ActivityThread 中一些常用的知识点记录

源码 · 2024-9-15 13:00:20

ActivityThread：
它管理应用步调进程中主线程的实验，调理和实验Activity，广播，
以及ActivityManager 哀求的其他操纵。
简朴的说，可以通过这个类，获取到当前应用的一些信息

TIPS:
(1).可以使用以下的开源代码网站检察源码
http://aosp.opersys.com/xref/android-12.0.0_r2/xref/frameworks/base/core/java/android/app/ActivityThread.java
(2).也可以通过AndroidStudio 下载SDK Source code 检察

1 代码目次分析

它在源码的目次是在framework下： /frameworks/base/core/java/android/app/
包名为 android.app;
但它有 @hide 标记，则在app无法直接访问，但是可以通过反射获取(如Hook 技能中常用)
package android.app;/** * This manages the execution of the main thread in an * application process, scheduling and executing activities, * broadcasts, and other operations on it as the activity * manager requests. * * {@hide} */public final class ActivityThread extends ClientTransactionHandler implements ActivityThreadInternal {2. 获取当前应用 currentApplication()

Application application = ActivityThread.currentApplication();即可以获取到当前代码运行到的地方，它所属的应用.
application.mLoadedApk 直接获取到当前加载的应用对象
3. 获取当前已加载的应用(LoadedApk) 对象 (getPackageInfo())

3. 1 资源目次成员变量 mResourcePackages

是一个map, 表现1个大概多个路径.
同时，相当于一个缓存，后续纵然App 更改了 LoadedApk里的内容，但是在这里生存的对象大概是稳定的.
@GuardedBy("mResourcesManager") @UnsupportedAppUsage final ArrayMap<String, WeakReference<LoadedApk>> mResourcePackages = new ArrayMap<>();

PS: 尚有别的一个变量mPackages是生存代码所在的目次
@GuardedBy("mResourcesManager")
@UnsupportedAppUsage
final ArrayMap<String, WeakReference<LoadedApk>> mPackages = new ArrayMap<>();

3. 2 public 方法

在通过API getPackageInfo 获取 LoadedApk ，由几个public 的方法，参数差别处置惩罚流程略有差别.
都是不公开的，@UnsupportedAppUsage
public final LoadedApk getPackageInfo(ApplicationInfo ai, CompatibilityInfo compatInfo, int flags) {} public final LoadedApk getPackageInfo(String packageName, CompatibilityInfo compatInfo, int flags) {} public final LoadedApk getPackageInfo(String packageName, CompatibilityInfo compatInfo, int flags, int userId) {       public final LoadedApk getPackageInfoNoCheck(ApplicationInfo ai, CompatibilityInfo compatInfo) {} 3. 3 private 实现方法

内部的私有方法，会根据packageName 查询 mResourcePackages 实验获取 LoadedApk 对象
假如不存在，大概会创建并生存(当进步程和传入的 appinfo 的userId差别时除外!!!)
判定userId的关键代码：
final boolean differentUser = (UserHandle.myUserId() != UserHandle.getUserId(aInfo.uid));重点在于是从哪个进程调用这个方法的，即UserHandle.myUserId() 的值取决于 !!调用者!! 的进程
私有API(1) 仅仅是获取：
private LoadedApk getPackageInfo(ApplicationInfo aInfo, CompatibilityInfo compatInfo,          ClassLoader baseLoader, boolean securityViolation, boolean includeCode,          boolean registerPackage, boolean isSdkSandbox, boolean isCallFromReceiver) {       /* APK_OPTIMIZATION } */       final boolean differentUser = (UserHandle.myUserId() != UserHandle.getUserId(aInfo.uid));       synchronized (mResourcesManager) {          WeakReference<LoadedApk> ref;          if (differentUser || isSdkSandbox) {             // Caching not supported across users and for sdk sandboxes             ref = null;          } else if (includeCode) {             ref = mPackages.get(aInfo.packageName);          } else {             ref = mResourcePackages.get(aInfo.packageName);          } 私有方法API(2)：会举行创建 LoadedApk 并缓存起来 ()
假如缓存中没有，则会根据传入的 appInfo 创建一个新的 loadedApk 对象。
当进步程和 appInfo是同个用户的话，生存到mResourcePackages
2485 private LoadedApk getPackageInfo(ApplicationInfo aInfo, CompatibilityInfo compatInfo,2486          ClassLoader baseLoader, boolean securityViolation, boolean includeCode,2487          boolean registerPackage) {2488       final boolean differentUser = (UserHandle.myUserId() != UserHandle.getUserId(aInfo.uid));2489       synchronized (mResourcesManager) {2490          WeakReference<LoadedApk> ref;2491          if (differentUser) {  ////>>>>>>>>>>>>>>>>>> 查抄用户userId2492             // Caching not supported across users2493             ref = null;2494          } else if (includeCode) {2495             ref = mPackages.get(aInfo.packageName);2496          } else {2497             ref = mResourcePackages.get(aInfo.packageName);2498          }24992500          LoadedApk packageInfo = ref != null ? ref.get() : null;25012502          if (packageInfo != null) {2503             if (!isLoadedApkResourceDirsUpToDate(packageInfo, aInfo)) {2504                   List<String> oldPaths = new ArrayList<>();2505                   LoadedApk.makePaths(this, aInfo, oldPaths);2506                   packageInfo.updateApplicationInfo(aInfo, oldPaths);2507             }25082509             return packageInfo; //////>>>>>>>>>>>>>>>>>> 非空则返回2510          }25112512          if (localLOGV) {2513             Slog.v(TAG, (includeCode ? "Loading code package "2514                      : "Loading resource-only package ") + aInfo.packageName2515                      + " (in " + (mBoundApplication != null2516                      ? mBoundApplication.processName : null)2517                      + ")");2518          }25192520          packageInfo =2521                   new LoadedApk(this, aInfo, compatInfo, baseLoader,2522                         securityViolation, includeCode2523                         && (aInfo.flags & ApplicationInfo.FLAG_HAS_CODE) != 0, registerPackage); //////>>创建新的25242525          if (mSystemThread && "android".equals(aInfo.packageName)) {2526             packageInfo.installSystemApplicationInfo(aInfo,2527                      getSystemContext().mPackageInfo.getClassLoader());2528          }25292530          if (differentUser) {2531             // Caching not supported across users2532          } else if (includeCode) {2533             mPackages.put(aInfo.packageName,2534                      new WeakReference<LoadedApk>(packageInfo));2535          } else {2536             mResourcePackages.put(aInfo.packageName,2537                      new WeakReference<LoadedApk>(packageInfo));//////>>做缓存2538          }25392540          return packageInfo;2541       }2542 }3.4 调用 ActivityThread.getPackageInfo() 的地方：

