Android应用程序包解析过程浅析

我在上一篇文件中Android应用程序安装过程浅析粗略分析了一下Android应用程序安装过程，其中有一步说到了apk包的解析，但是没有详细分析，这里我们就来粗略分析一下包的解析过程。

流程图

执行过程

从上面的流程图可以看到，包的解析过程比安装过程执行步骤少很多，也简单一点。那我们就来详细的一步一步的进行剖析一下，我们从外部调用该方法开始分析：

private void installPackageLI(InstallArgs args, PackageInstalledInfo res) {
final int installFlags = args.installFlags;
final String installerPackageName = args.installerPackageName;
final String volumeUuid = args.volumeUuid;
final File tmpPackageFile = new File(args.getCodePath());
final boolean forwardLocked = ((installFlags & PackageManager.INSTALL_FORWARD_LOCK) != 0);
final boolean onExternal = (((installFlags & PackageManager.INSTALL_EXTERNAL) != 0)
|| (args.volumeUuid != null));
boolean replace = false;
int scanFlags = SCAN_NEW_INSTALL | SCAN_UPDATE_SIGNATURE;
if (args.move != null) {
// moving a complete application; perfom an initial scan on the new install location
scanFlags |= SCAN_INITIAL;
}
// Result object to be returned
res.returnCode = PackageManager.INSTALL_SUCCEEDED;

if (DEBUG_INSTALL) Slog.d(TAG, "installPackageLI: path=" + tmpPackageFile);
// Retrieve PackageSettings and parse package
final int parseFlags = mDefParseFlags | PackageParser.PARSE_CHATTY
| (forwardLocked ? PackageParser.PARSE_FORWARD_LOCK : 0)
| (onExternal ? PackageParser.PARSE_EXTERNAL_STORAGE : 0);
PackageParser pp = new PackageParser();
pp.setSeparateProcesses(mSeparateProcesses);
pp.setDisplayMetrics(mMetrics);

final PackageParser.Package pkg;
try {
pkg = pp.parsePackage(tmpPackageFile, parseFlags);
} catch (PackageParserException e) {
res.setError("Failed parse during installPackageLI", e);
return;
}

// Mark that we have an install time CPU ABI override.
pkg.cpuAbiOverride = args.abiOverride;

String pkgName = res.name = pkg.packageName;
if ((pkg.applicationInfo.flags&ApplicationInfo.FLAG_TEST_ONLY) != 0) {
if ((installFlags & PackageManager.INSTALL_ALLOW_TEST) == 0) {
res.setError(INSTALL_FAILED_TEST_ONLY, "installPackageLI");
return;
}
}

try {
pp.collectCertificates(pkg, parseFlags);
pp.collectManifestDigest(pkg);
} catch (PackageParserException e) {
res.setError("Failed collect during installPackageLI", e);
return;
}
.......
}

可以看到在解析之前先构造了一个PackageParser，之后设置了mSeparateProcesses与mMetrics属性，mSeparateProcesses是一个数组，表示的独立的进程名列表，这个参数是在PackageManagerService的构造函数中调用的，以后会分析一下该函数是在什么地方调用的，这里就先看看mSeparateProcesses的获取过程：

String separateProcesses = SystemProperties.get("debug.separate_processes");
if (separateProcesses != null && separateProcesses.length() > 0) {
if ("*".equals(separateProcesses)) {
mDefParseFlags = PackageParser.PARSE_IGNORE_PROCESSES;
mSeparateProcesses = null;
Slog.w(TAG, "Running with debug.separate_processes: * (ALL)");
} else {
mDefParseFlags = 0;
mSeparateProcesses = separateProcesses.split(",");
Slog.w(TAG, "Running with debug.separate_processes: "
+ separateProcesses);
}
} else {
mDefParseFlags = 0;
mSeparateProcesses = null;
}

从系统属性中读取debug.separate_processes属性，如果改属性返回值不为空，表示设置了该属性，否则系统未设置改属性，如果值等于则mSeparateProcesses为空，如果不为，则逗号分隔该字符串，解析每个独立的进程名，那个debug.separate_processes究竟有什么用？是干什么的？我们来看看官方给出的解释：

Add android.separate_processes property you can use to force application components to run in their own process. There are two ways you can use this:

setprop debug.separate_processes - This will apply to every process in every package.

setprop debug.separate_processes “com.google.process.content,com.google.android.samples” - This will impact only the code whose manifest involves one of the given processes (here com.google.process.content com.google.android.samples)

– either as the manifest package name, or listed as an explicit android:process tag. Note that using this option will either split a process into parts (corresponding to the packages inside of it)or combine multiple processes into one (if they come from the same package). That is, it forces all impacted components to run in the process for their own .apk, regardless of what android:process attributes specify.

