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How To Read Android Source Code

Android源代码很大，怎么阅读

参考文档

Steps

  • source build/envsetup.sh
  • Android P
    • lunch mek_8q_car2-userdebug
    • lunch kvim3-userdebug
  • make idegen
  • ./development/tools/idegen/idegen.sh
  • ls android.* 
    android.iml  android.ipr
    • android.iml：项目中需要加载的Module配置文件sourceFolder、excludeFolder加载和忽略加载源代码；
      • vim android.iml
        • 由于默认modules实在太多，先全部禁止：:%s/<sourceFolder url=/<excludeFolder url=/
    • android.ipr：项目配置文件；
  • 由于加载的module很多，所以需要增大内存：
    images/Android_Studio_vmoptions.png
    • 参考：大牛们是怎么阅读 Android 系统源码的？ - nothing chen的回答 - 知乎
    • studio.exe.vmoptions 
      -server
-Xms768m
-Xmx768m
-XX:ReservedCodeCacheSize=240m
-XX:+UseConcMarkSweepGC
-XX:SoftRefLRUPolicyMSPerMB=50
-XX:CICompilerCount=2
-Dsun.io.useCanonCaches=false
-Djava.net.preferIPv4Stack=true
-Djdk.http.auth.tunneling.disabledSchemes=""
-Djna.nosys=true
-Djna.boot.library.path=

-da
    • studio64.exe.vmoptions 
      -Xms1280m
-Xmx1280m
-XX:ReservedCodeCacheSize=240m
-XX:+UseConcMarkSweepGC
-XX:SoftRefLRUPolicyMSPerMB=50
-XX:CICompilerCount=2
-Dsun.io.useCanonCaches=false
-Djava.net.preferIPv4Stack=true
-Djdk.http.auth.tunneling.disabledSchemes=""
-Djna.nosys=true
-Djna.boot.library.path=

-da
  • 用Android Studio打开ipr文件，即可开始方便阅读Android源代码了，右下角这个地方会等待很久，具体情况跟电脑配置有关： images/Scanning_files_to_index.png

优化

AOSP 源码文件较多，Android Studio 默认设置的 1280m 堆最大内存对于 AOSP 这样的大型项目已不再合适，为了更好的性能，向 studio.vmoptions 文件添加一个行，使用语法 -XmxHeapSize 设置最大堆内存。如图所示，笔者将Android Studio 的堆最大内存空间设置为6G。

  • android.iml 
    [...省略]
  <content url="file://$MODULE_DIR$">
   <sourceFolder url="file://$MODULE_DIR$/vendor/nxp-opensource/fsl_imx_demo/AudioRoute/src" isTestSource="false" />
   <sourceFolder url="file://$MODULE_DIR$/vendor/nxp-opensource/fsl_imx_demo/BleClient/src" isTestSource="false" />
   <sourceFolder url="file://$MODULE_DIR$/vendor/nxp-opensource/fsl_imx_demo/BleServerEmulator/src" isTestSource="false" />
   <sourceFolder url="file://$MODULE_DIR$/vendor/nxp-opensource/fsl_imx_demo/DirectAudioPlayer/java" isTestSource="false" />
   <sourceFolder url="file://$MODULE_DIR$/vendor/nxp-opensource/fsl_imx_demo/Ethernet" isTestSource="false" />
   <sourceFolder url="file://$MODULE_DIR$/vendor/nxp-opensource/fsl_imx_demo/FSLOta/src" isTestSource="false" />
   <sourceFolder url="file://$MODULE_DIR$/vendor/nxp-opensource/fsl_imx_demo/HdmiDualVideo/src" isTestSource="false" />
   <sourceFolder url="file://$MODULE_DIR$/vendor/nxp-opensource/fsl_imx_demo/SleepAwakeAutoTest/src" isTestSource="true" />
   <sourceFolder url="file://$MODULE_DIR$/vendor/nxp-opensource/fsl_imx_demo/Test_DualPlayback/src" isTestSource="true" />
   <sourceFolder url="file://$MODULE_DIR$/vendor/nxp/fsl_imx_omx/CactusPlayer/src" isTestSource="false" />
   <sourceFolder url="file://$MODULE_DIR$/gen" isTestSource="false" generated="true" />
   <excludeFolder url="file://$MODULE_DIR$/.repo" />
   <excludeFolder url="file://$MODULE_DIR$/art" />
   <excludeFolder url="file://$MODULE_DIR$/bionic" />
   <excludeFolder url="file://$MODULE_DIR$/bootable" />
   <excludeFolder url="file://$MODULE_DIR$/build" />
   <excludeFolder url="file://$MODULE_DIR$/cts" />
   <excludeFolder url="file://$MODULE_DIR$/dalvik" />
   <excludeFolder url="file://$MODULE_DIR$/developers" />
   <excludeFolder url="file://$MODULE_DIR$/development" />
   <excludeFolder url="file://$MODULE_DIR$/device" />
   <excludeFolder url="file://$MODULE_DIR$/docs" />
   <excludeFolder url="file://$MODULE_DIR$/external" />
   <excludeFolder url="file://$MODULE_DIR$/frameworks/base/docs" />
   <excludeFolder url="file://$MODULE_DIR$/hardware" />
   <excludeFolder url="file://$MODULE_DIR$/kernel" />
   <excludeFolder url="file://$MODULE_DIR$/libcore" />
   <excludeFolder url="file://$MODULE_DIR$/libnativehelper" />
   <excludeFolder url="file://$MODULE_DIR$/out" />
   <excludeFolder url="file://$MODULE_DIR$/pdk" />
   <excludeFolder url="file://$MODULE_DIR$/platform_testing" />
   <excludeFolder url="file://$MODULE_DIR$/prebuilt" />
   <excludeFolder url="file://$MODULE_DIR$/prebuilts" />
   <excludeFolder url="file://$MODULE_DIR$/sdk" />
   <excludeFolder url="file://$MODULE_DIR$/system" />
   <excludeFolder url="file://$MODULE_DIR$/test" />
   <excludeFolder url="file://$MODULE_DIR$/toolchain" />
   <excludeFolder url="file://$MODULE_DIR$/tools" />
 </content>
[...省略]
  • 为了加快加载速度，可以将不用的目录禁止掉，这样可以便于分析代码

images/Android_Studio_idegen.png