android tutorial pubsub don't work

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Hi,
I installed rosjava_core and android_core in my ros groovy pc, then i followed the tutorials and i tried the android_camera tutorial app which works fine.
Now i tried the android_tutorial_pubsub app because i must write an app which publish a string but it does't work. I followed this procedure:

$ roscd android_core
$ android update project --path ./android_tutorial_pubsub/ --target android-17
$ cd android_tutorial_pubsub
$ ../gradlew debug
$ adb -d install -r ./bin/MainActivity-debug.apk
$ roscore &
$ rosrun roscpp_tutorials listener

but it does't subscribe to anything. What is the issue?