可以知道该属性可以强制使应用程序组件运行在他自己的进程，主要作为调试用。

mMetrics是一个描述界面显示，尺寸，分辨率，密度的类。我们说完了这两个参数，我们来看看parsePackage(tmpPackageFile, parseFlags);tmpPackageFile是包的存放路径，parseFlags为解析标识，返回值一个Package对象。我们来看看parsePackage函数：

public Package parsePackage(File packageFile, int flags) throws PackageParserException {
if (packageFile.isDirectory()) {
return parseClusterPackage(packageFile, flags);
} else {
return parseMonolithicPackage(packageFile, flags);
}
}

如果传入的是一个文件目录，则表示有多个apk需要解析，否则单个apk需要解析，这我们就只看单个的解析，因为多个最终还是会一个一个调用单个解析。我们来根进单个解析代码看看执行逻辑：

public Package parseMonolithicPackage(File apkFile, int flags) throws PackageParserException {
if (mOnlyCoreApps) {
final PackageLite lite = parseMonolithicPackageLite(apkFile, flags);
if (!lite.coreApp) {
throw new PackageParserException(INSTALL_PARSE_FAILED_MANIFEST_MALFORMED,
"Not a coreApp: " + apkFile);
}
}

final AssetManager assets = new AssetManager();
try {
final Package pkg = parseBaseApk(apkFile, assets, flags);
pkg.codePath = apkFile.getAbsolutePath();
return pkg;
} finally {
IoUtils.closeQuietly(assets);
}
}

首先判断是不是mOnlyCoreApps，mOnlyCoreApps该标识表明解析只考虑应用清单属性有效的应用，主要是为了创建一个最小的启动环境，如果该标识为true则轻量级解析，调用parseMonolithicPackageLite来进行解析，返回一个PackageLite对象。我们就先看轻量级解析等会在返回看全部解析：

private static PackageLite parseMonolithicPackageLite(File packageFile, int flags)
throws PackageParserException {
final ApkLite baseApk = parseApkLite(packageFile, flags);
final String packagePath = packageFile.getAbsolutePath();
return new PackageLite(packagePath, baseApk, null, null, null);
}

parseMonolithicPackageLite内部又调用了parseApkLite函数并且返回一个ApkLite对象，根据返回的ApkLite对象和包的局对路径构造了一个PackageLite对象作为返回值。我们看看parseApkLite函数：

public static ApkLite parseApkLite(File apkFile, int flags)
throws PackageParserException {
final String apkPath = apkFile.getAbsolutePath();

AssetManager assets = null;
XmlResourceParser parser = null;
try {
assets = new AssetManager();
assets.setConfiguration(0, 0, null, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
Build.VERSION.RESOURCES_SDK_INT);

int cookie = assets.addAssetPath(apkPath);
if (cookie == 0) {
throw new PackageParserException(INSTALL_PARSE_FAILED_NOT_APK,
"Failed to parse " + apkPath);
}

final DisplayMetrics metrics = new DisplayMetrics();
metrics.setToDefaults();

final Resources res = new Resources(assets, metrics, null);
parser = assets.openXmlResourceParser(cookie, ANDROID_MANIFEST_FILENAME);

final Signature[] signatures;
if ((flags & PARSE_COLLECT_CERTIFICATES) != 0) {
// TODO: factor signature related items out of Package object
final Package tempPkg = new Package(null);
collectCertificates(tempPkg, apkFile, 0);
signatures = tempPkg.mSignatures;
} else {
signatures = null;
}

final AttributeSet attrs = parser;
return parseApkLite(apkPath, res, parser, attrs, flags, signatures);

} catch (XmlPullParserException | IOException | RuntimeException e) {
throw new PackageParserException(INSTALL_PARSE_FAILED_UNEXPECTED_EXCEPTION,
"Failed to parse " + apkPath, e);
} finally {
IoUtils.closeQuietly(parser);
IoUtils.closeQuietly(assets);
}
}

函数里首先初始化了一个AssetManager对象，一个DisplayMetrics对象，一个Resources，并且调用collectCertificates函数获取了应用的签名信息，这些对象都是后续解析中需要用到的，因此将这些参数传递给解析函数，解析完成后关闭资源管理器与解析器，这里主要是轻量级解析，只解析了包名，安装位置等少量信息，我们来看看解析过程：

private static ApkLite parseApkLite(String codePath, Resources res, XmlPullParser parser,
AttributeSet attrs, int flags, Signature[] signatures) throws IOException,
XmlPullParserException, PackageParserException {
final Pair<String, String> packageSplit = parsePackageSplitNames(parser, attrs, flags);

int installLocation = PARSE_DEFAULT_INSTALL_LOCATION;
int versionCode = 0;
int revisionCode = 0;
boolean coreApp = false;
boolean multiArch = false;
boolean extractNativeLibs = true;

for (int i = 0; i < attrs.getAttributeCount(); i++) {
final String attr = attrs.getAttributeName(i);
if (attr.equals("installLocation")) {
installLocation = attrs.getAttributeIntValue(i,
PARSE_DEFAULT_INSTALL_LOCATION);
} else if (attr.equals("versionCode")) {
versionCode = attrs.getAttributeIntValue(i, 0);
} else if (attr.equals("revisionCode")) {
revisionCode = attrs.getAttributeIntValue(i, 0);
} else if (attr.equals("coreApp")) {
coreApp = attrs.getAttributeBooleanValue(i, false);
}
}

