Android应用程序安装过程解析

1.程序安装的4大步骤

（1） 拷贝apk文件到指定目录

在Android系统中，apk安装文件是会被保存起来的，默认情况下，用户安装的apk首先会被拷贝到 /data/app 目录下。

/data/app目录是用户有权限访问的目录，在安装apk的时候会自动选择该目录存放用户安装的文件，而系统出厂的apk文件则被放到了 /system 分区下,包括 /system/app，/system/vendor/app，以及 /system/priv-app 等等，该分区只有Root权限的用户才能访问，这也就是为什么在没有Root手机之前，我们无法删除系统出厂的app的原因了。

（2） 解压apk，拷贝文件，创建应用的数据目录

为了加快app的启动速度，apk在安装的时候，会首先将app的可执行文件（dex）拷贝到 /data/dalvik-cache 目录，缓存起来。

然后，在/data/data/目录下创建应用程序的数据目录（以应用的包名命名），存放应用的相关数据，如数据库、xml文件、cache、二进制的so动态库等等。

（3） 解析apk的AndroidManifinest.xml文件

Android系统中，也有一个类似注册表的东西，用来记录当前所有安装的应用的基本信息，每次系统安装或者卸载了任何apk文件，都会更新这个文件。这个文件位于如下目录：

/data/system/packages.xml

系统在安装apk的过程中，会解析apk的AndroidManifinest.xml文件，提取出这个apk的重要信息写入到packages.xml文件中，这些信息包括：权限、应用包名、APK的安装位置、版本、userID等等。

由此，我们就知道了为啥一些应用市场和软件管理类的app能够很清楚地知道当前手机所安装的所有的app，以及这些app的详细信息了。

另外一件事就是Linux的用户Id和用户组Id，以便他可以获得合适的运行权限。

以上这些都是由PackageServiceManager完成的，下面我们会重点介绍PackageServiceManager。

（4） 显示快捷方式

这些应用程序只是相当于在PackageManagerService服务注册好了，如果我们想要在Android桌面上看到这些应用程序，还需要有一个Home应用程序，负责从PackageManagerService服务中把这些安装好的应用程序取出来，并以友好的方式在桌面上展现出来，例如以快捷图标的形式。在Android系统中，负责把系统中已经安装的应用程序在桌面中展现出来的Home应用程序就是Launcher了

2.PackageManagerService的启动过程

Android系统在启动的过程中，会启动一个应用程序管理服务PackageManagerService，这个服务负责扫描系统中特定的目录，找到里面的应用程序文件，即以Apk为后缀的文件，然后对这些文件进解析，得到应用程序的相关信息。应用程序管理服务PackageManagerService安装应用程序的过程，其实就是解析析应用程序配置文件AndroidManifest.xml的过程，并从里面得到得到应用程序的相关信息，例如得到应用程序的组件Activity、Service、Broadcast Receiver和Content Provider等信息，有了这些信息后，通过ActivityManagerService这个服务，我们就可以在系统中正常地使用这些应用程序了。应用程序管理服务PackageManagerService是系统启动的时候由SystemServer组件启动的，启后它就会执行应用程序安装的过程，因此，本文将从SystemServer启动PackageManagerService服务的过程开始分析系统中的应用程序安装的过程。

下面我们具体分析每一个步骤。

Step 1. SystemServer.main

这个函数定义在frameworks/base/services/Java/com/android/server/SystemServer.java文件中：

public class SystemServer  
{  
    ......  

    native public static void init1(String[] args);  

    ......  

    public static void main(String[] args) {  
        ......  

        init1(args);  

        ......  
    }  

    ......  
}  

SystemServer组件是由Zygote进程负责启动的，启动的时候就会调用它的main函数，这个函数主要调用了JNI方法init1来做一些系统初始化的工作。

Step 2. SystemServer.init1

这个函数是一个JNI方法，实现在 frameworks/base/services/jni/com_android_server_SystemServer.cpp文件中：

namespace android {  

extern "C" int system_init();  

static void android_server_SystemServer_init1(JNIEnv* env, jobject clazz)  
{  
    system_init();  
}  

/* 
 * JNI registration. 
 */  
static JNINativeMethod gMethods[] = {  
    /* name, signature, funcPtr */  
    { "init1", "([Ljava/lang/String;)V", (void*) android_server_SystemServer_init1 },  
};  

int register_android_server_SystemServer(JNIEnv* env)  
{  
    return jniRegisterNativeMethods(env, "com/android/server/SystemServer",  
            gMethods, NELEM(gMethods));  
}  

}; // namespace android  

这个函数很简单，只是调用了system_init函数来进一步执行操作。

Step 3. libsystem_server.system_init

函数system_init实现在libsystem_server库中，源代码位于frameworks/base/cmds/system_server/library/system_init.cpp文件中：

extern "C" status_t system_init()  
{  
    LOGI("Entered system_init()");  

    sp<ProcessState> proc(ProcessState::self());  

    sp<IServiceManager> sm = defaultServiceManager();  
    LOGI("ServiceManager: %p\n", sm.get());  

    sp<GrimReaper> grim = new GrimReaper();  
    sm->asBinder()->linkToDeath(grim, grim.get(), 0);  

    char propBuf[PROPERTY_VALUE_MAX];  
    property_get("system_init.startsurfaceflinger", propBuf, "1");  
    if (strcmp(propBuf, "1") == 0) {  
        // Start the SurfaceFlinger  
        SurfaceFlinger::instantiate();  
    }  

