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

我不是女神ヾ 2023-10-16 18:37 21阅读 0赞

### 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。

--------------------