Update build.gradle for latest AGP (#2026)

* update build.gradle for latest AGP

* bump Android Gradle Plugin version to 4.1.1
* ignore .cxx which was externalNativeBuild in old versions

Use variable 'rootDir' instead of using relative path.

* build.gradle copies AAR files to libs/

.gitignore

@@ -9,6 +9,7 @@ gradle/
 gradlew*
 local.properties
 build/
+support/.cxx
 
 bin/
 /_CPack_Packages

support/build.gradle

@@ -1,3 +1,4 @@
+import java.nio.file.Paths
 
 // General gradle arguments for root project
 buildscript {    
@@ -7,24 +8,25 @@ buildscript {
     }
     dependencies {
         //
-        // https://developer.android.com/studio/releases/gradle-plugin
+        // https://developer.android.com/studio/releases/gradle-plugin#updating-gradle
         //
-        // Notice that 3.3.0 here is the version of [Android Gradle Plugin]
-        // Accroding to URL above you will need Gradle 5.0 or higher
+        // Notice that 4.0.0 here is the version of [Android Gradle Plugin]
+        // Accroding to URL above you will need Gradle 6.1 or higher
         //
-        // If you are using Android Studio, and it is using Gradle's lower 
-        // version, Use the plugin version 3.1.3 ~ 3.2.0 for Gradle 4.4 ~ 4.10
-        classpath 'com.android.tools.build:gradle:3.3.0'
+        classpath "com.android.tools.build:gradle:4.1.1"
     }
 }
 repositories {
     google()
     jcenter()
 }
-    
-// Output: Shared library (.so) for Android 
-apply plugin: 'com.android.library'
 
+// Project's root where CMakeLists.txt exists: rootDir/support/.cxx -> rootDir
+def rootDir = Paths.get(project.buildDir.getParent()).getParent()
+println("rootDir: ${rootDir}")
+
+// Output: Shared library (.so) for Android 
+apply plugin: "com.android.library"
 android {
     compileSdkVersion 25    // Android 7.0
 
@@ -41,13 +43,13 @@ android {
             include  "arm64-v8a", "armeabi-v7a", "x86_64"
         }
     }
+    ndkVersion "21.3.6528147" // ANDROID_NDK_HOME is deprecated. Be explicit
 
     defaultConfig {
         minSdkVersion 21    // Android 5.0+
         targetSdkVersion 25 // Follow Compile SDK
-        versionCode 21      // Follow release count
-        versionName "5.3.0" // Follow Official version
-        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
+        versionCode 34      // Follow release count
+        versionName "7.1.2" // Follow Official version
         
         externalNativeBuild {
             cmake {
@@ -56,9 +58,9 @@ android {
                 arguments "-DFMT_TEST=false"            // Skip test
                 arguments "-DFMT_DOC=false"             // Skip document
                 cppFlags  "-std=c++17"
+                targets   "fmt"
             }
         }
-        println("Gradle CMake Plugin: ")
         println(externalNativeBuild.cmake.cppFlags)
         println(externalNativeBuild.cmake.arguments)
     }
@@ -69,16 +71,27 @@ android {
     //    neighbor of the top level cmake
     externalNativeBuild {
         cmake {
-            path "../CMakeLists.txt"
+            version "3.10.0+"
+            path "${rootDir}/CMakeLists.txt"
             // buildStagingDirectory "./build"  // Custom path for cmake output
         }
-        //println(cmake.path)
     }
     
     sourceSets{
         // Android Manifest for Gradle
         main {
-            manifest.srcFile 'AndroidManifest.xml'
+            manifest.srcFile "AndroidManifest.xml"
+        }
+    }
+
+    // https://developer.android.com/studio/build/native-dependencies#build_system_configuration
+    buildFeatures {
+        prefab true
+        prefabPublishing true
+    }
+    prefab {
+        fmt {
+            headers "${rootDir}/include"
         }
     }
 }
@@ -88,20 +101,32 @@ assemble.doLast
     // Instead of `ninja install`, Gradle will deploy the files.
     // We are doing this since FMT is dependent to the ANDROID_STL after build
     copy {
-        from 'build/intermediates/cmake'
-        into '../libs'
+        from "build/intermediates/cmake"
+        into "${rootDir}/libs"
     }
     // Copy debug binaries
     copy {
-        from '../libs/debug/obj'
-        into '../libs/debug'
+        from "${rootDir}/libs/debug/obj"
+        into "${rootDir}/libs/debug"
     }
     // Copy Release binaries
     copy {
-        from '../libs/release/obj'
-        into '../libs/release'
+        from "${rootDir}/libs/release/obj"
+        into "${rootDir}/libs/release"
     }
     // Remove empty directory
-    delete '../libs/debug/obj'
-    delete '../libs/release/obj'
+    delete "${rootDir}/libs/debug/obj"
+    delete "${rootDir}/libs/release/obj"
+
+    // Copy AAR files. Notice that the aar is named after the folder of this script.
+    copy {
+        from "build/outputs/aar/support-release.aar"
+        into "${rootDir}/libs"
+        rename "support-release.aar", "fmt-release.aar"
+    }
+    copy {
+        from "build/outputs/aar/support-debug.aar"
+        into "${rootDir}/libs"
+        rename "support-debug.aar", "fmt-debug.aar"
+    }
 }