PackageManagerService(Android5.1)深入分析（四）安装应用
一、安装的Activity
在Android，通过发送Intent可以启动应用的安装过程，如下所示：
Uri uri = Uri.fromFile(new File(filename)); Intent inent = new Intent(Intent.ACTION_VIEW); intent.SetDataAndType(uri, application/vnd.android.package-archive); startActivity(intent);
在Android的系统应用PackageInstaller中有一个PackageInstallActivity会响应这个Intent。在这个Activity中有两个重要的成员变量mPm和mInstaller，分别是ApplicationPackageManger和PackageInstaller的实例对象，这两个对象也是PackageManagerService和PackageInstallerService在应用中的代理对象。
PackageInstallerAcivity中创建这两个对象的代码如下：
protected void onCreate(Bundler icicle) {
super.onCreate(icicle);
mPm = getPackageManager();
mInstaller = mPm.getPackageInstaller();
......
}
二、管理安装会话
PackageManagerInstallerService是Android5.0新加入的服务，主要用于管理安装会话(Installer session)。在Android5.0中，可以通过PackageManagerInstallerService来分配一个SessionId，这个系统唯一的ID代表一次安装过程，如果一个应用的安装分成几个阶段来完成，即使设备重启了，也可以通过这个ID来继续安装过程。
PackageManagerInstallerService中提供的接口createSession来创建一个Session：
@Override
public int createSession(SessionParams params, String installerPackageName, int userId) {
try {
return createSessionInternal(params, installerPackageName, userId);
} catch (IOException e) {
throw ExceptionUtils.wrap(e);
}
}
这个方法返回一个系统唯一值作为SessionID，如果希望再次使用这个Session，可以通过接口openSession方法来打开它，代码如下：
@Override
public IPackageInstallerSession openSession(int sessionId) {
try {
return openSessionInternal(sessionId);
} catch (IOException e) {
throw ExceptionUtils.wrap(e);
}
}
openSession返回一个IPackageInstallerSession对象，它是Binder服务PackageInstallerSession的IBinder对象。每个Install Session都会在SystemServer中有一个对应的PackageInstallerSession对象。在PackageInstallerService中mSessions数组保存了所有PackageInstallerSession对象，定义如下：
private final SparseArray<PackageInstallerSession> mSessions = new SparseArray<>();
当系统启动时，PackageManageService初始化时会创建PackageManagerInstallerService服务，在这个服务的初始化函数中，会读取/data/system目录下的install_sessions.xml文件，这个文件保存系统未完成的Install Session。然后PackagemanagerInstallerService会根据文件的内容创建PackageInstallerSession对象并插入mSessions中。
PackageInstallerSession中保存了应用安装相关的数据。例如，安装包路径，安装进度、中间数据保存的目录等。
三、应用安装过程
应用可以调用PackageManager的installPackage方法来开始安装过程，最终会调用到PackageManagerService的installPackage或者installPackageAsUser来执行安装过程，整个安装过程比较复杂。
整个安装过程可以分成两个阶段：
1.第一阶段把需要安装的应用复制到/data/app目录下
2.第二阶段是对apk文件扫描优化，装载到内存中。
3.1 复制文件
PackageManagerService的installPackage方法只是用当前用户安装应用，最后也会调用installPackageAsUser
@Override
public void installPackage(String originPath, IPackageInstallObserver2 observer,
int installFlags, String installerPackageName, VerificationParams verificationParams,
String packageAbiOverride) {
installPackageAsUser(originPath, observer, installFlags, installerPackageName, verificationParams,
packageAbiOverride, UserHandle.getCallingUserId());
}
下面我们就来看看installPackageAsUser方法：
@Override
public void installPackageAsUser(String originPath, IPackageInstallObserver2 observer,
int installFlags, String installerPackageName, VerificationParams verificationParams,
String packageAbiOverride, int userId) {
mContext.enforceCallingOrSelfPermission(android.Manifest.permission.INSTALL_PACKAGES, null);//检查调用进程的权限
//检查调用进程的永华是否有权限安装应用
final int callingUid = Binder.getCallingUid();
enforceCrossUserPermission(callingUid, userId, true, true, "installPackageAsUser");
//检查指定的用户是否被限制安装应用
if (isUserRestricted(userId, UserManager.DISALLOW_INSTALL_APPS)) {
try {
if (observer != null) {
observer.onPackageInstalled("", INSTALL_FAILED_USER_RESTRICTED, null, null);
}
} catch (RemoteException re) {
}
return;
}
if ((callingUid == Process.SHELL_UID) || (callingUid == Process.ROOT_UID)) {
installFlags |= PackageManager.INSTALL_FROM_ADB;
} else {
// Caller holds INSTALL_PACKAGES permission, so we're less strict
// about installerPackageName.
