#定义默认的target即make命令后不加参数的默认目标# This is the default target.  It must be the first declared target..PHONY: droidDEFAULT_GOAL := droid$(DEFAULT_GOAL):#引入help.mk,help.mk    包含了名称为 help 的 Make 目标的定义，#该目标将列出主要的 Make 目标及其说明# Targets that provide quick help on the build system.include $(BUILD_SYSTEM)/help.mk#引入config.mk，定义产品，主机的各种基本变量# Set up various standard variables based on configuration# and host information.include $(BUILD_SYSTEM)/config.mk#引入clean操作的定义# This allows us to force a clean build - included after the config.mk# environment setup is done, but before we generate any dependencies.  This# file does the rm -rf inline so the deps which are all done below will# be generated correctlyinclude $(BUILD_SYSTEM)/cleanbuild.mk#引入基本编译系统的定义，提供了大量的实用函数# Bring in standard build system definitions.include $(BUILD_SYSTEM)/definitions.mk#读取android源码树中所有的Android.mkifneq ($(dont_bother),true)## Include all of the makefiles in the system## Can‘t use first-makefiles-under here because# --mindepth=2 makes the prunes not work.subdir_makefiles :=     $(shell build/tools/findleaves.py --prune=$(OUT_DIR) --prune=.repo --prune=.git $(subdirs) Android.mk)$(foreach mk, $(subdir_makefiles), $(info including $(mk) ...)$(eval include $(mk)))

#引入envsetup.mk定义大部分全局变量，配置编译时的环境变量。#该文件可以指定用户编译配置# ---------------------------------------------------------------# Define most of the global variables.  These are the ones that# are specific to the user‘s build configuration.include $(BUILD_SYSTEM)/envsetup.mk

#引入BoardConfig.mk,BoardConfig.mk主要写了product使用的硬件所支持和不支持的功能性内容。#BroadConfig.mk设置了每个设备的自己的一些变量值，来区别编译时的行为include $(board_config_mk)......# Boards may be defined under $(SRC_TARGET_DIR)/board/$(TARGET_DEVICE)# or under vendor/*/$(TARGET_DEVICE).  Search in both places, but# make sure only one exists.# Real boards should always be associated with an OEM vendor.board_config_mk :=     $(strip $(wildcard         $(SRC_TARGET_DIR)/board/$(TARGET_DEVICE)/BoardConfig.mk         $(shell test -d device && find device -maxdepth 4 -path ‘*/$(TARGET_DEVICE)/BoardConfig.mk‘) \        $(shell test -d vendor && find vendor -maxdepth 4 -path ‘*/$(TARGET_DEVICE)/BoardConfig.mk‘)     ))#设置版本信息# Set up version information.include $(BUILD_SYSTEM)/version_defaults.mk#引入产品级别的配置# Read the product specs so we can get TARGET_DEVICE and other# variables that we need in order to locate the output files.include $(BUILD_SYSTEM)/product_config.mk

#引用AndroidProducts.mk#读取AndrodProducts.mk文件中定义的产品信息ifneq ($(strip $(TARGET_BUILD_APPS)),)# An unbundled app build needs only the core product makefiles.all_product_configs := $(call get-product-makefiles,    $(SRC_TARGET_DIR)/product/AndroidProducts.mk)else# Read in all of the product definitions specified by the AndroidProducts.mk# files in the tree.all_product_configs := $(get-all-product-makefiles)endif