这一章我们介绍APK的卸载过程，从前一章分析安装APK的过程，我们应该大致了解这里的卸载的过程如下：
1.从PMS的内部结构上删除acitivity、service、provider等信息
2.删除code、library和resource等信息
3.调用installd删除/data/data/packageName以及/data/dalvik-cache下面的文件
4.更新Settings中的package信息
当我们在Settings中的应用页面找到一个安装了的应用程序，并点击卸载后，就会发送一个Intent给UninstallerActivity，在UninstallerActivity最后会启动UninstallAppProgress的initView方法，并调用如下卸载函数：
getPackageManager().deletePackage(mAppInfo.packageName, observer,
mAllUsers ? PackageManager.DELETE_ALL_USERS : 0);上面的mAllUsers默认是false。getPackageManager()函数的实现在ContextImpl.java，它最后会调用到ApplicantPackageManger.java的deletePackage方法：
public void deletePackage(String packageName, IPackageDeleteObserver observer, int flags) {
try {
mPM.deletePackageAsUser(packageName, observer, UserHandle.myUserId(), flags);
} catch (RemoteException e) {
// Should never happen!
}
}通过Binder调用，我们来看PMS中的deletePackageAsUser方法：
public void deletePackageAsUser(final String packageName,
final IPackageDeleteObserver observer,
final int userId, final int flags) {
mContext.enforceCallingOrSelfPermission(
android.Manifest.permission.DELETE_PACKAGES, null);
final int uid = Binder.getCallingUid();
if (isUserRestricted(userId, UserManager.DISALLOW_UNINSTALL_APPS)) {
try {
observer.packageDeleted(packageName, PackageManager.DELETE_FAILED_USER_RESTRICTED);
} catch (RemoteException re) {
}
return;
}
mHandler.post(new Runnable() {
public void run() {
mHandler.removeCallbacks(this);
final int returnCode = deletePackageX(packageName, userId, flags);
if (observer != null) {
try {
observer.packageDeleted(packageName, returnCode);
} catch (RemoteException e) {
Log.i(TAG, "Observer no longer exists.");
} //end catch
} //end if
} //end run
});
}
在deletePackageAsUser方法中，首先做权限检查，然后就调用deletePackageX方法去执行卸载任务：
private int deletePackageX(String packageName, int userId, int flags) {
final PackageRemovedInfo info = new PackageRemovedInfo();
final boolean res;
boolean removedForAllUsers = false;
boolean systemUpdate = false;
int[] allUsers;
boolean[] perUserInstalled;
synchronized (mPackages) {
PackageSetting ps = mSettings.mPackages.get(packageName);
allUsers = sUserManager.getUserIds();
perUserInstalled = new boolean[allUsers.length];
for (int i = 0; i < allUsers.length; i++) {
perUserInstalled[i] = ps != null ? ps.getInstalled(allUsers[i]) : false;
}
}
synchronized (mInstallLock) {
res = deletePackageLI(packageName,
(flags & PackageManager.DELETE_ALL_USERS) != 0
? UserHandle.ALL : new UserHandle(userId),
true, allUsers, perUserInstalled,
flags | REMOVE_CHATTY, info, true);
systemUpdate = info.isRemovedPackageSystemUpdate;
if (res && !systemUpdate && mPackages.get(packageName) == null) {
removedForAllUsers = true;
}
if (DEBUG_REMOVE) Slog.d(TAG, "delete res: systemUpdate=" + systemUpdate
+ " removedForAllUsers=" + removedForAllUsers);
}
if (res) {
info.sendBroadcast(true, systemUpdate, removedForAllUsers);
}
Runtime.getRuntime().gc();
if (info.args != null) {
synchronized (mInstallLock) {
info.args.doPostDeleteLI(true);
}
}
return res ? PackageManager.DELETE_SUCCEEDED : PackageManager.DELETE_FAILED_INTERNAL_ERROR;
}deletePackageX在这里我们只考虑当前只有一个user的情况，来看deletePackageLI的实现：
private boolean deletePackageLI(String packageName, UserHandle user,
boolean deleteCodeAndResources, int[] allUserHandles, boolean[] perUserInstalled,
int flags, PackageRemovedInfo outInfo,
boolean writeSettings) {
PackageSetting ps;
boolean dataOnly = false;
int removeUser = -1;
int appId = -1;
synchronized (mPackages) {
ps = mSettings.mPackages.get(packageName);
if (ps == null) {
Slog.w(TAG, "Package named '" + packageName + "' doesn't exist.");
return false;
}
if ((!isSystemApp(ps) || (flags&PackageManager.DELETE_SYSTEM_APP) != 0) && user != null
&& user.getIdentifier() != UserHandle.USER_ALL) {
ps.setUserState(user.getIdentifier(),
COMPONENT_ENABLED_STATE_DEFAULT,
false, //installed
true, //stopped
true, //notLaunched
false, //blocked
null, null, null);
if (!isSystemApp(ps)) {
if (ps.isAnyInstalled(sUserManager.getUserIds())) {
} else {
removeUser = user.getIdentifier();
appId = ps.appId;
mSettings.writePackageRestrictionsLPr(removeUser);
}
}
}
boolean ret = false;
mSettings.mKeySetManager.removeAppKeySetData(packageName);
if (isSystemApp(ps)) {
ret = deleteSystemPackageLI(ps, allUserHandles, perUserInstalled,
flags, outInfo, writeSettings);
} else {
// Kill application pre-emptively especially for apps on sd.
