Android源码分析-PackageManagerService（PMS）源码分析（二）- 利用PackageParser进行package的解析

liranke

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分类专栏： Android系统源码分析文章标签： packageParse android包简析 android apk简析 apk简析 android应用简析

于 2013-10-29 17:00:58 首次发布

本文链接：https://blog.youkuaiyun.com/liranke/article/details/13510821

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本文介绍了Android系统中如何解析APK文件。重点分析了PackageParser类的功能及其实现过程，包括PackageParser实例的创建、parsePackage方法的具体实现以及关键组件如Activity、Service的解析流程。

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一，PackageParser的作用：

PackageParser用于解析一个apk文件。

对于一个apk文件来说，系统是如何进行解析的？本节分析apk解析相关的代码。在上一节中，分析了PackageManagerService的初始化流程。其中，PMS的scanDirLI是关键方法，它用来扫描给定参数dir目录下的apk文件，并通过调用scanPackageLI来进行解析。
在scanPackageLI方法中，创建了解析器，正是通过这个解析器，实现了apk的解析。

二，PackageParser类的源码分析：

2.1 创建PackageParser实例：

在PMS的scanPackageLI方法中，初始化PackageParser，并且调用了它的parsePackage方法：

    private PackageParser.Package scanPackageLI(File scanFile,
            int parseFlags, int scanMode, long currentTime) {
        mLastScanError = PackageManager.INSTALL_SUCCEEDED;
        String scanPath = scanFile.getPath();
        parseFlags |= mDefParseFlags;
        PackageParser pp = new PackageParser(scanPath);

        //设置进程
        pp.setSeparateProcesses(mSeparateProcesses);
        //设置是否是核心app
        pp.setOnlyCoreApps(mOnlyCore);
        //简析
        final PackageParser.Package pkg = pp.parsePackage(scanFile,
                scanPath, mMetrics, parseFlags);

        ......

        //继续简析
        PackageParser.Package scannedPkg = scanPackageLI(pkg, parseFlags, scanMode
                | SCAN_UPDATE_SIGNATURE, currentTime);
    }

2.2 PackageParser的parsePackage方法：

parsePackage用于解析文件。根据解析的目标（用packageFile参数来判别）的不同，使用不同的解析方法。如果目标是文件夹，则解析这个文件夹下的所有apk文件；如果是文件，就解析单个文件。

parsePackage的代码如下：

public Package parsePackage(File sourceFile, String destCodePath,
            DisplayMetrics metrics, int flags) {
        mParseError = PackageManager.INSTALL_SUCCEEDED;

        //文件合法性检测
        mArchiveSourcePath = sourceFile.getPath();
        if (!sourceFile.isFile()) {
            Slog.w(TAG, "Skipping dir: " + mArchiveSourcePath);
            mParseError = PackageManager.INSTALL_PARSE_FAILED_NOT_APK;
            return null;
        }
        if (!isPackageFilename(sourceFile.getName())
                && (flags&PARSE_MUST_BE_APK) != 0) {
            if ((flags&PARSE_IS_SYSTEM) == 0) {
                // We expect to have non-.apk files in the system dir,
                // so don't warn about them.
                Slog.w(TAG, "Skipping non-package file: " + mArchiveSourcePath);
            }
            mParseError = PackageManager.INSTALL_PARSE_FAILED_NOT_APK;
            return null;
        }

        if (DEBUG_JAR)
            Slog.d(TAG, "Scanning package: " + mArchiveSourcePath);

        
        XmlResourceParser parser = null;
        AssetManager assmgr = null;
        Resources res = null;
        boolean assetError = true;
        try {

            assmgr = new AssetManager();
            int cookie = assmgr.addAssetPath(mArchiveSourcePath);
            if (cookie != 0) {
                res = new Resources(assmgr, metrics, null);
                assmgr.setConfiguration(0, 0, null, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
                        Build.VERSION.RESOURCES_SDK_INT);

