Added new Android build target and makefile utils.

Previously Android.mk only had a rule for the Flatbuffers test. There
is now an empty module definition so that flatbuffers can be included
as an Android module in other projects.

Additionally, android/jni/include.mk has been added which contains
some utility functions that can be used by projects using Flatbuffers
to generate header build rules and set up dependencies.

A sample project has been added to the samples directory to
demonstrate how to use flatbuffers with Android.

Tested by compiling Android project on Linux.

Change-Id: I25d6da40f6531777b22f7371187e0a2f4e903ad4

3 files changed, 205 insertions, 10 deletions

diff --git a/android/build_apk.sh b/android/build_apk.sh
index 3520626d..94a7275f 100755
--- a/android/build_apk.sh
+++ b/android/build_apk.sh
@@ -235,8 +235,18 @@ select_android_build_target() {
   local android_build_target=
   for android_target in $(echo "${android_targets_installed}" | \
                           awk -F- '{ print $2 }' | sort -n); do
-    if [[ $((android_target)) -ge \
+    local isNumber='^[0-9]+$'
+    # skip preview API releases e.g. 'android-L'
+    if [[ $android_target =~ $isNumber ]]; then
+      if [[ $((android_target)) -ge \
           $((BUILDAPK_ANDROID_TARGET_MINVERSION)) ]]; then
+        android_build_target="android-${android_target}"
+        break
+      fi
+    else
+      # The API version is a letter
+      # Letters are sorted to the end by 'sort -n'
+      # so we're out of numbered platforms.  Use this one.
       android_build_target="android-${android_target}"
       break
     fi
@@ -415,14 +425,18 @@ main() {
   local build_package=1
   for opt; do
     case ${opt} in
+      # NDK_DEBUG=0 tells ndk-build to build this as debuggable but to not
+      # modify the underlying code whereas NDK_DEBUG=1 also builds as debuggable
+      # but does modify the code
       NDK_DEBUG=1) ant_target=debug ;;
+      NDK_DEBUG=0) ant_target=debug ;;
       ADB_DEVICE*) adb_device="$(\
         echo "${opt}" | sed -E 's/^ADB_DEVICE=([^ ]+)$/-s \1/;t;s/.*//')" ;;
       BUILD=0) disable_build=1 ;;
       DEPLOY=0) disable_deploy=1 ;;
       RUN_DEBUGGER=1) run_debugger=1 ;;
       LAUNCH=0) launch=0 ;;
-      clean) build_package=0 ;;
+      clean) build_package=0 disable_deploy=1 launch=0 ;;
       -h|--help|help) usage ;;
     esac
   done
diff --git a/android/jni/Android.mk b/android/jni/Android.mk
index 47f2a87b..01e1141c 100755
--- a/android/jni/Android.mk
+++ b/android/jni/Android.mk
@@ -16,16 +16,25 @@
 
 LOCAL_PATH := $(call my-dir)
 
+# Empty static library so that other projects can include FlatBuffers as a
+# module.
 include $(CLEAR_VARS)
+LOCAL_MODULE := flatbuffers
+LOCAL_EXPORT_C_INCLUDES := $(LOCAL_PATH)/../../include
+LOCAL_EXPORT_CPPFLAGS := -std=c++11 -fexceptions -Wall -Wno-literal-suffix
+include $(BUILD_STATIC_LIBRARY)
 
-LOCAL_MODULE    := FlatBufferTest
-LOCAL_C_INCLUDES := $(LOCAL_PATH)/../../include
-LOCAL_SRC_FILES := main.cpp ../../tests/test.cpp ../../src/idl_parser.cpp ../../src/idl_gen_text.cpp ../../src/idl_gen_fbs.cpp
-LOCAL_LDLIBS    := -llog -landroid
-LOCAL_STATIC_LIBRARIES := android_native_app_glue
-LOCAL_ARM_MODE:=arm
-LOCAL_CPPFLAGS += -std=c++11 -fexceptions -Wall -Wno-literal-suffix
-
+# FlatBuffers test
+include $(CLEAR_VARS)
+LOCAL_MODULE := FlatBufferTest
+LOCAL_SRC_FILES := main.cpp \
+                   ../../tests/test.cpp \
+                   ../../src/idl_parser.cpp \
+                   ../../src/idl_gen_text.cpp \
+                   ../../src/idl_gen_fbs.cpp
+LOCAL_LDLIBS := -llog -landroid
+LOCAL_STATIC_LIBRARIES := android_native_app_glue flatbuffers
+LOCAL_ARM_MODE := arm
 include $(BUILD_SHARED_LIBRARY)
 
