今天講一下NDK編譯protobuf-3.12.0-rc2：
下載android-ndk-r13b-windows-x86_64.zip:https://dl.google.com/android/repository/android-ndk-r13b-windows-x86_64.zip?utm_source=androiddevtools&utm_medium=website,解壓到：：C:/android/android-ndk-r13b
下載protobuf-3.12.0-rc2：https://github.com/protocolbuffers/protobuf/releases/,解壓到：c:/protobuf-3.12.0-rc2
一。添加NDK環境變量：
我的NDK安裝路徑爲：C:/android/android-ndk-r13b,因爲在CMD下編譯，要運行 ndk-build命令，所有要加2個系統環境變量：
cocos2d-x要的變量爲：NDK_ROOT
ndk-build命令環境變量在Path中加：%NDK_ROOT%\build
二.在c:/protobuf-3.12.0-rc2/src 建立make文件（文件名注意大小寫）：
1.application.mk
APP_MODULES := protobuf
APP_PLATFORM := android-19
APP_ABI := armeabi-v7a
APP_STL := c++_static
APP_OPTIM := release
2.android.mk
LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE := protobuf
LOCAL_CFLAGS := -std=c++11 -fexceptions -frtti
LOCAL_MODULE_FILENAME := libprotobuf
LOCAL_SRC_FILES := google/protobuf/stubs/bytestream.cc \
google/protobuf/stubs/bytestream.h \
google/protobuf/stubs/common.cc \
google/protobuf/stubs/hash.h \
google/protobuf/stubs/int128.cc \
google/protobuf/stubs/int128.h \
google/protobuf/io/io_win32.cc \
google/protobuf/stubs/map_util.h \
google/protobuf/stubs/mathutil.h \
google/protobuf/stubs/status.cc \
google/protobuf/stubs/status.h \
google/protobuf/stubs/status_macros.h \
google/protobuf/stubs/statusor.cc \
google/protobuf/stubs/statusor.h \
google/protobuf/stubs/stringpiece.cc \
google/protobuf/stubs/stringpiece.h \
google/protobuf/stubs/stringprintf.cc \
google/protobuf/stubs/stringprintf.h \
google/protobuf/stubs/structurally_valid.cc \
google/protobuf/stubs/strutil.cc \
google/protobuf/stubs/time.cc \
google/protobuf/stubs/time.h \
google/protobuf/any_lite.cc \
google/protobuf/arena.cc \
google/protobuf/extension_set.cc \
google/protobuf/generated_enum_util.cc \
google/protobuf/generated_message_util.cc \
google/protobuf/generated_message_table_driven_lite.h \
google/protobuf/generated_message_table_driven_lite.cc \
google/protobuf/implicit_weak_message.cc \
google/protobuf/message_lite.cc \
google/protobuf/parse_context.cc \
google/protobuf/repeated_field.cc \
google/protobuf/wire_format_lite.cc \
google/protobuf/io/coded_stream.cc \
google/protobuf/io/strtod.cc \
google/protobuf/io/zero_copy_stream.cc \
google/protobuf/io/zero_copy_stream_impl.cc \
google/protobuf/io/zero_copy_stream_impl_lite.cc \
google/protobuf/any.pb.cc \
google/protobuf/api.pb.cc \
google/protobuf/any.cc \
google/protobuf/descriptor.cc \
google/protobuf/descriptor_database.cc \
google/protobuf/descriptor.pb.cc \
google/protobuf/duration.pb.cc \
google/protobuf/dynamic_message.cc \
google/protobuf/empty.pb.cc \
google/protobuf/extension_set_heavy.cc \
google/protobuf/field_mask.pb.cc \
google/protobuf/generated_message_reflection.cc \
google/protobuf/generated_message_table_driven_lite.h \
google/protobuf/generated_message_table_driven.cc \
google/protobuf/map_field.cc \
google/protobuf/message.cc \
google/protobuf/reflection_internal.h \
google/protobuf/reflection_ops.cc \
google/protobuf/service.cc \
google/protobuf/source_context.pb.cc \
google/protobuf/struct.pb.cc \
google/protobuf/stubs/substitute.cc \
google/protobuf/stubs/substitute.h \
google/protobuf/text_format.cc \
