【Android 系统开发】_“核心服务”篇 -- PMS（3）之 “PackageManager”

开篇

PackageManagerService 系列文章以下（基于 Android 9.0 源码）

         🍁   Framework 核心服务之 PackageManagerService 钻研（1）- 启动流程                          
         🍁   Framework 核心服务之 PackageManagerService 钻研（2）- 构造函数
         🍁   Framework 核心服务之 PackageManagerService 钻研（3）- PackageManager
         🍁   Framework 核心服务之 PackageManagerService 钻研（4）- PackageInstaller
         🍁   Framework 核心服务之 PackageManagerService 钻研（5）- APK 安装流程（PackageInstaller）
         🍁   Framework 核心服务之 PackageManagerService 钻研（6）- APK 安装流程（PMS）
         🍁   Framework 核心服务之 PackageManagerService 钻研（7）- PackageParser

核心源码

关键类	路径
Context.java	frameworks/base/core/java/android/content/Context.java
ContextImpl.java	frameworks/base/core/java/android/app/ContextImpl.java
PackageManager.java	frameworks/base/core/java/android/content/pm/PackageManager.java
ApplicationPackageManager.java	frameworks/base/core/java/android/app/ApplicationPackageManager.java
ActivityThread.java	frameworks/base/core/java/android/app/ActivityThread.java

PackageManager

简介

PackageManager 是一个抽象类：

/**
 * Class for retrieving various kinds of information related to the application
 * packages that are currently installed on the device.
 *
 * You can find this class through {@link Context#getPackageManager}.
 */
public abstract class PackageManager {

注释能够看出：PackageManager 这个类是检测当前已经安装在当前设备上的应用程序包的信息。你能够调用 Context 类的 getPackageManager() 方法来获取 PackageManager。

安装 APK

PackageManager 是一个实际上管理应用程序安装、卸载和升级的 API。当咱们安装 APK 文件时，PackageManager 会解析 APK 包文件和显示确认信息。当咱们点击 OK 按钮后，PackageManager 会调用一个叫 "InstallPackage" 的方法，这个方法有 4 个参数，也就是 uri、installFlags、observer、installPackagename。PackageManager 会启动一个叫 "package" 的 servcie 服务，如今全部模糊的东西会发生在这个 service 中。

实现功能

        ✨ 一、安装、卸载应用
        ✨ 二、查询 permission 相关信息
        ✨ 三、查询 Application 相关信息(application、activity、receiver、service、provider 及相应属性等)
        ✨ 四、查询已安装应用
        ✨ 五、增长、删除 permission
        ✨ 六、清除用户数据、缓存、代码等

抽象方法

getPackageInfo

/**
     * Retrieve overall information about an application package that is
     * installed on the system.
     *
     * @param packageName The full name (i.e. com.google.apps.contacts) of the
     *            desired package.
     * @param flags Additional option flags to modify the data returned.
     * @return A PackageInfo object containing information about the package. If
     *         flag {@code MATCH_UNINSTALLED_PACKAGES} is set and if the package
     *         is not found in the list of installed applications, the package
     *         information is retrieved from the list of uninstalled
     *         applications (which includes installed applications as well as
     *         applications with data directory i.e. applications which had been
     *         deleted with {@code DONT_DELETE_DATA} flag set).
     * @throws NameNotFoundException if a package with the given name cannot be
     *             found on the system.
     * 
     * 经过包名获取该包名对应的应用程序的 PackageInfo 对象，
     * PackageInfo 类包含了从 AndroidManifest.xml 文件中收集的全部信息。
     */
    public abstract PackageInfo getPackageInfo(String packageName, @PackageInfoFlags int flags)
            throws NameNotFoundException;

