APK 安装过程 及 原理 详解

APK为AndroidPackage的缩写

Android应用安装有如下四种方式：

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。

————————————-

应用安装涉及到如下几个目录：

system/app —————系统自带的应用程序，获得adb root权限才能删除

data/app —————用户程序安装的目录。用户 安装时把apk文件 复制 到此目录

data/data —————存放应用程序的数据

data/dalvik-cache——–将apk中的dex文件安装到dalvik-cache目录下(dex文件是dalvik虚拟机的可执行文件,其大小约为原始apk文件大小的四分之一)

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。

————————-

安装应用的过程解析

一.开机安装

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

(源文件路径：android\frameworks\base\services\Java\com\android\server\PackageManagerService.java)

PackageManagerService服务 启动的流程：

1.首先 扫描安装“system\framework”目录下的jar包

// 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);

2.扫描 安装系统system/app的应用程序

// 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);

3.制造商的目录下/vendor/app应用包

// 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);

4.扫描“data\app”目录，即用户安装的第三方应用

scanDirLI(mAppInstallDir, 0, scanMode, 0);

5.扫描” data\app-private”目录，即安装DRM保护的APK文件（一个受保护的歌曲或受保 护的视频是使用 DRM 保护的文件）

scanDirLI(mDrmAppPrivateInstallDir, PackageParser.PARSE_FORWARD_LOCK,
scanMode, 0);

扫描方法的代码清单

private void scanDirLI(File dir, int flags, int scanMode, long currentTime) {
String[] files = dir.list();
if (files == null) {
Log.d(TAG, "No files in app dir " + dir);
return;
}
if (false) {
Log.d(TAG, "Scanning app dir " + dir);
}
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();
}
}
}

并且从该扫描方法中可以看出调用了scanPackageLI（）

private PackageParser.Package scanPackageLI(File scanFile,

int parseFlags, int scanMode, long currentTime)

跟踪scanPackageLI（）方法后发现，程序经过很多次的if else 的筛选，最后判定 可以安装apk后，调用了 mInstaller.install

if (mInstaller != null) {
int ret = mInstaller.install(pkgName, useEncryptedFSDir,  pkg.applicationInfo.uid,pkg.applicationInfo.uid);
if(ret < 0) {
// Error from installer
mLastScanError =    PackageManager.INSTALL_FAILED_INSUFFICIENT_STORAGE;
return null;
}
}

mInstaller.install（） 通过

LocalSocketAddress address = new LocalSocketAddress(

”installd“, LocalSocketAddress.Namespace.RESERVED);

指挥installd在C语言的文件中完成工作

PackageManagerService小节 ：

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().

二、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（）

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

由英文注释可见PackageManagerService 类的installPackage（）函数为 安装程序 的入口。

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);
}

其中是通过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;
}

—————————————————————————————–

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。

三、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

[b]Pm.java 文件里的 showUsage[/b]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;
}
PackageInstallObserverobs = 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

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 最后 就是 相当于 调用 从网络下载安装的 入口了。

四,从SD卡安装

系统调用 PackageInstallerActivity.java

源码路径：android/packages/apps/PackageInstaller/src/com/android/packageinstaller/PackageInstallerActivity.java

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，相当于 又 调用了 网络安装。

—————————————

总结：

1.系统应用安装――开机时完成

2.网络下载应用安装――最后 会 调用
系统应用安装 的scanPackageLI 接口；

3.ADB工具安装――最后 会 调用 网络下载应用安装 的installPackage 接口，从而 相当于 走的 还是系统应用安装 的 路径；

4.第三方应用安装――由 packageinstaller.apk 应用处理安装及卸载，最后也会 调用
网络下载应用安装 的installPackage 接口，从而 相当于 走的 还是系统应用安装 的 路径。