Android系统应用程序安装过程源码分析

电玩女神 2022-08-06 05:17 240阅读 0赞

Step1、

这个函数定义在frameworks/base/services/java/com/android/server/SystemServer.java文件中：

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1.  **public****class** SystemServer 
2.  \{ 
3.   ...... 
4.  
5.  **public****static****final****void** init2() \{ 
6.   Slog.i(TAG, "Entered the Android system server!"); 
7.   Thread thr = **new** ServerThread(); 
8.   thr.setName("android.server.ServerThread"); 
9.   thr.start(); 
10.  \} 
11. \}

这个函数创建了一个ServerThread线程，PackageManagerService服务就是这个线程中启动的了。这里调用了ServerThread实例thr的start函数之后，下面就会执行这个实例的run函数了。

这个函数定义在frameworks/base/services/java/com/android/server/SystemServer.java文件中：

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1.  **class** ServerThread **extends** Thread \{ 
2.   ...... 
3.  
4.  @Override
5.  **public****void** run() \{ 
6.   ...... 
7.  
8.   IPackageManager pm = **null**; 
9.  
10.  ...... 
11. 
12. // Critical services...
13. **try** \{ 
14.  ...... 
15. 
16.  Slog.i(TAG, "Package Manager"); 
17.  pm = PackageManagerService.main(context, 
18.  factoryTest != SystemServer.FACTORY\_TEST\_OFF); 
19. 
20.  ...... 
21.  \} **catch** (RuntimeException e) \{ 
22.  Slog.e("System", "Failure starting core service", e); 
23.  \} 
24. 
25.  ...... 
26.  \} 
27. 
28.  ...... 
29. \}

这个函数除了启动PackageManagerService服务之外，还启动了其它很多的服务，例如在前面学习Activity和Service的几篇文章中经常看到的ActivityManagerService服务，有兴趣的读者可以自己研究一下。

这个函数定义在frameworks/base/services/java/com/android/server/PackageManagerService.java文件中：

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1.  **class** PackageManagerService extends IPackageManager.Stub \{ 
2.   ...... 
3.  
4.  **public****static** final IPackageManager main(Context context, boolean factoryTest) \{ 
5.   PackageManagerService m = **new** PackageManagerService(context, factoryTest); 
6.   ServiceManager.addService("package", m); 
7.  **return** m; 
8.   \} 
9.  
10.  ...... 
11. \}

这个函数创建了一个PackageManagerService服务实例，然后把这个服务添加到ServiceManager中去，ServiceManager是Android系统Binder进程间通信机制的守护进程，负责管理系统中的Binder对象。  
 在创建这个PackageManagerService服务实例时，会在PackageManagerService类的构造函数中开始执行安装应用程序的过程：