installFlags &= ~PackageManager.INSTALL_FROM_ADB;
installFlags &= ~PackageManager.INSTALL_ALL_USERS;
}
UserHandle user;
if ((installFlags & PackageManager.INSTALL_ALL_USERS) != 0) {//给所有用户安装
user = UserHandle.ALL;
} else {
user = new UserHandle(userId);
}
verificationParams.setInstallerUid(callingUid);
final File originFile = new File(originPath);
final OriginInfo origin = OriginInfo.fromUntrustedFile(originFile);
final Message msg = mHandler.obtainMessage(INIT_COPY);
msg.obj = new InstallParams(origin, observer, installFlags,//保存参数到InstallParamsm,发送消息
installerPackageName, verificationParams, user, packageAbiOverride);
mHandler.sendMessage(msg);
}
installPackageAsUser先检查调用进程是否有安装应用的权限，再检查调用进程所属的用户是否有权限安装应用，最后检查指定的用户是否被限制安装应用。如果参数installFlags带有INSTALL_ALL_USERS，则该应用将给系统中所有用户安装，否则只给指定用户安装。
安装应用实践比较长，因此不可能在一个函数中完成。上面函数把数据保存在installParams然后发送了INIT_COPY消息。
下面我们再来看看消息处理：
void doHandleMessage(Message msg) {
switch (msg.what) {
case INIT_COPY: {
HandlerParams params = (HandlerParams) msg.obj;
int idx = mPendingInstalls.size();
if (DEBUG_INSTALL) Slog.i(TAG, "init_copy idx=" + idx + ": " + params);
// If a bind was already initiated we dont really
// need to do anything. The pending install
// will be processed later on.
if (!mBound) {
// If this is the only one pending we might
// have to bind to the service again.
if (!connectToService()) {//绑定DefaultContainerService
Slog.e(TAG, "Failed to bind to media container service");
params.serviceError();
return;
} else {//连接成功把安装信息保存到mPendingInstalls
// Once we bind to the service, the first
// pending request will be processed.
mPendingInstalls.add(idx, params);
}
} else {//如果已经绑定好了
mPendingInstalls.add(idx, params);
// Already bound to the service. Just make
// sure we trigger off processing the first request.
if (idx == 0) {
mHandler.sendEmptyMessage(MCS_BOUND);
}
}
break;
}
INIT_COPY消息的处理将绑定DefaultContainerService，因为这是一个异步的过程，要等待绑定的结果通过onServiceConnected返回，所以这里的安装参数放到了mPendingInstalls列表中。如果这个Service以前就绑定好了，现在就不需要再绑定，安装信息也会先放到mPendingInstalls。如果有多个安装请求同时到达，这里通过mPendingInstalls列表对他们进行排队。如果列表中只有一项，说明没有更多的安装请求，因此这种情况下回立即发出MCS_BOUND消息。而onServiceConnected方法同样是发出MCS_BOUND消息：
class DefaultContainerConnection implements ServiceConnection {
public void onServiceConnected(ComponentName name, IBinder service) {
if (DEBUG_SD_INSTALL) Log.i(TAG, "onServiceConnected");
IMediaContainerService imcs =
IMediaContainerService.Stub.asInterface(service);
mHandler.sendMessage(mHandler.obtainMessage(MCS_BOUND, imcs));
}
public void onServiceDisconnected(ComponentName name) {
if (DEBUG_SD_INSTALL) Log.i(TAG, "onServiceDisconnected");
}
};
看下MCS_BOUND的消息处理
case MCS_BOUND: {
if (DEBUG_INSTALL) Slog.i(TAG, "mcs_bound");
if (msg.obj != null) {
mContainerService = (IMediaContainerService) msg.obj;
}
if (mContainerService == null) {//没有连接成功
// Something seriously wrong. Bail out
Slog.e(TAG, "Cannot bind to media container service");
for (HandlerParams params : mPendingInstalls) {
// Indicate service bind error
params.serviceError();//通知出错了
}
mPendingInstalls.clear();
} else if (mPendingInstalls.size() > 0) {
HandlerParams params = mPendingInstalls.get(0);
if (params != null) {
if (params.startCopy()) {//执行安装
// We are done... look for more work or to
// go idle.
