Set ndk path automatically in gradle (#1741)

README.md

@@ -21,8 +21,8 @@ Language mappings are defined in `.tx/config`, with the second code being the on
 # Building
 
 ### Dependencies
-- Android SDK (you can skip this if you are using Android Studio)
-- Android NDK (`$ANDROID_NDK_HOME` should point at the root directory of your NDK)
+- Android SDK, with `$ANDROID_HOME` pointing to it (you can skip this if you are using Android Studio)
+- Android NDK (you should install the required version (`ext.ndkVersionShared` in `./build.gradle`) with the usual tools, such that it's located within `$ANDROID_HOME/ndk/`).
 - Go (see [here](https://docs.syncthing.net/dev/building.html#prerequisites) for the required version)
 - Java Version 11 (you scan skip this if you are using Android Studio, otherwise you might need to set `$JAVA_HOME` accordingly)
 

app/build.gradle

@@ -24,10 +24,10 @@ dependencies {
 }
 
 android {
-    // Changes to these values need to be reflected in `.travis.yml`
+    // Changes to these values need to be reflected in `../docker/Dockerfile`
     compileSdkVersion 29
     buildToolsVersion '29.0.3'
-    ndkVersion = '23.0.7599858'
+    ndkVersion = "${ndkVersionShared}"
 
     buildTypes.debug.applicationIdSuffix ".debug"
     dataBinding.enabled = true

build.gradle

@@ -1,6 +1,11 @@
 // Top-level build file where you can add configuration options common to all sub-projects/modules.
 
 buildscript {
+    ext {
+        // Cannot be called "ndkVersion" as that leads to naming collision
+        // Changes to this value must be reflected in `./docker/Dockerfile`
+        ndkVersionShared = '23.0.7599858'
+    }
     repositories {
         google()
         jcenter()

docker/Dockerfile

@@ -35,9 +35,6 @@ RUN $SDKMANAGER tools platform-tools "build-tools;29.0.3" "platforms;android-29"
 # Accept licenses of newly installed packages
 RUN yes | $SDKMANAGER --licenses
 
-# Setup the NDK path
-ENV ANDROID_NDK_HOME ${ANDROID_HOME}/ndk/${NDK_VERSION}
-
 # Enable prebuild mode
 ENV SYNCTHING_ANDROID_PREBUILT 1
 

syncthing/build-syncthing.py

@@ -60,10 +60,11 @@ def get_min_sdk(project_dir):
 
 def get_ndk_home():
     if not os.environ.get('ANDROID_NDK_HOME', ''):
-        fail('ANDROID_NDK_HOME environment variable not defined')
+        if not os.environ.get('NDK_VERSION', '') or not os.environ.get('ANDROID_HOME', ''):
+            fail('ANDROID_NDK_HOME or NDK_VERSION and ANDROID_HOME environment variable must be defined')
+        return os.path.join(os.environ['ANDROID_HOME'], 'ndk', os.environ['NDK_VERSION'])
     return os.environ['ANDROID_NDK_HOME']
 
-
 if platform.system() not in PLATFORM_DIRS:
     fail('Unsupported python platform %s. Supported platforms: %s', platform.system(),
          ', '.join(PLATFORM_DIRS.keys()))

syncthing/build.gradle

@@ -1,4 +1,5 @@
 task buildNative(type: Exec) {
+    environment "NDK_VERSION", "$ndkVersionShared"
     inputs.dir("$projectDir/src/")
     outputs.dir("$projectDir/../app/src/main/jniLibs/")
     executable = 'python3'