文件目录：

android-1.6_r2\frameworks\base\core\java\android\content\pm\PackageParser.java

# PackageParser.java

1. 解析 APK 包名

 public static String parsePackageName(String packageFilePath, int flags) {
        XmlResourceParser parser = null;
        AssetManager assmgr = null;
        try {
            assmgr = new AssetManager(); // 创建 AssetManager 对象
            int cookie = assmgr.addAssetPath(packageFilePath); // 插入 安装包文件 路径
            parser = assmgr.openXmlResourceParser(cookie, "AndroidManifest.xml"); // 解析 Androidmanifest.xml 文件
        } catch (Exception e) {
            if (assmgr != null) assmgr.close();
            Log.w(TAG, "Unable to read AndroidManifest.xml of "
                    + packageFilePath, e);
            return null;
        }
        AttributeSet attrs = parser;
        String errors[] = new String[1];
        String packageName = null;
        try {
            packageName = parsePackageName(parser, attrs, flags, errors);
        } catch (IOException e) {
            Log.w(TAG, packageFilePath, e);
        } catch (XmlPullParserException e) {
            Log.w(TAG, packageFilePath, e);
        } finally {
            if (parser != null) parser.close();
            if (assmgr != null) assmgr.close();
        }
        if (packageName == null) {
            Log.e(TAG, "parsePackageName error: " + errors[0]);
            return null;
        }
        return packageName;
    }

private static String parsePackageName(XmlPullParser parser,
            AttributeSet attrs, int flags, String[] outError)
            throws IOException, XmlPullParserException {

        int type;
        while ((type=parser.next()) != parser.START_TAG
                   && type != parser.END_DOCUMENT) {
            ;
        }

        if (type != parser.START_TAG) {
            outError[0] = "No start tag found";
            return null;
        }
        if ((flags&PARSE_CHATTY) != 0 && Config.LOGV) Log.v(
            TAG, "Root element name: '" + parser.getName() + "'");
        if (!parser.getName().equals("manifest")) {
            outError[0] = "No <manifest> tag";
            return null;
        }
        String pkgName = attrs.getAttributeValue(null, "package"); // 解析 package tag
        if (pkgName == null || pkgName.length() == 0) {
            outError[0] = "<manifest> does not specify package";
            return null;
        }
        String nameError = validateName(pkgName, true); // 校验包名
        if (nameError != null && !"android".equals(pkgName)) { // 过滤 "android" 包名
            outError[0] = "<manifest> specifies bad package name \""
                + pkgName + "\": " + nameError;
            return null;
        }

        return pkgName.intern();
    }

    private static String validateName(String name, boolean requiresSeparator) {
        final int N = name.length();
        boolean hasSep = false;
        boolean front = true;
        for (int i=0; i<N; i++) {
            final char c = name.charAt(i);
            if ((c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z')) {
                front = false;
                continue;
            }
            if (!front) {
                if ((c >= '0' && c <= '9') || c == '_') {
                    continue;
                }
            }
            if (c == '.') {
                hasSep = true;
                front = true;
                continue;
            }
            return "bad character '" + c + "'";
        }
        return hasSep || !requiresSeparator
                ? null : "must have at least one '.' separator";
    }