// Only search the tree when the tag is directly below <manifest>
int type;
final int searchDepth = parser.getDepth() + 1;

final List<VerifierInfo> verifiers = new ArrayList<VerifierInfo>();
while ((type = parser.next()) != XmlPullParser.END_DOCUMENT
&& (type != XmlPullParser.END_TAG || parser.getDepth() >= searchDepth)) {
if (type == XmlPullParser.END_TAG || type == XmlPullParser.TEXT) {
continue;
}

if (parser.getDepth() == searchDepth && "package-verifier".equals(parser.getName())) {
final VerifierInfo verifier = parseVerifier(res, parser, attrs, flags);
if (verifier != null) {
verifiers.add(verifier);
}
}

if (parser.getDepth() == searchDepth && "application".equals(parser.getName())) {
for (int i = 0; i < attrs.getAttributeCount(); ++i) {
final String attr = attrs.getAttributeName(i);
if ("multiArch".equals(attr)) {
multiArch = attrs.getAttributeBooleanValue(i, false);
}
if ("extractNativeLibs".equals(attr)) {
extractNativeLibs = attrs.getAttributeBooleanValue(i, true);
}
}
}
}

return new ApkLite(codePath, packageSplit.first, packageSplit.second, versionCode,
revisionCode, installLocation, verifiers, signatures, coreApp, multiArch,
extractNativeLibs);
}

这里首先解析返回包名和split名（这个不知道是啥），这个说点额外的东西，在parsePackageSplitNames里面调用了validateName函数，我们来看看validateName函数：

private static String validateName(String name, boolean requireSeparator,
boolean requireFilename) {
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 + "'";
}
if (requireFilename && !FileUtils.isValidExtFilename(name)) {
return "Invalid filename";
}
return hasSep || !requireSeparator
? null : "must have at least one '.' separator";
}

可以看到主要检测了是否是数字，字母，下划线和点分割符，这也是取包名的规则，比如是字母数字下划线加点火分割符，否则都不是合法的应用包名。并且合法的包名至少包含有一个点分隔符。

解析完包名之后，循环解析installLocation，versionCode，revisionCode，coreApp,接着继续解析package-verifier节点，该节点主要是前面信息相关的信心，最后解析application节点，该节点主要解析两个属性：multiArch，extractNativeLibs属性，将上述解析的信息构造成一个ApkLite对象返回。

轻量级解析完成后，我们继续来看看parseBaseApk函数。先构造一个AssetManager对象传入该函数。我们来详细分析一个该函数：

private Package parseBaseApk(File apkFile, AssetManager assets, int flags)
throws PackageParserException {
final String apkPath = apkFile.getAbsolutePath();

String volumeUuid = null;
if (apkPath.startsWith(MNT_EXPAND)) {
final int end = apkPath.indexOf('/', MNT_EXPAND.length());
volumeUuid = apkPath.substring(MNT_EXPAND.length(), end);
}

mParseError = PackageManager.INSTALL_SUCCEEDED;
mArchiveSourcePath = apkFile.getAbsolutePath();

if (DEBUG_JAR) Slog.d(TAG, "Scanning base APK: " + apkPath);

final int cookie = loadApkIntoAssetManager(assets, apkPath, flags);

Resources res = null;
XmlResourceParser parser = null;
try {
res = new Resources(assets, mMetrics, null);
assets.setConfiguration(0, 0, null, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
Build.VERSION.RESOURCES_SDK_INT);
parser = assets.openXmlResourceParser(cookie, ANDROID_MANIFEST_FILENAME);

final String[] outError = new String[1];
final Package pkg = parseBaseApk(res, parser, flags, outError);
if (pkg == null) {
throw new PackageParserException(mParseError,
apkPath + " (at " + parser.getPositionDescription() + "): " + outError[0]);
}

pkg.volumeUuid = volumeUuid;
pkg.baseCodePath = apkPath;
pkg.mSignatures = null;

return pkg;

} catch (PackageParserException e) {
throw e;
} catch (Exception e) {
throw new PackageParserException(INSTALL_PARSE_FAILED_UNEXPECTED_EXCEPTION,
"Failed to read manifest from " + apkPath, e);
} finally {
IoUtils.closeQuietly(parser);
}
}

该函数的前几步与轻量级解析一致，主要多了一个步骤解析volumeUuid，如果apk路径的前置为/mnt/expand/，则获取从该前缀之后的uuid，具体干嘛用的，主要是根据这个获取文件路径。我们来看看详细解析的代码：

/**
* Parse the manifest of a <em>base APK</em>.
* <p>
* When adding new features, carefully consider if they should also be
* supported by split APKs.
*/
private Package parseBaseApk(Resources res, XmlResourceParser parser, int flags,
String[] outError) throws XmlPullParserException, IOException {
final boolean trustedOverlay = (flags & PARSE_TRUSTED_OVERLAY) != 0;

AttributeSet attrs = parser;

mParseInstrumentationArgs = null;
mParseActivityArgs = null;
mParseServiceArgs = null;
mParseProviderArgs = null;

final String pkgName;
final String splitName;
try {
Pair<String, String> packageSplit = parsePackageSplitNames(parser, attrs, flags);
pkgName = packageSplit.first;
splitName = packageSplit.second;
} catch (PackageParserException e) {
mParseError = PackageManager.INSTALL_PARSE_FAILED_BAD_PACKAGE_NAME;
return null;
}

int type;

if (!TextUtils.isEmpty(splitName)) {
outError[0] = "Expected base APK, but found split " + splitName;
mParseError = PackageManager.INSTALL_PARSE_FAILED_BAD_PACKAGE_NAME;
return null;
}

final Package pkg = new Package(pkgName);
boolean foundApp = false;