    // Start the sensor service  
    SensorService::instantiate();  

    // On the simulator, audioflinger et al don't get started the  
    // same way as on the device, and we need to start them here  
    if (!proc->supportsProcesses()) {  

        // Start the AudioFlinger  
        AudioFlinger::instantiate();  

        // Start the media playback service  
        MediaPlayerService::instantiate();  

        // Start the camera service  
        CameraService::instantiate();  

        // Start the audio policy service  
        AudioPolicyService::instantiate();  
    }  

    // And now start the Android runtime.  We have to do this bit  
    // of nastiness because the Android runtime initialization requires  
    // some of the core system services to already be started.  
    // All other servers should just start the Android runtime at  
    // the beginning of their processes's main(), before calling  
    // the init function.  
    LOGI("System server: starting Android runtime.\n");  

    AndroidRuntime* runtime = AndroidRuntime::getRuntime();  

    LOGI("System server: starting Android services.\n");  
    runtime->callStatic("com/android/server/SystemServer", "init2");  

    // If running in our own process, just go into the thread  
    // pool.  Otherwise, call the initialization finished  
    // func to let this process continue its initilization.  
    if (proc->supportsProcesses()) {  
        LOGI("System server: entering thread pool.\n");  
        ProcessState::self()->startThreadPool();  
        IPCThreadState::self()->joinThreadPool();  
        LOGI("System server: exiting thread pool.\n");  
    }  

    return NO_ERROR;  
}  

这个函数首先会初始化SurfaceFlinger、SensorService、AudioFlinger、MediaPlayerService、CameraService和AudioPolicyService这几个服务，然后就通过系统全局唯一的AndroidRuntime实例变量runtime的callStatic来调用SystemServer的init2函数了。关于这个AndroidRuntime实例变量runtime的相关资料，可能参考前面一篇文章Android应用程序进程启动过程的源代码分析一文。

Step 4. AndroidRuntime.callStatic

这个函数定义在frameworks/base/core/jni/AndroidRuntime.cpp文件中：

/* 
* Call a static Java Programming Language function that takes no arguments and returns void. 
*/  
status_t AndroidRuntime::callStatic(const char* className, const char* methodName)  
{  
    JNIEnv* env;  
    jclass clazz;  
    jmethodID methodId;  

    env = getJNIEnv();  
    if (env == NULL)  
        return UNKNOWN_ERROR;  

    clazz = findClass(env, className);  
    if (clazz == NULL) {  
        LOGE("ERROR: could not find class '%s'\n", className);  
        return UNKNOWN_ERROR;  
    }  
    methodId = env->GetStaticMethodID(clazz, methodName, "()V");  
    if (methodId == NULL) {  
        LOGE("ERROR: could not find method %s.%s\n", className, methodName);  
        return UNKNOWN_ERROR;  
    }  

    env->CallStaticVoidMethod(clazz, methodId);  

    return NO_ERROR;  
}

这个函数调用由参数className指定的java类的静态成员函数，这个静态成员函数是由参数methodName指定的。上面传进来的参数className的值为”com/android/server/SystemServer”，而参数methodName的值为”init2”，因此，接下来就会调用SystemServer类的init2函数了。

Step 5. SystemServer.init2

这个函数定义在frameworks/base/services/java/com/android/server/SystemServer.java文件中：

public class SystemServer  
{  
    ......  

    public static final void init2() {  
        Slog.i(TAG, "Entered the Android system server!");  
        Thread thr = new ServerThread();  
        thr.setName("android.server.ServerThread");  
        thr.start();  
    }  
}  

这个函数创建了一个ServerThread线程，PackageManagerService服务就是这个线程中启动的了。这里调用了ServerThread实例thr的start函数之后，下面就会执行这个实例的run函数了。

Step 6. ServerThread.run

这个函数定义在frameworks/base/services/java/com/android/server/SystemServer.java文件中：

class ServerThread extends Thread {  
    ......  

    @Override  
    public void run() {  
        ......  

        IPackageManager pm = null;  

        ......  

        // Critical services...  
        try {  
            ......  

            Slog.i(TAG, "Package Manager");  
            pm = PackageManagerService.main(context,  
                        factoryTest != SystemServer.FACTORY_TEST_OFF);  

            ......  
        } catch (RuntimeException e) {  
            Slog.e("System", "Failure starting core service", e);  
        }  

        ......  
    }  

    ......  
}  

这个函数除了启动PackageManagerService服务之外，还启动了其它很多的服务，例如在前面学习Activity和Service的几篇文章中经常看到的ActivityManagerService服务，有兴趣的读者可以自己研究一下。

Step 7. PackageManagerService.main

这个函数定义在frameworks/base/services/java/com/android/server/PackageManagerService.java文件中：

class PackageManagerService extends IPackageManager.Stub {  
    ......  

    public static final IPackageManager main(Context context, boolean factoryTest) {  
        PackageManagerService m = new PackageManagerService(context, factoryTest);  
        ServiceManager.addService("package", m);  
        return m;  
    }  

    ......  
}  

3.常见的4种安装场景

1.系统应用安装――开机时完成，没有安装界面

2.网络下载应用安装――通过market应用完成，没有安装界面

3.ADB工具安装――没有安装界面。

4.第三方应用安装――通过SD卡里的APK文件安装，有安装界面，由 packageinstaller.apk应用处理安装及卸载过程的界面。

安装过程：

复制APK安装包到data/app目录下，解压并扫描安装包，把dex文件(Dalvik字节码)保存到dalvik-cache目录，并data/data目录下创建对应的应用数据目录。

