PMS启动 APK 安装流程详解
Posted xyTianZhao
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文章目录
概述
PackageManagerService（以下简称 PMS）是一个常用的系统服务，主要负责系统中的 Package 的管理，应用程序的安装、卸载、查询等相关功能。其相关类图如下
相关类说明
- IPackageManager
定义了服务端和客户端通信的业务函数，还定义了内部类 Stub ，该类从 Binder 派生并实现了 IPackageManager 接口 - PackageManagerService
继承自 IPackageManager.Stub 类，由于 Stub 类从 Binder 派生，因此 PackageManagerService 将作为服务端参与 Binder 通信 - Stub
定义了一个内部类 Proxy ，该类有一个 IBinder 类型（实际类型为 BinderProxy ）的成员变量 mRemote ，根据 Binder 详解 中介绍的 Binder 系统的知识，mRemote 用于和服务端 PackageManagerService 通信 - ApplicationPackageManager
承自 PackageManager 类。它并没有直接参与 Binder 通信，而是通过 mPM 成员变量指向一个 IPackageManager.Stub.Proxy 类型的对象。
注：IPackageManager 在 android Studio 中可能找不到，因为他是一个 AIDL 处理后的文件，这里附上相关的 IPackageManager.aidl 文件
PMS 服务启动
分析 PMS 之前我们先来看下这玩意是在哪里启动的。
我们都知道系统启动的时候会调用 SystemServer 的 main 函数。
注释已经说明了，这个 main 函数是通过 zygote 调用的，这块的调用链涉及到了进程启动相关，此处先不多说。看到 main 创建了一个自己然后调用 run 方法。
可以看到在 run 方法中系统将服务类型按照级别分为了三大类，引导服务、内核服务、其他服务，而 PMS 的启动就在引导服务中启动。
/**
* The main entry point from zygote.
*/
public static void main(String[] args)
new SystemServer().run();
private void run()
// Start services.
try
//系统引导服务
startBootstrapServices();
//内核服务
startCoreServices();
//其他服务
startOtherServices();
catch (Throwable ex)
Slog.e("System", "******************************************");
Slog.e("System", "************ Failure starting system services", ex);
throw ex;
finally
traceEnd();
private void startBootstrapServices()
mPackageManagerService = PackageManagerService.main(mSystemContext, installer,
mFactoryTestMode != FactoryTest.FACTORY_TEST_OFF, mOnlyCore);
mFirstBoot = mPackageManagerService.isFirstBoot();
//标注①
mPackageManager = mSystemContext.getPackageManager();
我们进入 PackageManagerService 的 main 方法继续追踪。
可以看到在 main 方法中也是 new 了一把自己。然后将服务添加的 ServiceManager 中进行管理。到这，PMS 服务就启动完成了。
public class PackageManagerService extends IPackageManager.Stub
implements PackageSender
public static PackageManagerService main(Context context, Installer installer,
boolean factoryTest, boolean onlyCore)
// Self-check for initial settings.
PackageManagerServiceCompilerMapping.checkProperties();
PackageManagerService m = new PackageManagerService(context, installer,
factoryTest, onlyCore);
m.enableSystemUserPackages();
ServiceManager.addService("package", m);
final PackageManagerNative pmn = m.new PackageManagerNative();
ServiceManager.addService("package_native", pmn);
return m;
这里在额外看一下 PackageManager 的创建。上面 标注① 出获取了 PackageManager ，我们就以此为入口看下。mSystemContext 为 Content 的一个实现类，可以直接搜 ContextImpl。
可以看到和上面的类图完美的对应上了，这里拿到系统提供的 PM，然后创建一个 ApplicationPackageManager 持有这个 pm 去和系统服务进行交互。
class ContextImpl extends Context
@Override
public PackageManager getPackageManager()
if (mPackageManager != null)
return mPackageManager;
IPackageManager pm = ActivityThread.getPackageManager();
if (pm != null)
// Doesn't matter if we make more than one instance.
