今天我們一起看，看看系統(tǒng)是如何在你的手機(jī)上安裝應(yīng)用程序的。

入口

單擊Apk安裝后，將出現(xiàn)以下界面

這是Android Framework提供的軟件包安裝程序。頁(yè)面：packageInstallerActivity

package com . Android . package installer；

publicclasspackageinstalleractivityextendsactivity {

公共void onclick (viewv) {

If(v==mOk){

if(){

//.省略一些細(xì)節(jié)

start install()；//開(kāi)始安裝

}

}elseif(v==mCancel){

//Cancelandfinish

}

}

PrivatevoidstartInstall(){

//startsubactivitytoactuallyinstalltheapplication

intent new intent=new intent()；

紐因，

MPKGIN)；

紐因(MPACKAGEURI)；

新的in (this，in)；

.//newIn其他參數(shù)

start activity(newIntent)；

finish()；

}

}

在此頁(yè)面上單擊“安裝”后，安裝包信息將通過(guò)internet傳遞給installing。此activity.installing的作用主要是將包信息發(fā)送到PMS，并處理回調(diào)。

磷

當(dāng)然，從onCreate開(kāi)始。

protectedvoidoncreate(@ nullablebundlesavedinstancestate){

applicationinfoappinfo=getintent()

.getParcelableExtra)；

Mpackageuri=getintent()。get data()；

.

根據(jù)//mPackageURI創(chuàng)建相應(yīng)的文件

FinalFilesourceFile=newFile()；

//顯示應(yīng)用程序信息圖標(biāo)、應(yīng)用程序名稱或程序包名稱

Packageu (this，packageu (this，appinfo，

源文件)、r . id . app _ snippet)；

//創(chuàng)建并裝配傳遞會(huì)話參數(shù)的sessionParams

PackageInparams=newPackageIn(

帕克金。MODE _ FULL _ INSTALL)；

=package manager . install _ full _ app；

.

=

GetIntent()。getStringExtra)；

file file=newFile()；

對(duì)//APK執(zhí)行輕量級(jí)語(yǔ)法分析，并將語(yǔ)法分析結(jié)果分配給與SessionParams相關(guān)的字段

Packageparpkg=packagepar(文件，0)；

)；

)；

(請(qǐng)參閱)

PackageHel(pkg、false、)；

//在InstallEventReceiver中注冊(cè)觀察者時(shí)，將返回新的mInstallId

//InstallEventReceiver是可以通過(guò)EventResultPersister接收所有安裝事件的BroadcastReceiver

//其中事件將回調(diào)到this : launchfinishbasedonresult

min stallid=installeventreceiver

.addObserver(this、Even、

this :3360 launchfinishbasedonresult)；

Try{

?//?PackageInstaller?的?createSession? ????????//?方法內(nèi)部會(huì)通過(guò)?IPackageInstaller?與?PackageInstallerservice進(jìn)行進(jìn)程間通信， ????????//?最終調(diào)用的是?PackageInstallerService?的?createSession?方法來(lái)創(chuàng)建并返回?mSessionId ????????mSessionId?=?getPackageManager().getPackageInstaller().createSession(params); ????}?catch?(IOException?e)?{ ????????launchFailure,?null); ????} ??? ?? }

In

接下來(lái)是 onResume, 通過(guò) InstallingAsyncTask 做一些異步工作

protected?void?onResume()?{ ????(); ????//?This?is?the?first?onResume?in?a?single?life?of?the?activity ????if?(mInstallingTask?==?null)?{ ????????PackageInstaller?installer?=?getPackageManager().getPackageInstaller(); ????????PackageIn?sessionInfo?=?in(mSessionId); ????????if?(sessionInfo?!=?null?&&?!())?{ ????????????mInstallingTask?=?new?InstallingAsyncTask(); ????????????mIn(); ????????}?else?{ ????????????//?we?will?receive?a?broadcast?when?the?install?is?finished ????????????mCancelBu(false); ????????????setFinishOnTouchOutside(false); ????????} ????} }