if (DEBUG_SD_INSTALL) Log.i(TAG,
"Checking for more work or unbind...");
// Delete pending install
if (mPendingInstalls.size() > 0) {
mPendingInstalls.remove(0);//工作完成，删除第一项
}
if (mPendingInstalls.size() == 0) {//如果没有安装消息了，延时发送10秒MCS_UNBIND消息
if (mBound) {
if (DEBUG_SD_INSTALL) Log.i(TAG,
"Posting delayed MCS_UNBIND");
removeMessages(MCS_UNBIND);
Message ubmsg = obtainMessage(MCS_UNBIND);
// Unbind after a little delay, to avoid
// continual thrashing.
sendMessageDelayed(ubmsg, 10000);
}
} else {
// There are more pending requests in queue.
// Just post MCS_BOUND message to trigger processing
// of next pending install.
if (DEBUG_SD_INSTALL) Log.i(TAG,
"Posting MCS_BOUND for next work");
mHandler.sendEmptyMessage(MCS_BOUND);//还有消息继续发送MCS_BOUND消息
}
}
}
} else {
// Should never happen ideally.
Slog.w(TAG, "Empty queue");
}
break;
}
如果结束了我们看看MCS_UNBIND消息的处理
case MCS_UNBIND: {
// If there is no actual work left, then time to unbind.
if (DEBUG_INSTALL) Slog.i(TAG, "mcs_unbind");
if (mPendingInstalls.size() == 0 && mPendingVerification.size() == 0) {
if (mBound) {
if (DEBUG_INSTALL) Slog.i(TAG, "calling disconnectService()");
disconnectService();//断开连接
}
} else if (mPendingInstalls.size() > 0) {
// There are more pending requests in queue.
// Just post MCS_BOUND message to trigger processing
// of next pending install.
mHandler.sendEmptyMessage(MCS_BOUND);
}
break;
}
MCS_UNBIND消息的处理，如果处理的时候发现mPendingInstalls又有数据了，还是发送MCS_BOUND消息继续安装，否则断开和DefaultContainerService的连接，安装结束。
下面我们看执行安装的函数startCopy：
final boolean startCopy() {
boolean res;
try {
if (DEBUG_INSTALL) Slog.i(TAG, "startCopy " + mUser + ": " + this);
if (++mRetries > MAX_RETRIES) {//重试超过4次退出
Slog.w(TAG, "Failed to invoke remote methods on default container service. Giving up");
mHandler.sendEmptyMessage(MCS_GIVE_UP);
handleServiceError();
return false;
} else {
handleStartCopy();
res = true;
}
} catch (RemoteException e) {
if (DEBUG_INSTALL) Slog.i(TAG, "Posting install MCS_RECONNECT");
mHandler.sendEmptyMessage(MCS_RECONNECT);//安装出错，发送重新连接
res = false;
}
handleReturnCode();
return res;
}
handleStartCopy和copyApk代码就不分析了。
handleStartCopy函数先通过DefaultContainerService调用了getMinimallPackageInfo来确定安装位置是否有足够的空间，并在PackageInfoLite对象的recommendedIntallLocation记录错误原因。发现空间不够，会调用installer的freecache方法来释放一部分空间。
再接下来handleStartCopy有很长一段都在处理apk的校验，这个校验过程是通过发送Intent ACTION_PACKAGE_NEEDS_VERIFICATION给系统中所有接受该Intent的应用来完成。如果无需校验，直接调用InstallArgs对象的copyApk方法。
而copyApk方法同样是调用DefaultContainerService的copyPackage将应用的文件复制到/data/app下，如果还有native动态库，也会把包在apk文件中的动态库提取出来。
执行完copyApk后，应用安装到了data/app目录下了。
3.2 装载应用
接下来是第二阶段的工作，把应用的格式装换成oat格式，为应用创建数据目录。最后把应用信息装载进PackageManagerService的数据结构中。
接着上面startCopy方法最后会调用handleReturnCode方法，代码如下：
@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);
}
}
我们继续看下processPendingInstall函数。
private void processPendingInstall(final InstallArgs args, final int currentStatus) {
// Queue up an async operation since the package installation may take a little while.