卸载过程：

删除安装过程中在上述三个目录下创建的文件及目录。

(1)系统应用安装――开机时完成，没有安装界面

PackageManagerService处理各种应用的安装，卸载，管理等工作，开机时由systemServer启动此服务

在创建这个PackageManagerService服务实例时，会在PackageManagerService类的构造函数中开始执行安装应用程序的过程：

PackageManagerService核心代码

class PackageManagerService extends IPackageManager.Stub {  
    ......  

    public PackageManagerService(Context context, boolean factoryTest) {  
        ......  
    mSetting = new Setting();
        synchronized (mInstallLock) {  
            synchronized (mPackages) {  
                ......  

                File dataDir = Environment.getDataDirectory();  
                mAppDataDir = new File(dataDir, "data");  
                mSecureAppDataDir = new File(dataDir, "secure/data");  

        mRestoredSetting = mASetting.readLP();

                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(  
                mFrameworkDir.getPath(), OBSERVER_EVENTS, true);  
                mFrameworkInstallObserver.startWatching();  
                scanDirLI(mFrameworkDir, PackageParser.PARSE_IS_SYSTEM  
                    | PackageParser.PARSE_IS_SYSTEM_DIR,  
                    scanMode | SCAN_NO_DEX, 0);  

                // Collect all system packages.  
                mSystemAppDir = new File(Environment.getRootDirectory(), "app");  
                mSystemInstallObserver = new AppDirObserver(  
                    mSystemAppDir.getPath(), OBSERVER_EVENTS, true);  
                mSystemInstallObserver.startWatching();  
                scanDirLI(mSystemAppDir, PackageParser.PARSE_IS_SYSTEM  
                    | PackageParser.PARSE_IS_SYSTEM_DIR, scanMode, 0);  

                // Collect all vendor packages.  
                mVendorAppDir = new File("/vendor/app");  
                mVendorInstallObserver = new AppDirObserver(  
                    mVendorAppDir.getPath(), OBSERVER_EVENTS, true);  
                mVendorInstallObserver.startWatching();  
                scanDirLI(mVendorAppDir, PackageParser.PARSE_IS_SYSTEM  
                    | PackageParser.PARSE_IS_SYSTEM_DIR, scanMode, 0);  


                mAppInstallObserver = new AppDirObserver(  
                    mAppInstallDir.getPath(), OBSERVER_EVENTS, false);  
                mAppInstallObserver.startWatching();  
                scanDirLI(mAppInstallDir, 0, scanMode, 0);  

                mDrmAppInstallObserver = new AppDirObserver(  
                    mDrmAppPrivateInstallDir.getPath(), OBSERVER_EVENTS, false);  
                mDrmAppInstallObserver.startWatching();  
                scanDirLI(mDrmAppPrivateInstallDir, PackageParser.PARSE_FORWARD_LOCK,  
                    scanMode, 0);  

                ......  
        final boolean regrantPermissions = mSetting.mInternalSDKplatform != mSdkVersion;
        updatePermissionsLP(null,null,true,rregrantPermissions .regrantPermissions );
        msetting.writeLP();
            }  
        }  
    }  

    ......  
}  

这里会调用scanDirLI函数来扫描移动设备上的下面这五个目录中的Apk文件

    /system/framework

    /system/app

    /vendor/app

    /data/app

    /data/app-private

由于Android每次启动的时候都需要安装一次信息，但是有些信息是保持不变的，例如Linux用户组Id，PackageManagerService 每次安装程序之后，都会把这些程序的信息保存下来，以便下次使用，
恢复上一次程序的安装信息是通过PackageManagerService 的成员变量mSetting的readLP()来实现的，恢复信息之后就开始扫描和安装app了。

扫描安装app

PackageManagerService.scanDirLI

这个函数定义在frameworks/base/services/java/com/android/server/PackageManagerService.java文件中：

class PackageManagerService extends IPackageManager.Stub {  
    ......  

    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]);  
            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);  
            // Don't mess around with apps in system partition.  
            if (pkg == null && (flags & PackageParser.PARSE_IS_SYSTEM) == 0 &&  
                mLastScanError == PackageManager.INSTALL_FAILED_INVALID_APK) {  
                    // Delete the apk  
                    Slog.w(TAG, "Cleaning up failed install of " + file);  
                    file.delete();  
            }  
        }  
    }  


    ......  
}  

对于目录中的每一个文件，如果是以后Apk作为后缀名，那么就调用scanPackageLI函数来对它进行解析和安装。

PackageManagerService.scanPackageLI

这个函数定义在frameworks/base/services/java/com/android/server/PackageManagerService.java文件中：

class PackageManagerService extends IPackageManager.Stub {  
    ......  

    private PackageParser.Package scanPackageLI(File scanFile,  
            int parseFlags, int scanMode, long currentTime) {  
        ......  

