在前面两篇自己动手编译最新Android源码及自己动手调试Android源码中,我们掌握了Android源码的编译以及调试,现在呢,我们在这基础上分析一些源码的实现.首先从PMS服务开始.
PMS服务即PackageManagerService,主要用来进行APK的管理任务.但是今天,我们并不直接分析PMS的源码,而是从一个工具类PackageParse说起.
首先来认识PackageParser类,它主要用来解析手机上的apk文件(支持Single APK和Multiple APK),主要包含两个过程
- APK->Package:解析APK文件为Package对象的过程
- Package->PackageInfo:由Package对象生成PackageInfo的过程
介于不少童鞋不了解Single APK和Multiple APK,在这里做个简单解释:
Single APK是我们通常所开发的APK,即一个应用只有一个apk文件.而Google Play还允许你为一个应用中发布不同的apk文件,这些apk文件适用于不同设备.举例说明,假设你现在开发了一款APP叫做Monkey,但是目前该APP由于体积太大或者其他因素导致不能同时适用于手机和平板,此时你就可将原先的Monkey.apk拆分为了Monkey-Phone.apk和Monkey-Tablet,分别用于运行在Android手机和Android平板,只要保存两者拥有相同的包名,并用相同key进行签名就可以在发布Monkey应用的时候,一同发布Monkey-Phone.apk和Moneky-Tablet.apk,那么这种一个应用拥有多个APK文件的程序就称之为Multiple APK.
更多信息查看官网:multiple-apks
解析APK文件为Package对象
该过程目的是通过解析磁盘上的APK文件来生成与之相关的Package对象.而Pakcage对象是APK经过完整解析之后的结果.
该过程主要涉及到一系列parseXXX()格式的方法,起始方法是public Package parsePackage(File packageFile, int flags),那么我们就从该方法开始分析其流程:
public Package parsePackage(File packageFile, int flags) throws PackageParserException {
if (packageFile.isDirectory()) {
//多个apk文件的目录
return parseClusterPackage(packageFile, flags);
} else {
//单一APK文件
return parseMonolithicPackage(packageFile, flags);
}
}
该方法接受两个参数packageFile和flags.并根据packageFile是否是文件目录来确定具体的解析流程.通常我们都是Single APK,因此我们重点关注Single APK的解析,不难发现其具体解析过程给委托给parseMonolithicPackage(packageFile, flags)方法:
public Package parseMonolithicPackage(File apkFile, int flags) throws PackageParserException {
//如果是核心应用则以更轻量级的方式进行解析后,判断是否是核心应用,非核心应用不执行解析过程
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 {
//调用parseBaseAPK()继续解析操作
final Package pkg = parseBaseApk(apkFile, assets, flags);
pkg.codePath = apkFile.getAbsolutePath();
return pkg;
} finally {
IoUtils.closeQuietly(assets);
}
}
在该方法中首先通过mOnlyCoreApps属性判断当前系统是不是只解析核心APK,默认是全部解析.至于什么是核心APK后面再说.现在我们继续关注其解析过程.
这里其解析操作继续由parseBaseApk(apkFile, assets, flags)完成:
private Package parseBaseApk(File apkFile, AssetManager assets, int flags)
throws PackageParserException {
...
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);
//为AndroidManifest.xml生成xml文件解析器
parser = assets.openXmlResourceParser(cookie, ANDROID_MANIFEST_FILENAME);
final String[] outError = new String[1];
final Package pkg = parseBaseApk(res, parser, flags, outError);
...
pkg.baseCodePath = apkPath;
pkg.mSignatures = null;
return pkg;
}
...
}而真正的解析又是通过该方法的同名函数:parseBaseApk(Resources res, XmlResourceParser parser, int flags,String[] outError)完成的,为了突出重点,我对其方法进行了简化:
private Package parseBaseApk(Resources res, XmlResourceParser parser, int flags,
String[] outError) throws XmlPullParserException, IOException {
//....省略多行代码....
