本文档详细介绍了Android构建系统的原理及使用方法，包括makefile的理解、构建层级、平台和内核的构建过程、构建变体等内容，并提供了配置新产品及常见构建任务的代码示例。
Android Build System
Android uses a custom build system to generate tools, binaries, and documentation. This document provides an overview of Android's build system and instructions for doing a simple build.
Android's build system is make based and requires a recent version of GNU Make (note that Android uses advanced features of GNU Make that may not yet appear on the GNU Make web site). Before continuing, check your version of make by running % make -v. If you don't have version 3.80 or greater, you need toupgrade your version of make.
Understanding the makefile
A makefile defines how to build a particular application. Makefiles typically include all of the following elements:
- Name: Give your build a name (
LOCAL_MODULE := <build_name>). - Local Variables: Clear local variables with CLEAR_VARS (
include $(CLEAR_VARS)). - Files: Determine which files your application depends upon (
LOCAL_SRC_FILES := main.c). - Tags: Define tags, as necessary (
LOCAL_MODULE_TAGS := eng development). - Libraries: Define whether your application links with other libraries (
LOCAL_SHARED_LIBRARIES := cutils). - Template file: Include a template file to define underlining make tools for a particular target (
include $(BUILD_EXECUTABLE)).
The following snippet illustrates a typical makefile.
LOCAL_PATH := $(my-dir) include $(CLEAR_VARS) LOCAL_MODULE := <buil_name> LOCAL_SRC_FILES := main.c LOCAL_MODULE_TAGS := eng development LOCAL_SHARED_LIBRARIES := cutils include $(BUILD_EXECUTABLE) (HOST_)EXECUTABLE, (HOST_)JAVA_LIBRARY, (HOST_)PREBUILT, (HOST_)SHARED_LIBRARY, (HOST_)STATIC_LIBRARY, PACKAGE, JAVADOC, RAW_EXECUTABLE, RAW_STATIC_LIBRARY, COPY_HEADERS, KEY_CHAR_MAP
The snippet above includes artificial line breaks to maintain a print-friendly document.
Layers
The build hierarchy includes the abstraction layers described in the table below.
Each layer relates to the one above it in a one-to-many relationship. For example, an arch can have more than one board and each board can have more than one device. You may define an element in a given layer as a specialization of an element in the same layer, thus eliminating copying and simplifying maintenance.
| Layer | Example | Description |
|---|---|---|
| Product | myProduct, myProduct_eu, myProduct_eu_fr, j2, sdk | The product layer defines a complete specification of a shipping product, defining which modules to build and how to configure them. You might offer a device in several different versions based on locale, for example, or on features such as a camera. |
| Device | myDevice, myDevice_eu, myDevice_eu_lite | The device layer represents the physical layer of plastic on the device. For example, North American devices probably include QWERTY keyboards whereas devices sold in France probably include AZERTY keyboards. Peripherals typically connect to the device layer. |
| Board | sardine, trout, goldfish | The board layer represents the bare schematics of a product. You may still connect peripherals to the board layer. |
| Arch | arm (arm5te) (arm6), x86, 68k | The arch layer describes the processor running on your board. |
Building the Android Platform
This section describes how to build the default version of Android. Once you are comfortable with a generic build, then you can begin to modify Android for your own target device.
Device Code
To do a generic build of android, source build/envsetup.sh, which contains necessary variable and function definitions, as described below.
% cd $TOP % . build/envsetup.sh # pick a configuration using choosecombo % choosecombo % make -j4 PRODUCT-generic-user
You can also replace user with eng for a debug engineering build:
% make -j4 PRODUCT-generic-eng
These Build Variants differ in terms of debug options and packages installed.
Cleaning Up
Execute % m clean to clean up the binaries you just created. You can also execute % m clobber to get rid of the binaries of all combos. % m clobber is equivalent to removing the //out/ directory where all generated files are stored.
Speeding Up Rebuilds
The binaries of each combo are stored as distinct sub-directories of //out/, making it possible to quickly switch between combos without having to recompile all sources each time.
However, performing a clean rebuild is necessary if the build system doesn't catch changes to environment variables or makefiles. If this happens often, you should define the USE_CCACHE environment variable as shown below:
% export USE_CCACHE=1
Doing so will force the build system to use the ccache compiler cache tool, which reduces recompiling all sources.
ccache binaries are provided in //prebuilt/... and don't need to get installed on your system.