return (mPackageManager = new ApplicationPackageManager(this, pm));
return null;
注：Android 系统启动慢的原因就是在启动 PMS 的时候，需要执行扫描文件夹、处理权限、安装系统应用（文件的解压与copy）等比较耗时的操作。
应用程序（APK）安装
有界面安装
我们下载的安装包都是一个 .apk 文件，当我们点击该文件的时候，会启动系统的一个安装 apk 的应用，该应用是系统应用，在系统启动时就已经安装成功了。这里附上 PackageInstaller.apk 源码
首先这个 Intent 会启动 InstallStart ，在这里做一些校验后就跳转到 PackageInstallerActivity 进行确认安装后，进入 InstallInstalling 界面进行安装。
可以看到在 AndroidManifest.xml 中对外暴露了 InstallStart。
<activity android:name=".InstallStart"
android:exported="true"
android:excludeFromRecents="true">
<intent-filter android:priority="1">
<action android:name="android.intent.action.VIEW" />
<action android:name="android.intent.action.INSTALL_PACKAGE" />
<category android:name="android.intent.category.DEFAULT" />
<data android:scheme="file" />
<data android:scheme="content" />
<data android:mimeType="application/vnd.android.package-archive" />
</intent-filter>
<intent-filter android:priority="1">
<action android:name="android.intent.action.INSTALL_PACKAGE" />
<category android:name="android.intent.category.DEFAULT" />
<data android:scheme="file" />
<data android:scheme="package" />
<data android:scheme="content" />
</intent-filter>
<intent-filter android:priority="1">
<action android:name="android.content.pm.action.CONFIRM_PERMISSIONS" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
安装界面调用流程
public class InstallStart extends Activity
@Override
protected void onCreate(@Nullable Bundle savedInstanceState)
super.onCreate(savedInstanceState);
......
Intent nextActivity = new Intent(intent);
......
nextActivity.setClass(this, PackageInstallerActivity.class);
......
if (nextActivity != null)
startActivity(nextActivity);
finish();
public class PackageInstallerActivity extends OverlayTouchActivity implements OnClickListener
public void onClick(View v)
if (v == mOk)
if (mOk.isEnabled())
if (mOkCanInstall || mScrollView == null)
if (mSessionId != -1)
mInstaller.setPermissionsResult(mSessionId, true);
finish();
else
//确认安装
startInstall();
else
mScrollView.pageScroll(View.FOCUS_DOWN);
else if (v == mCancel)
// Cancel and finish
setResult(RESULT_CANCELED);
if (mSessionId != -1)
mInstaller.setPermissionsResult(mSessionId, false);
finish();
private void startInstall()
// Start subactivity to actually install the application
Intent newIntent = new Intent();
......
newIntent.setClass(this, InstallInstalling.class);
......
startActivity(newIntent);
finish();
public class InstallInstalling extends Activity
@Override
protected void onCreate(@Nullable Bundle savedInstanceState)
PackageInstaller.SessionParams params = new PackageInstaller.SessionParams(
PackageInstaller.SessionParams.MODE_FULL_INSTALL);
params.installFlags = PackageManager.INSTALL_FULL_APP;
......
try
//标注②
mSessionId = getPackageManager().getPackageInstaller().createSession(params);
catch (IOException e)
launchFailure(PackageManager.INSTALL_FAILED_INTERNAL_ERROR, null);
上面标注②中获取了 PackageInstaller 执行真正的安装
public class ApplicationPackageManager extends PackageManager
@Override
public PackageInstaller getPackageInstaller()
synchronized (mLock)
if (mInstaller == null)
try
mInstaller = new PackageInstaller(mPM.getPackageInstaller(),
mContext.getPackageName(), mContext.getUserId());
catch (RemoteException e)
throw e.rethrowFromSystemServer();
return mInstaller;
public class PackageInstaller
//标注③
private final IPackageInstaller mInstaller;
public int createSession(@NonNull SessionParams params) throws IOException
try
final String installerPackage;
if (params.installerPackageName == null)
installerPackage = mInstallerPackageName;
else
installerPackage = params.installerPackageName;
return mInstaller.createSession(params, installerPackage, mUserId);
catch (RuntimeException e)
ExceptionUtils.maybeUnwrapIOException(e);
throw e;
catch (RemoteException e)
throw e.rethrowFromSystemServer();
上面标注③ 中的 IPackageInstaller 为 PackageInstallerService 的 Binder 对象，看到这里是不发现，系统服务将 Binder 通信用的是淋漓尽致啊。
这里安装完成后通过 Binder 和 Handler 进行回调。
public class PackageInstallerService extends IPackageInstaller.Stub
@Override
public int createSession(SessionParams params, String installerPackageName, int userId)
try
return createSessionInternal(params, installerPackageName, userId);
catch (IOException e)
throw ExceptionUtils.wrap(e);
private int createSessionInternal(SessionParams params, String installerPackageName, int userId)
throws IOException
final int callingUid = Binder.getCallingUid();
mPermissionManager.enforceCrossUserPermission(
callingUid, userId, true, true, "createSession");
if (mPm.isUserRestricted(userId, UserManager.DISALLOW_INSTALL_APPS))
throw new SecurityException("User restriction prevents installing");
if ((callingUid == Process.SHELL_UID) || (callingUid == Process.ROOT_UID))
params.installFlags |= PackageManager.INSTALL_FROM_ADB;
else
// Only apps with INSTALL_PACKAGES are allowed to set an installer that is not the
// caller.