        String scanPath = scanFile.getPath();  
        parseFlags |= mDefParseFlags;  
        PackageParser pp = new PackageParser(scanPath);  

        ......  

        final PackageParser.Package pkg = pp.parsePackage(scanFile,  
            scanPath, mMetrics, parseFlags);  

        ......  

        return scanPackageLI(pkg, parseFlags, scanMode | SCAN_UPDATE_SIGNATURE, currentTime);  
    }  

    ......  
}  

这个函数首先会为这个Apk文件创建一个PackageParser实例，接着调用这个实例的parsePackage函数来对这个Apk文件进行解析。这个函数最后还会调用另外一个版本的scanPackageLI函数把来解析后得到的应用程序信息保存在PackageManagerService中。

PackageParser.parsePackage

这个函数定义在frameworks/base/core/java/android/content/pm/PackageParser.java文件中：

public class PackageParser {  
    ......  

    public Package parsePackage(File sourceFile, String destCodePath,  
            DisplayMetrics metrics, int flags) {  
        ......  

        mArchiveSourcePath = sourceFile.getPath();  

        ......  

        XmlResourceParser parser = null;  
        AssetManager assmgr = null;  
        boolean assetError = true;  
        try {  
            assmgr = new AssetManager();  
            int cookie = assmgr.addAssetPath(mArchiveSourcePath);  
            if(cookie != 0) {  
                parser = assmgr.openXmlResourceParser(cookie, "AndroidManifest.xml");  
                assetError = false;  
            } else {  
                ......  
            }  
        } catch (Exception e) {  
            ......  
        }  

        ......  

        String[] errorText = new String[1];  
        Package pkg = null;  
        Exception errorException = null;  
        try {  
            // XXXX todo: need to figure out correct configuration.  
            Resources res = new Resources(assmgr, metrics, null);  
            pkg = parsePackage(res, parser, flags, errorText);  
        } catch (Exception e) {  
            ......  
        }  

        ......  

        parser.close();  
        assmgr.close();  

        // Set code and resource paths  
        pkg.mPath = destCodePath;  
        pkg.mScanPath = mArchiveSourcePath;  
        //pkg.applicationInfo.sourceDir = destCodePath;  
        //pkg.applicationInfo.publicSourceDir = destRes;  
        pkg.mSignatures = null;  

        return pkg;  
    }  

    ......  
}  

每一个Apk文件都是一个归档文件，它里面包含了Android应用程序的配置文件AndroidManifest.xml，这里主要就是要对这个配置文件就行解析了，从Apk归档文件中得到这个配置文件后，就调用另一外版本的parsePackage函数对这个应用程序进行解析了：

public class PackageParser {  
    ......  

    private Package parsePackage(  
            Resources res, XmlResourceParser parser, int flags, String[] outError)  
            throws XmlPullParserException, IOException {  
        ......  

        String pkgName = parsePackageName(parser, attrs, flags, outError);  

        ......  

        final Package pkg = new Package(pkgName);  

        ......  

        int type;  

        ......  

        TypedArray sa = res.obtainAttributes(attrs,  
            com.android.internal.R.styleable.AndroidManifest);  

        ......  

        while ((type=parser.next()) != parser.END_DOCUMENT  
            && (type != parser.END_TAG || parser.getDepth() > outerDepth)) {  
                if (type == parser.END_TAG || type == parser.TEXT) {  
                    continue;  
                }  

                String tagName = parser.getName();  
                if (tagName.equals("application")) {  
                    ......  

                    if (!parseApplication(pkg, res, parser, attrs, flags, outError)) {  
                        return null;  
                    }  
                } else if (tagName.equals("permission-group")) {  
                    ......  
                } else if (tagName.equals("permission")) {  
                    ......  
                } else if (tagName.equals("permission-tree")) {  
                    ......  
                } else if (tagName.equals("uses-permission")) {  
                    ......  
                } else if (tagName.equals("uses-configuration")) {  
                    ......  
                } else if (tagName.equals("uses-feature")) {  
                    ......  
                } else if (tagName.equals("uses-sdk")) {  
                    ......  
                } else if (tagName.equals("supports-screens")) {  
                    ......  
                } else if (tagName.equals("protected-broadcast")) {  
                    ......  
                } else if (tagName.equals("instrumentation")) {  
                    ......  
                } else if (tagName.equals("original-package")) {  
                    ......  
                } else if (tagName.equals("adopt-permissions")) {  
                    ......  
                } else if (tagName.equals("uses-gl-texture")) {  
                    ......  
                } else if (tagName.equals("compatible-screens")) {  
                    ......  
                } else if (tagName.equals("eat-comment")) {  
                    ......  
                } else if (RIGID_PARSER) {  
                    ......  
                } else {  
                    ......  
                }  
        }  

        ......  

        return pkg;  
    }  

    ......  
}  

这里就是对AndroidManifest.xml文件中的各个标签进行解析了，各个标签的含义可以参考官方文档http://developer.android.com/guide/topics/manifest/manifest-intro.html，这里我们只简单看一下application标签的解析，这是通过调用parseApplication函数来进行的。

PackageParser.parseApplication

这个函数定义在frameworks/base/core/java/android/content/pm/PackageParser.java文件中：

public class PackageParser {  
    ......  

    private boolean parseApplication(Package owner, Resources res,  
            XmlPullParser parser, AttributeSet attrs, int flags, String[] outError)  
            throws XmlPullParserException, IOException {  
        final ApplicationInfo ai = owner.applicationInfo;  
        final String pkgName = owner.applicationInfo.packageName;  

        TypedArray sa = res.obtainAttributes(attrs,  
            com.android.internal.R.styleable.AndroidManifestApplication);  

        ......  