Troubleshooting
The following error is likely caused by running an outdated version of Java.
device Dex: core UNEXPECTED TOP-LEVEL ERROR: java.lang.NoSuchMethodError: method java.util.Arrays.hashCode with signature ([Ljava.lang.Object;)I was not found. at com.google.util.FixedSizeList.hashCode(FixedSizeList.java:66) at com.google.rop.code.Rop.hashCode(Rop.java:245) at java.util.HashMap.hash(libgcj.so.7) [...]
dx is a Java program that uses facilities first made available in Java version 1.5. Check your version of Java by executing % java -version in the shell you use to build. You should see something like:
java version "1.5.0_07" Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0_07-164) Java HotSpot(TM) Client VM (build 1.5.0_07-87, mixed mode, sharing)
If you do have Java 1.5 or later and your receive this error, verify that you have properly updated your PATH variable.
Building the Android Kernel
This section describes how to build Android's default kernel. Once you are comfortable with a generic build, then you can begin to modify Android drivers for your own target device.
To build the kernel base, switch to the device directory (/home/joe/android/device) in order to establish variables and run:
% . build/envsetup.sh % partner_setup generic
Then switch to the kernel directory /home/joe/android/kernel.
Checking Out a Branch
The default branch is always android. To check out a different branch, execute the following:
% git checkout --track -b android-mydevice origin/android-mydevice //Branch android-mydevice set up to track remote branch % refs/remotes/origin/android-mydevice. //Switched to a new branch "android-mydevice"
To simplify code management, give your local branch the same name as the remote branch it is tracking (as illustrated in the snippet above). Switch between branches by executing % git checkout <branchname>.
Verifying Location
Find out which branches exist (both locally and remotely) and which one is active (marked with an asterisk) by executing the following:
% git branch -a android * android-mydevice origin/HEAD origin/android origin/android-mydevice origin/android-mychipset
To only see local branches, omit the -a flag.
Building the Kernel
To build the kernel, execute:
% make -j4
Build Variants
When building for a particular product, it's often useful to have minor variations on what is ultimately the final release build. These are the currently-defined build variants:
eng | This is the default flavor. A plain make is the same as make eng.
|
user | make user This is the flavor intended to be the final release bits.
|
userdebug | make userdebug The same as
|
If you build one flavor and then want to build another, you should run make installclean between the two makes to guarantee that you don't pick up files installed by the previous flavor. make clean will also suffice, but it takes a lot longer.
Configuring a New Product
Detailed Instructions
The steps below describe how to configure makefiles for new mobile devices and products running Android.
- Create a company directory in
//vendor/.
mkdir vendor/<company_name>
- Create a
productsdirectory beneath the company directory you created in step 1.
mkdir vendor/<company_name>/products/
- Create a product-specific makefile, called
vendor/<company_name>/products/<first_product_name>.mk, that includes at least the following code:
$(call inherit-product, $(SRC_TARGET_DIR)/product/generic.mk) # # Overrides PRODUCT_NAME := <first_product_name> PRODUCT_DEVICE := <board_name>
- Additional product-specific variables can be added to this Product Definition file.
- In the
productsdirectory, create anAndroidProducts.mkfile that point to (and is responsible for finding) the individual product make files.
# # This file should set PRODUCT_MAKEFILES to a list of product makefiles # to expose to the build system. LOCAL_DIR will already be set to # the directory containing this file. # # This file may not rely on the value of any variable other than # LOCAL_DIR; do not use any conditionals, and do not look up the # value of any variable that isn't set in this file or in a file that # it includes. # PRODUCT_MAKEFILES := \ $(LOCAL_DIR)/first_product_name.mk \ - Create a board-specific directory beneath your company directory that matches the
PRODUCT_DEVICEvariable<board_name>referenced in the product-specific make file above. This will include a make file that gets accessed by any product using this board.
mkdir vendor/<company_name>/<board_name>
- Create a
BoardConfig.mkfile in the directory created in the previous step (vendor/<company_name>/<board_name>).
# These definitions override the defaults in config/config.make for <board_name> # # TARGET_NO_BOOTLOADER := false # TARGET_HARDWARE_3D := false # TARGET_USE_GENERIC_AUDIO := true
- If you wish to modify system properties, create a
system.propfile in your<board_name>directory(vendor/<company_name>/<board_name>).
# system.prop for # This overrides settings in the products/generic/system.prop file # # rild.libpath=/system/lib/libreference-ril.so # rild.libargs=-d /dev/ttyS0
- Add a pointer to
<second_product_name>.mkwithinproducts/AndroidProducts.mk.