google/protobuf/timestamp.pb.cc \
google/protobuf/type.pb.cc \
google/protobuf/unknown_field_set.cc \
google/protobuf/wire_format.cc \
google/protobuf/wrappers.pb.cc \
google/protobuf/io/gzip_stream.cc \
google/protobuf/io/printer.cc \
google/protobuf/io/tokenizer.cc \
google/protobuf/compiler/importer.cc \
google/protobuf/compiler/parser.cc \
google/protobuf/util/delimited_message_util.cc \
google/protobuf/util/field_comparator.cc \
google/protobuf/util/field_mask_util.cc \
google/protobuf/util/internal/constants.h \
google/protobuf/util/internal/datapiece.cc \
google/protobuf/util/internal/datapiece.h \
google/protobuf/util/internal/default_value_objectwriter.cc \
google/protobuf/util/internal/default_value_objectwriter.h \
google/protobuf/util/internal/error_listener.cc \
google/protobuf/util/internal/error_listener.h \
google/protobuf/util/internal/expecting_objectwriter.h \
google/protobuf/util/internal/field_mask_utility.cc \
google/protobuf/util/internal/field_mask_utility.h \
google/protobuf/util/internal/json_escaping.cc \
google/protobuf/util/internal/json_escaping.h \
google/protobuf/util/internal/json_objectwriter.cc \
google/protobuf/util/internal/json_objectwriter.h \
google/protobuf/util/internal/json_stream_parser.cc \
google/protobuf/util/internal/json_stream_parser.h \
google/protobuf/util/internal/location_tracker.h \
google/protobuf/util/internal/mock_error_listener.h \
google/protobuf/util/internal/object_location_tracker.h \
google/protobuf/util/internal/object_source.h \
google/protobuf/util/internal/object_writer.cc \
google/protobuf/util/internal/object_writer.h \
google/protobuf/util/internal/protostream_objectsource.cc \
google/protobuf/util/internal/protostream_objectsource.h \
google/protobuf/util/internal/protostream_objectwriter.cc \
google/protobuf/util/internal/protostream_objectwriter.h \
google/protobuf/util/internal/proto_writer.cc \
google/protobuf/util/internal/proto_writer.h \
google/protobuf/util/internal/structured_objectwriter.h \
google/protobuf/util/internal/type_info.cc \
google/protobuf/util/internal/type_info.h \
google/protobuf/util/internal/type_info_test_helper.cc \
google/protobuf/util/internal/type_info_test_helper.h \
google/protobuf/util/internal/utility.cc \
google/protobuf/util/internal/utility.h \
google/protobuf/util/json_util.cc \
google/protobuf/util/message_differencer.cc \
google/protobuf/util/time_util.cc \
google/protobuf/util/type_resolver_util.cc
LOCAL_EXPORT_C_INCLUDES :=
LOCAL_EXPORT_LDLIBS :=
LOCAL_C_INCLUDES := $(LOCAL_PATH) \
$(LOCAL_PATH)/src
LOCAL_LDLIBS := -llog -lz
#include $(BUILD_SHARED_LIBRARY)
include $(BUILD_STATIC_LIBRARY)
裏面包含的文件很多，其實要包含的文件都在Makefile.am文件中：
有兩個爲 libprotobuf_lite_la_SOURCES 的文件全部包含進來。還要注意的是，我的APP_PLATFORM := android-19,必須要下載 android-19 SDK，Android SDK 可在https://www.androiddevtools.cn/index.html下載。
準備好上面現在開始編譯：
Win+R 執行 cmd命令，進入c:/protobuf-3.12.0-rc2/src目錄 輸入：
ndk-build NDK_PROJECT_PATH=. APP_BUILD_SCRIPT=./android.mk NDK_APPLICATION_MK=./application.mk
會出現以下錯誤：
這個要修改一下C:/protobuf-3.12.0-rc2/src/google/protobuf/stubs/common.h文件就行了
打開加入下面內容：
#ifndef HAVE_PTHREAD
#define HAVE_PTHREAD
#endif
再次執行上次命令，就可以編譯了：
這樣就編譯好了！