 $(call import-module,android/native_app_glue)
diff --git a/android/jni/include.mk b/android/jni/include.mk
new file mode 100644
index 00000000..d1a373cf
--- /dev/null
+++ b/android/jni/include.mk
@@ -0,0 +1,172 @@
+# Copyright 2014 Google Inc. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# This file contains utility functions for Android projects using Flatbuffers.
+# To use this file, include it in your project's Android.mk by calling near the
+# top of your android makefile like so:
+#
+#     include $(FLATBUFFERS_DIR)/android/jni/include.mk
+#
+# You will also need to import the flatbuffers module using the standard
+# import-module function.
+#
+# The main functionality this file provides are the following functions:
+# flatbuffers_fbs_to_h: Converts flatbuffer schema paths to header paths.
+# flatbuffers_header_build_rule:
+#     Creates a build rule for a schema's generated header. This build rule
+#     has a dependency on the flatc compiler which will be built if necessary.
+# flatbuffers_header_build_rules:
+#     Creates build rules for generated headers for each schema listed and sets
+#     up depenedendies.
+#
+# More information and example usage can be found in the comments preceeding
+# each function.
+
+# Targets to build the Flatbuffers compiler as well as some utility definitions
+ifeq (,$(FLATBUFFERS_INCLUDE_MK_))
+FLATBUFFERS_INCLUDE_MK_ := 1
+
+PROJECT_OS := $(OS)
+ifeq (,$(OS))
+PROJECT_OS := $(shell uname -s)
+else
+ifneq ($(findstring Windows,$(PROJECT_OS)),)
+PROJECT_OS := Windows
+endif
+endif
+
+# The following block generates build rules which result in headers being
+# rebuilt from flatbuffers schemas.
+
+# Directory that contains the FlatBuffers compiler.
+FLATBUFFERS_FLATC_PATH?=$(CURDIR)/bin
+ifeq (Windows,$(PROJECT_OS))
+FLATBUFFERS_FLATC := $(FLATBUFFERS_FLATC_PATH)/Debug/flatc.exe
+endif
+ifeq (Linux,$(PROJECT_OS))
+FLATBUFFERS_FLATC := $(FLATBUFFERS_FLATC_PATH)/flatc
+endif
+ifeq (Darwin,$(PROJECT_OS))
+FLATBUFFERS_FLATC := $(FLATBUFFERS_FLATC_PATH)/Debug/flatc
+endif
+
+# Search for cmake.
+CMAKE_ROOT := $(realpath $(LOCAL_PATH)/../../../../../../prebuilts/cmake)
+ifeq (,$(CMAKE))
+ifeq (Linux,$(PROJECT_OS))
+CMAKE := $(wildcard $(CMAKE_ROOT)/linux-x86/current/bin/cmake*)
+endif
+ifeq (Darwin,$(PROJECT_OS))
+CMAKE := \
+  $(wildcard $(CMAKE_ROOT)/darwin-x86_64/current/*.app/Contents/bin/cmake)
+endif
+ifeq (Windows,$(PROJECT_OS))
+CMAKE := $(wildcard $(CMAKE_ROOT)/windows/current/bin/cmake*)
+endif
+endif
+ifeq (,$(CMAKE))
+CMAKE := cmake
+endif
+
+# Generate a host build rule for the flatbuffers compiler.
+FLATBUFFERS_CMAKELISTS_DIR := \
+  $(realpath $(dir $(lastword $(MAKEFILE_LIST)))/../..)
+ifeq (Windows,$(PROJECT_OS))
+define build_flatc_recipe
+	cd  & jni\build_flatc.bat $(CMAKE)
+endef
+endif
+ifeq (Linux,$(PROJECT_OS))
+define build_flatc_recipe