（1）通过 ApplicationInfo 创建 Context的时候
Context.createApplicationContext(mApplication, Context.CONTEXT_RESTRICTED);
---> ContextWrapper -> ContextImpl
此中 mApplication 为ApplicationInfo 对象.
//ContextImpl.java @Override public Context createApplicationContext(ApplicationInfo application, int flags)          throws NameNotFoundException {       LoadedApk pi = mMainThread.getPackageInfo(application, mResources.getCompatibilityInfo(),             flags | CONTEXT_REGISTER_PACKAGE);       if (pi != null) {          ContextImpl c = new ContextImpl(this, mMainThread, pi, ContextParams.EMPTY,                   mAttributionSource.getAttributionTag(),                   mAttributionSource.getNext(),                   null, mToken, new UserHandle(UserHandle.getUserId(application.uid)),                   flags, null, null);          final int displayId = getDisplayId();          final Integer overrideDisplayId = mForceDisplayOverrideInResources                   ? displayId : null;          c.setResources(createResources(mToken, pi, null, overrideDisplayId, null,                   getDisplayAdjustments(displayId).getCompatibilityInfo(), null));          if (c.mResources != null) {             return c;          }       }       throw new PackageManager.NameNotFoundException(             "Application package " + application.packageName + " not found"); }从上面可以看出，会先通过  ActivityThread.getPackageInfo 获取到 LoadedApk 实例对象.
3.5 拓展