getApplicationInfo

/**
     * Retrieve all of the information we know about a particular
     * package/application.
     *
     * @param packageName The full name (i.e. com.google.apps.contacts) of an
     *            application.
     * @param flags Additional option flags to modify the data returned.
     * @return An {@link ApplicationInfo} containing information about the
     *         package. If flag {@code MATCH_UNINSTALLED_PACKAGES} is set and if
     *         the package is not found in the list of installed applications,
     *         the application information is retrieved from the list of
     *         uninstalled applications (which includes installed applications
     *         as well as applications with data directory i.e. applications
     *         which had been deleted with {@code DONT_DELETE_DATA} flag set).
     * @throws NameNotFoundException if a package with the given name cannot be
     *             found on the system.
     *
     * 根据包名返回其对应的 ApplicationInfo 信息。
     */
    public abstract ApplicationInfo getApplicationInfo(String packageName,
            @ApplicationInfoFlags int flags) throws NameNotFoundException;

getActivityInfo

/**
     * Retrieve all of the information we know about a particular activity
     * class.
     *
     * @param component The full component name (i.e.
     *            com.google.apps.contacts/com.google.apps.contacts.
     *            ContactsList) of an Activity class.
     * @param flags Additional option flags to modify the data returned.
     * @return An {@link ActivityInfo} containing information about the
     *         activity.
     * @throws NameNotFoundException if a package with the given name cannot be
     *             found on the system.
     *
     * 检索出一个特定的 Activity 类的全部信息。
     */
    public abstract ActivityInfo getActivityInfo(ComponentName component,
            @ComponentInfoFlags int flags) throws NameNotFoundException;

getReceiverInfo

/**
     * Retrieve all of the information we know about a particular receiver
     * class.
     *
     * @param component The full component name (i.e.
     *            com.google.apps.calendar/com.google.apps.calendar.
     *            CalendarAlarm) of a Receiver class.
     * @param flags Additional option flags to modify the data returned.
     * @return An {@link ActivityInfo} containing information about the
     *         receiver.
     * @throws NameNotFoundException if a package with the given name cannot be
     *             found on the system.
     *
     * 检索出一个特定的 Receiver 类的全部信息(这里主要指 ActivityInfo)。
     */
    public abstract ActivityInfo getReceiverInfo(ComponentName component,
            @ComponentInfoFlags int flags) throws NameNotFoundException;

getServiceInfo

/**
     * Retrieve all of the information we know about a particular service class.
     *
     * @param component The full component name (i.e.
     *            com.google.apps.media/com.google.apps.media.
     *            BackgroundPlayback) of a Service class.
     * @param flags Additional option flags to modify the data returned.
     * @return A {@link ServiceInfo} object containing information about the
     *         service.
     * @throws NameNotFoundException if a package with the given name cannot be
     *             found on the system.
     *
     * 检索出一个特定的 Service 类的全部信息(这里主要指 ServiceInfo)。
     */
    public abstract ServiceInfo getServiceInfo(ComponentName component,
            @ComponentInfoFlags int flags) throws NameNotFoundException;

getProviderInfo

/**
     * Retrieve all of the information we know about a particular content
     * provider class.
     *
     * @param component The full component name (i.e.
     *            com.google.providers.media/com.google.providers.media.
     *            MediaProvider) of a ContentProvider class.
     * @param flags Additional option flags to modify the data returned.
     * @return A {@link ProviderInfo} object containing information about the
     *         provider.
     * @throws NameNotFoundException if a package with the given name cannot be
     *             found on the system.
     *
     * 检索出一个特定的 content provider 类的全部信息(这里主要指 ProviderInfo)。
     */
    public abstract ProviderInfo getProviderInfo(ComponentName component,
            @ComponentInfoFlags int flags) throws NameNotFoundException;

getInstalledPackages

/**
     * Return a List of all packages that are installed for the current user.
     *
     * @param flags Additional option flags to modify the data returned.
     * @return A List of PackageInfo objects, one for each installed package,
     *         containing information about the package. In the unlikely case
     *         there are no installed packages, an empty list is returned. If
     *         flag {@code MATCH_UNINSTALLED_PACKAGES} is set, the package
     *         information is retrieved from the list of uninstalled
     *         applications (which includes installed applications as well as
     *         applications with data directory i.e. applications which had been
     *         deleted with {@code DONT_DELETE_DATA} flag set).
     *
     * 获取设备上安装的全部软件包。
     */
    public abstract List<PackageInfo> getInstalledPackages(@PackageInfoFlags int flags);