InstallingAsyncTask

private?final?class?InstallingAsyncTask?extends?AsyncTask<Void,?Void, ????????????PackageIn;?{ ????????@Override ????????protected?PackageIn?doInBackground(Void...?params)?{ ????????????PackageIn?session; ????????????session?=?getPackageManager().getPackageInstaller().openSession(mSessionId); ????????????(0); ????????????File?file?=?new?File()); ????????????OutputStream?out?=?("PackageInstaller",?0,?sizeBytes) ????????????InputStream?in?=?new?FileInputStream(file) ????????????long?sizeBytes?=?(); ????????????byte[]?buffer?=?new?byte[1024?*?1024]; ????????????while?(true)?{ ????????????????int?numRead?=?in.read(buffer); ????????????????if?(numRead?==?-1)?{ ????????????????????(out); ????????????????????break; ????????????????} ???????????????//?將?APK?文件通過(guò)?IO?流的形式寫(xiě)入到?PackageIn?中 ????????????????out.write(buffer,?0,?numRead); ????????????????if?(sizeBytes?>?0)?{ ????????????????????float?fraction?=?((float)?numRead?/?(float)?sizeBytes); ????????????????????(fraction); ????????????????} ?????????????} ?????????????return?session;? ????????} ????????@Override ????????protected?void?onPostExecute(PackageIn?session)?{? ????????????Intent?broadcastIntent?=?new?Intent(BROADCAST_ACTION); ????????????broadca); ????????????broadca( ????????????????????getPackageManager().getPermissionControllerPackageName()); ????????????broadcastIn,?mInstallId); ????????????PendingIntent?pendingIntent?=?PendingIn( ????????????????????In, ????????????????????mInstallId, ????????????????????broadcastIntent, ????????????????????PendingIn); ????????????//?調(diào)用?PackageIn?的?commit?方法，進(jìn)行安裝 ????????????());? ????????} ????}

來(lái)看下 PackageIn 里的實(shí)現(xiàn)

public?static?class?Session?implements?Closeable?{ ????private?IPackageInstallerSession?mSession; ????public?void?commit(@NonNull?IntentSender?statusReceiver)?{ ????????try?{ ????????????mSe(statusReceiver,?false); ????????}?catch?(RemoteException?e)?{ ????????????throw?e.rethrowFromSystemServer(); ????????} ????} }

mSession 的類(lèi)型為 IPackageInstallerSession，這說(shuō)明要通過(guò) IPackageInstallerSession 來(lái)進(jìn)行進(jìn)程間的通信，最終會(huì)調(diào)用PackageInstallerSession 的 commit 方法，劇透一下在這個(gè)類(lèi)執(zhí)行完后，就會(huì)進(jìn)入鼎鼎大名的 PMS 去真正的執(zhí)行安裝了 ：

public?class?PackageInstallerSession?extends?IPackageIn?{ ????public?void?commit(@NonNull?IntentSender?statusReceiver,?boolean?forTransfer)?{ ????????//?將包的信息封裝為?PackageInstallObserverAdapter ????????final?PackageInstallObserverAdapter?adapter?=?new?PackageInstallObserverAdapter( ??????????mContext,?statusReceiver,?sessionId, ??????????isInstallerDeviceOwnerOrAffiliatedProfileOwnerLocked(),?userId); ????????mRemoteObserver?=?ada(); ????????//?通過(guò)?Handler?處理消息事件 ????????mHandler.obtainMessage(msg_COMMIT).sendToTarget(); ????} ?? ????private?final?Handler.Callback?mHandlerCallback?=?new?Handler.Callback()?{ ????????@Override ????????public?boolean?handleMessage(Message?msg)?{ ????????????switch?)?{ ????????????????case?MSG_COMMIT: ????????????????????commitLocked(); ????????????????????break; ????????????} ????????} ????}; ?? ????private?final?PackageManagerService?mPm; ????private?void?commitLocked()?throws?PackageManagerException?{ ????????mPm.installStage(mPackageName,?stageDir,?...); ????} ?? }

mPm 就是系統(tǒng)服務(wù) PackageManagerService。installStage 方法就是正式開(kāi)始 apk 的安裝過(guò)程。這個(gè)過(guò)程包括兩大步：拷貝安裝包、裝載代碼