        int type;  
        while ((type=parser.next()) != parser.END_DOCUMENT  
            && (type != parser.END_TAG || parser.getDepth() > innerDepth)) {  
                if (type == parser.END_TAG || type == parser.TEXT) {  
                    continue;  
                }  

                String tagName = parser.getName();  
                if (tagName.equals("activity")) {  
                    Activity a = parseActivity(owner, res, parser, attrs, flags, outError, false);  
                    ......  

                    owner.activities.add(a);  

                } else if (tagName.equals("receiver")) {  
                    Activity a = parseActivity(owner, res, parser, attrs, flags, outError, true);  
                    ......  

                    owner.receivers.add(a);  
                } else if (tagName.equals("service")) {  
                    Service s = parseService(owner, res, parser, attrs, flags, outError);  
                    ......  

                    owner.services.add(s);  
                } else if (tagName.equals("provider")) {  
                    Provider p = parseProvider(owner, res, parser, attrs, flags, outError);  
                    ......  

                    owner.providers.add(p);  
                } else if (tagName.equals("activity-alias")) {  
                    Activity a = parseActivityAlias(owner, res, parser, attrs, flags, outError);  
                    ......  

                    owner.activities.add(a);  
                } else if (parser.getName().equals("meta-data")) {  
                    ......  
                } else if (tagName.equals("uses-library")) {  
                    ......  
                } else if (tagName.equals("uses-package")) {  
                    ......  
                } else {  
                    ......  
                }  
        }  

        return true;  
    }  

    ......  
}  

这里就是对AndroidManifest.xml文件中的application标签进行解析了，我们常用到的标签就有activity、service、receiver和provider，各个标签的含义可以参考官方文档http://developer.android.com/guide/topics/manifest/manifest-intro.html。这里解析完成后，一层层返回到Step 9中，调用另一个版本的scanPackageLI函数把来解析后得到的应用程序信息保存下来。

PackageManagerService.scanPackageLI

这个函数定义在frameworks/base/services/java/com/android/server/PackageManagerService.java文件中：

class PackageManagerService extends IPackageManager.Stub {  
    ......  

    // Keys are String (package name), values are Package.  This also serves  
    // as the lock for the global state.  Methods that must be called with  
    // this lock held have the prefix "LP".  
    final HashMap<String, PackageParser.Package> mPackages =  
        new HashMap<String, PackageParser.Package>();  

    ......  

    // All available activities, for your resolving pleasure.  
    final ActivityIntentResolver mActivities =  
    new ActivityIntentResolver();  

    // All available receivers, for your resolving pleasure.  
    final ActivityIntentResolver mReceivers =  
        new ActivityIntentResolver();  

    // All available services, for your resolving pleasure.  
    final ServiceIntentResolver mServices = new ServiceIntentResolver();  

    // Keys are String (provider class name), values are Provider.  
    final HashMap<ComponentName, PackageParser.Provider> mProvidersByComponent =  
        new HashMap<ComponentName, PackageParser.Provider>();  

    ......  

    private PackageParser.Package scanPackageLI(PackageParser.Package pkg,  
            int parseFlags, int scanMode, long currentTime) {  
        ......  

        synchronized (mPackages) {  
            ......  

            // Add the new setting to mPackages  
            mPackages.put(pkg.applicationInfo.packageName, pkg);  

            ......  

            int N = pkg.providers.size();  
            int i;  
            for (i=0; i<N; i++) {  
                PackageParser.Provider p = pkg.providers.get(i);  
                p.info.processName = fixProcessName(pkg.applicationInfo.processName,  
                    p.info.processName, pkg.applicationInfo.uid);  
                mProvidersByComponent.put(new ComponentName(p.info.packageName,  
                    p.info.name), p);  

                ......  
            }  

            N = pkg.services.size();  
            for (i=0; i<N; i++) {  
                PackageParser.Service s = pkg.services.get(i);  
                s.info.processName = fixProcessName(pkg.applicationInfo.processName,  
                    s.info.processName, pkg.applicationInfo.uid);  
                mServices.addService(s);  

                ......  
            }  

            N = pkg.receivers.size();  
            r = null;  
            for (i=0; i<N; i++) {  
                PackageParser.Activity a = pkg.receivers.get(i);  
                a.info.processName = fixProcessName(pkg.applicationInfo.processName,  
                    a.info.processName, pkg.applicationInfo.uid);  
                mReceivers.addActivity(a, "receiver");  

                ......  
            }  

            N = pkg.activities.size();  
            for (i=0; i<N; i++) {  
                PackageParser.Activity a = pkg.activities.get(i);  
                a.info.processName = fixProcessName(pkg.applicationInfo.processName,  
                    a.info.processName, pkg.applicationInfo.uid);  
                mActivities.addActivity(a, "activity");  

                ......  
            }  

            ......  
        }  

        ......  

        return pkg;  
    }  

    ......  
}  

这个函数主要就是把前面解析应用程序得到的package、provider、service、receiver和activity等信息保存在PackageManagerService服务中了。

PackageManagerService的作用总结：

1)从apk, xml中载入pacakge信息, 存储到内部成员变量中, 用于后面的查找. 关键的方法是scanPackageLI().
2)各种查询操作, 包括query Intent操作.
3)install package和delete package的操作. 还有后面的关键方法是installPackageLI().

