Fix googlemaps#207 - Add Travis CI support

* This patch keeps the project at `compileSdkVersion 23` while running on the API Level 21 Google API emulator on Travis, because:
 a) Google API emulator image is needed to run tests that require Google Play Services (see https://developers.google.com/android/guides/setup, googlemaps#203 (comment))
 b) API Level 23 Google API emulator seems to have a bug preventing use on Travis - see googlemaps#207 (comment)
* When the issue with the API Level 23 Google API emulator is resolved, the `EMULATOR_API_LEVEL` variable in .travis.yml can be bumped to 23 as well.
* This patch also adds a command-line option to disable pre-dexing, which is used on Travis to decrease build times (see http://tools.android.com/tech-docs/new-build-system/tips#TOC-Improving-Build-Server-performance.)

Author: barbeau

.travis.yml

@@ -0,0 +1,47 @@
+language: android
+jdk: oraclejdk7
+# Use the Travis Container-Based Infrastructure
+sudo: false
+
+cache:
+  directories:
+    - ${TRAVIS_BUILD_DIR}/gradle/caches/
+    - ${TRAVIS_BUILD_DIR}/gradle/wrapper/dists/
+
+env:
+  global:
+    - ANDROID_API_LEVEL=23
+    - EMULATOR_API_LEVEL=21
+    - ANDROID_BUILD_TOOLS_VERSION=23.0.0
+    - ANDROID_ABI=google_apis/armeabi-v7a
+    - ADB_INSTALL_TIMEOUT=20 # minutes (2 minutes by default)
+
+android:
+  components:
+    - platform-tools
+    - tools
+    - build-tools-$ANDROID_BUILD_TOOLS_VERSION
+    - android-$ANDROID_API_LEVEL
+    - android-$EMULATOR_API_LEVEL
+    # For Google APIs
+    - addon-google_apis-google-$ANDROID_API_LEVEL
+    - addon-google_apis-google-$EMULATOR_API_LEVEL
+    # Google Play Services
+    - extra-google-google_play_services
+    # Support library
+    - extra-android-support
+    # Latest artifacts in local repository
+    - extra-google-m2repository
+    - extra-android-m2repository
+    # Specify at least one system image
+    - sys-img-armeabi-v7a-addon-google_apis-google-$ANDROID_API_LEVEL
+    - sys-img-armeabi-v7a-addon-google_apis-google-$EMULATOR_API_LEVEL
+
+before_script:
+  # Create and start emulator
+  - echo no | android create avd --force -n test -t "Google Inc.:Google APIs:"$EMULATOR_API_LEVEL --abi $ANDROID_ABI
+  - emulator -avd test -no-skin -no-audio -no-window &
+  - android-wait-for-emulator
+
+script:
+  - ./gradlew connectedCheck -x library:signArchives -PdisablePreDex

README.md

@@ -1,4 +1,4 @@
-[![Maven Central](https://maven-badges.herokuapp.com/maven-central/com.google.maps.android/android-maps-utils/badge.svg)](https://maven-badges.herokuapp.com/maven-central/com.google.maps.android/android-maps-utils)
+[![Maven Central](https://maven-badges.herokuapp.com/maven-central/com.google.maps.android/android-maps-utils/badge.svg)](https://maven-badges.herokuapp.com/maven-central/com.google.maps.android/android-maps-utils)[![Build Status](https://travis-ci.org/googlemaps/android-maps-utils.svg?branch=master)](https://travis-ci.org/googlemaps/android-maps-utils)
 
 # Google Maps Android API utility library
 

build.gradle

@@ -7,3 +7,18 @@ buildscript {
         classpath 'com.android.tools.build:gradle:1.3.0'
     }
 }
+/**
+ * Improve build server performance by allowing disabling of pre-dexing
+ * (see http://tools.android.com/tech-docs/new-build-system/tips#TOC-Improving-Build-Server-performance.)
+ */
+project.ext.preDexLibs = !project.hasProperty('disablePreDex')
+
+subprojects {
+    project.plugins.whenPluginAdded { plugin ->
+        if ("com.android.build.gradle.AppPlugin".equals(plugin.class.name)) {
+            project.android.dexOptions.preDexLibraries = rootProject.ext.preDexLibs
+        } else if ("com.android.build.gradle.LibraryPlugin".equals(plugin.class.name)) {
+            project.android.dexOptions.preDexLibraries = rootProject.ext.preDexLibs
+        }
+    }
+}