killApplication(packageName, ps.appId, "uninstall pkg");
ret = deleteInstalledPackageLI(ps, deleteCodeAndResources, flags,
allUserHandles, perUserInstalled,
outInfo, writeSettings);
}
return ret;
}在deletePackageLI函数中根据是否是systemApp调用不同的流程，如果是systemApp，则调用deleteSystemPackageLI完成卸载；如果非systemApp，则调用deleteInstalledPackageLI完成卸载，当然在卸载之前，首先会调用AMS的killApplication方法先让这个APP停止运行。我们主要介绍非systemApp的卸载过程，来看deleteInstalledPackageLI方法的实现：
private boolean deleteInstalledPackageLI(PackageSetting ps,
boolean deleteCodeAndResources, int flags,
int[] allUserHandles, boolean[] perUserInstalled,
PackageRemovedInfo outInfo, boolean writeSettings) {
if (outInfo != null) {
outInfo.uid = ps.appId;
}
removePackageDataLI(ps, allUserHandles, perUserInstalled, outInfo, flags, writeSettings);
if (deleteCodeAndResources && (outInfo != null)) {
outInfo.args = createInstallArgs(packageFlagsToInstallFlags(ps), ps.codePathString,
ps.resourcePathString, ps.nativeLibraryPathString);
}
return true;
}在deleteInstalledPackageLI方法中，分为两步去卸载应用：第一步删除/data/data下面的数据目录，并从PMS的内部数据结构上清除当前卸载的package信息；第二步就删除code和resource文件。我们先来看第一步：
private void removePackageDataLI(PackageSetting ps,
int[] allUserHandles, boolean[] perUserInstalled,
PackageRemovedInfo outInfo, int flags, boolean writeSettings) {
String packageName = ps.name;
removePackageLI(ps, (flags&REMOVE_CHATTY) != 0);
final PackageSetting deletedPs;
synchronized (mPackages) {
deletedPs = mSettings.mPackages.get(packageName);
if (outInfo != null) {
outInfo.removedPackage = packageName;
outInfo.removedUsers = deletedPs != null
? deletedPs.queryInstalledUsers(sUserManager.getUserIds(), true)
: null;
}
}
if ((flags&PackageManager.DELETE_KEEP_DATA) == 0) {
removeDataDirsLI(packageName);
schedulePackageCleaning(packageName, UserHandle.USER_ALL, true);
}
removePackageDataLI用于删除应用的/data/data数据目录，并且从PMS内部数据结构里面清除package的信息。首先调用removePackageLI从PMS内部的数据结构上删除要卸载的package信息：
void removePackageLI(PackageSetting ps, boolean chatty) {
synchronized (mPackages) {
mPackages.remove(ps.name);
if (ps.codePathString != null) {
mAppDirs.remove(ps.codePathString);
}
final PackageParser.Package pkg = ps.pkg;
if (pkg != null) {
cleanPackageDataStructuresLILPw(pkg, chatty);
}
}
}cleanPackageDataStructuresLILPw用于将package的providers、services、receivers、activities等信息去PMS的全局数据结构上移除，这部分代码比较简单。如果没有设置DELETE_KEEP_DATA这个flag，就会首先调用removeDataDirsLI去删除/data/data下面的目录：
private int removeDataDirsLI(String packageName) {
int[] users = sUserManager.getUserIds();
int res = 0;
for (int user : users) {
int resInner = mInstaller.remove(packageName, user);
if (resInner < 0) {
res = resInner;
}
}
final File nativeLibraryFile = new File(mAppLibInstallDir, packageName);
NativeLibraryHelper.removeNativeBinariesFromDirLI(nativeLibraryFile);
if (!nativeLibraryFile.delete()) {
Slog.w(TAG, "Couldn't delete native library directory " + nativeLibraryFile.getPath());
}
return res;
}这里首先调用installd的remove方法去删除/data/data下面的目录。然后去删除/data/app-lib下面的应用程序的library信息，但因为这里的nativeLibraryFile为/data/app-lib/packageName，和前面介绍的APK安装过程中的目录/data/app-lib/packageName-num不一样，所以实际上，这里并没有真正的去删除library目录。先来看installd的remove方法：
static int do_remove(char **arg, char reply[REPLY_MAX])
{
return uninstall(arg[0], atoi(arg[1])); /* pkgname, userid */
}
int uninstall(const char *pkgname, userid_t userid)