TypedArray sa = res.obtainAttributes(attrs,
com.android.internal.R.styleable.AndroidManifest);
pkg.mVersionCode = pkg.applicationInfo.versionCode = sa.getInteger(
com.android.internal.R.styleable.AndroidManifest_versionCode, 0);
pkg.baseRevisionCode = sa.getInteger(
com.android.internal.R.styleable.AndroidManifest_revisionCode, 0);
pkg.mVersionName = sa.getNonConfigurationString(
com.android.internal.R.styleable.AndroidManifest_versionName, 0);
if (pkg.mVersionName != null) {
pkg.mVersionName = pkg.mVersionName.intern();
}
String str = sa.getNonConfigurationString(
com.android.internal.R.styleable.AndroidManifest_sharedUserId, 0);
if (str != null && str.length() > 0) {
String nameError = validateName(str, true, false);
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);
}

pkg.installLocation = sa.getInteger(
com.android.internal.R.styleable.AndroidManifest_installLocation,
PARSE_DEFAULT_INSTALL_LOCATION);
pkg.applicationInfo.installLocation = pkg.installLocation;

pkg.coreApp = attrs.getAttributeBooleanValue(null, "coreApp", false);

sa.recycle();

/* Set the global "forward lock" flag */
if ((flags & PARSE_FORWARD_LOCK) != 0) {
pkg.applicationInfo.privateFlags |= ApplicationInfo.PRIVATE_FLAG_FORWARD_LOCK;
}

/* Set the global "on SD card" flag */
if ((flags & PARSE_EXTERNAL_STORAGE) != 0) {
pkg.applicationInfo.flags |= ApplicationInfo.FLAG_EXTERNAL_STORAGE;
}

// Resource boolean are -1, so 1 means we don't know the value.
int supportsSmallScreens = 1;
int supportsNormalScreens = 1;
int supportsLargeScreens = 1;
int supportsXLargeScreens = 1;
int resizeable = 1;
int anyDensity = 1;

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;
}

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;
if (!parseBaseApplication(pkg, res, parser, attrs, flags, outError)) {
return null;
}
} else if (tagName.equals("overlay")) {
pkg.mTrustedOverlay = trustedOverlay;

sa = res.obtainAttributes(attrs,
com.android.internal.R.styleable.AndroidManifestResourceOverlay);
pkg.mOverlayTarget = sa.getString(
com.android.internal.R.styleable.AndroidManifestResourceOverlay_targetPackage);
pkg.mOverlayPriority = sa.getInt(
com.android.internal.R.styleable.AndroidManifestResourceOverlay_priority,
-1);
sa.recycle();

if (pkg.mOverlayTarget == null) {
outError[0] = "<overlay> does not specify a target package";
mParseError = PackageManager.INSTALL_PARSE_FAILED_MANIFEST_MALFORMED;
return null;
}
if (pkg.mOverlayPriority < 0 || pkg.mOverlayPriority > 9999) {
outError[0] = "<overlay> priority must be between 0 and 9999";
mParseError =
PackageManager.INSTALL_PARSE_FAILED_MANIFEST_MALFORMED;
return null;
}
XmlUtils.skipCurrentTag(parser);

} else if (tagName.equals("key-sets")) {
if (!parseKeySets(pkg, res, parser, attrs, outError)) {
return null;
}
} else if (tagName.equals("permission-group")) {
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")) {
if (!parseUsesPermission(pkg, res, parser, attrs)) {
return null;
}
} else if (tagName.equals("uses-permission-sdk-m")
|| tagName.equals("uses-permission-sdk-23")) {
if (!parseUsesPermission(pkg, res, parser, attrs)) {
return null;
}
} else if (tagName.equals("uses-configuration")) {
ConfigurationInfo cPref = new ConfigurationInfo();
sa = res.obtainAttributes(attrs,
com.android.internal.R.styleable.AndroidManifestUsesConfiguration);
cPref.reqTouchScreen = sa.getInt(
com.android.internal.R.styleable.AndroidManifestUsesConfiguration_reqTouchScreen,
Configuration.TOUCHSCREEN_UNDEFINED);
cPref.reqKeyboardType = sa.getInt(
com.android.internal.R.styleable.AndroidManifestUsesConfiguration_reqKeyboardType,
Configuration.KEYBOARD_UNDEFINED);
if (sa.getBoolean(
com.android.internal.R.styleable.AndroidManifestUsesConfiguration_reqHardKeyboard,
false)) {
cPref.reqInputFeatures |= ConfigurationInfo.INPUT_FEATURE_HARD_KEYBOARD;
}
cPref.reqNavigation = sa.getInt(
com.android.internal.R.styleable.AndroidManifestUsesConfiguration_reqNavigation,
Configuration.NAVIGATION_UNDEFINED);
if (sa.getBoolean(
com.android.internal.R.styleable.AndroidManifestUsesConfiguration_reqFiveWayNav,
false)) {
cPref.reqInputFeatures |= ConfigurationInfo.INPUT_FEATURE_FIVE_WAY_NAV;
}
sa.recycle();
pkg.configPreferences = ArrayUtils.add(pkg.configPreferences, cPref);

XmlUtils.skipCurrentTag(parser);