//循环解析AndroidManifest.xml中的元素
while ((type = parser.next()) != XmlPullParser.END_DOCUMENT
&& (type != XmlPullParser.END_TAG || parser.getDepth() > outerDepth)) {
if (tagName.equals("application")) {
//....省略多行代码,重点关注其中调用的parseBaseApplication()方法
}else if (tagName.equals("overlay")) {
//....省略多行代码....
}else if (tagName.equals("key-sets")){
//paseKeySets()
}else if (tagName.equals("permission-group")) {
parsePermissionGroup(pkg, flags, res, parser, attrs,
}else if (tagName.equals("permission")) {
//parsePermission
}else if (tagName.equals("uses-configuration")) {
//....省略多行代码....
}else if (tagName.equals("uses-feature")) {
//parseUsesFeature()
}else if (tagName.equals("feature-group")) {
//....省略多行代码....
}else if (tagName.equals("uses-sdk")) {
//....省略多行代码....
}else if (tagName.equals("supports-screens")) {
//....省略多行代码....
}else if (tagName.equals("protected-broadcast")) {
//....省略多行代码....
}else if (tagName.equals("instrumentation")) {
//....省略多行代码....
}else if (tagName.equals("original-package")) {
//....省略多行代码....
}else if (tagName.equals("adopt-permissions")) {
//....省略多行代码....
}
//....省略多行代码....
}
//....省略多汗代码....
}
不难发现这里通过很多parseXXX()方法解析相应的数据,比如:parseBaseApplication(),parseKeySets(),parsePermissionGroup(),parseUsesPermission()等等.
下面,我们重点关注Application标签的解析,即:parseBaseApplication()方法:
private boolean parseBaseApplication(Package owner, Resources res,
XmlPullParser parser, AttributeSet attrs, int flags, String[] outError)
throws XmlPullParserException, IOException {
//....省略对Application元素属性解析多行代码....
//解析Application下的子元素结点,如activity,receiver,service等
while ((type = parser.next()) != XmlPullParser.END_DOCUMENT
&& (type != XmlPullParser.END_TAG || parser.getDepth() > innerDepth)) {
if (tagName.equals("activity")) {
//....省略多行代码,主要关注parseActivity()....
} else if (tagName.equals("receiver")) {
//....省略多行代码,主要关注parseActivity()....
}else if (tagName.equals("service")) {
//....省略多行代码,主要关注parseService()....
}else if (tagName.equals("provider")) {
//....省略多行代码,主要关注parseProvider()....
}else if (tagName.equals("activity-alias")) {
//....省略多行代码,主要关注parseActivityAlias()...
}else if (parser.getName().equals("meta-data")) {
//....省略多行代码,重点关注parseMetaData()....
}else if (tagName.equals("library")) {
//....省略多行代码....
}else if (tagName.equals("uses-library")) {
//....省略多行代码....
}else if (tagName.equals("uses-package")) {
//....省略多行代码....
}else{
//....省略多行代码....
}
}
return true;
}
在解析Application下子元素结点时,同样也是通过很多parseXXX()方法来完成的.比如在解析activity结点时是通过parseActivity()来完成的,其余自行查阅代码.
另外你可能已经注意到对receiver的解析也是通过parseActivity()实现的.
到此为止,整个为止,解析的整个流程完成,并返回一个Package对象.
附:PackageParser中所有相关解析方法
由Package对象生成PackageInfo
该过程的目的是从Package中提取相关属性,并封装成PackageInfo类型的对象.
