前言

在PM机制系列前三篇，我们着重分析了安装的整个流程，没有具体到很多细节问题。
这一篇文章我们就会具体到很多细节问题。本篇主要就是围绕一个问题展开：
安装APK到底需要多少空间不会报错INSTALL_FAILED_INSUFFICIENT_STORAGE？可以提高我们的安装成功率。

１. 分析结果时序图

DCS：　DefaultContainerService
SMS：　StorageManagerService
SM: StorageManager
调用关系图如下所示，后面会进行具体分析。

2. 开始安装

经过前三篇的安装流程，可以清楚的知道安装核心代码开始处就在handleStartCopy方法，代码如下：
/frameworks/base/services/core/java/com/android/server/pm/PackageManagerService.java

public void handleStartCopy() throws RemoteException {...// If we're already staged, we've firmly committed to an install locationif (origin.staged) {//安装时候，传参进来的origin.staged是为true,file != nullif (origin.file != null) {installFlags |= PackageManager.INSTALL_INTERNAL; //这样就会走到这里给installFlags赋值，installFlags &= ~PackageManager.INSTALL_EXTERNAL;//走内部安装逻辑} else {throw new IllegalStateException("Invalid stage location");}}/*确定APK的安装位置。onSd：安装到SD卡， onInt：内部存储即Data分区，ephemeral：安装到临时存储（Instant Apps安装）这里根据上面installFlags的赋值可知onSd=false;onInt＝true;ephemeral=false;*/      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;PackageInfoLite pkgLite = null;if (onInt && onSd) {// APK不能同时安装在SD卡和Data分区Slog.w(TAG, "Conflicting flags specified for installing on both internal and external");ret = PackageManager.INSTALL_FAILED_INVALID_INSTALL_LOCATION;//安装标志冲突，Instant Apps不能安装到SD卡中} else if (onSd && ephemeral) {Slog.w(TAG,  "Conflicting flags specified for installing ephemeral on external");ret = PackageManager.INSTALL_FAILED_INVALID_INSTALL_LOCATION;} else { //最终会走到这里来//获取APK的少量的信息pkgLite = mContainerService.getMinimalPackageInfo(origin.resolvedPath, installFlags,packageAbiOverride);//1if (DEBUG_EPHEMERAL && ephemeral) {Slog.v(TAG, "pkgLite for install: " + pkgLite);}...if (ret == PackageManager.INSTALL_SUCCEEDED) {//判断安装的位置int loc = pkgLite.recommendedInstallLocation;if (loc == PackageHelper.RECOMMEND_FAILED_INVALID_LOCATION) {ret = PackageManager.INSTALL_FAILED_INVALID_INSTALL_LOCATION;} else if (loc == PackageHelper.RECOMMEND_FAILED_ALREADY_EXISTS) {ret = PackageManager.INSTALL_FAILED_ALREADY_EXISTS;}  else if (loc == PackageHelper.RECOMMEND_FAILED_INSUFFICIENT_STORAGE) {ret = PackageManager.INSTALL_FAILED_INSUFFICIENT_STORAGE;　//2} ...}else{loc = installLocationPolicy(pkgLite);...}}//根据InstallParams创建InstallArgs对象final InstallArgs args = createInstallArgs(this);mArgs = args;if (ret == PackageManager.INSTALL_SUCCEEDED) {...if (!origin.existing && requiredUid != -1&& isVerificationEnabled(verifierUser.getIdentifier(), installFlags, installerUid)) {...} else{ret = args.copyApk(mContainerService, true);}}mRet = ret;}

handleStartCopy方法的代码很多，这里截取关键的部分。

1. 注释1处通过IMediaContainerService跨进程调用DefaultContainerService的getMinimalPackageInfo方法，该方法轻量解析APK并得到APK的少量信息，轻量解析的原因是这里不需要得到APK的全部信息，APK的少量信息会封装到PackageInfoLite中。在上一篇中我们一笔带过，这里信息量很多，里面就有我们这篇文章所涉及到的安装空间判断。
2. 注释2处，如果loc == PackageHelper.RECOMMEND_FAILED_INSUFFICIENT_STORAGE，就会返回INSTALL_FAILED_INSUFFICIENT_STORAGE。所以要从loc的返回值分析。下面看一下getMinimalPackageInfo方法。