} else if (tagName.equals("uses-feature")) {
FeatureInfo fi = parseUsesFeature(res, attrs);
pkg.reqFeatures = ArrayUtils.add(pkg.reqFeatures, fi);

if (fi.name == null) {
ConfigurationInfo cPref = new ConfigurationInfo();
cPref.reqGlEsVersion = fi.reqGlEsVersion;
pkg.configPreferences = ArrayUtils.add(pkg.configPreferences, cPref);
}

XmlUtils.skipCurrentTag(parser);

} else if (tagName.equals("feature-group")) {
FeatureGroupInfo group = new FeatureGroupInfo();
ArrayList<FeatureInfo> features = null;
final int innerDepth = parser.getDepth();
while ((type = parser.next()) != XmlPullParser.END_DOCUMENT
&& (type != XmlPullParser.END_TAG || parser.getDepth() > innerDepth)) {
if (type == XmlPullParser.END_TAG || type == XmlPullParser.TEXT) {
continue;
}

final String innerTagName = parser.getName();
if (innerTagName.equals("uses-feature")) {
FeatureInfo featureInfo = parseUsesFeature(res, attrs);
// FeatureGroups are stricter and mandate that
// any <uses-feature> declared are mandatory.
featureInfo.flags |= FeatureInfo.FLAG_REQUIRED;
features = ArrayUtils.add(features, featureInfo);
} else {
Slog.w(TAG, "Unknown element under <feature-group>: " + innerTagName +
" at " + mArchiveSourcePath + " " +
parser.getPositionDescription());
}
XmlUtils.skipCurrentTag(parser);
}

if (features != null) {
group.features = new FeatureInfo[features.size()];
group.features = features.toArray(group.features);
}
pkg.featureGroups = ArrayUtils.add(pkg.featureGroups, group);

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

int minVers = 0;
String minCode = null;
int targetVers = 0;
String targetCode = null;

TypedValue val = sa.peekValue(
com.android.internal.R.styleable.AndroidManifestUsesSdk_minSdkVersion);
if (val != null) {
if (val.type == TypedValue.TYPE_STRING && val.string != null) {
targetCode = minCode = val.string.toString();
} else {
// If it's not a string, it's an integer.
targetVers = minVers = val.data;
}
}

val = sa.peekValue(
com.android.internal.R.styleable.AndroidManifestUsesSdk_targetSdkVersion);
if (val != null) {
if (val.type == TypedValue.TYPE_STRING && val.string != null) {
targetCode = minCode = val.string.toString();
} else {
// If it's not a string, it's an integer.
targetVers = val.data;
}
}

sa.recycle();

if (minCode != null) {
boolean allowedCodename = false;
for (String codename : SDK_CODENAMES) {
if (minCode.equals(codename)) {
allowedCodename = true;
break;
}
}
if (!allowedCodename) {
if (SDK_CODENAMES.length > 0) {
outError[0] = "Requires development platform " + minCode
+ " (current platform is any of "
+ Arrays.toString(SDK_CODENAMES) + ")";
} else {
outError[0] = "Requires development platform " + minCode
+ " but this is a release platform.";
}
mParseError = PackageManager.INSTALL_FAILED_OLDER_SDK;
return null;
}
} else if (minVers > SDK_VERSION) {
outError[0] = "Requires newer sdk version #" + minVers
+ " (current version is #" + SDK_VERSION + ")";
mParseError = PackageManager.INSTALL_FAILED_OLDER_SDK;
return null;
}

if (targetCode != null) {
boolean allowedCodename = false;
for (String codename : SDK_CODENAMES) {
if (targetCode.equals(codename)) {
allowedCodename = true;
break;
}
}
if (!allowedCodename) {
if (SDK_CODENAMES.length > 0) {
outError[0] = "Requires development platform " + targetCode
+ " (current platform is any of "
+ Arrays.toString(SDK_CODENAMES) + ")";
} else {
outError[0] = "Requires development platform " + targetCode
+ " but this is a release platform.";
}
mParseError = PackageManager.INSTALL_FAILED_OLDER_SDK;
return null;
}
// If the code matches, it definitely targets this SDK.
pkg.applicationInfo.targetSdkVersion
= android.os.Build.VERSION_CODES.CUR_DEVELOPMENT;
} else {
pkg.applicationInfo.targetSdkVersion = targetVers;
}
}

XmlUtils.skipCurrentTag(parser);

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

pkg.applicationInfo.requiresSmallestWidthDp = sa.getInteger(
com.android.internal.R.styleable.AndroidManifestSupportsScreens_requiresSmallestWidthDp,
0);
pkg.applicationInfo.compatibleWidthLimitDp = sa.getInteger(
com.android.internal.R.styleable.AndroidManifestSupportsScreens_compatibleWidthLimitDp,
0);
pkg.applicationInfo.largestWidthLimitDp = sa.getInteger(
com.android.internal.R.styleable.AndroidManifestSupportsScreens_largestWidthLimitDp,
0);

