Fix Travis CI build. (#547)

.travis.yml

@@ -1,28 +1,35 @@
 sudo: true
 
-language: android
+language: java
 jdk: oraclejdk8
 
 dist: precise
 
-android:
-  components:
-    - tools
-    - platform-tools
-    - tools
-    - build-tools-26.0.0
-    - android-26
-    - extra-android-m2repository
-
-before_script:
+before_install:
   - export SKIP_OKBUCK=true
   - export EXTRA_OKBUCK_ARGS="--quiet --stacktrace"
-  - mkdir -p $ANDROID_HOME/licenses
-  - echo $android_sdk_license > $ANDROID_HOME/licenses/android-sdk-license
-  - echo $android_sdk_preview_license > $ANDROID_HOME/licenses/android-sdk-preview-license
-  - echo no | android create avd --force -n test -t android-18 --abi armeabi-v7a
+  - export ANDROID_HOME="$HOME"/android-sdk
+  - mkdir -p "$ANDROID_HOME"
+  - export ANDROID_SDK_FILE_NAME=sdk-tools-linux-3859397.zip
+  - sudo apt-get update -q
+  - sudo apt-get install -y curl unzip
+  - curl --fail https://dl.google.com/android/repository/$ANDROID_SDK_FILE_NAME --silent --location --output $ANDROID_SDK_FILE_NAME
+  - unzip -qq $ANDROID_SDK_FILE_NAME -d "$ANDROID_HOME"
+  - rm $ANDROID_SDK_FILE_NAME
+  - export ANDROID_SDK_INSTALL_COMPONENT="echo \"y\" | \"$ANDROID_HOME\"/tools/bin/sdkmanager > /dev/null"
+  - eval $ANDROID_SDK_INSTALL_COMPONENT '"tools"'
+  - eval $ANDROID_SDK_INSTALL_COMPONENT '"platform-tools"'
+  - eval $ANDROID_SDK_INSTALL_COMPONENT '"build-tools;26.0.0"'
+  - eval $ANDROID_SDK_INSTALL_COMPONENT '"platforms;android-26"'
+  - eval $ANDROID_SDK_INSTALL_COMPONENT '"extras;android;m2repository"'
+  - eval $ANDROID_SDK_INSTALL_COMPONENT '"system-images;android-18;default;armeabi-v7a"'
+  - export PATH="$PATH:$ANDROID_HOME/tools/bin:$ANDROID_HOME/platform-tools:$ANDROID_HOME/emulator"
+  - echo no | avdmanager create avd -f -n test -k "system-images;android-18;default;armeabi-v7a"
   - emulator -avd test -no-audio -no-window &
 
+install:
+  - echo "Override default Travis install step to avoid unnecessary './gradlew assemble'."
+
 script:
   - SKIP_OKBUCK= ./buckw --version
   - ./buckw targets --type android_binary java_test groovy_test robolectric_test kotlin_test scala_test | xargs ./buckw build -v 0