后面重点介绍installPackageLI，后面的额方式本质都会调用它。

（2）从网络上下载应用：

下载完成后，会自动调用Packagemanager的安装方法installPackage（）

public void installPackage(  
           final Uri packageURI, final IPackageInstallObserver observer, final int flags,  
           final String installerPackageName) {  
       mContext.enforceCallingOrSelfPermission(  
               android.Manifest.permission.INSTALL_PACKAGES, null);  
       Message msg = mHandler.obtainMessage(INIT_COPY);  
       msg.obj = new InstallParams(packageURI, observer, flags,  
               installerPackageName);  
       mHandler.sendMessage(msg);  
   }  

通过PackageHandler的实例mhandler.sendMessage（msg）把信息发给继承Handler的类HandleMessage()方法

class PackageHandler extends Handler{  

*****************省略若干********************  
         public void handleMessage(Message msg) {  
            try {  
                doHandleMessage(msg);  
            } finally {  
                Process.setThreadPriority(Process.THREAD_PRIORITY_BACKGROUND);  
            }  
        }  
   ******************省略若干**********************  
 }  

把信息发给doHandleMessage()方法,方法中用switch（）语句进行判定传来Message

 void doHandleMessage(Message msg) {  
            switch (msg.what) {  

                case INIT_COPY: {  
                    if (DEBUG_SD_INSTALL) Log.i(TAG, "init_copy");  
                    HandlerParams params = (HandlerParams) msg.obj;  
                    int idx = mPendingInstalls.size();  
                    if (DEBUG_SD_INSTALL) Log.i(TAG, "idx=" + idx);  
                    // 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()) {  
                            Slog.e(TAG, "Failed to bind to media container service");  
                            params.serviceError();  
                            return;  
                        } else {  
                            // Once we bind to the service, the first  
                            // pending request will be processed.  
                            mPendingInstalls.add(idx, params);  
                        }  
                    } else {  
                        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;  
                }  
                case MCS_BOUND: {  
                    if (DEBUG_SD_INSTALL) Log.i(TAG, "mcs_bound");  
                    if (msg.obj != null) {  
                        mContainerService = (IMediaContainerService) msg.obj;  
                    }  
                    if (mContainerService == null) {  
                        // Something seriously wrong. Bail out  
                        Slog.e(TAG, "Cannot bind to media container service");  
                        for (HandlerParams params : mPendingInstalls) {  
                            mPendingInstalls.remove(0);  
                            // Indicate service bind error  
                            params.serviceError();  
                        }  
                        mPendingInstalls.clear();  
                    } else if (mPendingInstalls.size() > 0) {  
                        HandlerParams params = mPendingInstalls.get(0);  
                        if (params != null) {  
                            params.startCopy();  
                        }  
                    } else {  
                        // Should never happen ideally.  
                        Slog.w(TAG, "Empty queue");  
                    }  
                    break;  
                }  
            ****************省略若干**********************  
}  
}  

public final boolean sendMessage (Message msg)

public final boolean sendEmptyMessage (int what)

两者参数有别。

然后调用抽象类HandlerParams中的一个startCopy（）方法

abstract class HandlerParams {

final void startCopy() {

*****若干if语句判定否这打回handler消息*

handleReturnCode();

}
}

handleReturnCode（）复写了两次其中有一次是删除时要调用的，只列出安装调用的一个方法

@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);  
           }  
       }  

这时可以清楚的看见 processPendingInstall（）被调用。

其中run（）方法如下

run(){  
synchronized (mInstallLock) {  
                        ************省略*****************  
                        installPackageLI(args, true, res);  

 }  
}  

instaPacakgeLI（）args,res参数分析

---

//InstallArgs 是在PackageService定义的static abstract class InstallArgs 静态抽象类。

static abstract class InstallArgs {  
*********************************************************************  
其中定义了flag标志，packageURL，创建文件，拷贝apk，修改包名称，  
                    还有一些删除文件的清理，释放存储函数。  
    *********************************************************************  
}  
  class PackageInstalledInfo {  
        String name;  
        int uid;  
        PackageParser.Package pkg;  
        int returnCode;  
        PackageRemovedInfo removedInfo;  
 }  

-----------------------------------------------------------------------------------------