/frameworks/base/packages/DefaultContainerService/src/com/android/defcontainer/DefaultContainerService.java

/*** Parse given package and return minimal details.** @param packagePath absolute path to the package to be copied. Can be*            a single monolithic APK file or a cluster directory*            containing one or more APKs.*/
@Override
public PackageInfoLite getMinimalPackageInfo(String packagePath, int flags,String abiOverride) {final Context context = DefaultContainerService.this;PackageInfoLite ret = new PackageInfoLite();if (packagePath == null) {Slog.i(TAG, "Invalid package file " + packagePath);ret.recommendedInstallLocation = PackageHelper.RECOMMEND_FAILED_INVALID_APK;return ret;}final File packageFile = new File(packagePath);final PackageParser.PackageLite pkg;final long sizeBytes;try {pkg = PackageParser.parsePackageLite(packageFile, 0);sizeBytes = PackageHelper.calculateInstalledSize(pkg, abiOverride); //1} catch (PackageParserException | IOException e) {Slog.w(TAG, "Failed to parse package at " + packagePath + ": " + e);if (!packageFile.exists()) {ret.recommendedInstallLocation = PackageHelper.RECOMMEND_FAILED_INVALID_URI;} else {ret.recommendedInstallLocation = PackageHelper.RECOMMEND_FAILED_INVALID_APK;}return ret;}final int recommendedInstallLocation;final long token = Binder.clearCallingIdentity();try {recommendedInstallLocation = PackageHelper.resolveInstallLocation(context,pkg.packageName, pkg.installLocation, sizeBytes, flags);//2} finally {Binder.restoreCallingIdentity(token);}ret.packageName = pkg.packageName;ret.splitNames = pkg.splitNames;ret.versionCode = pkg.versionCode;ret.versionCodeMajor = pkg.versionCodeMajor;ret.baseRevisionCode = pkg.baseRevisionCode;ret.splitRevisionCodes = pkg.splitRevisionCodes;ret.installLocation = pkg.installLocation;ret.verifiers = pkg.verifiers;ret.recommendedInstallLocation = recommendedInstallLocation;ret.multiArch = pkg.multiArch;return ret;
}

1. 注释１处计算安装apk需要的空间大小。
2. 注释２处是核心代码，根据apk需要的空间大小计算推荐存储位置，参数flags就是就是我们之前赋值的内部存储。

下面看一下resolveInstallLocation方法
/frameworks/base/core/java/com/android/internal/content/PackageHelper.java