// This is a trick to get a boolean and still able to detect
// if a value was actually set.
supportsSmallScreens = sa.getInteger(
com.android.internal.R.styleable.AndroidManifestSupportsScreens_smallScreens,
supportsSmallScreens);
supportsNormalScreens = sa.getInteger(
com.android.internal.R.styleable.AndroidManifestSupportsScreens_normalScreens,
supportsNormalScreens);
supportsLargeScreens = sa.getInteger(
com.android.internal.R.styleable.AndroidManifestSupportsScreens_largeScreens,
supportsLargeScreens);
supportsXLargeScreens = sa.getInteger(
com.android.internal.R.styleable.AndroidManifestSupportsScreens_xlargeScreens,
supportsXLargeScreens);
resizeable = sa.getInteger(
com.android.internal.R.styleable.AndroidManifestSupportsScreens_resizeable,
resizeable);
anyDensity = sa.getInteger(
com.android.internal.R.styleable.AndroidManifestSupportsScreens_anyDensity,
anyDensity);

sa.recycle();

XmlUtils.skipCurrentTag(parser);

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

// 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.AndroidManifestProtectedBroadcast_name);

sa.recycle();

if (name != null && (flags&PARSE_IS_SYSTEM) != 0) {
if (pkg.protectedBroadcasts == null) {
pkg.protectedBroadcasts = new ArrayList<String>();
}
if (!pkg.protectedBroadcasts.contains(name)) {
pkg.protectedBroadcasts.add(name.intern());
}
}

XmlUtils.skipCurrentTag(parser);

} else if (tagName.equals("instrumentation")) {
if (parseInstrumentation(pkg, res, parser, attrs, outError) == null) {
return null;
}

} else if (tagName.equals("original-package")) {
sa = res.obtainAttributes(attrs,
com.android.internal.R.styleable.AndroidManifestOriginalPackage);

String orig =sa.getNonConfigurationString(
com.android.internal.R.styleable.AndroidManifestOriginalPackage_name, 0);
if (!pkg.packageName.equals(orig)) {
if (pkg.mOriginalPackages == null) {
pkg.mOriginalPackages = new ArrayList<String>();
pkg.mRealPackage = pkg.packageName;
}
pkg.mOriginalPackages.add(orig);
}

sa.recycle();

XmlUtils.skipCurrentTag(parser);

} else if (tagName.equals("adopt-permissions")) {
sa = res.obtainAttributes(attrs,
com.android.internal.R.styleable.AndroidManifestOriginalPackage);

String name = sa.getNonConfigurationString(
com.android.internal.R.styleable.AndroidManifestOriginalPackage_name, 0);

sa.recycle();

if (name != null) {
if (pkg.mAdoptPermissions == null) {
pkg.mAdoptPermissions = new ArrayList<String>();
}
pkg.mAdoptPermissions.add(name);
}

XmlUtils.skipCurrentTag(parser);

} else if (tagName.equals("uses-gl-texture")) {
// Just skip this tag
XmlUtils.skipCurrentTag(parser);
continue;

} else if (tagName.equals("compatible-screens")) {
// Just skip this tag
XmlUtils.skipCurrentTag(parser);
continue;
} else if (tagName.equals("supports-input")) {
XmlUtils.skipCurrentTag(parser);
continue;

} else if (tagName.equals("eat-comment")) {
// Just skip this tag
XmlUtils.skipCurrentTag(parser);
continue;

} else if (RIGID_PARSER) {
outError[0] = "Bad element under <manifest>: "
+ parser.getName();
mParseError = PackageManager.INSTALL_PARSE_FAILED_MANIFEST_MALFORMED;
return null;

} else {
Slog.w(TAG, "Unknown element under <manifest>: " + parser.getName()
+ " at " + mArchiveSourcePath + " "
+ parser.getPositionDescription());
XmlUtils.skipCurrentTag(parser);
continue;
}
}

if (!foundApp && pkg.instrumentation.size() == 0) {
outError[0] = "<manifest> does not contain an <application> or <instrumentation>";
mParseError = PackageManager.INSTALL_PARSE_FAILED_MANIFEST_EMPTY;
}

final int NP = PackageParser.NEW_PERMISSIONS.length;
StringBuilder implicitPerms = null;
for (int ip=0; ip<NP; ip++) {
final PackageParser.NewPermissionInfo npi
= PackageParser.NEW_PERMISSIONS[ip];
if (pkg.applicationInfo.targetSdkVersion >= npi.sdkVersion) {
break;
}
if (!pkg.requestedPermissions.contains(npi.name)) {
if (implicitPerms == null) {
implicitPerms = new StringBuilder(128);
implicitPerms.append(pkg.packageName);
implicitPerms.append(": compat added ");
} else {
implicitPerms.append(' ');
}
implicitPerms.append(npi.name);
pkg.requestedPermissions.add(npi.name);
}
}
if (implicitPerms != null) {
Slog.i(TAG, implicitPerms.toString());
}

final int NS = PackageParser.SPLIT_PERMISSIONS.length;
for (int is=0; is<NS; is++) {
final PackageParser.SplitPermissionInfo spi
= PackageParser.SPLIT_PERMISSIONS[is];
if (pkg.applicationInfo.targetSdkVersion >= spi.targetSdk
|| !pkg.requestedPermissions.contains(spi.rootPerm)) {
continue;
}
for (int in=0; in<spi.newPerms.length; in++) {
final String perm = spi.newPerms[in];
if (!pkg.requestedPermissions.contains(perm)) {
pkg.requestedPermissions.add(perm);
}
}
}