currentToCanonicalPackageNames

/**
     * Map from the current package names in use on the device to whatever
     * the current canonical name of that package is.
     * @param names Array of current names to be mapped.
     * @return Returns an array of the same size as the original, containing
     * the canonical name for each package.
     *
     * 从设备上使用当前包名映射到该软件包名的当前规范名称，
     * 若是修改包名会用到，没有修改过包名通常不会用到。
     */
    public abstract String[] currentToCanonicalPackageNames(String[] names);

canonicalToCurrentPackageNames

/**
     * Map from a packages canonical name to the current name in use on the device.
     * @param names Array of new names to be mapped.
     * @return Returns an array of the same size as the original, containing
     * the current name for each package.
     *
     * 将软件包规范名称映射到设备上正在使用的当前名称，
     * 咱们发现：canonicalToCurrentPackageNames() 和 currentToCanonicalPackageNames() 方法是相反的两个方法
     */
    public abstract String[] canonicalToCurrentPackageNames(String[] names);

getPermissionInfo

/**
     * Retrieve all of the information we know about a particular permission.
     *
     * @param name The fully qualified name (i.e. com.google.permission.LOGIN)
     *            of the permission you are interested in.
     * @param flags Additional option flags to modify the data returned.
     * @return Returns a {@link PermissionInfo} containing information about the
     *         permission.
     * @throws NameNotFoundException if a package with the given name cannot be
     *             found on the system.
     *
     * 检测出咱们想要知道的全部关于权限的信息。
     */
    public abstract PermissionInfo getPermissionInfo(String name, @PermissionInfoFlags int flags)
            throws NameNotFoundException;

queryPermissionsByGroup

/**
     * Query for all of the permissions associated with a particular group.
     *
     * @param group The fully qualified name (i.e. com.google.permission.LOGIN)
     *            of the permission group you are interested in. Use null to
     *            find all of the permissions not associated with a group.
     * @param flags Additional option flags to modify the data returned.
     * @return Returns a list of {@link PermissionInfo} containing information
     *         about all of the permissions in the given group.
     * @throws NameNotFoundException if a package with the given name cannot be
     *             found on the system.
     *
     * 查询与特定组相关的全部权限。
     */
    public abstract List<PermissionInfo> queryPermissionsByGroup(String group,
            @PermissionInfoFlags int flags) throws NameNotFoundException;

getAllPermissionGroups

/**
     * Retrieve all of the known permission groups in the system.
     *
     * @param flags Additional option flags to modify the data returned.
     * @return Returns a list of {@link PermissionGroupInfo} containing
     *         information about all of the known permission groups.
     *
     * 检索出系统中全部已知的权限。
     */
    public abstract List<PermissionGroupInfo> getAllPermissionGroups(
            @PermissionGroupInfoFlags int flags);

固然除了上面列举出来的方法之外，还有其余不少方法，咱们再也不一一列出来，若是后面分析遇到会再单独拿出来分析！

安装方法

接下来咱们来看看 PackageManager 中关于安装的几个方法！

InstallPackage

/**
     * packageURI：表示安装的路径，能够是 "file:" 或者 "content:" 的 URI
     * observer：  一个回调的观察者，有了这个观察者，就能够在软件包安装完成后获得安装结果的通知。
     *             若是安装完成会调用这个观察者 IPackageInstallObserver 的 packageInstalled(String，int)方法，observer这个入参不能为空。
     * flags：     标志位参数
     * nstallerPackageName：正在进行安装的安装包包名
     */
     