ContextImpl 有几个通过差别参数，获取Context 的方法：
这里关注的是createApplicationContext 和 createPackageContextAsUser，
紧张差别在于前者传入 applicationInfo ，而后者是 packageName。
以是，差别会提如今 ActivityThread.getPackageInfo 获取 LoadedApk 对象上，
在根据 packageName查找缓存数组mResourcePackage，后
假如不存在，前者会根据 applicationInfo 创建对象loadedApk对象,  后者则是通过packageName获取applicationInfo再创建.
//ContextImpl.java 获取Context 的几个方法  @Override public Context createApplicationContext(ApplicationInfo application, int flags)          throws NameNotFoundException {       LoadedApk pi = mMainThread.getPackageInfo(application, mResources.getCompatibilityInfo(),             flags | CONTEXT_REGISTER_PACKAGE);       if (pi != null) {          ContextImpl c = new ContextImpl(this, mMainThread, pi, ContextParams.EMPTY,                   mAttributionSource.getAttributionTag(),                   mAttributionSource.getNext(),                   null, mToken, new UserHandle(UserHandle.getUserId(application.uid)),                   flags, null, null);          final int displayId = getDisplayId();          final Integer overrideDisplayId = mForceDisplayOverrideInResources                   ? displayId : null;          c.setResources(createResources(mToken, pi, null, overrideDisplayId, null,                   getDisplayAdjustments(displayId).getCompatibilityInfo(), null));          if (c.mResources != null) {             return c;          }       }       throw new PackageManager.NameNotFoundException(             "Application package " + application.packageName + " not found"); } @Override public Context createPackageContext(String packageName, int flags)          throws NameNotFoundException {       return createPackageContextAsUser(packageName, flags, mUser); } @Override public Context createPackageContextAsUser(String packageName, int flags, UserHandle user)          throws NameNotFoundException {       if (packageName.equals("system") || packageName.equals("android")) {          // The system resources are loaded in every application, so we can safely copy          // the context without reloading Resources.          return new ContextImpl(this, mMainThread, mPackageInfo, mParams,                   mAttributionSource.getAttributionTag(),                   mAttributionSource.getNext(),                   null, mToken, user, flags, null, null);       }       LoadedApk pi = mMainThread.getPackageInfo(packageName, mResources.getCompatibilityInfo(),             flags | CONTEXT_REGISTER_PACKAGE, user.getIdentifier());       if (pi != null) {          ContextImpl c = new ContextImpl(this, mMainThread, pi, mParams,                   mAttributionSource.getAttributionTag(),                   mAttributionSource.getNext(),                   null, mToken, user, flags, null, null);          final int displayId = getDisplayId();          final Integer overrideDisplayId = mForceDisplayOverrideInResources                   ? displayId : null;          c.setResources(createResources(mToken, pi, null, overrideDisplayId, null,                   getDisplayAdjustments(displayId).getCompatibilityInfo(), null));          if (c.mResources != null) {             return c;          }       }       // Should be a better exception.       throw new PackageManager.NameNotFoundException(             "Application package " + packageName + " not found"); } @Override public Context createContextAsUser(UserHandle user, @CreatePackageOptions int flags) {       try {          return createPackageContextAsUser(getPackageName(), flags, user);       } catch (NameNotFoundException e) {          throw new IllegalStateException("Own package not found: package=" + getPackageName());       } }createPackageContextAsUser 涉及在ActivityThread获取applicationInfo 的逻辑如下
（终极照旧回归到包罗applicationInfo参数的  getPackageInfo方法）
@UnsupportedAppUsage(maxTargetSdk = Build.VERSION_CODES.P, trackingBug = 115609023) public final LoadedApk getPackageInfo(String packageName, CompatibilityInfo compatInfo,          int flags) {       return getPackageInfo(packageName, compatInfo, flags, UserHandle.myUserId()); } public final LoadedApk getPackageInfo(String packageName, CompatibilityInfo compatInfo,          int flags, int userId) {       final boolean differentUser = (UserHandle.myUserId() != userId);       ApplicationInfo ai = PackageManager.getApplicationInfoAsUserCached(             packageName,             PackageManager.GET_SHARED_LIBRARY_FILES             | PackageManager.MATCH_DEBUG_TRIAGED_MISSING,             (userId < 0) ? UserHandle.myUserId() : userId);       synchronized (mResourcesManager) {          WeakReference<LoadedApk> ref;          if (differentUser) {             // Caching not supported across users             ref = null;          } else if ((flags & Context.CONTEXT_INCLUDE_CODE) != 0) {             ref = mPackages.get(packageName);          } else {             ref = mResourcePackages.get(packageName);          }          LoadedApk packageInfo = ref != null ? ref.get() : null;          if (ai != null && packageInfo != null) {             if (!isLoadedApkResourceDirsUpToDate(packageInfo, ai)) {                   List<String> oldPaths = new ArrayList<>();                   LoadedApk.makePaths(this, ai, oldPaths);                   packageInfo.updateApplicationInfo(ai, oldPaths);             }             if (packageInfo.isSecurityViolation()                      && (flags&Context.CONTEXT_IGNORE_SECURITY) == 0) {                   throw new SecurityException(                         "Requesting code from " + packageName                         + " to be run in process "                         + mBoundApplication.processName                         + "/" + mBoundApplication.appInfo.uid);             }             return packageInfo;          }       }       if (ai != null) {          return getPackageInfo(ai, compatInfo, flags);       }       return null; } @UnsupportedAppUsage(trackingBug = 171933273) public final LoadedApk getPackageInfo(ApplicationInfo ai, CompatibilityInfo compatInfo,          int flags) {       boolean includeCode = (flags&Context.CONTEXT_INCLUDE_CODE) != 0;       boolean securityViolation = includeCode && ai.uid != 0             && ai.uid != Process.SYSTEM_UID && (mBoundApplication != null                      ? !UserHandle.isSameApp(ai.uid, mBoundApplication.appInfo.uid)                      : true);       boolean registerPackage = includeCode && (flags&Context.CONTEXT_REGISTER_PACKAGE) != 0;       if ((flags&(Context.CONTEXT_INCLUDE_CODE             |Context.CONTEXT_IGNORE_SECURITY))             == Context.CONTEXT_INCLUDE_CODE) {          if (securityViolation) {             String msg = "Requesting code from " + ai.packageName                      + " (with uid " + ai.uid + ")";             if (mBoundApplication != null) {                   msg = msg + " to be run in process "                      + mBoundApplication.processName + " (with uid "                      + mBoundApplication.appInfo.uid + ")";             }             throw new SecurityException(msg);          }       }       return getPackageInfo(ai, compatInfo, null, securityViolation, includeCode,             registerPackage); }4. App 创建 Application对象

(20230322更新)
单进程，创建1个application对象，实验一次onCreate()方法
多进程(N)，创建N个application对象，实验N次onCreate()方法
固然Application的假造内存地址类似（打印出来的），但它们的真实物理地址却差别
反射去调用Java的 "sun.misc.Unsafe" 类，获取物理内存地址.
参考>https://juejin.cn/post/7208345469658415159
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ActivityThread 中一些常用的知识点记录

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