Android(安卓)APK应用安装原理(1)-解析AndroidManifest原理-PackageParser.parserPackage

Android 安装一个 APK 的时候首先会解析 APK ，这里要做很多事情，其中一个事情就是解析 Manifest.xml 文件，并将所有 APK 的 Manifest 封装到各种对象中并保存在内存当中

解析Manifest的类是非常重要的，该类就是frameworks\base\core\java\android\content\pm\PackageParser

PackageManagerService会调用PackageParser.parserPackage方法来解析APK清单，下面开始分析PackageParser的实现：

PackageParser是使用的XMLPullParser工具来对XML进行解析的，然后分别通过android.content.pm下各种xxxInfo类来进行封装：

public Package parsePackage(File sourceFile, String destCodePath,            DisplayMetrics metrics, int flags) {    //最后要跑出的解析错误信息        mParseError = PackageManager.INSTALL_SUCCEEDED;        //获得要解析的文件的路径        mArchiveSourcePath = sourceFile.getPath();                //如果要解析的不是文件类型就跳过并且返回该方法        if (!sourceFile.isFile()) {            Log.w(TAG, "Skipping dir: " + mArchiveSourcePath);            //更新错误信息            mParseError = PackageManager.INSTALL_PARSE_FAILED_NOT_APK;            return null;        }                //如果文件不是以.apk结尾并且flag没有确定一定是APK，那么也返回        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.                Log.w(TAG, "Skipping non-package file: " + mArchiveSourcePath);            }            //更新错误信息            mParseError = PackageManager.INSTALL_PARSE_FAILED_NOT_APK;            return null;        }        if ((flags&PARSE_CHATTY) != 0 && Config.LOGD) Log.d(            TAG, "Scanning package: " + mArchiveSourcePath);        XmlResourceParser parser = null;        AssetManager assmgr = null;        boolean assetError = true;        try {            assmgr = new AssetManager();                        //将一个文件添加到AssetManager中并返回一个唯一标识            int cookie = assmgr.addAssetPath(mArchiveSourcePath);            if(cookie != 0) {            //通过标识去AssetManager中找到标识对应资源中的Manifest清单文件，并返回一个XML的解析器                parser = assmgr.openXmlResourceParser(cookie, "AndroidManifest.xml");                //走到这里证明一切顺利                assetError = false;            } else {                Log.w(TAG, "Failed adding asset path:"+mArchiveSourcePath);            }        } catch (Exception e) {            Log.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 {            // XXXX todo: need to figure out correct configuration.            Resources res = new Resources(assmgr, metrics, null);            //这个是真正在解析的package的方法，是private method            pkg = parsePackage(res, parser, flags, errorText);        } catch (Exception e) {            errorException = e;            mParseError = PackageManager.INSTALL_PARSE_FAILED_UNEXPECTED_EXCEPTION;        }        if (pkg == null) {            if (errorException != null) {                Log.w(TAG, mArchiveSourcePath, errorException);            } else {                Log.w(TAG, mArchiveSourcePath + " (at "                        + parser.getPositionDescription()                        + "): " + errorText[0]);            }            parser.close();            assmgr.close();            if (mParseError == PackageManager.INSTALL_SUCCEEDED) {                mParseError = PackageManager.INSTALL_PARSE_FAILED_MANIFEST_MALFORMED;            }            return null;        }

parserPackage调用了重载的另外一个parserPackage

private Package parsePackage(        Resources res, XmlResourceParser parser, int flags, String[] outError)        throws XmlPullParserException, IOException {        AttributeSet attrs = parser;        //每次调用这个方法时候清空这些变量        mParseInstrumentationArgs = null;        mParseActivityArgs = null;        mParseServiceArgs = null;        mParseProviderArgs = null;                //这里调用这个方法获得包名        String pkgName = parsePackageName(parser, attrs, flags, outError);        if (pkgName == null) {            mParseError = PackageManager.INSTALL_PARSE_FAILED_BAD_PACKAGE_NAME;            return null;        }        int type;        final Package pkg = new Package(pkgName);        boolean foundApp = false;                //从资源里获得AndroidManifest的数组        TypedArray sa = res.obtainAttributes(attrs,                com.android.internal.R.styleable.AndroidManifest);                //继续挖掘出版本号        pkg.mVersionCode = sa.getInteger(                com.android.internal.R.styleable.AndroidManifest_versionCode, 0);                //获取版本名        pkg.mVersionName = sa.getNonConfigurationString(                com.android.internal.R.styleable.AndroidManifest_versionName, 0);        if (pkg.mVersionName != null) {            pkg.mVersionName = pkg.mVersionName.intern();        }                //获得sharedUserId        String str = sa.getNonConfigurationString(                com.android.internal.R.styleable.AndroidManifest_sharedUserId, 0);        if (str != null && str.length() > 0) {        //验证包名是否符合规则            String nameError = validateName(str, true);            if (nameError != null && !"android".equals(pkgName)) {                outError[0] = "<manifest> specifies bad sharedUserId name \""                    + str + "\": " + nameError;                mParseError = PackageManager.INSTALL_PARSE_FAILED_BAD_SHARED_USER_ID;                return null;            }            pkg.mSharedUserId = str.intern();            pkg.mSharedUserLabel = sa.getResourceId(                    com.android.internal.R.styleable.AndroidManifest_sharedUserLabel, 0);        }        sa.recycle();        //安装的位置        pkg.installLocation = sa.getInteger(                com.android.internal.R.styleable.AndroidManifest_installLocation,                PARSE_DEFAULT_INSTALL_LOCATION);        // Resource boolean are -1, so 1 means we don't know the value.        int supportsSmallScreens = 1;        int supportsNormalScreens = 1;        int supportsLargeScreens = 1;        int resizeable = 1;        int anyDensity = 1;                int outerDepth = parser.getDepth();                //关键时刻到了，真正的开始解析了        while ((type=parser.next()) != parser.END_DOCUMENT               && (type != parser.END_TAG || parser.getDepth() > outerDepth)) {            if (type == parser.END_TAG || type == parser.TEXT) {                continue;            }            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 {                        Log.w(TAG, "<manifest> has more than one <application>");                        XmlUtils.skipCurrentTag(parser);                        continue;                    }                }                foundApp = true;                if (!parseApplication(pkg, res, parser, attrs, flags, outError)) {                    return null;                }            } else if (tagName.equals("permission-group")) {                if (parsePermissionGroup(pkg, 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);                sa.recycle();              ...................................................              ...................................................              ...................................................篇幅有限

这里分别把每种不同的element用不同的小方法去解析，他们的调用顺序是：

这些小方法里其实还是有很多小技巧的，有兴趣的话可以细细品位

更多相关文章

随机推荐