                //xml解析器的创建
                parser = assmgr.openXmlResourceParser(cookie, ANDROID_MANIFEST_FILENAME);
                assetError = false;
            } else {
                Slog.w(TAG, "Failed adding asset path:"+mArchiveSourcePath);
            }
        } catch (Exception e) {
            Slog.w(TAG, "Unable to read AndroidManifest.xml of "
                    + mArchiveSourcePath, e);
        }
        if (assetError) {
            if (assmgr != null) assmgr.close();
            mParseError = PackageManager.INSTALL_PARSE_FAILED_BAD_MANIFEST;
            return null;
        }
        String[] errorText = new String[1];
        Package pkg = null;
        Exception errorException = null;
        try {
            //真正的解析
            pkg = parsePackage(res, parser, flags, errorText);
        } catch (Exception e) {
            errorException = e;
            mParseError = PackageManager.INSTALL_PARSE_FAILED_UNEXPECTED_EXCEPTION;
        }


        if (pkg == null) {
            // If we are only parsing core apps, then a null with INSTALL_SUCCEEDED
            // just means to skip this app so don't make a fuss about it.
            if (!mOnlyCoreApps || mParseError != PackageManager.INSTALL_SUCCEEDED) {
                if (errorException != null) {
                    Slog.w(TAG, mArchiveSourcePath, errorException);
                } else {
                    Slog.w(TAG, mArchiveSourcePath + " (at "
                            + parser.getPositionDescription()
                            + "): " + errorText[0]);
                }
                if (mParseError == PackageManager.INSTALL_SUCCEEDED) {
                    mParseError = PackageManager.INSTALL_PARSE_FAILED_MANIFEST_MALFORMED;
                }
            }
            parser.close();
            assmgr.close();
            return null;
        }

        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;
    }

其中，重载函数parsePackage是关键。

2.3 parsePackage方法的定义：


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

        //包名的解析        
        String pkgName = parsePackageName(parser, attrs, flags, outError);
        if (pkgName == null) {
            mParseError = PackageManager.INSTALL_PARSE_FAILED_BAD_PACKAGE_NAME;
            return null;
        }
        int type;

        if (mOnlyCoreApps) {
            boolean core = attrs.getAttributeBooleanValue(null, "coreApp", false);
            if (!core) {
                mParseError = PackageManager.INSTALL_SUCCEEDED;
                return null;
            }
        }

        //创建Package实例
        final Package pkg = new Package(pkgName);
        boolean foundApp = false;
        //获取资源属性
        TypedArray sa = res.obtainAttributes(attrs,
                com.android.internal.R.styleable.AndroidManifest);
        //获取versioncode，versionName
        pkg.mVersionCode = sa.getInteger(
                com.android.internal.R.styleable.AndroidManifest_versionCode, 0);
        pkg.mVersionName = sa.getNonConfigurationString(
                com.android.internal.R.styleable.AndroidManifest_versionName, 0);
        if (pkg.mVersionName != null) {
            pkg.mVersionName = pkg.mVersionName.intern();
        }
        
        ......

        //AndroidManifest.xml清单文件的解析
        int outerDepth = parser.getDepth();
        while ((type = parser.next()) != XmlPullParser.END_DOCUMENT
                && (type != XmlPullParser.END_TAG || parser.getDepth() > outerDepth)) {
            if (type == XmlPullParser.END_TAG || type == XmlPullParser.TEXT) {
                continue;
            }

            //app名称的获取
            String tagName = parser.getName();
            if (tagName.equals("application")) {
                if (foundApp) {
                    if (RIGID_PARSER) {
                        outError[0] = "<manifest> has more than one <application>";
                        mParseError = PackageManager.INSTALL_PARSE_FAILED_MANIFEST_MALFORMED;
                        return null;
                    } else {
                        Slog.w(TAG, "<manifest> has more than one <application>");
                        XmlUtils.skipCurrentTag(parser);
                        continue;
                    }
                }

                foundApp = true;
                //简析Application节点
                if (!parseApplication(pkg, res, parser, attrs, flags, outError)) {
                    return null;
                }
            } else if (tagName.equals("permission-group")) {
                //简析permission-group节点
                if (parsePermissionGroup(pkg, flags, res, parser, attrs, outError) == null) {
                    return null;
                }
            } else if (tagName.equals("permission")) {
                if (parsePermission(pkg, res, parser, attrs, outError) == null) {
                    return null;
                }
            } else if (tagName.equals("permission-tree")) {
                if (parsePermissionTree(pkg, res, parser, attrs, outError) == null) {
                    return null;
                }
            } else if (tagName.equals("uses-permission")) {
                sa = res.obtainAttributes(attrs,
                        com.android.internal.R.styleable.AndroidManifestUsesPermission);

