Android.mk解析

Android.mk文件用来向编译系统描述如何编译你的源代码。在编译整个工程的情况下，系统所找到的所有的Android.mk将会先存入subdir_makefiles变量中，随后一次性一次性include进整个编译文件中。

(1)Android.mk文件首先需要指定LOCAL_PATH变量，用于查找源文件。

由于一般情况下Android.mk和需要编译的源文件在同一目录下，所以定义成如下形式：

LOCAL_PATH:=$(call my-dir)

上面的语句的意思是将LOCAL_PATH变量定义成本文件所在目录路径。

(2)Android.mk中可以定义多个编译模块，每个编译模块都是以include $(CLEAR_VARS)开始以include $(BUILD_XXX)结束。

①include $(CLEAR_VARS)

CLEAR_VARS的定义在build/core/clear_vars.mk中，它清除了上百个除LOCAL_PATH外的变量，因而LOCAL_PATH通常被认为是一个编译模块的开始标志。

②include $(BUILD_XXX)

这个是Android.mk的重点，它表示将源码编译成什么目标文件，如动态库、可执行程序、APK等，它一般被认为是一个编译模块的结束标志。

(3)编译一个应用程序(APK)

  LOCAL_PATH := $(call my-dir)
  include $(CLEAR_VARS)
  # Build all java files in the java subdirectory
  LOCAL_SRC_FILES := $(call all-subdir-java-files)
  # Name of the APK to build
  LOCAL_PACKAGE_NAME := LocalPackage
  # Tell it to build an APK
  include $(BUILD_PACKAGE)

(4)编译一个依赖于静态Java库(static.jar)的应用程序

 LOCAL_PATH := $(call my-dir)
 include $(CLEAR_VARS)
 # List of static libraries to include in the package
 LOCAL_STATIC_JAVA_LIBRARIES := static-library
 # Build all java files in the java subdirectory
 LOCAL_SRC_FILES := $(call all-subdir-java-files)
 # Name of the APK to build
 LOCAL_PACKAGE_NAME := LocalPackage
 # Tell it to build an APK
 include $(BUILD_PACKAGE)

(5)编译一个需要用平台的key签名的应用程序

 LOCAL_PATH := $(call my-dir)
 include $(CLEAR_VARS)
 # Build all java files in the java subdirectory
 LOCAL_SRC_FILES := $(call all-subdir-java-files)
 # Name of the APK to build
 LOCAL_PACKAGE_NAME := LocalPackage 
 LOCAL_CERTIFICATE := platform
 # Tell it to build an APK
 include $(BUILD_PACKAGE)

(6)编译一个需要用特定key前面的应用程序

 LOCAL_PATH := $(call my-dir)
 include $(CLEAR_VARS) 
 # Build all java files in the java subdirectory
 LOCAL_SRC_FILES := $(call all-subdir-java-files)
 # Name of the APK to build
 LOCAL_PACKAGE_NAME := LocalPackage   
 LOCAL_CERTIFICATE := vendor/example/certs/app   
 # Tell it to build an APK
 include $(BUILD_PACKAGE)

(7)添加一个预编译应用程序

  LOCAL_PATH := $(call my-dir)
  include $(CLEAR_VARS)
  # Module name should match apk name to be installed.
  LOCAL_MODULE := LocalModuleName
  LOCAL_SRC_FILES := $(LOCAL_MODULE).apk
  LOCAL_MODULE_CLASS := APPS
  LOCAL_MODULE_SUFFIX := $(COMMON_ANDROID_PACKAGE_SUFFIX)
  include $(BUILD_PREBUILT)

(8)添加一个静态JAVA库

  LOCAL_PATH := $(call my-dir)
  include $(CLEAR_VARS)   
  # Build all java files in the java subdirectory
  LOCAL_SRC_FILES := $(call all-subdir-java-files)   
  # Any libraries that this library depends on
  LOCAL_JAVA_LIBRARIES := android.test.runner   
  # The name of the jar file to create
  LOCAL_MODULE := sample
  # Build a static jar file.
  include $(BUILD_STATIC_JAVA_LIBRARY)

(9)编译生成可执行文件

 

LOCAL_PATH:= $(call my-dir)  
  
include $(CLEAR_VARS)  
  
LOCAL_MODULE_TAGS := optional  
  
LOCAL_C_INCLUDES += \  
     $(LOCAL_PATH)  
       
LOCAL_SRC_FILES:= \  
        gpio-server.c  
  
LOCAL_SHARED_LIBRARIES := \  
    libcurl \  
    libcutils  
  
LOCAL_MODULE:= gpio-server  
  
include $(BUILD_EXECUTABLE)  
  
include $(call all-makefiles-under,$(LOCAL_PATH))

 

(10)编译生成动态库

 

LOCAL_PATH:= $(call my-dir)  
include $(CLEAR_VARS)  
  
LOCAL_SRC_FILES:= \  
    com_android_server_AlarmManagerService.cpp \  
    com_android_server_BatteryService.cpp \  
    com_android_server_InputApplicationHandle.cpp \  
    com_android_server_InputManager.cpp \  
    com_android_server_InputWindowHandle.cpp \  
    com_android_server_LightsService.cpp \  
    com_android_server_PowerManagerService.cpp \  
    com_android_server_SystemServer.cpp \  
    com_android_server_UsbDeviceManager.cpp \  
    com_android_server_UsbHostManager.cpp \  
    com_android_server_VibratorService.cpp \  
    com_android_server_location_GpsLocationProvider.cpp \  
    com_android_server_connectivity_Vpn.cpp \  
    com_android_server_ConnectivityService.cpp \  
    onload.cpp  
  