mHandler.post(new Runnable() {
public void run() {
mHandler.removeCallbacks(this);//防止重复调用
// Result object to be returned
PackageInstalledInfo res = new PackageInstalledInfo();
res.returnCode = currentStatus;
res.uid = -1;
res.pkg = null;
res.removedInfo = new PackageRemovedInfo();
if (res.returnCode == PackageManager.INSTALL_SUCCEEDED) {//如果安装成功了
args.doPreInstall(res.returnCode);
synchronized (mInstallLock) {
installPackageLI(args, res);//装载安装的应用
}
args.doPostInstall(res.returnCode, res.uid);
}
..........
if (!doRestore) {
// 发送POST_INSTALL消息
Message msg = mHandler.obtainMessage(POST_INSTALL, token, 0);
mHandler.sendMessage(msg);
}
}
});
}
processPendingInstall方法post了一个消息，这样安装过程以异步的方式继续执行。在post消息的处理中，首先调用installPackageLI来装载应用，然后很大的代码在执行备份，备份是通过BackupManagerService来完成的。备份完成后，通过发送POST_INSTALL消息来继续处理。而这个消息的处理主要就是在发送广播，应用安装完成后要通知系统中其他的应用开始处理，比如Launcher中需要增加应用的图标等。
我们来分析下installPackageLI方法：
private void installPackageLI(InstallArgs args, PackageInstalledInfo res) {
final int installFlags = args.installFlags;
String installerPackageName = args.installerPackageName;
File tmpPackageFile = new File(args.getCodePath());
boolean forwardLocked = ((installFlags & PackageManager.INSTALL_FORWARD_LOCK) != 0);
boolean onSd = ((installFlags & PackageManager.INSTALL_EXTERNAL) != 0);
boolean replace = false;
final int scanFlags = SCAN_NEW_INSTALL | SCAN_FORCE_DEX | SCAN_UPDATE_SIGNATURE;
// Result object to be returned
res.returnCode = PackageManager.INSTALL_SUCCEEDED;
if (DEBUG_INSTALL) Slog.d(TAG, "installPackageLI: path=" + tmpPackageFile);
// Retrieve PackageSettings and parse package
final int parseFlags = mDefParseFlags | PackageParser.PARSE_CHATTY
| (forwardLocked ? PackageParser.PARSE_FORWARD_LOCK : 0)
| (onSd ? PackageParser.PARSE_ON_SDCARD : 0);
PackageParser pp = new PackageParser();
pp.setSeparateProcesses(mSeparateProcesses);
pp.setDisplayMetrics(mMetrics);
final PackageParser.Package pkg;
try {
pkg = pp.parsePackage(tmpPackageFile, parseFlags);//解析apk文件
} catch (PackageParserException e) {
res.setError("Failed parse during installPackageLI", e);
return;
}
这里先调用parsePackage解析apk文件，这个之前分析过，我们就不再分析了。
继续分析processPendingInstall函数
if ((installFlags & PackageManager.INSTALL_REPLACE_EXISTING) != 0) {//如果安装的升级应用，继续使用以前的老的包名
String oldName = mSettings.mRenamedPackages.get(pkgName);
if (pkg.mOriginalPackages != null
&& pkg.mOriginalPackages.contains(oldName)
&& mPackages.containsKey(oldName)) {
// This package is derived from an original package,
// and this device has been updating from that original
// name. We must continue using the original name, so
// rename the new package here.
pkg.setPackageName(oldName);//设置老的包名
pkgName = pkg.packageName;
replace = true;
if (DEBUG_INSTALL) Slog.d(TAG, "Replacing existing renamed package: oldName="
+ oldName + " pkgName=" + pkgName);
} else if (mPackages.containsKey(pkgName)) {
// This package, under its official name, already exists
// on the device; we should replace it.