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1.  **class** PackageManagerService **extends** IPackageManager.Stub \{ 
2.   ...... 
3.  
4.  **public** PackageManagerService(Context context, **boolean** factoryTest) \{ 
5.   ...... 
6.  
7.  **synchronized** (mInstallLock) \{ 
8.  **synchronized** (mPackages) \{ 
9.   ...... 
10. 
11.  File dataDir = Environment.getDataDirectory(); 
12.  mAppDataDir = **new** File(dataDir, "data"); 
13.  mSecureAppDataDir = **new** File(dataDir, "secure/data"); 
14.  mDrmAppPrivateInstallDir = **new** File(dataDir, "app-private"); 
15. 
16.  ...... 
17. 
18.  mFrameworkDir = **new** File(Environment.getRootDirectory(), "framework"); 
19.  mDalvikCacheDir = **new** File(dataDir, "dalvik-cache"); 
20. 
21.  ...... 
22. 
23. // Find base frameworks (resource packages without code).
24.  mFrameworkInstallObserver = **new** AppDirObserver( 
25.  mFrameworkDir.getPath(), OBSERVER\_EVENTS, **true**); 
26.  mFrameworkInstallObserver.startWatching(); 
27.  scanDirLI(mFrameworkDir, PackageParser.PARSE\_IS\_SYSTEM 
28.  | PackageParser.PARSE\_IS\_SYSTEM\_DIR, 
29.  scanMode | SCAN\_NO\_DEX, 0); 
30. 
31. // Collect all system packages.
32.  mSystemAppDir = **new** File(Environment.getRootDirectory(), "app"); 
33.  mSystemInstallObserver = **new** AppDirObserver( 
34.  mSystemAppDir.getPath(), OBSERVER\_EVENTS, **true**); 
35.  mSystemInstallObserver.startWatching(); 
36.  scanDirLI(mSystemAppDir, PackageParser.PARSE\_IS\_SYSTEM 
37.  | PackageParser.PARSE\_IS\_SYSTEM\_DIR, scanMode, 0); 
38. 
39. // Collect all vendor packages.
40.  mVendorAppDir = **new** File("/vendor/app"); 
41.  mVendorInstallObserver = **new** AppDirObserver( 
42.  mVendorAppDir.getPath(), OBSERVER\_EVENTS, **true**); 
43.  mVendorInstallObserver.startWatching(); 
44.  scanDirLI(mVendorAppDir, PackageParser.PARSE\_IS\_SYSTEM 
45.  | PackageParser.PARSE\_IS\_SYSTEM\_DIR, scanMode, 0); 
46. 
47. 
48.  mAppInstallObserver = **new** AppDirObserver( 
49.  mAppInstallDir.getPath(), OBSERVER\_EVENTS, **false**); 
50.  mAppInstallObserver.startWatching(); 
51.  scanDirLI(mAppInstallDir, 0, scanMode, 0); 
52. 
53.  mDrmAppInstallObserver = **new** AppDirObserver( 
54.  mDrmAppPrivateInstallDir.getPath(), OBSERVER\_EVENTS, **false**); 
55.  mDrmAppInstallObserver.startWatching(); 
56.  scanDirLI(mDrmAppPrivateInstallDir, PackageParser.PARSE\_FORWARD\_LOCK, 
57.  scanMode, 0); 
58. 
59.  ...... 
60.  \} 
61.  \} 
62.  \} 
63. 
64.  ...... 
65. \}

这里会调用scanDirLI函数来扫描移动设备上的下面这五个目录中的Apk文件：

***/system/framework***

***/system/app***

***/vendor/app***

***/data/app***

***/data/app-private***

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1.  **class** PackageManagerService **extends** IPackageManager.Stub \{ 
2.   ...... 
3.  
4.  **private****void** scanDirLI(File dir, **int** flags, **int** scanMode, **long** currentTime) \{ 
5.   String\[\] files = dir.list(); 
6.   ...... 
7.  
8.  **int** i; 
9.  **for** (i=0; i<files.length; i++) \{ 
10.  File file = **new** File(dir, files\[i\]); 
11. **if** (!isPackageFilename(files\[i\])) \{ 
12. // Ignore entries which are not apk's
13. **continue**; 
14.  \} 
15.  PackageParser.Package pkg = scanPackageLI(file, 
16.  flags|PackageParser.PARSE\_MUST\_BE\_APK, scanMode, currentTime); 
17. // Don't mess around with apps in system partition.
18. **if** (pkg == **null** && (flags & PackageParser.PARSE\_IS\_SYSTEM) == 0 && 
19.  mLastScanError == PackageManager.INSTALL\_FAILED\_INVALID\_APK) \{ 
20. // Delete the apk
21.  Slog.w(TAG, "Cleaning up failed install of " \+ file); 
22.  file.delete(); 
23.  \} 
24.  \} 
25.  \} 
26. 
27. 
28.  ...... 
29. \}