该过程主要涉及到一系列generateXXXInfo()格式的方法,起始方法是generatePackageInfo(),那么我们就从该方法开始分析其流程:
public static PackageInfo generatePackageInfo(PackageParser.Package p,
int gids[], int flags, long firstInstallTime, long lastUpdateTime,
ArraySet<String> grantedPermissions, PackageUserState state) {
return generatePackageInfo(p, gids, flags, firstInstallTime, lastUpdateTime,
grantedPermissions, state, UserHandle.getCallingUserId());
}
不难看出这里由调用了其同名方法generatePackageInfo(PackageParser.Package p,
int gids[], int flags, long firstInstallTime, long lastUpdateTime,
ArraySet<String> grantedPermissions, PackageUserState state, int userId)来进行继续解析工作:
public static PackageInfo generatePackageInfo(PackageParser.Package p,
int gids[], int flags, long firstInstallTime, long lastUpdateTime,
ArraySet<String> grantedPermissions, PackageUserState state, int userId)
if (!checkUseInstalledOrHidden(flags, state)) {
return null;
}
//从Package对象p中取出一系列的属性值用来初始化pi
PackageInfo pi = new PackageInfo();
pi.packageName = p.packageName;
pi.splitNames = p.splitNames;
pi.versionCode = p.mVersionCode;
pi.baseRevisionCode = p.baseRevisionCode;
pi.splitRevisionCodes = p.splitRevisionCodes;
pi.versionName = p.mVersionName;
pi.sharedUserId = p.mSharedUserId;
pi.sharedUserLabel = p.mSharedUserLabel;
pi.applicationInfo = generateApplicationInfo(p, flags, state, userId);
pi.installLocation = p.installLocation;
pi.coreApp = p.coreApp;
if ((pi.applicationInfo.flags&ApplicationInfo.FLAG_SYSTEM) != 0
|| (pi.applicationInfo.flags&ApplicationInfo.FLAG_UPDATED_SYSTEM_APP) != 0) {
pi.requiredForAllUsers = p.mRequiredForAllUsers;
}
pi.restrictedAccountType = p.mRestrictedAccountType;
pi.requiredAccountType = p.mRequiredAccountType;
pi.overlayTarget = p.mOverlayTarget;
pi.firstInstallTime = firstInstallTime;
pi.lastUpdateTime = lastUpdateTime;
if ((flags&PackageManager.GET_GIDS) != 0) {
pi.gids = gids;
}
if ((flags&PackageManager.GET_CONFIGURATIONS) != 0) {
//....省略多行代码....
}
if ((flags&PackageManager.GET_ACTIVITIES) != 0) {
//....省略多行代码,关注generateActivityInfo()....
}
if ((flags&PackageManager.GET_RECEIVERS) != 0) {
//....省略多行代码,关注generateActivityInfo()....
}
if ((flags&PackageManager.GET_SERVICES) != 0) {
//....省略多行代码,关注generateServiceInfo()....
}
if ((flags&PackageManager.GET_PROVIDERS) != 0) {
//....省略多行代码,关注generateProviderInfo()....
}
if ((flags&PackageManager.GET_INSTRUMENTATION) != 0) {
//....省略多行代码,关注generateInstrumentationInfo()....
}
if ((flags&PackageManager.GET_PERMISSIONS) != 0) {
//....省略多行代码,generatePermissionInfo....
}
if ((flags&PackageManager.GET_SIGNATURES) != 0) {
//....省略多行代码....
}
return pi;
}
上面的过程主要从Package对象取出一系列的属性用来初始化PackageInfo对象,该过程不再涉及磁盘文件的解析操作.
和解析过程相对,该过程借助了很多generateXXXInfo()方法来实现.在解析过程中对于Application元素的解析提供了parseApplication(),而在该过程中也提供了generateApplicationInfo()来实现Application的取值操作
附:PackageParser中所有相关的generate方法
中途小结
到现在为止,我们已经了解Package的生成和PackageInfo生成,不难发现Package的生成是以磁盘APK文件作为输入,而PackageInfo是以Package对象作为输入.得益于Google工程师良好的设计,PackageParse具有非常好的对称性,非常容易理解.在这里,我只是简单的介绍了该类,对于具体的操作并没有深入的说明,其原因在于,其核心就是通过使用Pull Parser对xml文件进行解析的操作.