LOCAL_C_INCLUDES += \  
    $(JNI_H_INCLUDE) \  
    frameworks/base/services \  
    frameworks/base/core/jni \  
    external/skia/include/core  
  
LOCAL_SHARED_LIBRARIES := \  
    libandroid_runtime \  
    libcutils \  
    libhardware \  
    libhardware_legacy \  
    libnativehelper \  
    libsystem_server \  
    libutils \  
    libui \  
    libinput \  
    libskia \  
    libgui \  
    libusbhost  
  
ifeq ($(WITH_MALLOC_LEAK_CHECK),true)  
    LOCAL_CFLAGS += -DMALLOC_LEAK_CHECK  
endif  
  
LOCAL_MODULE:= libandroid_servers  
  
include $(BUILD_SHARED_LIBRARY) 

 

(11)通过Android.mk添加一个编译模块到系统中的顺序如下

①LOCAL_PATH

②CLEAR_VARS

③LOCAL_SRC_FILES

④LOCAL_CFLAGS(可选)

⑤LOCAL_MODULE

⑥LOCAL_STATIC_LIBRARIES(可选)

⑦BUILD_XXX

 

(12)Android.mk常用的变量

变量名	说明
LOCAL_PATH	用于确定源码所在的目录，最好把它放在CLEAR_VARS变量引用的前面，因为它不会被清除，每个Android.mk只需要定义 一次即可。
CLEAR_VARS	它清空了很多以LOCAL_开头的变量（LOCAL_PATH除外）。由于所有的MakeFile都是在一个编译环境下执行的，因此 变量的定义理论上是全局的，在每个模块编译开始前进行清理工作是必要的。
LOCAL_MODULE	模块名，需保证在整个编译系统中是唯一存在的，而且中间不可以有空格
LOCAL_MODULE_PATH	模块的输出路径
LOCAL_SRC_FILES	模块编译过程中涉及到的源文件。如果是JAVA程序，可以考虑调用all-subdir-java-files来一次性添加目录（包括子目录）下所有的java文件 因为有LOCAL_PATH，这里只需要给出文件名（相对路径）即可；而且编译系统有比较强的推导功能，可以自动计算依赖关系。
LOCAL_CC	用于指定C编译器
LOCAL_CXX	用于指定C++编译器
LOCAL_CPP_EXTENSION	用于指定特殊的C++文件后缀名
LOCAL_CFLAGS	C语言编译时的额外选项
LOCAL_CXXFLAGS	C++语言编译时的额外选项
LOCAL_C_INCLUDE	编译C和C++程序所需要的额外头文件
LOCAL_STATIC_LIBRARIES	编译所需的静态库列表
LOCAL_SHARED_LIBRARIES	编译时所需要的动态库列表
LOCAL_JAVA_LIBRARIES	编译时所需要的JAVA类库
LOCAL_LDLIBS	编译时所需要的链接选项
LOCAL_COPY_HEADERS	安装应用程序时所需要复制的头文件列表，需要和LOCAL_COPY_HEARERS_TO变量配合使用
LOCAL_MODULE_CLASS	标识所编译模块最后放置的位置。ETC表示放置在/system/etc.目录下，APPS表示放置在/system/app目录下，SHARED_LIBRARIES表示放置在/system/lib目录下。如果具体指定，则编译的模块不会放到编译系统中，最后会在out对应product的obj目录下的对应目录中。
LOCAL_MODULE_TAGS	当前模块所包含的标签，一个模块可以包含多个标签。标签的值可能是eng、user、debug、development、optional。其中，optional是默认标签。
LOCAL_DEX_PREOPT	apk的odex优化开关，默认是false
$(call my-dir)	获取当前文件夹的路径
$(call all-java-files-under,)	获取指定目录下的所有java文件
$(call all-c-files-under, )	获取指定目录下的所有c文件
$(call all-Iaidl-files-under, )	获取指定目录下的所有AIDL文件
$(call all-makefiles-under, )	获取指定目录下的所有Make文件
$(call intermediates-dir-for, , , , )	获取Build输入的目标文件夹路径
BUILD_HOST_STATIC_LIBRARY BUILD_HOST_SHARED_LIBRARY BUILD_STATIC_LIBRARY BUILD_RAW_STATIC-LIBRARY BUILD_SHARED_LIBRARY BUILD_EXECUTABLE BUILD_RAW_EXECUTABLE BUILD_HOST_EXECUTABLE BUILD_PACKAGE BUILD_HOST_PREBUILT BUILD_PREBUILT BUILD_MULTI_PREBUILT BUILD_JAVA_LIBRARY BUILD_STATIC_JAVA_LIBRARY BUILD_HOST_JAVA_LIBRARY BUILD_DROIDDOC BUILD_COPY_HEADERS BUILD_KEY_CHAR_MAP	各种形式的编译模板，如静态、动态库文件，可执行文件，文档等