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

samples/android/jni/Android.mk

@@ -0,0 +1,56 @@
+# Copyright (c) 2013 Google, Inc.
+#
+# This software is provided 'as-is', without any express or implied
+# warranty.  In no event will the authors be held liable for any damages
+# arising from the use of this software.
+# Permission is granted to anyone to use this software for any purpose,
+# including commercial applications, and to alter it and redistribute it
+# freely, subject to the following restrictions:
+# 1. The origin of this software must not be misrepresented; you must not
+# claim that you wrote the original software. If you use this software
+# in a product, an acknowledgment in the product documentation would be
+# appreciated but is not required.
+# 2. Altered source versions must be plainly marked as such, and must not be
+# misrepresented as being the original software.
+# 3. This notice may not be removed or altered from any source distribution.
+
+LOCAL_PATH := $(call my-dir)
+FLATBUFFERS_ROOT_DIR := $(LOCAL_PATH)/../../..
+
+# FlatBuffers test
+include $(CLEAR_VARS)
+
+# Include the FlatBuffer utility function to generate header files from schemas.
+include $(FLATBUFFERS_ROOT_DIR)/android/jni/include.mk
+
+LOCAL_MODULE := sample_android_project
+
+# Set up some useful variables to identify schema and output directories and
+# schema files.
+ANDROID_SAMPLE_GENERATED_OUTPUT_DIR := $(LOCAL_PATH)/gen/include
+ANDROID_SAMPLE_SCHEMA_DIR := $(LOCAL_PATH)/schemas
+ANDROID_SAMPLE_SCHEMA_FILES := $(ANDROID_SAMPLE_SCHEMA_DIR)/animal.fbs
+
+LOCAL_C_INCLUDES := $(ANDROID_SAMPLE_GENERATED_OUTPUT_DIR)
+
+$(info $(LOCAL_C_INCLUDES))
+
+LOCAL_SRC_FILES := main.cpp
+
+LOCAL_CPPFLAGS := -std=c++11 -fexceptions -Wall -Wno-literal-suffix
+LOCAL_LDLIBS := -llog -landroid
+LOCAL_ARM_MODE := arm
+LOCAL_STATIC_LIBRARIES := android_native_app_glue flatbuffers
+
+ifeq (,$(ANDROID_SAMPLE_RUN_ONCE))
+ANDROID_SAMPLE_RUN_ONCE := 1
+$(call flatbuffers_header_build_rules,$(ANDROID_SAMPLE_SCHEMA_FILES),$(ANDROID_SAMPLE_SCHEMA_DIR),$(ANDROID_SAMPLE_GENERATED_OUTPUT_DIR),,$(LOCAL_SRC_FILES))
+endif
+
+include $(BUILD_SHARED_LIBRARY)
+
+# Path to Flatbuffers root directory.
+$(call import-add-path,$(FLATBUFFERS_ROOT_DIR)/..)
+
+$(call import-module,flatbuffers/android/jni)
+$(call import-module,android/native_app_glue)

samples/android/jni/Application.mk

@@ -0,0 +1,22 @@
+# Copyright (c) 2014 Google, Inc.
+#
+# This software is provided 'as-is', without any express or implied
+# warranty.  In no event will the authors be held liable for any damages
+# arising from the use of this software.
+# Permission is granted to anyone to use this software for any purpose,
+# including commercial applications, and to alter it and redistribute it
+# freely, subject to the following restrictions:
+# 1. The origin of this software must not be misrepresented; you must not
+# claim that you wrote the original software. If you use this software
+# in a product, an acknowledgment in the product documentation would be
+# appreciated but is not required.
+# 2. Altered source versions must be plainly marked as such, and must not be
+# misrepresented as being the original software.
+# 3. This notice may not be removed or altered from any source distribution.
+APP_PLATFORM := android-10
+APP_PROJECT_PATH := $(call my-dir)/..
+APP_STL := gnustl_static
+
+APP_ABI := armeabi-v7a
+NDK_TOOLCHAIN_VERSION := 4.8
+APP_CPPFLAGS += -std=c++11

samples/android/jni/main.cpp

@@ -0,0 +1,28 @@
+// Copyright 2015 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.
+
+#include "android_native_app_glue.h"
+#include "animal_generated.h"
+#include "flatbuffers/flatbuffers.h"
+
+void android_main(android_app *app) {
+  app_dummy();
+
+  flatbuffers::FlatBufferBuilder builder;
+  auto name = builder.CreateString("Dog");
+  auto sound = builder.CreateString("Bark");
+  auto animal_buffer = sample::CreateAnimal(builder, name, sound);
+  builder.Finish(animal_buffer);
+}
+

samples/android/jni/schemas/animal.fbs

@@ -0,0 +1,22 @@
+// Copyright 2015 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.
+
+namespace sample;
+
+table Animal {
+  name:string;
+  sound:string;
+}
+
+root_type Animal;