@Deprecated
public static int resolveInstallLocation(Context context, String packageName,int installLocation, long sizeBytes, int installFlags) {final SessionParams params = new SessionParams(SessionParams.MODE_INVALID);params.appPackageName = packageName;params.installLocation = installLocation;params.sizeBytes = sizeBytes;params.installFlags = installFlags;try {return resolveInstallLocation(context, params); //1} catch (IOException e) {throw new IllegalStateException(e);}
}/*** Given a requested {@link PackageInfo#installLocation} and calculated* install size, pick the actual location to install the app.*/
public static int resolveInstallLocation(Context context, SessionParams params)throws IOException {ApplicationInfo existingInfo = null;try {existingInfo = context.getPackageManager().getApplicationInfo(params.appPackageName,PackageManager.MATCH_ANY_USER);} catch (NameNotFoundException ignored) {}final int prefer;final boolean checkBoth;boolean ephemeral = false;if ((params.installFlags & PackageManager.INSTALL_INSTANT_APP) != 0) {prefer = RECOMMEND_INSTALL_INTERNAL;ephemeral = true;checkBoth = false;} else if ((params.installFlags & PackageManager.INSTALL_INTERNAL) != 0) {　//2prefer = RECOMMEND_INSTALL_INTERNAL;checkBoth = false;} else if ((params.installFlags & PackageManager.INSTALL_EXTERNAL) != 0) {prefer = RECOMMEND_INSTALL_EXTERNAL;checkBoth = false;} else if (params.installLocation == PackageInfo.INSTALL_LOCATION_INTERNAL_ONLY) {prefer = RECOMMEND_INSTALL_INTERNAL;checkBoth = false;} else if (params.installLocation == PackageInfo.INSTALL_LOCATION_PREFER_EXTERNAL) {prefer = RECOMMEND_INSTALL_EXTERNAL;checkBoth = true;} else if (params.installLocation == PackageInfo.INSTALL_LOCATION_AUTO) {// When app is already installed, prefer same mediumif (existingInfo != null) {// TODO: distinguish if this is external ASECif ((existingInfo.flags & ApplicationInfo.FLAG_EXTERNAL_STORAGE) != 0) {prefer = RECOMMEND_INSTALL_EXTERNAL;} else {prefer = RECOMMEND_INSTALL_INTERNAL;}} else {prefer = RECOMMEND_INSTALL_INTERNAL;}checkBoth = true;} else {prefer = RECOMMEND_INSTALL_INTERNAL;checkBoth = false;}boolean fitsOnInternal = false;if (checkBoth || prefer == RECOMMEND_INSTALL_INTERNAL) {fitsOnInternal = fitsOnInternal(context, params); //3}boolean fitsOnExternal = false;if (checkBoth || prefer == RECOMMEND_INSTALL_EXTERNAL) {fitsOnExternal = fitsOnExternal(context, params);}if (prefer == RECOMMEND_INSTALL_INTERNAL) {  //4// The ephemeral case will either fit and return EPHEMERAL, or will not fit// and will fall through to return INSUFFICIENT_STORAGEif (fitsOnInternal) {return (ephemeral)? PackageHelper.RECOMMEND_INSTALL_EPHEMERAL: PackageHelper.RECOMMEND_INSTALL_INTERNAL;　//5}} else if (prefer == RECOMMEND_INSTALL_EXTERNAL) {if (fitsOnExternal) {return PackageHelper.RECOMMEND_INSTALL_EXTERNAL;}}if (checkBoth) {if (fitsOnInternal) {return PackageHelper.RECOMMEND_INSTALL_INTERNAL;} else if (fitsOnExternal) {return PackageHelper.RECOMMEND_INSTALL_EXTERNAL;}}return PackageHelper.RECOMMEND_FAILED_INSUFFICIENT_STORAGE;  //6
}

1. 注释1处将我们传入的参数全部都放入SessionParams内，执行resolveInstallLocation
2. 根据之前传入的flags值代码会运营到注释２处。此处赋值：
   prefer = RECOMMEND_INSTALL_INTERNAL;
   checkBoth = false;
3. 根据之前的赋值，会走到注释3处，调用fitsOnInternal()方法。
   如果fitsOnInternal为true，就会走到注释５处，返回RECOMMEND_INSTALL_INTERNAL
   如果fitsOnInternal为false，就会走到注释６处，返回RECOMMEND_FAILED_INSUFFICIENT_STORAGE。

下面我们看一下fitsOnInternal()方法
/frameworks/base/core/java/com/android/internal/content/PackageHelper.java

public static boolean fitsOnInternal(Context context, SessionParams params) throws IOException {final StorageManager storage = context.getSystemService(StorageManager.class);final UUID target = storage.getUuidForPath(Environment.getDataDirectory());return (params.sizeBytes <= storage.getAllocatableBytes(target,translateAllocateFlags(params.installFlags)));　　//1
}

1. 就是判断安装需要的空间大小是否小于系统能分配的存储大小。
2. translateAllocateFlags方法如下，由于installFlags并没有设置INSTALL_ALLOCATE_AGGRESSIVE标识符，所以返回０。

   public static int translateAllocateFlags(int installFlags) {if ((installFlags & PackageManager.INSTALL_ALLOCATE_AGGRESSIVE) != 0) {return StorageManager.FLAG_ALLOCATE_AGGRESSIVE;} else {return 0;}
   }
   

