原创内容，转载请注明出处，多谢配合。

APK经过复制、创建对应包文件夹、安装之后，还剩一个比较重要的点需要分析，那就是dex编译。

上篇在installPackageLI中：

private void installPackageLI(InstallArgs args, PackageInstalledInfo res) {
           ...
       mPackageDexOptimizer.performDexOpt(pkg, pkg.usesLibraryFiles,
                               null /* instructionSets */, false /* checkProfiles */,
                               getCompilerFilterForReason(REASON_INSTALL),
                              getOrCreateCompilerPackageStats(pkg),
       mDexManager.isUsedByOtherApps(pkg.packageName));
              ...
}

执行dex编译优化

frameworks/base/services/core/java/com/android/server/pm/PackageDexOptimizer.java

int performDexOpt(PackageParser.Package pkg, String[] sharedLibraries,
       String[] instructionSets, boolean checkProfiles, String targetCompilationFilter,
       CompilerStats.PackageStats packageStats, boolean isUsedByOtherApps) {
    ...
            return performDexOptLI(pkg, sharedLibraries, instructionSets, checkProfiles,
      ...
}

继续看performDexOptLI

/**
* Performs dexopt on all code paths and libraries of the specified package for specified
* instruction sets.
*
* <p>Calls to {@link com.android.server.pm.Installer#dexopt} on {@link #mInstaller} are
* synchronized on {@link #mInstallLock}.
*/
private int performDexOptLI(PackageParser.Package pkg, String[] sharedLibraries,
       String[] targetInstructionSets, boolean checkForProfileUpdates,
       String targetCompilerFilter, CompilerStats.PackageStats packageStats,
       boolean isUsedByOtherApps) {
  ...
        for (String dexCodeIsa : dexCodeInstructionSets) {
            int newResult = dexOptPath(pkg, path, dexCodeIsa, compilerFilter, profileUpdated,
                   sharedLibrariesPathWithSplits, dexoptFlags, sharedGid, packageStats);
           // The end result is:
           //  - FAILED if any path failed,
           //  - PERFORMED if at least one path needed compilation,
           //  - SKIPPED when all paths are up to date
           if ((result != DEX_OPT_FAILED) && (newResult != DEX_OPT_SKIPPED)) {
                result = newResult;
           }
        }
    }
    return result;
}

循环执行dexOptPath

/**
* Performs dexopt on the {@code path} belonging to the package {@code pkg}.
*
* @return
*      DEX_OPT_FAILED if there was any exception during dexopt
*      DEX_OPT_PERFORMED if dexopt was performed successfully on the given path.
*      DEX_OPT_SKIPPED if the path does not need to be deopt-ed.
*/
@GuardedBy("mInstallLock")
private int dexOptPath(PackageParser.Package pkg, String path, String isa,
       String compilerFilter, boolean profileUpdated, String sharedLibrariesPath,
       int dexoptFlags, int uid, CompilerStats.PackageStats packageStats) {
...
       mInstaller.dexopt(path, uid, pkg.packageName, isa, dexoptNeeded, oatDir, dexoptFlags,
               compilerFilter, pkg.volumeUuid, sharedLibrariesPath, pkg.applicationInfo.seInfo);
...
}

frameworks/base/services/core/java/com/android/server/pm/Installer.java

private volatile IInstalld mInstalld;
...
IBinder binder = ServiceManager.getService("installd”);
...
mInstalld = IInstalld.Stub.asInterface(binder);
…
public void dexopt(String apkPath, int uid, @Nullable String pkgName, String instructionSet,
       int dexoptNeeded, @Nullable String outputPath, int dexFlags,
       String compilerFilter, @Nullable String volumeUuid, @Nullable String sharedLibraries,
       @Nullable String seInfo)
        throws InstallerException {
    assertValidInstructionSet(instructionSet);
   if (!checkBeforeRemote()) return;
   try {
        mInstalld.dexopt(apkPath, uid, pkgName, instructionSet, dexoptNeeded, outputPath,
               dexFlags, compilerFilter, volumeUuid, sharedLibraries, seInfo);
   } catch (Exception e) {
        throw InstallerException.from(e);
   }
}

这里installd是init启动的native进程，7.0及之前它与Installer是进行socket通信，8.0之后换成了binder，如上代码也明显能看出。

frameworks/native/cmds/installd/installd.cpp

8.0之后也不像7.0的时候在installd.cpp中通过cmds命令对应depot了 { "dexopt", , do_dexopt }，现在操作是在dexopt.cpp中进行。

frameworks/native/cmds/installd/dexopt.cpp
int dexopt(const char* dex_path, uid_t uid, const char* pkgname, const char* instruction_set,
        int dexopt_needed, const char* oat_dir, int dexopt_flags, const char* compiler_filter,
        const char* volume_uuid, const char* shared_libraries, const char* se_info) {
...
        run_dex2oat(input_fd.get(),
                    out_oat_fd.get(),
                    in_vdex_fd.get(),
                    out_vdex_fd.get(),
                    image_fd.get(),
                    dex_path,
                    out_oat_path,
                    swap_fd.get(),
                    instruction_set,
                    compiler_filter,
                    debuggable,
                    boot_complete,
                    reference_profile_fd.get(),
                    shared_libraries);
...
    return 0;
}

最终调用dex2oat进行编译操作。

好了，3篇文章对PMS的安装过程扫了个盲，非常多的细节没有分析，只简单捋了个框架。想深入学习的可以看看这个系列，总结的还挺全面的：APK安装流程详解

最后站在巨人的肩膀上盗两张图来总结下：

安装流程图

整体架构图（与installd通信 8.0之前是socket，之后是binder）

参考：
https://blog.csdn.net/shuttlecheng/article/details/79018014