声明：此文章来自http://shuwoom.com/?p=60的学习记录
启动式安装
public static final IPackageManager main(Context context, Installer installer,
boolean factoryTest, boolean onlyCore) {
PackageManagerService m = new PackageManagerService(context, installer, factoryTest, onlyCore);
ServiceManager.addService("package", m);
return m;
}main函数中创建PackageManagerService服务对象，并把服务添加到ServiceManager中
ServiceManager是Android系统Binder进程通信机制的守护进程，一直运行在后台。它主要负责管理系统中的Binder对象。
应用程序在安装时涉及到如下几个重要目录：
| system/app | 系统应用程序的目录 |
| data/app | 用户程序安装的目录 |
| data/data | 存放应用程序数据的目录 |
| data/dalvik-cache | 存放的是经过优化的dex文件 |
PackageManagerService是Android系统的核心服务之一，在系统启动的时候由SystemServer组件负责启动起来。PackageManagerService用于管理系统中的所有安装包信息以及应用程序的安装和卸载，但是实际应用程序的安装卸载并不是由PackageManagerService亲自完成，而是通过socket通信，PackageManagerService来访问installd服务来实现应用程序的安装和卸载。
public class SystemServer {
...
/**
* Called to initialize native system services.
*/
private static native void nativeInit();
public static void main(String[] args) {
...
System.loadLibrary("android_servers");
Slog.i(TAG, "Entered the Android system server!");
// Initialize native services.
nativeInit();
// This used to be its own separate thread, but now it is
// just the loop we run on the main thread.
ServerThread thr = new ServerThread();
thr.initAndLoop();
}
}SystemServer中的ServerThread来启动PackageManagerService
class ServerThread {
private static final String TAG = "SystemServer";
……
ContentResolver mContentResolver;
……
public void initAndLoop() {
EventLog.writeEvent(EventLogTags.BOOT_PROGRESS_SYSTEM_RUN,
SystemClock.uptimeMillis());
Looper.prepareMainLooper();
……
boolean onlyCore = false;
boolean firstBoot = false;
……
try {
Slog.i(TAG, "Display Manager");
display = new DisplayManagerService(context, wmHandler);
ServiceManager.addService(Context.DISPLAY_SERVICE, display, true);
Slog.i(TAG, "Telephony Registry");
telephonyRegistry = new TelephonyRegistry(context);
ServiceManager.addService("telephony.registry", telephonyRegistry);
Slog.i(TAG, "Scheduling Policy");
ServiceManager.addService("scheduling_policy", new SchedulingPolicyService());
AttributeCache.init(context);
if (!display.waitForDefaultDisplay()) {
reportWtf("Timeout waiting for default display to be initialized.",
new Throwable());
}
Slog.i(TAG, "Package Manager");
// 处于加密状态时，紧解析核心应用
String cryptState = SystemProperties.get("vold.decrypt");
if (ENCRYPTING_STATE.equals(cryptState)) {
Slog.w(TAG, "Detected encryption in progress - only parsing core apps");
onlyCore = true;
} else if (ENCRYPTED_STATE.equals(cryptState)) {
Slog.w(TAG, "Device encrypted - only parsing core apps");
onlyCore = true;
}
pm = PackageManagerService.main(context, installer,
factoryTest != SystemServer.FACTORY_TEST_OFF,
onlyCore);
……
}
}PackageManagerService构造函数如下
public PackageManagerService(Context context, Installer installer,
boolean factoryTest, boolean onlyCore) {
synchronized (mInstallLock) {
// writer
synchronized (mPackages) {
mHandlerThread.start();
mHandler = new PackageHandler(mHandlerThread.getLooper());
Watchdog.getInstance().addThread(mHandler, mHandlerThread.getName(),
WATCHDOG_TIMEOUT);
File dataDir = Environment.getDataDirectory();
mAppDataDir = new File(dataDir, "data");
mAppInstallDir = new File(dataDir, "app");
mAppLibInstallDir = new File(dataDir, "app-lib");
mAsecInternalPath = new File(dataDir, "app-asec").getPath();
mUserAppDataDir = new File(dataDir, "user");
mDrmAppPrivateInstallDir = new File(dataDir, "app-private");
……
mFrameworkDir = new File(Environment.getRootDirectory(), "framework");
mDalvikCacheDir = new File(dataDir, "dalvik-cache");
……
// Find base frameworks (resource packages without code).