    /**
     * @deprecated replaced by {@link PackageInstaller}
     * @hide
     */
    @Deprecated
    public abstract void installPackage(      // 弃用
            Uri packageURI,
            IPackageInstallObserver observer,
            @InstallFlags int flags,
            String installerPackageName);
    /**
     * @deprecated replaced by {@link PackageInstaller}
     * @hide
     */
    @Deprecated
    public abstract void installPackage(      // 弃用
            Uri packageURI,
            PackageInstallObserver observer,
            @InstallFlags int flags,
            String installerPackageName);

从 8.1 开始，已经弃用了 installPackage 方法（9.0 的代码中已经去除 installPackage 代码了），而是使用 PackageInstaller 执行应用的安装、升级和删除操做。

/**
     * Return interface that offers the ability to install, upgrade, and remove
     * applications on the device.
     */
    public abstract @NonNull PackageInstaller getPackageInstaller();

installExistingPackage

/**
     * If there is already an application with the given package name installed
     * on the system for other users, also install it for the calling user.
     * @hide
     */
    @SystemApi   // 系统 API
    public abstract int installExistingPackage(String packageName) throws NameNotFoundException;

经过注释能够看出这个方法的用途：若是系统上已经安装相同包名的应用程序，则重复从新安装。

具体实现类

咱们知道 PackageManager 是一个抽象类，它里面很重要的方法都是抽象的，因此在具体执行的时候，确定是它的实现子类，那么咱们就来看下它的具体实现类。

前面咱们讲解 PackageManager 类的时候，官网推荐获取 PackageManager 对象的方法是 Context 的 Context#getPackageManager() 方法，那咱们来看下：

// frameworks/base/core/java/android/content/Context.java

/** Return PackageManager instance to find global package information. */
public abstract PackageManager getPackageManager();

咱们知道 Context 也是一个抽象类，而它的 getPackageManager() 也是抽象方法，但 Context 的具体实现类是 ContextImpl，那咱们就去 ContextImpl 里面看下：

/**
 * Common implementation of Context API, which provides the base
 * context object for Activity and other application components.
 * @hide
 */
public class ContextImpl extends Context {
    private PackageManager mPackageManager;
    ... ...

    @Override
    public PackageManager getPackageManager() {
        // 判断 mPackageManager 是否为空，若是为空，则说明是第一次调用
        if (mPackageManager != null) {
            return mPackageManager;
        }
        
        // 调用 ActivityThread 的静态方法 getPackageManager() 获取一个 IPackageManager 对象
        IPackageManager pm = ActivityThread.getPackageManager();
        
        // 若是获取的 IPackageManager 对象不为空，则构造一个 ApplicationPackageManager 对象，ApplicationPackageManager 是 PackageManager 的子类
        if (pm != null) {
            // Doesn't matter if we make more than one instance.
            return (mPackageManager = new ApplicationPackageManager(this, pm));
        }

        return null;
    }
    ... ...
}

因此，在咱们平时调用 Context 的 getPackageManager()方法后，其实返回的是 ApplicationPackageManager 这个类。

ApplicationPackageManager

简介

咱们先来看下 ApplicationPackageManager 类的源码：

/** @hide */
public class ApplicationPackageManager extends PackageManager {

经过源码咱们知道 ApplicationPackageManager 继承自PackageManager，并且 ApplicationPackageManager 类不是抽象的，因此 ApplicationPackageManager 必然实现了 PackageManager 的全部抽象方法。

构造函数

protected ApplicationPackageManager(ContextImpl context, IPackageManager pm) {
        mContext = context;
        mPM = pm;
    }

InstallPackage

在讲解 PackageManager 的时候，咱们提到过安装 APK 会调用 InstallPackage 方法（Android 8.1，9.0 已弃用），咱们看下在 ApplicationPackageManager 中的具体实现：

@Override
    public void installPackage(Uri packageURI, IPackageInstallObserver observer, int flags,
                               String installerPackageName) {
        installCommon(packageURI, new LegacyPackageInstallObserver(observer), flags,
                installerPackageName, mContext.getUserId());
    }

installCommon

// 源码来自：Android 8.1，9.0 已弃用
    private void installCommon(Uri packageURI,
            PackageInstallObserver observer, int flags, String installerPackageName,
            int userId) {
        // scheme 判断，若是非 "file" 则抛异常，由于只支持 file 格式的 URI
        if (!"file".equals(packageURI.getScheme())) {
            throw new UnsupportedOperationException("Only file:// URIs are supported");
        }

