APK安装过程及原理详解
原文出处：APK安装过程及原理详解
应用程序包的安装是android的特点
一、 APK为AndroidPackage的缩写；
二、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过程的界面。
三、应用安装的流程及路径
1、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。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)。
2、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。
3、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。
四、安装应用的过程解析：
1、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 = 0;
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()。
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()
/* 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);
}
}
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。