{
char pkgdir[PKG_PATH_MAX];
if (create_pkg_path(pkgdir, pkgname, PKG_DIR_POSTFIX, userid))
return -1;
return delete_dir_contents(pkgdir, 1, NULL);
}
int delete_dir_contents(const char *pathname,
int also_delete_dir,
const char *ignore)
{
int res = 0;
DIR *d;
d = opendir(pathname);
if (d == NULL) {
ALOGE("Couldn't opendir %s: %s\n", pathname, strerror(errno));
return -errno;
}
res = _delete_dir_contents(d, ignore);
closedir(d);
if (also_delete_dir) {
if (rmdir(pathname)) {
ALOGE("Couldn't rmdir %s: %s\n", pathname, strerror(errno));
res = -1;
}
}
return res;
}create_pkg_path方法构造/data/data/packageName的文件路径名，然后调用delete_dir_contents来删除文件内容以及目录，前面介绍过，/data/data/packageName的文件其实都是符号链接，所以_delete_dir_contents的实现中都是调用unlinkat去删除这些符号链接。回到removePackageDataLI中，接着调用schedulePackageCleaning来安排清理动作：
void schedulePackageCleaning(String packageName, int userId, boolean andCode) {
mHandler.sendMessage(mHandler.obtainMessage(START_CLEANING_PACKAGE,
userId, andCode ? 1 : 0, packageName));
}这里向PackageHandler发送START_CLEANING_PACKAGE消息，PMS会调用ContainService的函数去删除/storage/sdcard0/Android/data和/storage/sdcard0/Android/media下面与package相关的文件，有兴趣可以去看一下这部分的code。接着来看removePackageDataLI方法：
synchronized (mPackages) {
if (deletedPs != null) {
if ((flags&PackageManager.DELETE_KEEP_DATA) == 0) {
if (outInfo != null) {
outInfo.removedAppId = mSettings.removePackageLPw(packageName);
}
if (deletedPs != null) {
updatePermissionsLPw(deletedPs.name, null, 0);
if (deletedPs.sharedUser != null) {
// remove permissions associated with package
mSettings.updateSharedUserPermsLPw(deletedPs, mGlobalGids);
}
}
clearPackagePreferredActivitiesLPw(deletedPs.name, UserHandle.USER_ALL);
}
}
if (writeSettings) {
mSettings.writeLPr();
}
}
if (outInfo != null) {
removeKeystoreDataIfNeeded(UserHandle.USER_ALL, outInfo.removedAppId);
}
}这里首先从Settings中删除PackageSettings的信息：
int removePackageLPw(String name) {
final PackageSetting p = mPackages.get(name);
if (p != null) {
mPackages.remove(name);
if (p.sharedUser != null) {
p.sharedUser.removePackage(p);
if (p.sharedUser.packages.size() == 0) {
mSharedUsers.remove(p.sharedUser.name);
removeUserIdLPw(p.sharedUser.userId);
return p.sharedUser.userId;
}
} else {
removeUserIdLPw(p.appId);
return p.appId;
}
}
return -1;
}removePackageLPw首先从mPackages这个map中删除PackageSettings信息，如果不存在sharedUser，则从mUserIds这个数组中删除对应的Package UID信息；如果存在sharedUser，则首先检查这个sharedUser是否所有的package都已经被卸载了，如果都被卸载了，这个sharedUser也就可以删除。然后removePackageDataLI调用updatePermissionsLPw去检查mPermissionTrees和mPermissions两个数组中的权限是否是被删除的Package提供，如果有，则删除。Settings的updateSharedUserPermsLPw方法用于清除sharedUser不用的gid信息，防止权限泄露：
void updateSharedUserPermsLPw(PackageSetting deletedPs, int[] globalGids) {
SharedUserSetting sus = deletedPs.sharedUser;
for (String eachPerm : deletedPs.pkg.requestedPermissions) {
boolean used = false;
if (!sus.grantedPermissions.contains(eachPerm)) {
continue;
}
for (PackageSetting pkg:sus.packages) {
if (pkg.pkg != null &&
!pkg.pkg.packageName.equals(deletedPs.pkg.packageName) &&
pkg.pkg.requestedPermissions.contains(eachPerm)) {
used = true;
break;
}
}
if (!used) {
sus.grantedPermissions.remove(eachPerm);
}
}
int newGids[] = globalGids;
for (String eachPerm : sus.grantedPermissions) {
BasePermission bp = mPermissions.get(eachPerm);