下面就会调用到StorageManager的getAllocatableBytes方法
/frameworks/base/core/java/android/os/storage/StorageManager.java

public long getAllocatableBytes(@NonNull UUID storageUuid,@RequiresPermission @AllocateFlags int flags) throws IOException {try {return mStorageManager.getAllocatableBytes(convert(storageUuid), flags,mContext.getOpPackageName());　//1} catch (ParcelableException e) {e.maybeRethrow(IOException.class);throw new RuntimeException(e);} catch (RemoteException e) {throw e.rethrowFromSystemServer();}
}

1. 注释１继续调用StorageManagerService的getAllocatableBytes方法
   /frameworks/base/services/core/java/com/android/server/StorageManagerService.java

 @Override
public long getAllocatableBytes(String volumeUuid, int flags, String callingPackage) {flags = adjustAllocateFlags(flags, Binder.getCallingUid(), callingPackage);final StorageManager storage = mContext.getSystemService(StorageManager.class);final StorageStatsManager stats = mContext.getSystemService(StorageStatsManager.class);final long token = Binder.clearCallingIdentity();try {// In general, apps can allocate as much space as they want, except// we never let them eat into either the minimum cache space or into// the low disk warning space. To avoid user confusion, this logic// should be kept in sync with getFreeBytes().final File path = storage.findPathForUuid(volumeUuid);final long usable = path.getUsableSpace();//1final long lowReserved = storage.getStorageLowBytes(path);//2final long fullReserved = storage.getStorageFullBytes(path);if (stats.isQuotaSupported(volumeUuid)) {   //3final long cacheTotal = stats.getCacheBytes(volumeUuid);final long cacheReserved = storage.getStorageCacheBytes(path, flags);final long cacheClearable = Math.max(0, cacheTotal - cacheReserved);if ((flags & StorageManager.FLAG_ALLOCATE_AGGRESSIVE) != 0) {return Math.max(0, (usable + cacheClearable) - fullReserved);} else {return Math.max(0, (usable + cacheClearable) - lowReserved); //4}} else {// When we don't have fast quota information, we ignore cached// data and only consider unused bytes.if ((flags & StorageManager.FLAG_ALLOCATE_AGGRESSIVE) != 0) {return Math.max(0, usable - fullReserved);} else {return Math.max(0, usable - lowReserved);//5}}} catch (IOException e) {throw new ParcelableException(e);} finally {Binder.restoreCallingIdentity(token);}
}

1. 注释1处会先求出分区可用的空间
2. 注释2处会求出系统运行需要的最低存储
3. 注释3处会 判断是否支持Quota，在9.0虚拟机上和真机上测试都是支持的。
4. 注释４如果支持，就会计算cacheTotal（总共的cache大小），cacheReserved（需要保留的cache大小），求出可以清理的ｃａｃｈｅ大小。返回getTotalSpace + 可清理ｃａｃｈｅ大小－需要保留的
5. 注释５如果不支持返回getTotalSpace的5%和500M之间的最小值

下面我们看一下getStorageLowBytes方法
/frameworks/base/core/java/android/os/storage/StorageManager.java

private static final int DEFAULT_THRESHOLD_PERCENTAGE = 5;
private static final long DEFAULT_THRESHOLD_MAX_BYTES = DataUnit.MEBIBYTES.toBytes(500);public long getStorageLowBytes(File path) {final long lowPercent = Settings.Global.getInt(mResolver,Settings.Global.SYS_STORAGE_THRESHOLD_PERCENTAGE, DEFAULT_THRESHOLD_PERCENTAGE);final long lowBytes = (path.getTotalSpace() * lowPercent) / 100;final long maxLowBytes = Settings.Global.getLong(mResolver,Settings.Global.SYS_STORAGE_THRESHOLD_MAX_BYTES, DEFAULT_THRESHOLD_MAX_BYTES);return Math.min(lowBytes, maxLowBytes);
}

我们发现。系统设置的默认阈值是5%，最终返回值为getTotalSpace的5%和500M之间的最小值。

总结

至此，算是全部结束了，我们发现只要系统空间小于Math.min(getTotalSpace的5%，500M)+ PackageHelper.calculateInstalledSize(pkg, abiOverride)，系统就会报空间不足。

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