对于目录中的每一个文件，如果是以后Apk作为后缀名，那么就调用scanPackageLI函数来对它进行解析和安装。

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1.  **class** PackageManagerService **extends** IPackageManager.Stub \{ 
2.   ...... 
3.  
4.  **private** PackageParser.Package scanPackageLI(File scanFile, 
5.  **int** parseFlags, **int** scanMode, **long** currentTime) \{ 
6.   ...... 
7.  
8.   String scanPath = scanFile.getPath(); 
9.   parseFlags |= mDefParseFlags; 
10.  PackageParser pp = **new** PackageParser(scanPath); 
11. 
12.  ...... 
13. 
14. **final** PackageParser.Package pkg = pp.parsePackage(scanFile, 
15.  scanPath, mMetrics, parseFlags); 
16. 
17.  ...... 
18. 
19. **return** scanPackageLI(pkg, parseFlags, scanMode | SCAN\_UPDATE\_SIGNATURE, currentTime); 
20.  \} 
21. 
22.  ...... 
23. \}

这个函数首先会为这个Apk文件创建一个PackageParser实例，接着调用这个实例的parsePackage函数来对这个Apk文件进行解析。这个函数最后还会调用另外一个版本的scanPackageLI函数把来解析后得到的应用程序信息保存在PackageManagerService中。

这个函数定义在frameworks/base/core/java/android/content/pm/PackageParser.java文件中：

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1.  **public****class** PackageParser \{ 
2.   ...... 
3.  
4.  **public** Package parsePackage(File sourceFile, String destCodePath, 
5.   DisplayMetrics metrics, **int** flags) \{ 
6.   ...... 
7.  
8.   mArchiveSourcePath = sourceFile.getPath(); 
9.  
10.  ...... 
11. 
12.  XmlResourceParser parser = **null**; 
13.  AssetManager assmgr = **null**; 
14. **boolean** assetError = **true**; 
15. **try** \{ 
16.  assmgr = **new** AssetManager(); 
17. **int** cookie = assmgr.addAssetPath(mArchiveSourcePath); 
18. **if**(cookie != 0) \{ 
19.  parser = assmgr.openXmlResourceParser(cookie, "AndroidManifest.xml"); 
20.  assetError = **false**; 
21.  \} **else** \{ 
22.  ...... 
23.  \} 
24.  \} **catch** (Exception e) \{ 
25.  ...... 
26.  \} 
27. 
28.  ...... 
29. 
30.  String\[\] errorText = **new** String\[1\]; 
31.  Package pkg = **null**; 
32.  Exception errorException = **null**; 
33. **try** \{ 
34. // XXXX todo: need to figure out correct configuration.
35.  Resources res = **new** Resources(assmgr, metrics, **null**); 
36.  pkg = parsePackage(res, parser, flags, errorText); 
37.  \} **catch** (Exception e) \{ 
38.  ...... 
39.  \} 
40. 
41.  ...... 
42. 
43.  parser.close(); 
44.  assmgr.close(); 
45. 
46. // Set code and resource paths
47.  pkg.mPath = destCodePath; 
48.  pkg.mScanPath = mArchiveSourcePath; 
49. //pkg.applicationInfo.sourceDir = destCodePath;
50. //pkg.applicationInfo.publicSourceDir = destRes;
51.  pkg.mSignatures = **null**; 
52. 
53. **return** pkg; 
54.  \} 
55. 
56.  ...... 
57. \}

每一个Apk文件都是一个归档文件，它里面包含了Android应用程序的配置文件AndroidManifest.xml，这里主要就是要对这个配置文件就行解析了，从Apk归档文件中得到这个配置文件后，就调用另一外版本的parsePackage函数对这个应用程序进行解析了：