PRODUCT_MAKEFILES := \ $(LOCAL_DIR)/first_product_name.mk \ $(LOCAL_DIR)/second_product_name.mk - An
Android.mkfile must be included invendor/<company_name>/<board_name>with at least the following code:
# make file for new hardware from # LOCAL_PATH := $(call my-dir) # # this is here to use the pre-built kernel ifeq ($(TARGET_PREBUILT_KERNEL),) TARGET_PREBUILT_KERNEL := $(LOCAL_PATH)/kernel endif # file := $(INSTALLED_KERNEL_TARGET) ALL_PREBUILT += $(file) $(file): $(TARGET_PREBUILT_KERNEL) | $(ACP) $(transform-prebuilt-to-target) # # no boot loader, so we don't need any of that stuff.. # LOCAL_PATH := vendor/<company_name>/<board_name> # include $(CLEAR_VARS) # # include more board specific stuff here? Such as Audio parameters. #
- To create a second product for the same board, create a second product-specific make file called
vendor/company_name/products/<second_product_name>.mkthat includes:
$(call inherit-product, $(SRC_TARGET_DIR)/product/generic.mk) # # Overrides PRODUCT_NAME := <second_product_name> PRODUCT_DEVICE := <board_name>
By now, you should have two new products, called <first_product_name> and <second_product_name> associated with <company_name>. To verify that a product is properly configured (<first_product_name>, for example), execute the following:
. build/envsetup.sh make PRODUCT-<first_product_name>-user
You should find new build binaries located in /out/target/product/<board_name>.
New Product File Tree
The file tree below illustrates what your own system should look like after completing the steps above.
<company_name><board_name>Android.mkproduct_config.mksystem.prop
productsAndroidProducts.mk<first_product_name>.mk<second_product_name>.mk
Product Definition Files
Product-specific variables are defined in product definition files. A product definition file can inherit from other product definition files, thus reducing the need to copy and simplifying maintenance.
Variables maintained in a product definition files include:
| Parameter | Description | Example |
|---|---|---|
| PRODUCT_NAME | End-user-visible name for the overall product. Appears in the "About the phone" info. | |
| PRODUCT_MODEL | End-user-visible name for the end product | |
| PRODUCT_LOCALES | A space-separated list of two-letter language code, two-letter country code pairs that describe several settings for the user, such as the UI language and time, date and currency formatting. The first locale listed in PRODUCT_LOCALES is is used if the locale has never been set before. | en_GB de_DE es_ES fr_CA |
| PRODUCT_PACKAGES | Lists the APKs to install. | Calendar Contacts |
| PRODUCT_DEVICE | Name of the industrial design | dream |
| PRODUCT_MANUFACTURER | Name of the manufacturer | acme |
| PRODUCT_BRAND | The brand (e.g., carrier) the software is customized for, if any | |
| PRODUCT_PROPERTY_OVERRIDES | List of property assignments in the format "key=value" | |
| PRODUCT_COPY_FILES | List of words like source_path:destination_path. The file at the source path should be copied to the destination path when building this product. The rules for the copy steps are defined in config/Makefile | |
| PRODUCT_OTA_PUBLIC_KEYS | List of OTA public keys for the product | |
| PRODUCT_POLICY | Indicate which policy this product should use | |
| PRODUCT_PACKAGE_OVERLAYS | Indicate whether to use default resources or add any product specific overlays | vendor/acme/overlay |
| PRODUCT_CONTRIBUTORS_FILE | HTML file containing the contributors to the project. | |
| PRODUCT_TAGS | list of space-separated words for a given product |
The snippet below illustrates a typical product definition file.
$(call inherit-product, build/target/product/generic.mk) #Overrides PRODUCT_NAME := MyDevice PRODUCT_MANUFACTURER := acme PRODUCT_BRAND := acme_us PRODUCT_LOCALES := en_GB es_ES fr_FR PRODUCT_PACKAGE_OVERLAYS := vendor/acme/overlay
Build Cookbook
The Android Build Cookbook offers code snippets to help you quickly implement some common build tasks. For additional instruction, please see the other build documents in this section.
