APK安装过程及原理详解

应用程序包的安装是android的特点

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过程的界面。

应用安装的流程及路径 
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)

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

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。

四,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。