if (supportsSmallScreens < 0 || (supportsSmallScreens > 0
&& pkg.applicationInfo.targetSdkVersion
>= android.os.Build.VERSION_CODES.DONUT)) {
pkg.applicationInfo.flags |= ApplicationInfo.FLAG_SUPPORTS_SMALL_SCREENS;
}
if (supportsNormalScreens != 0) {
pkg.applicationInfo.flags |= ApplicationInfo.FLAG_SUPPORTS_NORMAL_SCREENS;
}
if (supportsLargeScreens < 0 || (supportsLargeScreens > 0
&& pkg.applicationInfo.targetSdkVersion
>= android.os.Build.VERSION_CODES.DONUT)) {
pkg.applicationInfo.flags |= ApplicationInfo.FLAG_SUPPORTS_LARGE_SCREENS;
}
if (supportsXLargeScreens < 0 || (supportsXLargeScreens > 0
&& pkg.applicationInfo.targetSdkVersion
>= android.os.Build.VERSION_CODES.GINGERBREAD)) {
pkg.applicationInfo.flags |= ApplicationInfo.FLAG_SUPPORTS_XLARGE_SCREENS;
}
if (resizeable < 0 || (resizeable > 0
&& pkg.applicationInfo.targetSdkVersion
>= android.os.Build.VERSION_CODES.DONUT)) {
pkg.applicationInfo.flags |= ApplicationInfo.FLAG_RESIZEABLE_FOR_SCREENS;
}
if (anyDensity < 0 || (anyDensity > 0
&& pkg.applicationInfo.targetSdkVersion
>= android.os.Build.VERSION_CODES.DONUT)) {
pkg.applicationInfo.flags |= ApplicationInfo.FLAG_SUPPORTS_SCREEN_DENSITIES;
}

return pkg;
}

首先解析了包名，之后详细解析了AndroidManifest下面的每一个节点。可以看到有application，overlay，key-sets，permission-group，permission，permission-tree，uses-permission等等节点，整个清单目录可以查看清单目录。android的四大组件主要是在application节点下，我们也主要看看这个节点的解析：

private boolean parseBaseApplication(Package owner, Resources res,
XmlPullParser parser, AttributeSet attrs, int flags, String[] outError)
throws XmlPullParserException, IOException {
final ApplicationInfo ai = owner.applicationInfo;
final String pkgName = owner.applicationInfo.packageName;

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

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,
Configuration.NATIVE_CONFIG_VERSION);
if (manageSpaceActivity != null) {
ai.manageSpaceActivityName = buildClassName(pkgName, manageSpaceActivity,
outError);
}

boolean allowBackup = sa.getBoolean(
com.android.internal.R.styleable.AndroidManifestApplication_allowBackup, true);
if (allowBackup) {
.............
}

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

ai.icon = sa.getResourceId(
com.android.internal.R.styleable.AndroidManifestApplication_icon, 0);
ai.logo = sa.getResourceId(
com.android.internal.R.styleable.AndroidManifestApplication_logo, 0);
ai.banner = sa.getResourceId(
com.android.internal.R.styleable.AndroidManifestApplication_banner, 0);
ai.theme = sa.getResourceId(
com.android.internal.R.styleable.AndroidManifestApplication_theme, 0);
ai.descriptionRes = sa.getResourceId(
com.android.internal.R.styleable.AndroidManifestApplication_description, 0);

..............
owner.baseHardwareAccelerated = sa.getBoolean(
com.android.internal.R.styleable.AndroidManifestApplication_hardwareAccelerated,
owner.applicationInfo.targetSdkVersion >= Build.VERSION_CODES.ICE_CREAM_SANDWICH);
if (owner.baseHardwareAccelerated) {
ai.flags |= ApplicationInfo.FLAG_HARDWARE_ACCELERATED;
}

if (sa.getBoolean(
com.android.internal.R.styleable.AndroidManifestApplication_hasCode,
true)) {
ai.flags |= ApplicationInfo.FLAG_HAS_CODE;
}
..............

String str;
str = sa.getNonConfigurationString(
com.android.internal.R.styleable.AndroidManifestApplication_permission, 0);
ai.permission = (str != null && str.length() > 0) ? str.intern() : null;

if (owner.applicationInfo.targetSdkVersion >= Build.VERSION_CODES.FROYO) {
str = sa.getNonConfigurationString(
com.android.internal.R.styleable.AndroidManifestApplication_taskAffinity,
Configuration.NATIVE_CONFIG_VERSION);
} else {
// Some older apps have been seen to use a resource reference
// here that on older builds was ignored (with a warning).  We
// need to continue to do this for them so they don't break.
str = sa.getNonResourceString(
com.android.internal.R.styleable.AndroidManifestApplication_taskAffinity);
}
ai.taskAffinity = buildTaskAffinityName(ai.packageName, ai.packageName,
str, outError);

if (outError[0] == null) {
CharSequence pname;
if (owner.applicationInfo.targetSdkVersion >= Build.VERSION_CODES.FROYO) {
pname = sa.getNonConfigurationString(
com.android.internal.R.styleable.AndroidManifestApplication_process,
Configuration.NATIVE_CONFIG_VERSION);
} else {
// Some older apps have been seen to use a resource reference
// here that on older builds was ignored (with a warning).  We
// need to continue to do this for them so they don't break.
pname = sa.getNonResourceString(
com.android.internal.R.styleable.AndroidManifestApplication_process);
}
ai.processName = buildProcessName(ai.packageName, null, pname,
flags, mSeparateProcesses, outError);

ai.enabled = sa.getBoolean(
com.android.internal.R.styleable.AndroidManifestApplication_enabled, true);

if (sa.getBoolean(
com.android.internal.R.styleable.AndroidManifestApplication_isGame, false)) {
ai.flags |= ApplicationInfo.FLAG_IS_GAME;
}

if (false) {
if (sa.getBoolean(
com.android.internal.R.styleable.AndroidManifestApplication_cantSaveState,
false)) {
ai.privateFlags |= ApplicationInfo.PRIVATE_FLAG_CANT_SAVE_STATE;