if (bp != null) {
newGids = PackageManagerService.appendInts(newGids, bp.gids);
}
}
sus.gids = newGids;
}循环的从要被卸载的Package所在的sharedUser组中找被申请的权限是否还被同一组的其它package使用，如果没有使用者，就从sharedUser的grantedPermissions删除。clearPackagePreferredActivitiesLPw与AMS相关，我们留到以后再来介绍。在removePackageDataLI方法最好调用Settings.writeLPr()方法将改动的信息写到Package.xml中。到这里，我们前面所说的deleteInstalledPackageLI方法中的第一步已经完成，来看第二部分：
if (deleteCodeAndResources && (outInfo != null)) {
outInfo.args = createInstallArgs(packageFlagsToInstallFlags(ps), ps.codePathString,
ps.resourcePathString, ps.nativeLibraryPathString);
}
private InstallArgs createInstallArgs(int flags, String fullCodePath, String fullResourcePath,
String nativeLibraryPath) {
final boolean isInAsec;
if (installOnSd(flags)) {
isInAsec = true;
} else if (installForwardLocked(flags)
&& !fullCodePath.startsWith(mDrmAppPrivateInstallDir.getAbsolutePath())) {
isInAsec = true;
} else {
isInAsec = false;
}
if (isInAsec) {
return new AsecInstallArgs(fullCodePath, fullResourcePath, nativeLibraryPath,
installOnSd(flags), installForwardLocked(flags));
} else {
return new FileInstallArgs(fullCodePath, fullResourcePath, nativeLibraryPath);
}
}这里根据安装目录的不同，分别构造FileInstallArgs和AsecInstallArgs来完成code和resource资源的清除。这里我们主要介绍卸载内部存储空间上面的APK，来看FileInstallArgs的doPostDeleteLI方法：
boolean doPostDeleteLI(boolean delete) {
cleanUpResourcesLI();
return true;
}
void cleanUpResourcesLI() {
String sourceDir = getCodePath();
if (cleanUp()) {
int retCode = mInstaller.rmdex(sourceDir);
if (retCode < 0) {
Slog.w(TAG, "Couldn't remove dex file for package: "
+ " at location "
+ sourceDir + ", retcode=" + retCode);
// we don't consider this to be a failure of the core package deletion
}
}
}cleanUpResourcesLI方法中首先调用cleanUp方法去删除code、resource以及library文件：
private boolean cleanUp() {
boolean ret = true;
String sourceDir = getCodePath();
String publicSourceDir = getResourcePath();
if (sourceDir != null) {
File sourceFile = new File(sourceDir);
if (!sourceFile.exists()) {
Slog.w(TAG, "Package source " + sourceDir + " does not exist.");
ret = false;
}
sourceFile.delete();
}
if (publicSourceDir != null && !publicSourceDir.equals(sourceDir)) {
final File publicSourceFile = new File(publicSourceDir);
if (!publicSourceFile.exists()) {
Slog.w(TAG, "Package public source " + publicSourceFile + " does not exist.");
}
if (publicSourceFile.exists()) {
publicSourceFile.delete();
}
}
if (libraryPath != null) {
File nativeLibraryFile = new File(libraryPath);
NativeLibraryHelper.removeNativeBinariesFromDirLI(nativeLibraryFile);
if (!nativeLibraryFile.delete()) {
Slog.w(TAG, "Couldn't delete native library directory " + libraryPath);
}
}
return ret;
}然后cleanUpResourcesLI调用installd的rmdex方法去删除存在/data/dalvik-cache文件：
static int do_rm_dex(char **arg, char reply[REPLY_MAX])
{
return rm_dex(arg[0]); /* pkgname */
}
int rm_dex(const char *path)
{
char dex_path[PKG_PATH_MAX];
if (validate_apk_path(path)) return -1;
if (create_cache_path(dex_path, path)) return -1;
ALOGV("unlink %s\n", dex_path);
if (unlink(dex_path) < 0) {
ALOGE("Couldn't unlink %s: %s\n", dex_path, strerror(errno));
return -1;
} else {
return 0;
}
}create_cache_path依据path构造/data/dalvik-cache下的文件目录，调用unlink去删除文件。到这里卸载APK的deletePackageAsUser函数就已经分析完了。这时会通过observer把卸载结果返回给UninstallAppProgress。