+	mkdir -p bin && cd bin && $(CMAKE) $(FLATBUFFERS_CMAKELISTS_DIR) \
+	  && $(MAKE) flatc
+endef
+endif
+ifeq (Darwin,$(PROJECT_OS))
+define build_flatc_recipe
+	cd $(FLATBUFFERS_CMAKELISTS_DIR) && "$(CMAKE)" -GXcode . && \
+        xcodebuild -target flatc
+endef
+endif
+ifeq (,$(build_flatc_recipe))
+ifeq (,$(FLATBUFFERS_FLATC))
+$(error flatc binary not found!)
+endif
+endif
+
+# Generate a build rule for flatc.
+ifeq ($(strip $(FLATBUFFERS_FLATC)),)
+flatc_target := build_flatc
+.PHONY: $(flatc_target)
+else
+flatc_target := $(FLATBUFFERS_FLATC)
+endif
+$(flatc_target):
+	$(call build_flatc_recipe)
+
+# $(flatbuffers_fbs_to_h schema_dir,output_dir,path)
+#
+# Convert the specified schema path to a Flatbuffers generated header path.
+# For example:
+#
+# $(call flatbuffers_fbs_to_h,$(MY_PROJ_DIR)/schemas,\
+#   $(MY_PROJ_DIR)/gen/include,$(MY_PROJ_DIR)/schemas/example.fbs)
+#
+# This will convert the file path `$(MY_PROJ_DIR)/schemas/example.fbs)` to
+# `$(MY_PROJ_DIR)/gen/include/example_generated.h`
+define flatbuffers_fbs_to_h
+$(subst $(1),$(2),$(patsubst %.fbs,%_generated.h,$(3)))
+endef
+
+# $(flatbuffers_header_build_rule schema_file,schema_dir,output_dir,\
+#   schema_include_dirs)
+#
+# Generate a build rule that will convert a Flatbuffers schema to a generated
+# header derived from the schema filename using flatbuffers_fbs_to_h. For
+# example:
+#
+# $(call flatbuffers_header_build_rule,$(MY_PROJ_DIR)/schemas/example.fbs,\
+#   $(MY_PROJ_DIR)/schemas,$(MY_PROJ_DIR)/gen/include)
+#
+# The final argument, schema_include_dirs, is optional and is only needed when
+# the schema files depend on other schema files outside their own directory.
+define flatbuffers_header_build_rule
+$(eval \
+  $(call flatbuffers_fbs_to_h,$(2),$(3),$(1)): $(1) $(flatc_target)
+	$(call host-echo-build-step,generic,Generate) \
+		$(subst $(LOCAL_PATH)/,,$(call flatbuffers_fbs_to_h,$(2),$(3),$(1)))
+	$(hide) $$(FLATBUFFERS_FLATC) --gen-includes \
+	  $(foreach include,$(4),-I $(include)) -o $$(dir $$@) -c $$<)
+endef
+
+# $(flatbuffers_header_build_rules schema_files,schema_dir,output_dir,\
+#   schema_include_dirs,src_files))
+#
+# Use this in your own Android.mk file to generate build rules that will
+# generate header files for your flatbuffer schemas as well as automatically
+# set your source files to be dependent on the generated headers. For example:
+#
+# $(call flatbuffers_header_build_rules,$(MY_PROJ_SCHEMA_FILES),\
+#   $(MY_PROJ_SCHEMA_DIR),$(MY_PROJ_GENERATED_OUTPUT_DIR),
+#   $(MY_PROJ_SCHEMA_INCLUDE_DIRS),$(LOCAL_SRC_FILES))
+define flatbuffers_header_build_rules
+$(foreach schema,$(1),\
+  $(call flatbuffers_header_build_rule,$(schema),$(2),$(3),$(4)))\
+$(foreach src,$(5),\
+  $(eval $(LOCAL_PATH)/$$(src): \
+	  $(foreach schema,$(1),$(call flatbuffers_fbs_to_h,$(2),$(3),$(schema)))))
+endef
+
+endif  # FLATBUFFERS_INCLUDE_MK_
+