[java] view plain copy
private void installPackageLI(InstallArgs args,  
          boolean newInstall, PackageInstalledInfo res) {  
      int pFlags = args.flags;  
      String installerPackageName = args.installerPackageName;  
      File tmpPackageFile = new File(args.getCodePath());  
      boolean forwardLocked = ((pFlags & PackageManager.INSTALL_FORWARD_LOCK) != 0);  
      boolean onSd = ((pFlags & PackageManager.INSTALL_EXTERNAL) != 0);  
      boolean replace = false;  
      int scanMode = (onSd ? 0 : SCAN_MONITOR) | SCAN_FORCE_DEX | SCAN_UPDATE_SIGNATURE  
              | (newInstall ? SCAN_NEW_INSTALL : 0);  
      // Result object to be returned  
      res.returnCode = PackageManager.INSTALL_SUCCEEDED;  
      // Retrieve PackageSettings and parse package  
      int parseFlags = PackageParser.PARSE_CHATTY |  
      (forwardLocked ? PackageParser.PARSE_FORWARD_LOCK : 0) |  
      (onSd ? PackageParser.PARSE_ON_SDCARD : 0);  
      parseFlags |= mDefParseFlags;  
      PackageParser pp = new PackageParser(tmpPackageFile.getPath());  
      pp.setSeparateProcesses(mSeparateProcesses);  
      final PackageParser.Package pkg = pp.parsePackage(tmpPackageFile,  
              null, mMetrics, parseFlags);  
      if (pkg == null) {  
          res.returnCode = pp.getParseError();  
          return;  
      }  
      String pkgName = res.name = pkg.packageName;  
      if ((pkg.applicationInfo.flags&ApplicationInfo.FLAG_TEST_ONLY) != 0) {  
          if ((pFlags&PackageManager.INSTALL_ALLOW_TEST) == 0) {  
              res.returnCode = PackageManager.INSTALL_FAILED_TEST_ONLY;  
              return;  
          }  
      }  
      if (GET_CERTIFICATES && !pp.collectCertificates(pkg, parseFlags)) {  
          res.returnCode = pp.getParseError();  
          return;  
      }  
      // Get rid of all references to package scan path via parser.  
      pp = null;  
      String oldCodePath = null;  
      boolean systemApp = false;  
      synchronized (mPackages) {  
          // Check if installing already existing package  
          if ((pFlags&PackageManager.INSTALL_REPLACE_EXISTING) != 0) {  
              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);  
                  pkgName = pkg.packageName;  
                  replace = true;  
              } else if (mPackages.containsKey(pkgName)) {  
                  // This package, under its official name, already exists  
                  // on the device; we should replace it.  
                  replace = true;  
              }  
          }  
          PackageSetting ps = mSettings.mPackages.get(pkgName);  
          if (ps != null) {  
              oldCodePath = mSettings.mPackages.get(pkgName).codePathString;  
              if (ps.pkg != null && ps.pkg.applicationInfo != null) {  
                  systemApp = (ps.pkg.applicationInfo.flags &  
                          ApplicationInfo.FLAG_SYSTEM) != 0;  
              }  
          }  
      }  
      if (systemApp && onSd) {  
          // Disable updates to system apps on sdcard  
          Slog.w(TAG, "Cannot install updates to system apps on sdcard");  
          res.returnCode = PackageManager.INSTALL_FAILED_INVALID_INSTALL_LOCATION;  
          return;  
      }  
      if (!args.doRename(res.returnCode, pkgName, oldCodePath)) {  
          res.returnCode = PackageManager.INSTALL_FAILED_INSUFFICIENT_STORAGE;  
          return;  
      }  
      // Set application objects path explicitly after the rename  
      setApplicationInfoPaths(pkg, args.getCodePath(), args.getResourcePath());  
      pkg.applicationInfo.nativeLibraryDir = args.getNativeLibraryPath();  
      if (replace) {  
          replacePackageLI(pkg, parseFlags, scanMode,  
                  installerPackageName, res);  
      } else {  
          installNewPackageLI(pkg, parseFlags, scanMode,  
                  installerPackageName,res);  
      }  
  }  

最后判断如果以前不存在那么调用installNewPackageLI(）

private void installNewPackageLI(PackageParser.Package pkg,  
            int parseFlags,int scanMode,  
            String installerPackageName, PackageInstalledInfo res) {  
     ***********************省略若干*************************************************  
        PackageParser.Package newPackage = scanPackageLI(pkg, parseFlags, scanMode,  
               System.currentTimeMillis());  
     ***********************省略若干**************************************************    
}  

最后终于回到了和开机安装一样的地方.与开机方式安装调用统一方法。

(3)从ADB工具安装

其入口函数源文件为pm.java

(源文件路径：android\frameworks\base\cmds\pm\src\com\android\commands\pm\pm.java)

其中\system\framework\pm.jar 包管理库

包管理脚本 \system\bin\pm 解析

showUsage就是使用方法

private static void showUsage() {   
        System.err.println("usage: pm [list|path|install|uninstall]");   
        System.err.println("       pm list packages [-f]");   
        System.err.println("       pm list permission-groups");   
        System.err.println("       pm list permissions [-g] [-f] [-d] [-u] [GROUP]");   
        System.err.println("       pm list instrumentation [-f] [TARGET-PACKAGE]");   
        System.err.println("       pm list features");   
        System.err.println("       pm path PACKAGE");   
        System.err.println("       pm install [-l] [-r] [-t] [-i INSTALLER_PACKAGE_NAME] [-s] [-f] PATH");   
        System.err.println("       pm uninstall [-k] PACKAGE");   
        System.err.println("       pm enable PACKAGE_OR_COMPONENT");   
        System.err.println("       pm disable PACKAGE_OR_COMPONENT");   
        System.err.println("       pm setInstallLocation [0/auto] [1/internal] [2/external]");  
      **********************省略**************************  
   }  