Building a simple 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)
Building a APK that depends on a static .jar file
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)
Building a APK that should be signed with the platform key
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)
Building a APK that should be signed with a specific vendor key
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)
Adding a prebuilt APK
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)
Adding a Static Java Library
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)
Android.mk Variables
These are the variables that you'll commonly see in Android.mk files, listed alphabetically. First, a note on the variable naming:
- LOCAL_ - These variables are set per-module. They are cleared by the
include $(CLEAR_VARS)line, so you can rely on them being empty after including that file. Most of the variables you'll use in most modules are LOCAL_ variables. - PRIVATE_ - These variables are make-target-specific variables. That means they're only usable within the commands for that module. It also means that they're unlikely to change behind your back from modules that are included after yours. This link to the make documentation describes more about target-specific variables.
- HOST_ and TARGET_ - These contain the directories and definitions that are specific to either the host or the target builds. Do not set variables that start with HOST_ or TARGET_ in your makefiles.
- BUILD_ and CLEAR_VARS - These contain the names of well-defined template makefiles to include. Some examples are CLEAR_VARS and BUILD_HOST_PACKAGE.
- Any other name is fair-game for you to use in your Android.mk. However, remember that this is a non-recursive build system, so it is possible that your variable will be changed by another Android.mk included later, and be different when the commands for your rule / module are executed.
| Parameter | Description |
|---|---|
| LOCAL_AAPT_FLAGS | |
| LOCAL_ACP_UNAVAILABLE | |
| LOCAL_ADDITIONAL_JAVA_DIR | |
| LOCAL_AIDL_INCLUDES | |
| LOCAL_ALLOW_UNDEFINED_SYMBOLS | |
| LOCAL_ARM_MODE | |
| LOCAL_ASFLAGS | |
| LOCAL_ASSET_DIR | |
| LOCAL_ASSET_FILES | In Android.mk files that include $(BUILD_PACKAGE) set this to the set of files you want built into your app. Usually:
|
| LOCAL_BUILT_MODULE_STEM | |
| LOCAL_C_INCLUDES | Additional directories to instruct the C/C++ compilers to look for header files in. These paths are rooted at the top of the tree. Use You should not add subdirectories of include to |
| LOCAL_CC | If you want to use a different C compiler for this module, set LOCAL_CC to the path to the compiler. If LOCAL_CC is blank, the appropriate default compiler is used. |
| LOCAL_CERTIFICATE | |
| LOCAL_CFLAGS | If you have additional flags to pass into the C or C++ compiler, add them here. For example:
|
| LOCAL_CLASSPATH | |
| LOCAL_COMPRESS_MODULE_SYMBOLS | |
| LOCAL_COPY_HEADERS | The set of files to copy to the install include tree. You must also supply This is going away because copying headers messes up the error messages, and may lead to people editing those headers instead of the correct ones. It also makes it easier to do bad layering in the system, which we want to avoid. We also aren't doing a C/C++ SDK, so there is no ultimate requirement to copy any headers. |
| LOCAL_COPY_HEADERS_TO | The directory within "include" to copy the headers listed in This is going away because copying headers messes up the error messages, and may lead to people editing those headers instead of the correct ones. It also makes it easier to do bad layering in the system, which we want to avoid. We also aren't doing a C/C++ SDK, so there is no ultimate requirement to copy any headers. |
| LOCAL_CPP_EXTENSION | If your C++ files end in something other than ".cpp", you can specify the custom extension here. For example: |
| LOCAL_CPPFLAGS | If you have additional flags to pass into only the C++ compiler, add them here. For example:
LOCAL_CPPFLAGS is guaranteed to be after LOCAL_CFLAGS on the compile line, so you can use it to override flags listed in LOCAL_CFLAGS |
| LOCAL_CXX | If you want to use a different C++ compiler for this module, set LOCAL_CXX to the path to the compiler. If LOCAL_CXX is blank, the appropriate default compiler is used. |
| LOCAL_DX_FLAGS | |
| LOCAL_EXPORT_PACKAGE_RESOURCES | |
| LOCAL_FORCE_STATIC_EXECUTABLE | If your executable should be linked statically, set |
| LOCAL_GENERATED_SOURCES | Files that you add to |
| LOCAL_INSTRUMENTATION_FOR | |
| LOCAL_INSTRUMENTATION_FOR_PACKAGE_NAME | |
| LOCAL_INTERMEDIATE_SOURCES | |
| LOCAL_INTERMEDIATE_TARGETS | |
| LOCAL_IS_HOST_MODULE | |
| LOCAL_JAR_MANIFEST | |
| LOCAL_JARJAR_RULES | |
| LOCAL_JAVA_LIBRARIES | When linking Java apps and libraries, Note that setting |
| LOCAL_JAVA_RESOURCE_DIRS | |
| LOCAL_JAVA_RESOURCE_FILES | |
| LOCAL_JNI_SHARED_LIBRARIES | |
| LOCAL_LDFLAGS | You can pass additional flags to the linker by setting |
| LOCAL_LDLIBS | |
| LOCAL_MODULE | LOCAL_MODULE is the name of what's supposed to be generated from your Android.mk. For exmample, for libkjs, the LOCAL_MODULE is "libkjs" (the build system adds the appropriate suffix -- .so .dylib .dll). For app modules, use LOCAL_PACKAGE_NAME instead of LOCAL_MODULE. |
| LOCAL_MODULE_PATH | Instructs the build system to put the module somewhere other than what's normal for its type. If you override this, make sure you also set LOCAL_UNSTRIPPED_PATH if it's an executable or a shared library so the unstripped binary has somewhere to go. An error will occur if you forget to.
