Android.mk文件用來向編譯系統描述如何編譯你的源代碼。在編譯整個工程的情況下，系統所找到的所有的Android.mk將會先存入subdir_makefiles變量中，隨后一次性一次性include進整個編譯文件中。
(1)Android.mk文件首先需要指定LOCAL_PATH變量，用於查找源文件。
由於一般情況下Android.mk和需要編譯的源文件在同一目錄下，所以定義成如下形式：
LOCAL_PATH:=$(call my-dir)
上面的語句的意思是將LOCAL_PATH變量定義成本文件所在目錄路徑。
(2)Android.mk中可以定義多個編譯模塊，每個編譯模塊都是以include $(CLEAR_VARS)開始以include $(BUILD_XXX)結束。
①include $(CLEAR_VARS)
CLEAR_VARS的定義在build/core/clear_vars.mk中，它清除了上百個除LOCAL_PATH外的變量，因而LOCAL_PATH通常被認為是一個編譯模塊的開始標志。
②include $(BUILD_XXX)
這個是Android.mk的重點，它表示將源碼編譯成什么目標文件，如動態庫、可執行程序、APK等，它一般被認為是一個編譯模塊的結束標志。
(3)編譯一個應用程序(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)編譯一個依賴於靜態Java庫(static.jar)的應用程序
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)編譯一個需要用平台的key簽名的應用程序
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)編譯一個需要用特定key前面的應用程序
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)添加一個預編譯應用程序
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)添加一個靜態JAVA庫
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)編譯生成可執行文件
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)編譯生成動態庫
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)通過Android.mk添加一個編譯模塊到系統中的順序如下
①LOCAL_PATH
②CLEAR_VARS
③LOCAL_SRC_FILES
④LOCAL_CFLAGS(可選)
⑤LOCAL_MODULE
⑥LOCAL_STATIC_LIBRARIES(可選)
⑦BUILD_XXX
(12)Android.mk常用的變量
| 變量名 | 說明 |
| LOCAL_PATH | 用於確定源碼所在的目錄，最好把它放在CLEAR_VARS變量引用的前面，因為它不會被清除，每個Android.mk只需要定義 一次即可。 |
| CLEAR_VARS | 它清空了很多以LOCAL_開頭的變量（LOCAL_PATH除外）。由於所有的MakeFile都是在一個編譯環境下執行的，因此 變量的定義理論上是全局的，在每個模塊編譯開始前進行清理工作是必要的。 |
| LOCAL_MODULE | 模塊名，需保證在整個編譯系統中是唯一存在的，而且中間不可以有空格 |
| LOCAL_MODULE_PATH | 模塊的輸出路徑 |
| LOCAL_SRC_FILES | 模塊編譯過程中涉及到的源文件。如果是JAVA程序，可以考慮調用all-subdir-java-files來一次性添加目錄（包括子目錄）下所有的java文件 因為有LOCAL_PATH，這里只需要給出文件名（相對路徑）即可；而且編譯系統有比較強的推導功能，可以自動計算依賴關系。 |
| LOCAL_CC | 用於指定C編譯器 |
| LOCAL_CXX | 用於指定C++編譯器 |
| LOCAL_CPP_EXTENSION | 用於指定特殊的C++文件后綴名 |
| LOCAL_CFLAGS | C語言編譯時的額外選項 |
| LOCAL_CXXFLAGS | C++語言編譯時的額外選項 |
| LOCAL_C_INCLUDE | 編譯C和C++程序所需要的額外頭文件 |
| LOCAL_STATIC_LIBRARIES | 編譯所需的靜態庫列表 |
| LOCAL_SHARED_LIBRARIES | 編譯時所需要的動態庫列表 |
| LOCAL_JAVA_LIBRARIES | 編譯時所需要的JAVA類庫 |
| LOCAL_LDLIBS | 編譯時所需要的鏈接選項 |
| LOCAL_COPY_HEADERS | 安裝應用程序時所需要復制的頭文件列表，需要和LOCAL_COPY_HEARERS_TO變量配合使用 |
| LOCAL_MODULE_CLASS | 標識所編譯模塊最后放置的位置。ETC表示放置在/system/etc.目錄下，APPS表示放置在/system/app目錄下，SHARED_LIBRARIES表示放置在/system/lib目錄下。如果具體指定，則編譯的模塊不會放到編譯系統中，最后會在out對應product的obj目錄下的對應目錄中。 |
| LOCAL_MODULE_TAGS | 當前模塊所包含的標簽，一個模塊可以包含多個標簽。標簽的值可能是eng、user、debug、development、optional。其中，optional是默認標簽。 |
| LOCAL_DEX_PREOPT | apk的odex優化開關，默認是false |
| $(call my-dir) | 獲取當前文件夾的路徑 |
| $(call all-java-files-under,<src>) | 獲取指定目錄下的所有java文件 |
| $(call all-c-files-under, <src>) | 獲取指定目錄下的所有c文件 |
| $(call all-Iaidl-files-under, <src>) | 獲取指定目錄下的所有AIDL文件 |
| $(call all-makefiles-under, <folder>) | 獲取指定目錄下的所有Make文件 |
| $(call intermediates-dir-for, <class>, <app_name>, <host or target>, <common?>) | 獲取Build輸入的目標文件夾路徑 |
| 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 |
各種形式的編譯模板，如靜態、動態庫文件，可執行文件，文檔等 |