安装时候会调用 runInstall（）方法

private void runInstall() {  
      int installFlags = 0;  
      String installerPackageName = null;  
      String opt;  
      while ((opt=nextOption()) != null) {  
          if (opt.equals("-l")) {  
              installFlags |= PackageManager.INSTALL_FORWARD_LOCK;  
          } else if (opt.equals("-r")) {  
              installFlags |= PackageManager.INSTALL_REPLACE_EXISTING;  
          } else if (opt.equals("-i")) {  
              installerPackageName = nextOptionData();  
              if (installerPackageName == null) {  
                  System.err.println("Error: no value specified for -i");  
                  showUsage();  
                  return;  
              }  
          } else if (opt.equals("-t")) {  
              installFlags |= PackageManager.INSTALL_ALLOW_TEST;  
          } else if (opt.equals("-s")) {  
              // Override if -s option is specified.  
              installFlags |= PackageManager.INSTALL_EXTERNAL;  
          } else if (opt.equals("-f")) {  
              // Override if -s option is specified.  
              installFlags |= PackageManager.INSTALL_INTERNAL;  
          } else {  
              System.err.println("Error: Unknown option: " + opt);  
              showUsage();  
              return;  
          }  
      }  
      String apkFilePath = nextArg();  
      System.err.println("\tpkg: " + apkFilePath);  
      if (apkFilePath == null) {  
          System.err.println("Error: no package specified");  
          showUsage();  
          return;  
      }  
      PackageInstallObserver obs = new PackageInstallObserver();  
      try {  
          mPm.installPackage(Uri.fromFile(new File(apkFilePath)), obs, installFlags,  
                  installerPackageName);  
          synchronized (obs) {  
              while (!obs.finished) {  
                  try {  
                      obs.wait();  
                  } catch (InterruptedException e) {  
                  }  
              }  
              if (obs.result == PackageManager.INSTALL_SUCCEEDED) {  
                  System.out.println("Success");  
              } else {  
                  System.err.println("Failure ["  
                          + installFailureToString(obs.result)  
                          + "]");  
              }  
          }  
      } catch (RemoteException e) {  
          System.err.println(e.toString());  
          System.err.println(PM_NOT_RUNNING_ERR);  
      }  
  }  

其中的

PackageInstallObserver obs = new PackageInstallObserver();

            mPm.installPackage(Uri.fromFile(new File(apkFilePath)), obs, installFlags,
                    installerPackageName);

如果安装成功

obs.result == PackageManager.INSTALL_SUCCEEDED)

又因为有

IPackageManage mPm；

    mPm = IpackageManager.Stub.asInterface(ServiceManager.getService("package"));

Stub是接口IPackageManage的静态抽象类，asInterface是返回IPackageManager代理的静态方法。

因为class PackageManagerService extends IPackageManager.Stub

所以mPm.installPackage 调用

/* Called when a downloaded package installation has been confirmed by the user */

public void installPackage(

        final Uri packageURI, final IPackageInstallObserver observer, final int flags,final String installerPackageName) 

这样就是从网络下载安装的入口了。

(4)从SD卡安装

系统调用PackageInstallerActivity.java（/home/zhongda/androidSRC/vortex-8inch-for-hoperun/packages/apps/PackageInstaller/src/com/android/packageinstaller）

进入这个Activity会判断信息是否有错，然后调用

  private void initiateInstall()判断是否曾经有过同名包的安装，或者包已经安装

通过后执行private void startInstallConfirm() 点击OK按钮后经过一系列的安装信息的判断Intent跳转到

public class InstallAppProgress extends Activity implements View.OnClickListener, OnCancelListener  
   public void onCreate(Bundle icicle) {  
        super.onCreate(icicle);  
        Intent intent = getIntent();  
        mAppInfo = intent.getParcelableExtra(PackageUtil.INTENT_ATTR_APPLICATION_INFO);  
        mPackageURI = intent.getData();  
        initView();  
    }  

方法中调用了initView（）方法

public void initView() {  
       requestWindowFeature(Window.FEATURE_NO_TITLE);  
       setContentView(R.layout.op_progress);  
       int installFlags = 0;  
       PackageManager pm = getPackageManager();  
       try {  
           PackageInfo pi = pm.getPackageInfo(mAppInfo.packageName,   
                   PackageManager.GET_UNINSTALLED_PACKAGES);  
           if(pi != null) {  
               installFlags |= PackageManager.INSTALL_REPLACE_EXISTING;  
           }  
       } catch (NameNotFoundException e) {  
       }  
       if((installFlags & PackageManager.INSTALL_REPLACE_EXISTING )!= 0) {  
           Log.w(TAG, "Replacing package:" + mAppInfo.packageName);  
       }  
       PackageUtil.AppSnippet as = PackageUtil.getAppSnippet(this, mAppInfo,  
               mPackageURI);  
       mLabel = as.label;  
       PackageUtil.initSnippetForNewApp(this, as, R.id.app_snippet);  
       mStatusTextView = (TextView)findViewById(R.id.center_text);  
       mStatusTextView.setText(R.string.installing);  
       mProgressBar = (ProgressBar) findViewById(R.id.progress_bar);  
       mProgressBar.setIndeterminate(true);  
       // Hide button till progress is being displayed  
       mOkPanel = (View)findViewById(R.id.buttons_panel);  
       mDoneButton = (Button)findViewById(R.id.done_button);  
       mLaunchButton = (Button)findViewById(R.id.launch_button);  
       mOkPanel.setVisibility(View.INVISIBLE);  
       String installerPackageName = getIntent().getStringExtra(  
               Intent.EXTRA_INSTALLER_PACKAGE_NAME);  
       PackageInstallObserver observer = new PackageInstallObserver();  
       pm.installPackage(mPackageURI, observer, installFlags, installerPackageName);  
   }  

方法最后我们可以看到再次调用安装接口完成安装。

对于mSetting的介绍还不完善，后续会继续补充

本文是读过下面的几篇博客和Android系统源代码情景分析之后写成的，感谢各位作者。

参考：

http://ticktick.blog.51cto.com/823160/1669525
http://blog.csdn.net/hdhd588/article/details/6739281
http://blog.csdn.net/luoshengyang/article/details/6766010
《Android系统源代码情景分析》