Proguard leads to crash

When setting

minifyEnabled true

useProguard true

in my gradle I get a NullPointerException like this :

java.lang.RuntimeException: Unable to start activity ComponentInfo{com.jafari.farhad.ubazdidcontroller/com.jafari.farhad.ubazdidcontroller.LoginActivity}: java.lang.NullPointerException
  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
  at android.app.ActivityThread.access$600(ActivityThread.java:141)
  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
  at android.os.Handler.dispatchMessage(Handler.java:99)
  at android.os.Looper.loop(Looper.java:137)
  at android.app.ActivityThread.main(ActivityThread.java:5041)
  at java.lang.reflect.Method.invokeNative(Native Method)
  at java.lang.reflect.Method.invoke(Method.java:511)
  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
  at dalvik.system.NativeStart.main(Native Method)
 Caused by: java.lang.NullPointerException
  at com.jafari.farhad.ubazdidcontroller.LoginActivity.onCreate(Unknown Source)
  at android.app.Activity.performCreate(Activity.java:5104)
  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230) 
  at android.app.ActivityThread.access$600(ActivityThread.java:141) 
  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234) 
  at android.os.Handler.dispatchMessage(Handler.java:99) 
  at android.os.Looper.loop(Looper.java:137) 
  at android.app.ActivityThread.main(ActivityThread.java:5041) 
  at java.lang.reflect.Method.invokeNative(Native Method) 
  at java.lang.reflect.Method.invoke(Method.java:511) 
  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793) 
  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560) 
  at dalvik.system.NativeStart.main(Native Method) 

Gradle is :

buildTypes {
    debug {
        minifyEnabled false
        proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
    }
    release {
        minifyEnabled true
        useProguard true
        proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
    }
}

While reading through StackOverflow I found some settings for the proguard-rules.pro file like this:

    -dontusemixedcaseclassnames
    -dontskipnonpubliclibraryclasses
    -verbose
    
    
    -dontoptimize
    -dontpreverify
    
    -keepattributes *Annotation*
    -keep public class com.google.vending.licensing.ILicensingService
    -keep public class com.android.vending.licensing.ILicensingService
    
    # For native methods, see http://proguard.sourceforge.net/manual/examples.html#native
    -keepclasseswithmembernames class * {
        native ;
    }
    
    # keep setters in Views so that animations can still work.
    # see http://proguard.sourceforge.net/manual/examples.html#beans
    -keepclassmembers public class * extends android.view.View {
       void set*(***);
       *** get*();
    }
    
    # We want to keep methods in Activity that could be used in the XML attribute onClick
    -keepclassmembers class * extends android.app.Activity {
       public void *(android.view.View);
    }
    
    # For enumeration classes, see http://proguard.sourceforge.net/manual/examples.html#enumerations
    -keepclassmembers enum * {
        public static **[] values();
        public static ** valueOf(java.lang.String);
    }
    
    -keepclassmembers class * implements android.os.Parcelable {
      public static final android.os.Parcelable$Creator CREATOR;
    }
    
    -keepclassmembers class **.R$* {
        public static ;
    }
    
    -dontwarn android.support.**
    
    # Understand the @Keep support annotation.
    -keep class android.support.annotation.Keep
    
    -keep @android.support.annotation.Keep class * {*;}
    
    -keepclasseswithmembers class * {
        @android.support.annotation.Keep ;
    }
    
    -keepclasseswithmembers class * {
        @android.support.annotation.Keep ;
    }
    
    -keepclasseswithmembers class * {
        @android.support.annotation.Keep (...);
    }

When I disbale minifyEnabled everthing works fine. Thancks