拷貝安裝包

繼續(xù)看 installStage 的代碼

//?PackageManagerService.java void?installStage(String?packageName,?File?stagedDir,...)?{ ????final?Message?msg?=?mHandler.obtainMessage(INIT_COPY); ????//?把之前傳入的?sessionParams?安裝信息，及其它信息封裝成?InstallParams ????final?InstallParams?params?=?new?InstallParams(origin,?null,?observer, ????????,?installerPackageName,?, ????????verificationInfo,?user,?, ????????,?signingDetails,?installReason); ????mHandler.sendMessage(msg); }

發(fā)送的消息 INIT_COPY 從名字上就知道是去初始化復(fù)制

class?PackageHandler?extends?Handler?{ ????void?doHandleMessage(Message?msg)?{ ????????switch?)?{ ????????????case?INIT_COPY:?{ ????????????????HandlerParams?params?=?(HandlerParams)?m; ????????????????//?調(diào)用 connectToService 方法連接安裝 apk 的 Service 服務(wù)。 ????????????????if?(!connectToService())?{ ????????????????????return; ????????????????}?else?{ ?????????????????????//?Once?we?bind?to?the?service,?the?first ?????????????????????//?pending?request?will?be?processed. ?????????????????????mPendingIn(idx,?params); ????????????????} ????????????} ????????} ????} ????private?boolean?connectToService()?{ ?????????//?通過(guò)隱式?Intent?綁定?Service，實(shí)際綁定的?Service?是?DefaultContainerService? ?????????Intent?service?=?new?Intent().setComponent(DEFAULT_CONTAINER_COMPONENT); ?????????if?(service,?mDefContainerConn, ?????????????????Con,?U))?{ ?????????????mBound?=?true; ?????????????return?true; ?????????} ?????????return?false; ???} }

當(dāng)綁定 Service 成功之后，會(huì)在 mDefContainerConn 的 onServiceConnection 方法中發(fā)送一個(gè)綁定操作的 Message，如下所示：

class?DefaultContainerConnection?implements?ServiceConnection?{ ????public?void?onServiceConnected(ComponentName?name,?IBinder?service)?{ ????????final?IMediaContainerService?imcs?=?IMediaCon ????????????????.asInterface(service)); ????????mHandler.sendMessage(MCS_BOUND,?imcs)); ????} } //?MCS_BOUND?還是在前面的?PackageHandler?處理，直接截取相關(guān)代碼 { ????HandlerParams?params?=?mPendingIn(0); ????if?())?{ ????????if?()?>?0)?{ ????????????mPendingIn(0); ????????} ????} }

mPendingInstalls 是一個(gè)等待隊(duì)列，里面保存所有需要安裝的 apk 解析出來(lái)的 HandlerParams 參數(shù)（前面在 INIT_COPY 處理時(shí) add），從 mPendingInstalls 中取出第一個(gè)需要安裝的 HandlerParams 對(duì)象，并調(diào)用其 startCopy 方法，在 startCopy 方法中會(huì)繼續(xù)調(diào)用一個(gè)抽象方法 handleStartCopy 處理安裝請(qǐng)求。通過(guò)之前的分析，我們知道 HandlerParams 實(shí)際類(lèi)型是 InstallParams 類(lèi)型，因此最終調(diào)用的是 InstallParams 的 handlerStartCopy 方法，這是整個(gè)安裝包拷貝的核心。

class?InstallParams?extends?HandlerParams?{ ?? ????public?void?handleStartCopy()?throws?RemoteException?{ ????????if?)?{ ????????????//?設(shè)置安裝標(biāo)志位，決定是安裝在手機(jī)內(nèi)部存儲(chǔ)空間還是?sdcard?中 ????????????if??!=?null)?{ ????????????????installFlags?|=?PackageManager.INSTALL_INTERNAL; ????????????????installFlags?&=?~PackageManager.INSTALL_EXTERNAL; ????????????}? ????????} ???????? ????????//?判斷安裝位置 ????????final?boolean?onSd?=?(installFlags?&?PackageManager.INSTALL_EXTERNAL)?!=?0; ????????final?boolean?onInt?=?(installFlags?&?PackageManager.INSTALL_INTERNAL)?!=?0; ????????final?boolean?ephemeral?=?(installFlags?&?PackageManager.INSTALL_INSTANT_APP)?!=?0; ?????? ????????final?InstallArgs?args?=?createInstallArgs(this);? ????????//?...?? ????????ret?=?args.copyApk(mContainerService,?true); ????} ?? ????private?InstallArgs?createInstallArgs(InstallParams?params)?{ ????????if??!=?null)?{ ????????????return?new?MoveInstallArgs(params); ????????}?else?{ ????????????return?new?FileInstallArgs(params); ????????} ????} }