附:PackageParser所有内部类:
细心的同学已经发现在上面所示的内部类中也存在Activity,Service等类,要注意这些并不是我们平常使用的Activity组件.PackageParser中的内部类,如Activity,Service,Provider,Permission,皆对应于AndroidManifest.xml文件中的某个标签,用于存储解析出来相关的信息.
这里我们同样用类图来简单的描述期间的关系:
相关实体类
接下来,我们来介绍与上述过程相关的几个实体类,以便你有一个宏观的认识,从而为理解后面的PMS打下基础.
对于这几个实体类,我们值做简单的说明,其具体的点还是需要我们自己进行深究.
Package
PackageParser的静态内部类,代表磁盘上APK文件完整解析后的对象,相当于在内存中Package的对象是对磁盘APK的描述.这里我们只需要关注其属性即可,大部分属性对你而来都是很熟悉的:
public final static class Package {
public String packageName;
/** Names of any split APKs, ordered by parsed splitName */
public String[] splitNames;
//apk文件在磁盘的路径.可能是一个apk的路径,也可能是包含多个apk文件的目录
public String codePath;
/** Path of base APK */
public String baseCodePath;
/** Paths of any split APKs, ordered by parsed splitName */
public String[] splitCodePaths;
/** Revision code of base APK */
public int baseRevisionCode;
/** Revision codes of any split APKs, ordered by parsed splitName */
public int[] splitRevisionCodes;
/** Flags of any split APKs; ordered by parsed splitName */
public int[] splitFlags;
public boolean baseHardwareAccelerated;
public final ApplicationInfo applicationInfo = new ApplicationInfo();
//权限
public final ArrayList<Permission> permissions = new ArrayList<Permission>(0);
public final ArrayList<PermissionGroup> permissionGroups = new ArrayList<PermissionGroup>(0);
//四大组件Activity,Receiver,Service,Provider
public final ArrayList<Activity> activities = new ArrayList<Activity>(0);
public final ArrayList<Activity> receivers = new ArrayList<Activity>(0);
public final ArrayList<Provider> providers = new ArrayList<Provider>(0);
public final ArrayList<Service> services = new ArrayList<Service>(0);
public final ArrayList<Instrumentation> instrumentation = new ArrayList<Instrumentation>(0);
public final ArrayList<String> requestedPermissions = new ArrayList<String>();
public final ArrayList<Boolean> requestedPermissionsRequired = new ArrayList<Boolean>();
public ArrayList<String> protectedBroadcasts;
public ArrayList<String> libraryNames = null;
public ArrayList<String> usesLibraries = null;
public ArrayList<String> usesOptionalLibraries = null;
public String[] usesLibraryFiles = null;
public ArrayList<ActivityIntentInfo> preferredActivityFilters = null;
public ArrayList<String> mOriginalPackages = null;
public String mRealPackage = null;
public ArrayList<String> mAdoptPermissions = null;
// We store the application meta-data independently to avoid multiple unwanted references
public Bundle mAppMetaData = null;
// The version code declared for this package.
public int mVersionCode;
// The version name declared for this package.
public String mVersionName;
// The shared user id that this package wants to use.
public String mSharedUserId;
// The shared user label that this package wants to use.
public int mSharedUserLabel;
// Signatures that were read from the package.
public Signature[] mSignatures;
public Certificate[][] mCertificates;
// For use by package manager service for quick lookup of
// preferred up order.
public int mPreferredOrder = 0;
// For use by package manager to keep track of where it needs to do dexopt.
public final ArraySet<String> mDexOptPerformed = new ArraySet<>(4);
// For use by package manager to keep track of when a package was last used.
public long mLastPackageUsageTimeInMills;
// // User set enabled state.
// public int mSetEnabled = PackageManager.COMPONENT_ENABLED_STATE_DEFAULT;
//
// // Whether the package has been stopped.
