Jadex (MAS) Android. Unable to run a test application

After making project in Android Studio 3.0.1 I do not receive any errors or warnings. When I try to run application on emulated device, I get fatal exception. Below I am posting logs. Could you tell me how could I fix that?

E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.kosmos.jadextest, PID: 4377
    java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.kosmos.jadextest/com.example.kosmos.jadextest.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.view.Window.setContentView(int)' on a null object reference
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2718)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2892)
        at android.app.ActivityThread.-wrap11(Unknown Source:0)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1593)
        at android.os.Handler.dispatchMessage(Handler.java:105)
        at android.os.Looper.loop(Looper.java:164)
        at android.app.ActivityThread.main(ActivityThread.java:6541)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767)
    Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.view.Window.setContentView(int)' on a null object reference
        at android.app.Activity.setContentView(Activity.java:2654)
        at com.example.kosmos.jadextest.MainActivity.<init>(MainActivity.java:23)
        at java.lang.Class.newInstance(Native Method)
        at android.app.Instrumentation.newActivity(Instrumentation.java:1173)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2708)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2892) 
        at android.app.ActivityThread.-wrap11(Unknown Source:0) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1593) 
        at android.os.Handler.dispatchMessage(Handler.java:105) 
        at android.os.Looper.loop(Looper.java:164) 
        at android.app.ActivityThread.main(ActivityThread.java:6541) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767) 
Application terminated.