正常的流程下，createInstallArgs 返回的是 FileInstallArgs 對(duì)象

FileInstallArgs 的 copyApk 方法

int?copyApk(IMediaContainerService?imcs,?boolean?temp)?throws?RemoteException?{ ????return?doCopyApk(imcs,?temp); } private?int?doCopyApk(IMediaContainerService?imcs,?boolean?temp)?throws?RemoteException?{ ????//?創(chuàng)建存儲(chǔ)安裝包的目標(biāo)路徑，實(shí)際上是?/data/app/?應(yīng)用包名目錄 ????final?File?tempDir?=?mIn(volumeUuid,?isEphemeral); ????final?IParcelFileDescriptorFactory?target?=?new?IParcelFileDe()?{ ????????@Override ????????public?ParcelFileDescriptor?open(String?name,?int?mode)?throws?RemoteException?{ ????????????final?File?file?=?new?File(codeFile,?name); ????????????final?FileDescriptor?fd?=?Os.open(), ????????????????????O_RDWR?|?O_CREAT,?0644); ????????????Os.chmod(),?0644); ????????????return?new?ParcelFileDescriptor(fd); ????????} ????}; ????//?調(diào)用服務(wù)的 copyPackage 方法將安裝包 apk 拷貝到目標(biāo)路徑中； ????ret?=?imcs.copyPackage.getAbsolutePath(),?target); ????//?將 apk 中的動(dòng)態(tài)庫(kù) .so 文件也拷貝到目標(biāo)路徑中。 ????ret?=?Na(handle,?libraryRoot, ????????????????????????abiOverride); }

這里的 IMediaContainerService imcs 就是之前連接上的 DefaultContainerService

DefaultContainerService

copyPackage 方法本質(zhì)上就是執(zhí)行 IO 流操作，具體如下：

//?new?IMediaCon() public?int?copyPackage(String?packagePath,?IParcelFileDescriptorFactory?target)?{ ????PackageLite?pkg?=?null; ????final?File?packageFile?=?new?File(packagePath); ????pkg?=?PackagePar(packageFile,?0); ????return?copyPackageInner(pkg,?target); } //?DefaultContainerService private?int?copyPackageInner(PackageLite?pkg,?IParcelFileDescriptorFactory?target){ ????copyFile,?target,?"ba;); ????if?(!ArrayU))?{ ????????for?(int?i?=?0;?i?<?;?i++)?{ ????????????copyFile[i],?target,?"split_"?+?[i]?+?".apk"); ????????} ????} ????return?PackageManager.INSTALL_SUCCEEDED; } private?void?copyFile(String?sourcePath,?IParcelFileDescriptorFactory?target,?String?targetName){ ????InputStream?in?=?null; ????OutputStream?out?=?null; ????try?{ ????????in?=?new?FileInputStream(sourcePath); ????????out?=?new?ParcelFileDe( ????????????????(targetName,?ParcelFileDe)); ????????FileU(in,?out); ????}?finally?{ ????????IoU(out); ????????IoU(in); ????} }

