumentation.java:1065)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2199)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
            at android.app.ActivityThread.access$800(ActivityThread.java:144)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5221)
            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:899)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
02-20 18:26:01.144    1754-1766/com.universo91.towersrock I/art﹕ Background sticky concurrent mark sweep GC freed 1745(118KB) AllocSpace objects, 0(0B) LOS objects, 38% free, 382KB/623KB, paused 950us total 131.218ms
02-20 18:26:04.429    1754-1754/com.universo91.towersrock I/Process﹕ Sending signal. PID: 1754 SIG: 9

See Question&Answers more detail:<a href="https://stackoverflow.com/quest

Answer 1

Android activities can have constructors as long as they take zero arguments. And in fact there is such a constructor as soon as you initialize any field when declaring it.

But as your log says, System services not available to Activities before onCreate(), so you can't call getSystemService from the constructor.

So the code in https://stackoverflow.com/a/28636652/53974 is correct, but the reason isn't.