mFrameworkInstallObserver = new AppDirObserver(
frameworkDir.getPath(), OBSERVER_EVENTS, true, false);
mFrameworkInstallObserver.startWatching();
//扫描”/system/framework”目录下的apk
scanDirLI(frameworkDir, PackageParser.PARSE_IS_SYSTEM
| PackageParser.PARSE_IS_SYSTEM_DIR
| PackageParser.PARSE_IS_PRIVILEGED,
scanMode | SCAN_NO_DEX, 0);
// Collected privileged system packages.
File privilegedAppDir = new File(Environment.getRootDirectory(), "priv-app");
mPrivilegedInstallObserver = new AppDirObserver(
privilegedAppDir.getPath(), OBSERVER_EVENTS, true, true);
mPrivilegedInstallObserver.startWatching();
//扫描”/system/priv-app”目录下的apk
scanDirLI(privilegedAppDir, PackageParser.PARSE_IS_SYSTEM
| PackageParser.PARSE_IS_SYSTEM_DIR
| PackageParser.PARSE_IS_PRIVILEGED, scanMode, 0);
// Collect ordinary system packages.
File systemAppDir = new File(Environment.getRootDirectory(), "app");
mSystemInstallObserver = new AppDirObserver(
systemAppDir.getPath(), OBSERVER_EVENTS, true, false);
mSystemInstallObserver.startWatching();
//扫描”/system/app”目录下的apk
scanDirLI(systemAppDir, PackageParser.PARSE_IS_SYSTEM
| PackageParser.PARSE_IS_SYSTEM_DIR, scanMode, 0);
// Collect all vendor packages.
File vendorAppDir = new File("/vendor/app");
mVendorInstallObserver = new AppDirObserver(
vendorAppDir.getPath(), OBSERVER_EVENTS, true, false);
mVendorInstallObserver.startWatching();
// vender目录其实连接到/system/vendor，实际扫描:/system/vendor/app目录下的apk
scanDirLI(vendorAppDir, PackageParser.PARSE_IS_SYSTEM
| PackageParser.PARSE_IS_SYSTEM_DIR, scanMode, 0);
if (DEBUG_UPGRADE) Log.v(TAG, "Running installd update commands");
mInstaller.moveFiles();
// Prune any system packages that no longer exist.
final List<String> possiblyDeletedUpdatedSystemApps = new ArrayList<String>();
//由上一部分内容知道，默认情况下磁盘加密状态关闭，即mOnlyCore状态false
if (!mOnlyCore) {
EventLog.writeEvent(EventLogTags.BOOT_PROGRESS_PMS_DATA_SCAN_START,
SystemClock.uptimeMillis());
mAppInstallObserver = new AppDirObserver(
mAppInstallDir.getPath(), OBSERVER_EVENTS, false, false);
mAppInstallObserver.startWatching();
//扫描”/data/app”目录下的apk
scanDirLI(mAppInstallDir, 0, scanMode, 0);
mDrmAppInstallObserver = new AppDirObserver(
mDrmAppPrivateInstallDir.getPath(), OBSERVER_EVENTS, false, false);
mDrmAppInstallObserver.startWatching();
//扫描”/data/app-private”目录下的apk
scanDirLI(mDrmAppPrivateInstallDir, PackageParser.PARSE_FORWARD_LOCK,
scanMode, 0);
……
}
……..
