Run emulator tests on travis.

Also parallelizes the build a bit so that samples, the library, and the
emulator tests are built and run independently.

.travis.yml

 language: android
+sudo: required
+dist: trusty
+
 android:
   components:
   - tools
   - platform-tools
+  - tools
   - build-tools-26.0.1
   - android-26
+  - android-22
+  - sys-img-armeabi-v7a-android-22
 
-  licenses:
+licenses:
   - 'android-sdk-license.*'
 
 jdk:
   - oraclejdk8
 
-sudo: false
+env: 
+  matrix:
+    - COMPONENT=unit
+    - COMPONENT=instrumentation
+    - COMPONENT=samples
+
+before_script:
+  - ./scripts/travis_before_script.sh
 
-script: 'travis_retry ./gradlew build --parallel'
+script: 
+  - ./scripts/travis_script.sh
 
 after_success:
-- scripts/travis-sonatype-publish.sh
-- ./gradlew jacocoTestReport coveralls
+  - ./scripts/travis_after_success.sh
 
 before_cache:
   - rm -f $HOME/.gradle/caches/modules-2/modules-2.lock

scripts/travis_after_success.sh

+#!/usr/bin/env bash
+
+set -e
+
+if [ "$COMPONENT" == "unit" ]; then
+  ./scripts/travis_sonatype_publish.sh
+  ./gradlew jacocoTestReport coveralls
+fi

scripts/travis_before_script.sh

+#!/usr/bin/env bash
+
+set -e
+
+if [ "$COMPONENT" == "instrumentation" ]; then
+  echo "Starting emulator for $COMPONENT tests"
+  ./scripts/travis_create_emulator.sh &
+
+fi
+

scripts/travis_create_emulator.sh

+#!/usr/bin/env bash
+
+set -e
+
+echo no | android create avd --force -n test -t android-22 --abi armeabi-v7a
+QEMU_AUDIO_DRV=none emulator -engine classic -avd test -no-window &
+
+exit 0

scripts/travis_instrumentation.sh

+#!/usr/bin/env bash
+
+set -e
+
+./gradlew :library:assembleDebug :library:assembleDebugAndroidTest --parallel
+
+echo "Waiting for emulator..."
+android-wait-for-emulator
+
+./gradlew :library:connectedCheck
+

scripts/travis_samples.sh

+#!/usr/bin/env bash
+
+set -e
+
+./gradlew :samples:flickr:build \
+  :samples:giphy:build \
+  :samples:contacturi:build \
+  :samples:gallery:build \
+  :samples:imgur:build \
+  :samples:svg:build \
+  --parallel

scripts/travis_script.sh

+#!/usr/bin/env bash
+
+set -e
+
+if [ "$COMPONENT" == "unit" ]; then
+  ./scripts/travis_unit.sh
+elif [ "$COMPONENT" == "instrumentation" ]; then
+  ./scripts/travis_instrumentation.sh
+elif [ "$COMPONENT" == "samples" ]; then
+  ./scripts/travis_samples.sh
+else
+  echo "Unrecognized component: $COMPONENT"
+  exit 1
+fi

scripts/travis_unit.sh

+#!/usr/bin/env bash
+
+set -e
+
+./gradlew build \
+  -x :samples:flickr:build \
+  -x :samples:giphy:build \
+  -x :samples:contacturi:build \
+  -x :samples:gallery:build \
+  -x :samples:imgur:build \
+  -x :samples:svg:build \
+  -x testReleaseUnitTest --parallel