// public boolean mSetStopped = false;
// Additional data supplied by callers.
public Object mExtras;
// Whether an operation is currently pending on this package
public boolean mOperationPending;
// Applications hardware preferences
public ArrayList<ConfigurationInfo> configPreferences = null;
// Applications requested features
public ArrayList<FeatureInfo> reqFeatures = null;
// Applications requested feature groups
public ArrayList<FeatureGroupInfo> featureGroups = null;
public int installLocation;
public boolean coreApp;
/* An app that‘s required for all users and cannot be uninstalled for a user */
public boolean mRequiredForAllUsers;
/* The restricted account authenticator type that is used by this application */
public String mRestrictedAccountType;
/* The required account type without which this application will not function */
public String mRequiredAccountType;
/**
* 代表一个包文件的摘要,用于确定两个package是否不一致
*/
public ManifestDigest manifestDigest;
public String mOverlayTarget;
public int mOverlayPriority;
public boolean mTrustedOverlay;
/**
* Data used to feed the KeySetManagerService
*/
public ArraySet<PublicKey> mSigningKeys;
public ArraySet<String> mUpgradeKeySets;
public ArrayMap<String, ArraySet<PublicKey>> mKeySetMapping;
public String cpuAbiOverride;
}PackageInfo
该类代表包的整体描述信息,即AndroidManifest.xml中的信息.如果说Package在内存中代表完整的APK描述,那么PackageInfo则是其子集,来简单的看一下其代码:
public class PackageInfo implements Parcelable {
public String packageName;
public String[] splitNames;
public int versionCode;
public String versionName;
public int baseRevisionCode;
public int[] splitRevisionCodes;
public String sharedUserId;
public int sharedUserLabel;
public ApplicationInfo applicationInfo;
public long firstInstallTime;
public long lastUpdateTime;
public int[] gids;
public ActivityInfo[] activities;
public ActivityInfo[] receivers;
public ServiceInfo[] services;
public ProviderInfo[] providers;
public InstrumentationInfo[] instrumentation;
public PermissionInfo[] permissions;
public String[] requestedPermissions;
public int[] requestedPermissionsFlags;
public Signature[] signatures;
public ConfigurationInfo[] configPreferences;
public FeatureInfo[] reqFeatures;
public FeatureGroupInfo[] featureGroups;
}对比Package和PackageInfo很容易发现期间的关系,接下来顺便介绍PackageInfo中涉及到的实体类:
| 类名 | 描述 |
|---|---|
| ActivityInfo | 该实体类代表AndroidManiest.xml中的<activity>和<recevier>元素的信息 |
| ServiceInfo | 该实体类代表AndroidManiest.xml中的<service>元素中的信息 |
| ProviderInfo | 该实体类代表AndroidManiest.xml中的<provider>元素的信息 |
| InstrumentationInfo | 该实体类代表AndroidManiest.xml中的<instrumentation>元素的信息 |
| PermissionInfo | 该实体类代表AndroidManiest.xml中的<permission>元素的信息 |
| ConfigurationInfo | 关于程序要求的硬件信息,该实体类代表AndroidManiest.xml中<uses-configuration>和<uses-feature>元素的信息. |
| FeatureInfo | 该实体类代表AndroidManiest.xml中的<uses-feature>元素的信息 |
| FeatureGroupInfo | 该实体类代表AndroidManiest.xml中的<feature-group>元素的信息 |
| ManifestDigest | 代表一个包文件的摘要信息 |
这里我们用一张类图来描述其类间的关系:
总结
到现在PackageParser的基本解释已经完成,之所以在分析PMS之前先来谈PackageParser的原因在于,该工具类可以脱离上下文,单独进行理解,而无关你目前的状态,这也就避免我们面对一大堆源码,在阅读过程找不到侧重点的问题.接下来,是对PackageManager的分析.