        // 获取相应的路径
        final String originPath = packageURI.getPath();
        try {
            // 调用 installPackageAsUser 方法
            mPM.installPackageAsUser(originPath, observer.getBinder(), flags, installerPackageName, userId);
        } catch (RemoteException e) {
            throw e.rethrowFromSystemServer();
        }
    }

能够发现，public abstract void installPackage() 方法其内部本质是调用的 IPackageManager 的 installPackageAsUser() 方法。

IPackageManager

ActivityThread

咱们先来看看以下代码（上面没有分析）：

// 调用 ActivityThread 的静态方法 getPackageManager() 获取一个 IPackageManager 对象
IPackageManager pm = ActivityThread.getPackageManager();

跟踪 getPackageManager()：

static volatile IPackageManager sPackageManager;
    
    public static IPackageManager getPackageManager() {
        // 判断 sPackageManager 是否为空，若是为空，则说明是的第一次调用，走第二步，若是不为空，则直接返回 sPackageManager
        if (sPackageManager != null) {
            return sPackageManager;
        }
        
        // 能走到第二步，说明这是第一次调用，则调用 ServiceManager 的 getService(String) 方法获取一个 IBinder 对象
        IBinder b = ServiceManager.getService("package");
        
        // 调用 IPackageManager.Stub.asInterface(IBinder) 获取一个 sPackageManager 对象
        sPackageManager = IPackageManager.Stub.asInterface(b);
        return sPackageManager;
    }

IPM/PM/PMS 三者关联

APM/PMS/IPM

在上面分析 ContextImpl 的 getPackageManager() 方法里面，咱们知道：

IPackageManager pm = ActivityThread.getPackageManager();
        if (pm != null) {
            // Doesn't matter if we make more than one instance.
            return (mPackageManager = new ApplicationPackageManager(this, pm));
        }

而在 ActivityThread 的静态方法 getPackageManager() 里面：

sPackageManager = IPackageManager.Stub.asInterface(b);
        return sPackageManager;

因此在 ApplicationPackageManager 里面的 mPM 其实就是 IPackageManager.Stub 内部类 Proxy 对象。

那对应的 IPackageManager.Stub 是什么？其实就是 PackageManagerService.java 。

public class PackageManagerService extends IPackageManager.Stub implements PackageSender {

以下图所示：

小结

结合上面的知识，再结合 PackageManager、ApplicationPackageManager 和 PackageManagerService 总结以下：

        ✨  IPackageManager 负责通讯：IPackageManager 接口类中定义了不少业务方法，可是因为安全等方面的考虑，Android 对外(即SDK)提供的仅仅是一个子集，该子集被封装在抽象类 PackageManager 中。客户端通常经过 Context 的 getPackageManager 函数返回一个类型为 PackageManager 的对象，该对象的实际类型是 PackageManager 的子类 ApplicationPackageManager 。ApplicationPackageManager 并无直接参与 Binder 通讯，而是经过 mPM 成员变量指向了一个 IPackageManager.Stub.Proxy 类型的对象。
        ✨  AIDL中 的 Binder 服务端是 PackageManagerService，由于 PackageManagerService 继承自 IPackageManager.Stub 。因为 IPackageManager.Stub 类从 Binder 派生，因此 PackageManagerService 将做为服务端参与 Binder 通讯。
        ✨  AIDL中 的 Binder 客户端是 ApplicationPackageManager 中成员变量 mPM，由于mPM内部指向的是 IPackageManager.Stub.Proxy。

总体流程的 Binder 结构大体以下：

参考

                  01. https://www.jianshu.com/p/c56...
                  02. https://www.jianshu.com/p/a30...