PMS负责扫描系统中特定的目录，找到里面的apk文件，然后对这些文件进行解析得到相关信息，然后完成安装的过程。
PMS安装APP，其实也就是解析APP配置文件AndroidManifest.xml的过程。
解析apk文件的核心类是PackageParser，这个类负责从apk文件中解析各种标签以及权限等信息，并将这些信息注册进PMS。
以下就以4.2.2_r1版本的PackageParser为例来看看PackageParser是如何解析apk文件的。
PackageParser的核心方法是parsePackage（）
public Package parsePackage(File sourceFile, String destCodePath,
DisplayMetrics metrics, int flags) {
mParseError = PackageManager.INSTALL_SUCCEEDED;
/** 首先对apk文件进行检查，如果出错则打印相应的错误日志并返回null. **/
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);
/** 这里则是尝试读取AndroidManifest.xml文件和资源文件以及通过apk来初始化AssetManager.
如果出错，则打印相应的日志并记录错误同时返回空值；否则将调用另一个parsePackage方法继续解析apk.
另一个方法的解析贴在本方法的下方。 **/
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);
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 {
// XXXX todo: need to figure out correct configuration.
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;
}
另外一个parsePackage()方法，该方法为私有方法，在上面个公有的parsePackage()方法中调用：
private Package parsePackage(
Resources res, XmlResourceParser parser, int flags, String[] outError)
throws XmlPullParserException, IOException {
/** 由于XmlResourceParser实现了AttributeSet接口，因此这里直接当作AttributeSet来使用 **/
AttributeSet attrs = parser;
mParseInstrumentationArgs = null;
mParseActivityArgs = null;
mParseServiceArgs = null;
mParseProviderArgs = null;
/** 先检查包名，如果包名有问题则直接失败返回 **/
String pkgName = parsePackageName(parser, attrs, flags, outError);
if (pkgName == null) {
mParseError = PackageManager.INSTALL_PARSE_FAILED_BAD_PACKAGE_NAME;
return null;
}
int type;
/** coreApp 同加密机制有关 **/
if (mOnlyCoreApps) {
boolean core = attrs.getAttributeBooleanValue(null, "coreApp", false);
if (!core) {
mParseError = PackageManager.INSTALL_SUCCEEDED;
return null;
}
}
final Package pkg = new Package(pkgName);
boolean foundApp = false;
/** 获取版本号、版本名和shareUserId,并检查shareUserId是否正确 **/
TypedArray sa = res.obtainAttributes(attrs,
com.android.internal.R.styleable.AndroidManifest);
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();
}
String str = sa.getNonConfigurationString(
com.android.internal.R.styleable.AndroidManifest_sharedUserId, 0);
if (str != null && str.length() > 0) {
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();
pkg.installLocation = sa.getInteger(
com.android.internal.R.styleable.AndroidManifest_installLocation,
PARSE_DEFAULT_INSTALL_LOCATION);
pkg.applicationInfo.installLocation = pkg.installLocation;
/* Set the global "forward lock" flag */
if ((flags & PARSE_FORWARD_LOCK) != 0) {
pkg.applicationInfo.flags |= ApplicationInfo.FLAG_FORWARD_LOCK;
}
/* Set the global "on SD card" flag */
if ((flags & PARSE_ON_SDCARD) != 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();
/** 开始迭代处理各种标签
对于大多数Android开发者来说，这里最重要的是parseApplication.
这里会将Application标签下的各种信息解析出来，并注册进PMS.
迭代检查完所有预定义的标签之后如果没有问题，则将记录了apk信息的Package对象返回。**/
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 (!parseApplication(pkg, res, parser, attrs, flags, 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")) {
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();
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.add(cPref);
XmlUtils.skipCurrentTag(parser);
} else if (tagName.equals("uses-feature")) {
FeatureInfo fi = new FeatureInfo();
sa = res.obtainAttributes(attrs,
com.android.internal.R.styleable.AndroidManifestUsesFeature);
// Note: don't allow this value to be a reference to a resource
// that may change.
fi.name = sa.getNonResourceString(
com.android.internal.R.styleable.AndroidManifestUsesFeature_name);
if (fi.name == null) {
fi.reqGlEsVersion = sa.getInt(
com.android.internal.R.styleable.AndroidManifestUsesFeature_glEsVersion,
FeatureInfo.GL_ES_VERSION_UNDEFINED);
}
if (sa.getBoolean(
com.android.internal.R.styleable.AndroidManifestUsesFeature_required,
true)) {
fi.flags |= FeatureInfo.FLAG_REQUIRED;
}
sa.recycle();
if (pkg.reqFeatures == null) {
pkg.reqFeatures = new ArrayList<FeatureInfo>();
}
pkg.reqFeatures.add(fi);
if (fi.name == null) {
ConfigurationInfo cPref = new ConfigurationInfo();
cPref.reqGlEsVersion = fi.reqGlEsVersion;
pkg.configPreferences.add(cPref);
}
XmlUtils.skipCurrentTag(parser);
} 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) {
if (!minCode.equals(SDK_CODENAME)) {
if (SDK_CODENAME != null) {
outError[0] = "Requires development platform " + minCode
+ " (current platform is " + SDK_CODENAME + ")";
} 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) {
if (!targetCode.equals(SDK_CODENAME)) {
if (SDK_CODENAME != null) {
outError[0] = "Requires development platform " + targetCode
+ " (current platform is " + SDK_CODENAME + ")";
} 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("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);
pkg.requestedPermissionsRequired.add(Boolean.TRUE);
}
}
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);
pkg.requestedPermissionsRequired.add(Boolean.TRUE);
}
}
}
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;
}
在解析以上方法中调用的类似parseApplication()、parsePermission() ...之类的方法就不贴出来了，他们都是从属于parsePackage()，负责解析相应标签的。
而从源码中也可以看到，整个PackageParser做的工作就是从apk中AndroidManifest.xml里各个属性和标签的内容。