if (mContext.checkCallingOrSelfPermission(Manifest.permission.INSTALL_PACKAGES) !=
PackageManager.PERMISSION_GRANTED)
mAppOps.checkPackage(callingUid, installerPackageName);
params.installFlags &= ~PackageManager.INSTALL_FROM_ADB;
params.installFlags &= ~PackageManager.INSTALL_ALL_USERS;
params.installFlags |= PackageManager.INSTALL_REPLACE_EXISTING;
if ((params.installFlags & PackageManager.INSTALL_VIRTUAL_PRELOAD) != 0
&& !mPm.isCallerVerifier(callingUid))
params.installFlags &= ~PackageManager.INSTALL_VIRTUAL_PRELOAD;
// Only system components can circumvent runtime permissions when installing.
if ((params.installFlags & PackageManager.INSTALL_GRANT_RUNTIME_PERMISSIONS) != 0
&& mContext.checkCallingOrSelfPermission(Manifest.permission
.INSTALL_GRANT_RUNTIME_PERMISSIONS) == PackageManager.PERMISSION_DENIED)
throw new SecurityException("You need the "
+ "android.permission.INSTALL_GRANT_RUNTIME_PERMISSIONS permission "
+ "to use the PackageManager.INSTALL_GRANT_RUNTIME_PERMISSIONS flag");
if ((params.installFlags & PackageManager.INSTALL_FORWARD_LOCK) != 0
|| (params.installFlags & PackageManager.INSTALL_EXTERNAL) != 0)
throw new IllegalArgumentException(
"New installs into ASEC containers no longer supported");
// Defensively resize giant app icons
if (params.appIcon != null)
final ActivityManager am = (ActivityManager) mContext.getSystemService(
Context.ACTIVITY_SERVICE);
final int iconSize = am.getLauncherLargeIconSize();
if ((params.appIcon.getWidth() > iconSize * 2)
|| (params.appIcon.getHeight() > iconSize * 2))
params.appIcon = Bitmap.createScaledBitmap(params.appIcon, iconSize, iconSize,
true);
switch (params.mode)
case SessionParams.MODE_FULL_INSTALL:
case SessionParams.MODE_INHERIT_EXISTING:
break;
default:
throw new IllegalArgumentException("Invalid install mode: " + params.mode);
// If caller requested explicit location, sanity check it, otherwise
// resolve the best internal or adopted location.
if ((params.installFlags & PackageManager.INSTALL_INTERNAL) != 0)
if (!PackageHelper.fitsOnInternal(mContext, params))
throw new IOException("No suitable internal storage available");
else if ((params.installFlags & PackageManager.INSTALL_EXTERNAL) != 0)
if (!PackageHelper.fitsOnExternal(mContext, params))
throw new IOException("No suitable external storage available");
else if ((params.installFlags & PackageManager.INSTALL_FORCE_VOLUME_UUID) != 0)
// For now, installs to adopted media are treated as internal from
// an install flag point-of-view.
params.setInstallFlagsInternal();
else
// For now, installs to adopted media are treated as internal from
// an install flag point-of-view.
params.setInstallFlagsInternal();
// Resolve best location for install, based on combination of
// requested install flags, delta size, and manifest settings.
final long ident = Binder.clearCallingIdentity();
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