android: change ANDROID_STL='c++_shared'

- fixes crashes in face-detector application
- libc++_shared.so is bundled automatically via CMake helper project

modules/java/android_sdk/CMakeLists.txt

@@ -123,6 +123,16 @@ foreach(file ${seed_project_files_rel})
   endif()
 endforeach()
 
+# copy libcxx_helper
+set(__base_dir "${CMAKE_CURRENT_SOURCE_DIR}/")
+file(GLOB_RECURSE __files_rel RELATIVE "${__base_dir}/" "${__base_dir}/libcxx_helper/*")
+foreach(file ${__files_rel})
+  configure_file("${__base_dir}/${file}" "${OPENCV_JAVA_DIR}/${file}" @ONLY)
+  list(APPEND depends "${__base_dir}/${file}")
+  get_filename_component(install_subdir "${file}" PATH)
+  install(FILES "${OPENCV_JAVA_DIR}/${file}" DESTINATION "${JAVA_INSTALL_ROOT}/../${install_subdir}" COMPONENT java)
+endforeach()
+
 list(APPEND depends gen_opencv_java_source "${OPENCV_DEPHELPER}/gen_opencv_java_source")
 ocv_copyfiles_add_target(${the_module}_android_source_copy JAVA_SRC_COPY "Copy Java(Andoid SDK) source files" ${depends})
 file(REMOVE "${OPENCV_DEPHELPER}/${the_module}_android_source_copy")  # force rebuild after CMake run

modules/java/android_sdk/android_gradle_lib/build.gradle

@@ -7,6 +7,13 @@ android {
     defaultConfig {
         minSdkVersion @ANDROID_MIN_SDK_VERSION@
         targetSdkVersion @ANDROID_TARGET_SDK_VERSION@
+
+        externalNativeBuild {
+            cmake {
+                arguments "-DANDROID_STL=@ANDROID_STL@"
+                targets "opencv_jni_shared"
+            }
+        }
     }
 
     buildTypes {
@@ -37,6 +44,12 @@ android {
             manifest.srcFile 'AndroidManifest.xml'
         }
     }
+
+    externalNativeBuild {
+        cmake {
+            path (project.projectDir.toString() + '/libcxx_helper/CMakeLists.txt')
+        }
+    }
 }
 
 dependencies {

modules/java/android_sdk/build.gradle.in

@@ -99,6 +99,13 @@ android {
     defaultConfig {
         minSdkVersion @ANDROID_MIN_SDK_VERSION@
         targetSdkVersion @ANDROID_TARGET_SDK_VERSION@
+
+        externalNativeBuild {
+            cmake {
+                arguments "-DANDROID_STL=@ANDROID_STL@"
+                targets "opencv_jni_shared"
+            }
+        }
     }
 
     buildTypes {
@@ -129,6 +136,12 @@ android {
             manifest.srcFile 'java/AndroidManifest.xml'
         }
     }
+
+    externalNativeBuild {
+        cmake {
+            path (project.projectDir.toString() + '/libcxx_helper/CMakeLists.txt')
+        }
+    }
 }
 
 dependencies {

modules/java/android_sdk/libcxx_helper/CMakeLists.txt

@@ -0,0 +1,4 @@
+cmake_minimum_required(VERSION 3.6)
+
+# dummy target to bring libc++_shared.so into packages
+add_library(opencv_jni_shared STATIC dummy.cpp)

modules/java/android_sdk/libcxx_helper/dummy.cpp

@@ -0,0 +1 @@
+// empty