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1.  **public****class** PackageParser \{ 
2.   ...... 
3.  
4.  **private** Package parsePackage( 
5.   Resources res, XmlResourceParser parser, **int** flags, String\[\] outError) 
6.  **throws** XmlPullParserException, IOException \{ 
7.   ...... 
8.  
9.   String pkgName = parsePackageName(parser, attrs, flags, outError); 
10. 
11.  ...... 
12. 
13. **final** Package pkg = **new** Package(pkgName); 
14. 
15.  ...... 
16. 
17. **int** type; 
18. 
19.  ...... 
20. 
21.  TypedArray sa = res.obtainAttributes(attrs, 
22.  com.android.internal.R.styleable.AndroidManifest); 
23. 
24.  ...... 
25. 
26. **while** ((type=parser.next()) != parser.END\_DOCUMENT 
27.  && (type != parser.END\_TAG || parser.getDepth() > outerDepth)) \{ 
28. **if** (type == parser.END\_TAG || type == parser.TEXT) \{ 
29. **continue**; 
30.  \} 
31. 
32.  String tagName = parser.getName(); 
33. **if** (tagName.equals("application")) \{ 
34.  ...... 
35. 
36. **if** (!parseApplication(pkg, res, parser, attrs, flags, outError)) \{ 
37. **return****null**; 
38.  \} 
39.  \} **else****if** (tagName.equals("permission-group")) \{ 
40.  ...... 
41.  \} **else****if** (tagName.equals("permission")) \{ 
42.  ...... 
43.  \} **else****if** (tagName.equals("permission-tree")) \{ 
44.  ...... 
45.  \} **else****if** (tagName.equals("uses-permission")) \{ 
46.  ...... 
47.  \} **else****if** (tagName.equals("uses-configuration")) \{ 
48.  ...... 
49.  \} **else****if** (tagName.equals("uses-feature")) \{ 
50.  ...... 
51.  \} **else****if** (tagName.equals("uses-sdk")) \{ 
52.  ...... 
53.  \} **else****if** (tagName.equals("supports-screens")) \{ 
54.  ...... 
55.  \} **else****if** (tagName.equals("protected-broadcast")) \{ 
56.  ...... 
57.  \} **else****if** (tagName.equals("instrumentation")) \{ 
58.  ...... 
59.  \} **else****if** (tagName.equals("original-package")) \{ 
60.  ...... 
61.  \} **else****if** (tagName.equals("adopt-permissions")) \{ 
62.  ...... 
63.  \} **else****if** (tagName.equals("uses-gl-texture")) \{ 
64.  ...... 
65.  \} **else****if** (tagName.equals("compatible-screens")) \{ 
66.  ...... 
67.  \} **else****if** (tagName.equals("eat-comment")) \{ 
68.  ...... 
69.  \} **else****if** (RIGID\_PARSER) \{ 
70.  ...... 
71.  \} **else** \{ 
72.  ...... 
73.  \} 
74.  \} 
75. 
76.  ...... 
77. 
78. **return** pkg; 
79.  \} 
80. 
81.  ...... 
82. \}

这里就是对AndroidManifest.xml文件中的各个标签进行解析了，各个标签的含义可以参考官方文档  [http://developer.android.com/guide/topics/manifest/manifest-intro.html][http_developer.android.com_guide_topics_manifest_manifest-intro.html] ，这里我们只简单看一下application标签的解析，这是通过调用parseApplication函数来进行的。