}这里调用了很多scanDirLI，这个函数调用了scanPackageLI
private void scanDirLI(File dir, int flags, int scanMode, long currentTime) {
String[] files = dir.list();
……
int i;
for (i=0; i<files.length; i++) {
File file = new File(dir, files[i]);
//只扫描apk后缀的文件
if (!isPackageFilename(files[i])) {
// Ignore entries which are not apk's
continue;
}
PackageParser.Package pkg = scanPackageLI(file,
flags|PackageParser.PARSE_MUST_BE_APK, scanMode, currentTime, null);
……
}
}scanPackageLI功能如下
private PackageParser.Package scanPackageLI(File scanFile,
int parseFlags, int scanMode, long currentTime, UserHandle user) {
……
String scanPath = scanFile.getPath();
parseFlags |= mDefParseFlags;
PackageParser pp = new PackageParser(scanPath);
pp.setSeparateProcesses(mSeparateProcesses);
pp.setOnlyCoreApps(mOnlyCore);
//解析安装包
final PackageParser.Package pkg = pp.parsePackage(scanFile, scanPath, mMetrics, parseFlags);
……
//保存解析后的安装包
PackageParser.Package scannedPkg = scanPackageLI(pkg, parseFlags, scanMode
| SCAN_UPDATE_SIGNATURE, currentTime, user);
……
return scannedPkg;
}其调用了parsePackage用于获取apk中的资源对象res和对Androidmanifest.xml文件进行格式化，并调用另一个parsePackage函数进一步做解析，也是package类真正生成的地方
啥是package？
package类是安卓框架中用于表示一个应用程序包的结构和信息的类。它包含了应用程序的多个方面的信息，包括：
- 包名：唯一标识应用程序的字符串，通常是反向域名格式（例如，
com.example.myapp）。 - 版本信息：包括应用程序的版本号和版本代码，帮助识别应用的更新和兼容性。
- 权限：声明应用所需的权限，例如访问互联网、读取联系人等。
- 组件：描述应用程序包含的组件，如活动（Activity）、服务（Service）、内容提供者（Content Provider）和广播接收器（Broadcast Receiver）。
保存了app的信息之后 调用createDataDirsLI进行真正的安装操作
private int createDataDirsLI(String packageName, int uid, String seinfo) {
int[] users = sUserManager.getUserIds();
int res = mInstaller.install(packageName, uid, uid, seinfo);
if (res < 0) {
return res;
}
for (int user : users) {
if (user != 0) {
res = mInstaller.createUserData(packageName,
UserHandle.getUid(user, uid), user);
if (res < 0) {
return res;
}
}
}
return res;
}调用了install类的install方法 install调用execute execute调用transaction transaction进行客户端-服务端通信，首先判断客户端-服务端是否连接
然后调用writeCommand向服务端通过socket，向服务端发送指令
如果发送的指令是install 服务端就会调用do_install进行安装 do_install调用了commands.c文件的install函数执行安装
int install(const char *pkgname, uid_t uid, gid_t gid, const char *seinfo)
{
char pkgdir[PKG_PATH_MAX]; //程序目录路径最长256
char libsymlink[PKG_PATH_MAX];
char applibdir[PKG_PATH_MAX];
struct stat libStat;
// 权限判断
if ((uid < AID_SYSTEM) || (gid < AID_SYSTEM)) {
ALOGE("invalid uid/gid: %d %d\n", uid, gid);
return -1;
}
// 组合应用程序安装目录pkgdir=”/data/data/应用程序包名”
if (create_pkg_path(pkgdir, pkgname, PKG_DIR_POSTFIX, 0)) {
ALOGE("cannot create package path\n");
return -1;
}
……
// 创建应用程序安装目录pkgdir=”/data/data/应用程序包名”
if (mkdir(pkgdir, 0751) < 0) {
ALOGE("cannot create dir '%s': %s\n", pkgdir, strerror(errno));
return -1;
}
// 修改应用程序安装目录pkgdir=”/data/data/应用程序包名”权限
if (chmod(pkgdir, 0751) < 0) {
ALOGE("cannot chmod dir '%s': %s\n", pkgdir, strerror(errno));
unlink(pkgdir);
return -1;
}
……
return 0;
}
点击安装
ADB安装
商店安装
总结：实际上四种安装方式都有用到PackageManagerService，而PackageManagerService也都是通过客户端-服务端的方式，向服务端发送命令进行安装的，也是四种安装方式的共同点。