// A heavy-weight application can not be in a custom process.
// We can do direct compare because we intern all strings.
if (ai.processName != null && ai.processName != ai.packageName) {
outError[0] = "cantSaveState applications can not use custom processes";
}
}
}
}

ai.uiOptions = sa.getInt(
com.android.internal.R.styleable.AndroidManifestApplication_uiOptions, 0);

sa.recycle();

if (outError[0] != null) {
mParseError = PackageManager.INSTALL_PARSE_FAILED_MANIFEST_MALFORMED;
return false;
}

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

owner.activities.add(a);

} 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);

} 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);

} 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);

} else if (tagName.equals("activity-alias")) {
Activity a = parseActivityAlias(owner, res, parser, attrs, flags, outError);
if (a == null) {
mParseError = PackageManager.INSTALL_PARSE_FAILED_MANIFEST_MALFORMED;
return false;
}

owner.activities.add(a);

} else if (parser.getName().equals("meta-data")) {
// note: application meta-data is stored off to the side, so it can
// remain null in the primary copy (we like to avoid extra copies because
// it can be large)
if ((owner.mAppMetaData = parseMetaData(res, parser, attrs, owner.mAppMetaData,
outError)) == null) {
mParseError = PackageManager.INSTALL_PARSE_FAILED_MANIFEST_MALFORMED;
return false;
}

} else if (tagName.equals("library")) {
sa = res.obtainAttributes(attrs,
com.android.internal.R.styleable.AndroidManifestLibrary);

// Note: don't allow this value to be a reference to a resource
// that may change.
String lname = sa.getNonResourceString(
com.android.internal.R.styleable.AndroidManifestLibrary_name);

sa.recycle();

if (lname != null) {
lname = lname.intern();
if (!ArrayUtils.contains(owner.libraryNames, lname)) {
owner.libraryNames = ArrayUtils.add(owner.libraryNames, lname);
}
}

XmlUtils.skipCurrentTag(parser);

} else if (tagName.equals("uses-library")) {
sa = res.obtainAttributes(attrs,
com.android.internal.R.styleable.AndroidManifestUsesLibrary);

// Note: don't allow this value to be a reference to a resource
// that may change.
String lname = sa.getNonResourceString(
com.android.internal.R.styleable.AndroidManifestUsesLibrary_name);
boolean req = sa.getBoolean(
com.android.internal.R.styleable.AndroidManifestUsesLibrary_required,
true);

sa.recycle();

if (lname != null) {
lname = lname.intern();
if (req) {
owner.usesLibraries = ArrayUtils.add(owner.usesLibraries, lname);
} else {
owner.usesOptionalLibraries = ArrayUtils.add(
owner.usesOptionalLibraries, lname);
}
}

XmlUtils.skipCurrentTag(parser);

} else if (tagName.equals("uses-package")) {
// Dependencies for app installers; we don't currently try to
// enforce this.
XmlUtils.skipCurrentTag(parser);

} else {
if (!RIGID_PARSER) {
Slog.w(TAG, "Unknown element under <application>: " + tagName
+ " at " + mArchiveSourcePath + " "
+ parser.getPositionDescription());
XmlUtils.skipCurrentTag(parser);
continue;
} else {
outError[0] = "Bad element under <application>: " + tagName;
mParseError = PackageManager.INSTALL_PARSE_FAILED_MANIFEST_MALFORMED;
return false;
}
}
}

modifySharedLibrariesForBackwardCompatibility(owner);

if (hasDomainURLs(owner)) {
owner.applicationInfo.privateFlags |= ApplicationInfo.PRIVATE_FLAG_HAS_DOMAIN_URLS;
} else {
owner.applicationInfo.privateFlags &= ~ApplicationInfo.PRIVATE_FLAG_HAS_DOMAIN_URLS;
}

return true;
}

其中省略号省略了部分代码，可以看到解析了application节点下的所有信息，比如activity，receiver，provider，library，uses-library，service等信息，同时将解析后的每一个属性生成相应的对象，添加到传入的package里面。这些信息最后都会在PackageManagerService中用到。到此解析就已经完成了。

我们在回到PackageManagerService的installPackageLI函数中，看到解析完成后，继续做了collectCertificates与collectManifestDigest操作。collectCertificates做签名验证，collectManifestDigest主要做包的清单摘要收集，这主要适合用来比较两个包的表现是一样的。

总结

到此就真的分析完成了整个解析过程，很多都是大概的侃侃而谈，没有一步一步的去详细解析，需要了解的人可以看源代码来进行理解，最后，整篇文字可能有理解错误的地方，望指正。