Android应用程序安装过程解析(源码解析)

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() {

[b]*****[/b]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》

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