                // Note: don't allow this value to be a reference to a resource
                // that may change.
                String name = sa.getNonResourceString(
                        com.android.internal.R.styleable.AndroidManifestUsesPermission_name);
                /* Not supporting optional permissions yet.
                boolean required = sa.getBoolean(
                        com.android.internal.R.styleable.AndroidManifestUsesPermission_required, true);
                */

                sa.recycle();

                if (name != null && !pkg.requestedPermissions.contains(name)) {
                    pkg.requestedPermissions.add(name.intern());
                    pkg.requestedPermissionsRequired.add(Boolean.TRUE);
                }

                XmlUtils.skipCurrentTag(parser);

            } else if (tagName.equals("uses-configuration")) {
                ConfigurationInfo cPref = new ConfigurationInfo();
                ......

            } else if (tagName.equals("uses-feature")) {
                FeatureInfo fi = new FeatureInfo();
                ......

            } else if (tagName.equals("uses-sdk")) {
                if (SDK_VERSION > 0) {
                    sa = res.obtainAttributes(attrs,
                            com.android.internal.R.styleable.AndroidManifestUsesSdk);

                    ......
                }

                XmlUtils.skipCurrentTag(parser);

            } else if (tagName.equals("supports-screens")) {
                sa = res.obtainAttributes(attrs,
                        com.android.internal.R.styleable.AndroidManifestSupportsScreens);

                ......
                
            } else if (tagName.equals("protected-broadcast")) {
                sa = res.obtainAttributes(attrs,
                        com.android.internal.R.styleable.AndroidManifestProtectedBroadcast);

                ......
                
            } else if (tagName.equals("instrumentation")) {
                if (parseInstrumentation(pkg, res, parser, attrs, outError) == null) {
                    return null;
                }
                
            } else if (tagName.equals("original-package")) {
                ......
                
            } else if (tagName.equals("adopt-permissions")) {
                sa = res.obtainAttributes(attrs,
                        com.android.internal.R.styleable.AndroidManifestOriginalPackage);

                ......
                
            } 
            ......
        }

        ......

        return pkg;
    }

可见，主要是进行了清单文件的简析，并进行Package实例化。

其中，Application是进行Application标签的解析，解析出Activity，Service等组件。

2.4 parseApplication代码分析:



    private boolean parseApplication(Package owner, Resources res,
            XmlPullParser parser, AttributeSet attrs, int flags, String[] outError)
        throws XmlPullParserException, IOException {

        //应用信息，，，应用图标，等的获取
        final ApplicationInfo ai = owner.applicationInfo;
        //包名
        final String pkgName = owner.applicationInfo.packageName;

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

        //应用名称
        String name = sa.getNonConfigurationString(
                com.android.internal.R.styleable.AndroidManifestApplication_name, 0);
        if (name != null) {
            ai.className = buildClassName(pkgName, name, outError);
            if (ai.className == null) {
                sa.recycle();
                mParseError = PackageManager.INSTALL_PARSE_FAILED_MANIFEST_MALFORMED;
                return false;
            }
        }

        String manageSpaceActivity = sa.getNonConfigurationString(
                com.android.internal.R.styleable.AndroidManifestApplication_manageSpaceActivity, 0);
        if (manageSpaceActivity != null) {
            ai.manageSpaceActivityName = buildClassName(pkgName, manageSpaceActivity,
                    outError);
        }

        boolean allowBackup = sa.getBoolean(
                com.android.internal.R.styleable.AndroidManifestApplication_allowBackup, true);
        if (allowBackup) {
            ai.flags |= ApplicationInfo.FLAG_ALLOW_BACKUP;