最終安裝包在 data/app 目錄下以 ba 的方式保存，至此安裝包拷貝工作就已經(jīng)完成。

裝載代碼

安裝包拷貝完成，就要開(kāi)始真正安裝了。代碼回到上述的 HandlerParams 中的 startCopy 方法：

private?abstract?class?HandlerParams?{ ????final?boolean?startCopy()?{ ????????... ????????handleStartCopy(); ????????handleReturnCode(); ????} } class?InstallParams?extends?HandlerParams?{ ????@Override ????void?handleReturnCode()?{ ????????//?If?mArgs?is?null,?then?MCS?couldn't?be?reached.?When?it ????????//?reconnects,?it?will?try?again?to?install.?At?that?point,?this ????????//?will?succeed. ????????if?(mArgs?!=?null)?{ ????????????processPendingInstall(mArgs,?mRet); ????????} ????}?? ?? ????private?void?processPendingInstall(final?InstallArgs?args,?final?int?currentStatus)?{ ?????????mHandler.post(new?Runnable()?{ ?????????????public?void?run()?{ ?????????????????PackageInstalledInfo?res?=?new?PackageInstalledInfo(); ?????????????????if??==?PackageManager.INSTALL_SUCCEEDED)?{ ????????????????????//?預(yù)安裝操作，主要是檢查安裝包的狀態(tài)，確保安裝環(huán)境正常，如果安裝環(huán)境有問(wèn)題會(huì)清理拷貝文件 ????????????????????args.doPreInstall); ????????????????????synchronized?(mInstallLock)?{ ????????????????????????//?安裝階段 ????????????????????????installPackageTracedLI(args,?res); ????????????????????} ????????????????????args.doPostInstall,?res.uid); ????????????????} ????????????????... ?????????????} ?????????} ????} }

installPackageLI

installPackageTracedLI 方法中添加跟蹤 Trace，然后調(diào)用 installPackageLI 方法進(jìn)行安裝。這個(gè)方法有 600 行，取部分關(guān)鍵代碼：

private?void?installPackageLI(InstallArgs?args,?PackageInstalledInfo?res)?{ ????... ????PackageParser?pp?=?new?PackageParser(); ????final?PackagePar?pkg; ????//?1.?parsePackage ????pkg?=?(tmpPackageFile,?parseFlags); ???? ????//?2.?校驗(yàn)安裝包簽名 ????final?KeySetManagerService?ksms?=?mSe; ????if?(signatureCheckPs,?scanFlags))?{ ????????if?(!k(signatureCheckPs,?pkg))?{ ????????????res.setError(INSTALL_FAILED_UPDATE_INCOMPATIBLE,?"Package?" ????????????????????+??+?"?upgrade?keys?do?not?match?the?" ????????????????????+?"previously?installed?version"); ????????????return; ????????} ????} ???? ????//?3.?設(shè)置相關(guān)權(quán)限，生成、移植權(quán)限? ????int?N?=?(); ????for?(int?i?=?N-1;?i?>=?0;?i--)?{ ????????final?PackagePar?perm?=?(i); ????????... ????} ?? ????//?4.?生成安裝包Abi(Application?binary?interface，應(yīng)用二進(jìn)制接口) ????try?{ ????????String?abiOverride?=?(TextU)?? ????????????args.abiOverride?:?); ????????final?boolean?extractNativeLibs?=?!(); ????????derivePackageAbi(pkg,?abiOverride,?extractNativeLibs); ????}?catch?(PackageManagerException?pme)?{ ????????res.setError(INSTALL_FAILED_INTERNAL_ERROR,?"Error?deriving?application?ABI"); ????????return; ????} ?? ????//?5.?凍結(jié)?APK，執(zhí)行替換安裝?或?新安裝，? ????try?(PackageFreezer?freezer?=?freezePackageForInstall(pkgName,?installFlags, ????????????"installPackageLI"))?{ ????????if?(replace)?{ ????????????replacePackageLIF(pkg,?parseFlags,?scanFlags,?args.user, ????????????????????installerPackageName,?res,?args.installReason); ????????}?else?{ ????????????private?void?installNewPackageLIF((pkg,?parseFlags,?scanFlags?|?SCAN_DELETE_DATA_ON_FAILURES, ????????????????????args.user,?installerPackageName,?volumeUuid,?res,?args.installReason); ????????} ????} ?? ????//?5.?優(yōu)化dex文件（實(shí)際為?dex2oat?操作，用來(lái)將?apk?中的?dex?文件轉(zhuǎn)換為?oat?文件） ????if?(performDexopt)?{? ??????????mPackageDexO(pkg,?, ??????????????????null?/*?instructionSets?*/, ??????????????????getOrCreateCompilerPackageStats(pkg), ??????????????????mDexManager.getPackageUseInfoOrDefault), ??????????????????dexoptOptions);? ????} ????... }