See Putting modules elsewhere for more. |
| LOCAL_MODULE_STEM | |
| LOCAL_MODULE_TAGS | Set This variable controls what build flavors the package gets included in. For example:
|
| LOCAL_NO_DEFAULT_COMPILER_FLAGS | |
| LOCAL_NO_EMMA_COMPILE | |
| LOCAL_NO_EMMA_INSTRUMENT | |
| LOCAL_NO_STANDARD_LIBRARIES | |
| LOCAL_OVERRIDES_PACKAGES | |
| LOCAL_PACKAGE_NAME | LOCAL_PACKAGE_NAME is the name of an app. For example, Dialer, Contacts, etc. |
| LOCAL_POST_PROCESS_COMMAND | For host executables, you can specify a command to run on the module after it's been linked. You might have to go through some contortions to get variables right because of early or late variable evaluation: |
| LOCAL_PREBUILT_EXECUTABLES | When including $(BUILD_PREBUILT) or $(BUILD_HOST_PREBUILT), set these to executables that you want copied. They're located automatically into the right bin directory. |
| LOCAL_PREBUILT_JAVA_LIBRARIES | |
| LOCAL_PREBUILT_LIBS | When including $(BUILD_PREBUILT) or $(BUILD_HOST_PREBUILT), set these to libraries that you want copied. They're located automatically into the right lib directory. |
| LOCAL_PREBUILT_OBJ_FILES | |
| LOCAL_PREBUILT_STATIC_JAVA_LIBRARIES | |
| LOCAL_PRELINK_MODULE | |
| LOCAL_REQUIRED_MODULES | Set |
| LOCAL_RESOURCE_DIR | |
| LOCAL_SDK_VERSION | |
| LOCAL_SHARED_LIBRARIES | These are the libraries you directly link against. You don't need to pass transitively included libraries. Specify the name without the suffix:
|
| LOCAL_SRC_FILES | The build system looks at LOCAL_SRC_FILES to know what source files to compile -- .cpp .c .y .l .java. For lex and yacc files, it knows how to correctly do the intermediate .h and .c/.cpp files automatically. If the files are in a subdirectory of the one containing the Android.mk, prefix them with the directory name:
|
| LOCAL_STATIC_JAVA_LIBRARIES | |
| LOCAL_STATIC_LIBRARIES | These are the static libraries that you want to include in your module. Mostly, we use shared libraries, but there are a couple of places, like executables in sbin and host executables where we use static libraries instead. |
| LOCAL_UNINSTALLABLE_MODULE | |
| LOCAL_UNSTRIPPED_PATH | Instructs the build system to put the unstripped version of the module somewhere other than what's normal for its type. Usually, you override this because you overrode LOCAL_MODULE_PATH for an executable or a shared library. If you overrode LOCAL_MODULE_PATH, but not LOCAL_UNSTRIPPED_PATH, an error will occur.
See Putting modules elsewhere for more. |
| LOCAL_WHOLE_STATIC_LIBRARIES | These are the static libraries that you want to include in your module without allowing the linker to remove dead code from them. This is mostly useful if you want to add a static library to a shared library and have the static library's content exposed from the shared library. |
| LOCAL_YACCFLAGS | Any flags to pass to invocations of yacc for your module. A known limitation here is that the flags will be the same for all invocations of YACC for your module. This can be fixed. If you ever need it to be, just ask.
|
| OVERRIDE_BUILT_MODULE_PATH |
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