            // backupAgent, killAfterRestore, and restoreAnyVersion are only relevant
            // if backup is possible for the given application.
            String backupAgent = sa.getNonConfigurationString(
                    com.android.internal.R.styleable.AndroidManifestApplication_backupAgent, 0);
            if (backupAgent != null) {
                ai.backupAgentName = buildClassName(pkgName, backupAgent, outError);
                if (DEBUG_BACKUP) {
                    Slog.v(TAG, "android:backupAgent = " + ai.backupAgentName
                            + " from " + pkgName + "+" + backupAgent);
                }

                if (sa.getBoolean(
                        com.android.internal.R.styleable.AndroidManifestApplication_killAfterRestore,
                        true)) {
                    ai.flags |= ApplicationInfo.FLAG_KILL_AFTER_RESTORE;
                }
                if (sa.getBoolean(
                        com.android.internal.R.styleable.AndroidManifestApplication_restoreAnyVersion,
                        false)) {
                    ai.flags |= ApplicationInfo.FLAG_RESTORE_ANY_VERSION;
                }
            }
        }

        TypedValue v = sa.peekValue(
                com.android.internal.R.styleable.AndroidManifestApplication_label);
        if (v != null && (ai.labelRes=v.resourceId) == 0) {
            ai.nonLocalizedLabel = v.coerceToString();
        }

        //应用图标
        ai.icon = sa.getResourceId(
                com.android.internal.R.styleable.AndroidManifestApplication_icon, 0);
        ai.logo = sa.getResourceId(
                com.android.internal.R.styleable.AndroidManifestApplication_logo, 0);
        //应用主题
        ai.theme = sa.getResourceId(
                com.android.internal.R.styleable.AndroidManifestApplication_theme, 0);
        

        //其它属性
        ......
        ......

        final int innerDepth = parser.getDepth();

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

            String tagName = parser.getName();
            //简析activity
            if (tagName.equals("activity")) {
                Activity a = parseActivity(owner, res, parser, attrs, flags, outError, false,
                        hardwareAccelerated);
                if (a == null) {
                    mParseError = PackageManager.INSTALL_PARSE_FAILED_MANIFEST_MALFORMED;
                    return false;
                }

                owner.activities.add(a);

            } 
            //简析receiver
            else if (tagName.equals("receiver")) {
                Activity a = parseActivity(owner, res, parser, attrs, flags, outError, true, false);
                if (a == null) {
                    mParseError = PackageManager.INSTALL_PARSE_FAILED_MANIFEST_MALFORMED;
                    return false;
                }

                owner.receivers.add(a);

            }
            //简析service
             else if (tagName.equals("service")) {
                Service s = parseService(owner, res, parser, attrs, flags, outError);
                if (s == null) {
                    mParseError = PackageManager.INSTALL_PARSE_FAILED_MANIFEST_MALFORMED;
                    return false;
                }

                owner.services.add(s);

            }

            //简析provider

             else if (tagName.equals("provider")) {
                Provider p = parseProvider(owner, res, parser, attrs, flags, outError);
                if (p == null) {
                    mParseError = PackageManager.INSTALL_PARSE_FAILED_MANIFEST_MALFORMED;
                    return false;
                }

                owner.providers.add(p);

            } 
            //简析其它属性
            。。。。。。

        }

        return true;
    }

可见，进行了activity，Service，Provider，Receiver等组件的简析，并且返回相应的组件的一个实例。例如，parseActivity方法返回一个解析成功的Activity实例。

现在，我们来看一下简析完成后，又做了什么工作，即scanPackageLI方法的实现原理。

2.5 scanPackageLI方法分析：

在“2.1 创建PackageParser实例”中，PackageParser函数的实现的最后，有scanPackageLI的调用。现在，来分析scanPackageLI的实现：


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

            ......

            // activity的添加

            N = pkg.activities.size();
            r = null;
            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");
                if ((parseFlags&PackageParser.PARSE_CHATTY) != 0) {
                    if (r == null) {
                        r = new StringBuilder(256);
                    } else {
                        r.append(' ');
                    }
                    r.append(a.info.name);
                }
            }
            if (r != null) {
                if (DEBUG_PACKAGE_SCANNING) Log.d(TAG, "  Activities: " + r);
            }

            ......
        }

        return pkg;
    }

这样，mActivity中就保存了所有的activity。

而mActivity的定义如下：

// 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();

至此，整个解析就完成了。简析完成后，诸如Activity，Service等组件都保存在了内存中，例如mActivity保存了所有的Activity的信息。