AndroidManifest使用PackageParser.parserPackage原理分析

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;
}

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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] = "

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