Upgrade to AndroidX SDK

[BlaidddDrwg]

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• [ X] Bug exists Release Version 1.1.1 (Java Repository Master Branch)
• Bug exists in Snapshot Version 1.1.2-SNAPSHOT (Android Service Repository Master Branch) - Couldn't find this branch. But the same issue is there in the 'develop' branch. There does not seem to be a 1.1.2 tag anywhere.
• Bug is just in the Sample Application.

__Android API Version Bug Seen on:__1.1.0

Android Version Bug Seen on:

Please also check that if you have found the bug in the Release version (1.1.1) that you check that it also exists in the Snapshot (1.1.2-SNAPSHOT) before raising a bug.
Seriously, looked for 1.1.2-SNAPSHOT, but was not able to find it anywhere. This is what I have:

Description of Bug:

Basically, the unit tests for the MQTT Android Service (specifically AndroidServiceWithActionListenerTest.java and https://github.com/eclipse/paho.mqtt.android/blob/master/org.eclipse.paho.android.service/src/androidTest/java/org/eclipse/paho/android/AndroidServiceTest.java) reference ServiceTestCase that is loooooong gone.

Transitioning all the tests to the (now recommended ServiceTestRule in AndroidX makes Paho more future-proof, and we can run the entire test suite without being tied down to obsolete Android releases/SDK versions.

Console Log output (if available):