最后我們來(lái)看一下 installNewPackageLIF

private?void?installNewPackageLIF(PackagePar?pkg,?final?@ParseFlags?int?parseFlags, ????????????final?@ScanFlags?int?scanFlags,...)?{ ????//?繼續(xù)掃描解析?apk?安裝包文件，保存?apk?相關(guān)信息到?PMS?中，并創(chuàng)建?apk?的?data?目錄，具體路徑為?/data/data/應(yīng)用包名 ????PackagePar?newPackage?=?scanPackageTracedLI(pkg,?parseFlags,?scanFlags, ????????Sy(),?user); ????//?更新系統(tǒng)設(shè)置中的應(yīng)用信息，比如應(yīng)用的權(quán)限信息 ????updateSettingsLI(newPackage,?installerPackageName,?null,?res,?user,?installReason); ????if??==?PackageManager.INSTALL_SUCCEEDED)?{ ?????????//?安裝然后準(zhǔn)備?APP?數(shù)據(jù)? ?????????prepareAppDataAfterInstallLIF(newPackage); ?????}?else?{ ?????????//?如果安裝失敗，則將安裝包以及各種緩存文件刪除 ?????????deletePackageLIF(pkgName,?U,?false,?null, ?????????????????PackageManager.DELETE_KEEP_DATA,?res.removedInfo,?true,?null); ?????} }

prepareAppDataAfterInstallLIF 還會(huì)有一系列的調(diào)用

???prepareAppDataAfterInstallLIF() ->?prepareAppDataLIF() ->?prepareAppDataLeafLIF() ->?mIn(...) final?Installer?mInstaller; private?void?prepareAppDataLeafLIF(...)?{ ???//?最終調(diào)用?系統(tǒng)服務(wù)?Installer?安裝 ???ceDataInode?=?mIn(volumeUuid,?packageName,?userId,?flags, ????????????????????appId,?seInfo,?a);????? }??? public?class?Installer?extends?SystemService?{ ???... }

至此整個(gè) apk 的安裝過(guò)程結(jié)束，實(shí)際上安裝成功之后，還會(huì)發(fā)送一個(gè) App 安裝成功的廣播 ACTION_PACKAGE_ADDED。手機(jī)桌面應(yīng)用注冊(cè)了這個(gè)廣播，當(dāng)接收到應(yīng)用安裝成功之后，就將 apk 的啟動(dòng) icon 顯示在桌面上。

總結(jié)

在手機(jī)上僅僅是點(diǎn)一下安裝按鈕而已，背后卻有著這么繁瑣的流程，相信通過(guò)今天的學(xué)習(xí)大家應(yīng)該能對(duì)系統(tǒng)的應(yīng)用安裝流程有一個(gè)完整的認(rèn)知。回顧一下安裝的流程如下：

• 點(diǎn)擊 APK 安裝，會(huì)啟動(dòng) PackageInstallerActivity，再進(jìn)入 InstallInstalling 這兩個(gè) Activity 顯示應(yīng)用信息
• 點(diǎn)擊頁(yè)面上的安裝，將 APK 信息存入 PackageIn 傳到 PMS
• PMS會(huì)做兩件事，拷貝安裝包和裝載代碼
• 在拷貝安裝包過(guò)程中會(huì)開(kāi)啟 Service 來(lái) copyAPK 、檢查apk安裝路徑，包的狀態(tài)
• 拷貝完成以 ba 形式存在/data/app包名下
• 裝載代碼過(guò)程中，會(huì)繼續(xù)解析 APK，把清單文件內(nèi)容存放于 PMS
• 對(duì) apk 進(jìn)行簽名校驗(yàn)
• 安裝成功后，更新應(yīng)用設(shè)置權(quán)限，發(fā)送廣播通知桌面顯示APP圖標(biāo)，安裝失敗則刪除安裝包和各種緩存文件
• 執(zhí)行 dex2oat 優(yōu)化

「本文源碼基于 Android 28」