1、首先安装git：去 http://code.google.com/p/msysgit/downloads/list
下载并安装。
Git在Wikipedia上的定义：它是一个免费的、分布式的版本控制工具，或是一个强调了速度快的源代码管理工具。Git最初被Linus
Torvalds开发出来用于管理Linux内核的开发。每一个Git的工作目录都是一个完全独立的代码库，并拥有完整的历史记录和版本追踪能力，不依赖于网络和中心服务器。
2、打开git命令窗口输入（下载frameworks/base中的源码）：
git clone: 这是较为简单的一种初始化方式，当你已经有一个远程的Git版本库，只需要在本地克隆一份，例如'git clone git://github.com/someone/some_project.git some_project'命令就是将'git://github.com/someone/some_project.git'这个URL地址的远程版
本库完全克隆到本地some_project目录下面
3、查看版本：
git tag：可以将某个具体的版本打上一个标签，这样你就不需要记忆复杂的版本号哈希值了，例如你可以使用'git tag revert_version bbaf6fb5060b4875b18ff9ff637ce118256d6f20'来标记这个被你还原的版本，那么以后你想查看该版本时，就可以使用
revert_version标签名，而不是哈希值了
4、切换到android-4.0.4_r1.2版本，也可以切换到上面git tag 列出的其他版本。
git checkout：Git的checkout有两个作用，其一是在不同的branch之间进行切换，例如'git checkout new_branch'就会切换到new_branch的分支上去；另一个功能是还原代码的作用，例如'git checkout
app/model/user.rb'就会将user.rb文件从上一个已提交的版本中更新回来，未提交的内容全部会回滚
5、上边是下载 frameworks/base 的源码，你也可以按此步骤下载其他的源码，见下边的附3。
你也许要下好多个源码，可以写个脚本，将附表一中的全部或者一部分粘贴到一个.txt文件中，然后将后缀改为.sh（本例为xiazai.sh）。
下载所需时间很长。
附1：有关更多的git操作详见：http://blog.csdn.net/yesterdaylike/article/details/7525525
附2：android源码结构：http://zhujianjia.iteye.com/blog/1177854
附3：http://hi.baidu.com/440700383685/item/c977d6eeb045cbd2ea34c98a
git clone http://android.git.kernel.org/kernel/common.git
git clone
git clone http://android.googlesource.com/platform/external/webkit.git
git clone http://android.googlesource.com/platform/development.git
git clone http://android.googlesource.com/platform/system/bluetooth.git
git clone http://android.googlesource.com/platform/external/freetype.git
git clone
git clone http://android.googlesource.com/platform/system/vold.git
git clone http://android.googlesource.com/platform/system/extras.git
git clone http://android.googlesource.com/platform/system/core.git
git clone http://android.googlesource.com/platform/frameworks/ex.git
git clone http://android.googlesource.com/platform/system/media.git
git clone http://android.googlesource.com/platform/frameworks/base.git
git clone http://android.googlesource.com/platform/system/netd.git
git clone http://android.googlesource.com/platform/packages/apps/AlarmClock.git
git clone http://android.googlesource.com/platform/packages/apps/Nfc.git
git clone http://android.googlesource.com/platform/system/wlan/ti.git
git clone http://android.googlesource.com/platform/packages/providers/ImProvider.git
git clone http://android.googlesource.com/platform/packages/apps/CertInstaller.git
git clone http://android.googlesource.com/platform/packages/apps/Tag.git
git clone http://android.googlesource.com/platform/packages/providers/TelephonyProvider.git
git clone http://android.googlesource.com/platform/hardware/qcom/media.git
git clone http://android.googlesource.com/platform/packages/providers/WebSearchProvider.git
git clone http://android.googlesource.com/platform/frameworks/opt/carddav.git
git clone
git clone http://android.googlesource.com/toolchain/manifest.git
git clone http://android.googlesource.com/toolchain/mpc.git
git clone http://android.googlesource.com/toolchain/build.git
git clone http://android.googlesource.com/device/sample.git
git clone http://android.googlesource.com/toolchain/gmp.git
git clone http://android.googlesource.com/toolchain/gold.git
git clone http://android.googlesource.com/toolchain/gcc.git
git clone http://android.googlesource.com/toolchain/mpfr.git
git clone http://android.googlesource.com/toolchain/benchmark.git
git clone http://android.googlesource.com/toolchain/gdb.git
git clone http://android.googlesource.com/kernel/omap.git
git clone http://android.googlesource.com/platform/packages/apps/Sync.git
git clone http://android.googlesource.com/platform/prebuilt.git
git clone http://android.googlesource.com/platform/dalvik.git
git clone
git clone http://android.googlesource.com/platform/external/tinyxml.git
git clone http://android.googlesource.com/platform/external/srec.git
git clone http://android.googlesource.com/platform/external/neven.git
git clone http://android.googlesource.com/platform/external/dhcpcd.git
git clone http://android.googlesource.com/platform/external/skia.git
git clone http://android.googlesource.com/platform/external/clearsilver.git
git clone http://android.googlesource.com/platform/external/elfutils.git
git clone http://android.googlesource.com/platform/hardware/ril.git