replace = true;
if (DEBUG_INSTALL) Slog.d(TAG, "Replace existing pacakge: " + pkgName);
}
}
继续分析
if (systemApp && onSd) {//不能将系统应用装载sd卡
// Disable updates to system apps on sdcard
res.setError(INSTALL_FAILED_INVALID_INSTALL_LOCATION,
"Cannot install updates to system apps on sdcard");
return;
}
if (!args.doRename(res.returnCode, pkg, oldCodePath)) {//重命名出错
res.setError(INSTALL_FAILED_INSUFFICIENT_STORAGE, "Failed rename");
return;
}
继续分析
if (replace) {//如果安装的是升级包，调用replacePackageLI
replacePackageLI(pkg, parseFlags, scanFlags | SCAN_REPLACING, args.user,
installerPackageName, res);
} else {//如果是新应用，调用installNewPackageLI继续处理
installNewPackageLI(pkg, parseFlags, scanFlags | SCAN_DELETE_DATA_ON_FAILURES,
args.user, installerPackageName, res);
}
synchronized (mPackages) {
final PackageSetting ps = mSettings.mPackages.get(pkgName);
if (ps != null) {
res.newUsers = ps.queryInstalledUsers(sUserManager.getUserIds(), true);
}
}
下面我们分析下installNewPackageLI函数
private void installNewPackageLI(PackageParser.Package pkg,
int parseFlags, int scanFlags, UserHandle user,
String installerPackageName, PackageInstalledInfo res) {
// Remember this for later, in case we need to rollback this install
String pkgName = pkg.packageName;
if (DEBUG_INSTALL) Slog.d(TAG, "installNewPackageLI: " + pkg);
boolean dataDirExists = getDataPathForPackage(pkg.packageName, 0).exists();
synchronized(mPackages) {
if (mSettings.mRenamedPackages.containsKey(pkgName)) {
// A package with the same name is already installed, though
// it has been renamed to an older name. The package we
// are trying to install should be installed as an update to
// the existing one, but that has not been requested, so bail.
res.setError(INSTALL_FAILED_ALREADY_EXISTS, "Attempt to re-install " + pkgName
+ " without first uninstalling package running as "
+ mSettings.mRenamedPackages.get(pkgName));
return;
}
if (mPackages.containsKey(pkgName)) {
// Don't allow installation over an existing package with the same name.
res.setError(INSTALL_FAILED_ALREADY_EXISTS, "Attempt to re-install " + pkgName
+ " without first uninstalling.");
return;
}
}
try {
PackageParser.Package newPackage = scanPackageLI(pkg, parseFlags, scanFlags,//调用scanPackageLI
System.currentTimeMillis(), user);
updateSettingsLI(newPackage, installerPackageName, null, null, res);
// delete the partially installed application. the data directory will have to be
// restored if it was already existing
if (res.returnCode != PackageManager.INSTALL_SUCCEEDED) {
// remove package from internal structures. Note that we want deletePackageX to
// delete the package data and cache directories that it created in
// scanPackageLocked, unless those directories existed before we even tried to
// install.
deletePackageLI(pkgName, UserHandle.ALL, false, null, null,
dataDirExists ? PackageManager.DELETE_KEEP_DATA : 0,
res.removedInfo, true);
}
} catch (PackageManagerException e) {
res.setError("Package couldn't be installed in " + pkg.codePath, e);
}
}
这里和上篇博客分析扫描apk文件类似，我们来看下这个函数scanPackageLI
private PackageParser.Package scanPackageLI(PackageParser.Package pkg, int parseFlags,
int scanFlags, long currentTime, UserHandle user) throws PackageManagerException {
boolean success = false;
try {
final PackageParser.Package res = scanPackageDirtyLI(pkg, parseFlags, scanFlags,
currentTime, user);
success = true;
return res;
} finally {
if (!success && (scanFlags & SCAN_DELETE_DATA_ON_FAILURES) != 0) {
removeDataDirsLI(pkg.packageName);
}
}
}scanPackageLI函数主要调用了scanPackageDirtyLI函数，这个函数前面分析过了就不分析了。
这样安装应用的流程就讲完了。