git clone http://android.googlesource.com/platform/external/icu4c.git
git clone http://android.googlesource.com/platform/external/netperf.git
git clone http://android.googlesource.com/platform/external/sqlite.git
git clone http://android.googlesource.com/platform/external/ping.git
git clone http://android.googlesource.com/platform/external/googleclient.git
git clone http://android.googlesource.com/platform/external/tremor.git
git clone http://android.googlesource.com/platform/packages/apps/Settings.git
git clone http://android.googlesource.com/platform/packages/providers/MediaProvider.git
git clone http://android.googlesource.com/platform/packages/apps/Email.git
git clone http://android.googlesource.com/platform/packages/providers/ContactsProvider.git
git clone http://android.googlesource.com/platform/packages/apps/Contacts.git
git clone http://android.googlesource.com/platform/packages/apps/Updater.git
git clone http://android.googlesource.com/platform/packages/apps/Stk.git
git clone http://android.googlesource.com/platform/packages/apps/Camera.git
git clone http://android.googlesource.com/platform/packages/apps/Launcher.git
git clone http://android.googlesource.com/platform/external/safe-iop.git
git clone http://android.googlesource.com/platform/packages/providers/DrmProvider.git
git clone http://android.googlesource.com/platform/external/bluetooth/bluez.git
git clone http://android.googlesource.com/platform/packages/apps/Mms.git
git clone http://android.googlesource.com/platform/packages/apps/Browser.git
git clone http://android.googlesource.com/platform/packages/providers/CalendarProvider.git
git clone http://android.googlesource.com/platform/packages/apps/Calculator.git
git clone http://android.googlesource.com/platform/frameworks/opt/com.google.android.git
git clone http://android.googlesource.com/platform/packages/apps/AccountsAndSyncSettings.git
git clone http://android.googlesource.com/platform/packages/apps/HTMLViewer.git
git clone http://android.googlesource.com/platform/packages/apps/GlobalSearch.git
git clone http://android.googlesource.com/platform/packages/providers/ManagementProvider.git
git clone http://android.googlesource.com/platform/packages/apps/PackageInstaller.git
git clone http://android.googlesource.com/platform/packages/providers/UserDictionaryProvider.git
git clone http://android.googlesource.com/platform/packages/apps/Provision.git
git clone http://android.googlesource.com/platform/packages/apps/Gallery3D.git
git clone http://android.googlesource.com/platform/frameworks/opt/emoji.git
git clone http://android.googlesource.com/platform/packages/apps/Phone.git
git clone http://android.googlesource.com/platform/packages/apps/Gallery.git
git clone http://android.googlesource.com/platform/external/svox.git
git clone http://android.googlesource.com/platform/system/vold.git
git clone http://android.googlesource.com/platform/system/wlan/ti.git
git clone http://android.googlesource.com/platform/packages/providers/ImProvider.git
git clone http://android.googlesource.com/platform/packages/providers/GoogleSubscribedFeedsProvider.git
git clone http://android.googlesource.com/platform/packages/apps/Launcher2.git
git clone http://android.googlesource.com/platform/packages/providers/DownloadProvider.git
git clone http://android.googlesource.com/platform/packages/apps/DeskClock.git
git clone http://android.googlesource.com/platform/packages/apps/SoundRecorder.git
git clone http://android.googlesource.com/platform/packages/apps/Protips.git
git clone http://android.googlesource.com/platform/packages/apps/Stk.git
git clone http://android.googlesource.com/platform/packages/apps/SpeechRecorder.git
git clone http://android.googlesource.com/platform/packages/apps/Music.git
git clone http://android.googlesource.com/platform/packages/apps/VoiceDialer.git
git clone http://android.googlesource.com/platform/packages/providers/GoogleContactsProvider.git
git clone http://android.googlesource.com/platform/packages/apps/IM.git
git clone http://android.googlesource.com/platform/packages/apps/QuickSearchBox.git
git clone http://android.googlesource.com/platform/packages/apps/GoogleSearch.git
git clone http://android.googlesource.com/platform/packages/providers/ApplicationsProvider.git
git clone http://android.googlesource.com/platform/frameworks/opt/com.google.android.googlelogin.git