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1.  **public****class** PackageParser \{ 
2.   ...... 
3.  
4.  **private****boolean** parseApplication(Package owner, Resources res, 
5.   XmlPullParser parser, AttributeSet attrs, **int** flags, String\[\] outError) 
6.  **throws** XmlPullParserException, IOException \{ 
7.  **final** ApplicationInfo ai = owner.applicationInfo; 
8.  **final** String pkgName = owner.applicationInfo.packageName; 
9.  
10.  TypedArray sa = res.obtainAttributes(attrs, 
11.  com.android.internal.R.styleable.AndroidManifestApplication); 
12. 
13.  ...... 
14. 
15. **int** type; 
16. **while** ((type=parser.next()) != parser.END\_DOCUMENT 
17.  && (type != parser.END\_TAG || parser.getDepth() > innerDepth)) \{ 
18. **if** (type == parser.END\_TAG || type == parser.TEXT) \{ 
19. **continue**; 
20.  \} 
21. 
22.  String tagName = parser.getName(); 
23. **if** (tagName.equals("activity")) \{ 
24.  Activity a = parseActivity(owner, res, parser, attrs, flags, outError, **false**); 
25.  ...... 
26. 
27.  owner.activities.add(a); 
28. 
29.  \} **else****if** (tagName.equals("receiver")) \{ 
30.  Activity a = parseActivity(owner, res, parser, attrs, flags, outError, **true**); 
31.  ...... 
32. 
33.  owner.receivers.add(a); 
34.  \} **else****if** (tagName.equals("service")) \{ 
35.  Service s = parseService(owner, res, parser, attrs, flags, outError); 
36.  ...... 
37. 
38.  owner.services.add(s); 
39.  \} **else****if** (tagName.equals("provider")) \{ 
40.  Provider p = parseProvider(owner, res, parser, attrs, flags, outError); 
41.  ...... 
42. 
43.  owner.providers.add(p); 
44.  \} **else****if** (tagName.equals("activity-alias")) \{ 
45.  Activity a = parseActivityAlias(owner, res, parser, attrs, flags, outError); 
46.  ...... 
47. 
48.  owner.activities.add(a); 
49.  \} **else****if** (parser.getName().equals("meta-data")) \{ 
50.  ...... 
51.  \} **else****if** (tagName.equals("uses-library")) \{ 
52.  ...... 
53.  \} **else****if** (tagName.equals("uses-package")) \{ 
54.  ...... 
55.  \} **else** \{ 
56.  ...... 
57.  \} 
58.  \} 
59. 
60. **return****true**; 
61.  \} 
62. 
63.  ...... 
64. \}

这里就是对AndroidManifest.xml文件中的application标签进行解析了，我们常用到的标签就有activity、service、receiver和provider，各个标签的含义可以参考官方文档  [http://developer.android.com/guide/topics/manifest/manifest-intro.html][http_developer.android.com_guide_topics_manifest_manifest-intro.html] 。

这里解析完成后，一层层返回到Step 9中，调用另一个版本的scanPackageLI函数把来解析后得到的应用程序信息保存下来。

这个函数定义在frameworks/base/services/java/com/android/server/PackageManagerService.java文件中：

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1.  **class** PackageManagerService **extends** IPackageManager.Stub \{ 
2.   ...... 
3.  
4.  // Keys are String (package name), values are Package. This also serves
5.  // as the lock for the global state. Methods that must be called with
6.  // this lock held have the prefix "LP".
7.  **final** HashMap<String, PackageParser.Package> mPackages = 
8.  **new** HashMap<String, PackageParser.Package>(); 
9.  
10.  ...... 
11. 
12. // All available activities, for your resolving pleasure.
13. **final** ActivityIntentResolver mActivities = 
14. **new** ActivityIntentResolver(); 
15. 
16. // All available receivers, for your resolving pleasure.
17. **final** ActivityIntentResolver mReceivers = 
18. **new** ActivityIntentResolver(); 
19. 
20. // All available services, for your resolving pleasure.
21. **final** ServiceIntentResolver mServices = **new** ServiceIntentResolver(); 
22. 
23. // Keys are String (provider class name), values are Provider.
24. **final** HashMap<ComponentName, PackageParser.Provider> mProvidersByComponent = 
25. **new** HashMap<ComponentName, PackageParser.Provider>(); 
26. 
27.  ...... 
28. 
29. **private** PackageParser.Package scanPackageLI(PackageParser.Package pkg, 
30. **int** parseFlags, **int** scanMode, **long** currentTime) \{ 
31.  ...... 
32. 
33. **synchronized** (mPackages) \{ 
34.  ...... 
35. 
36. // Add the new setting to mPackages
37.  mPackages.put(pkg.applicationInfo.packageName, pkg); 
38. 
39.  ...... 
40. 
41. **int** N = pkg.providers.size(); 
42. **int** i; 
43. **for** (i=0; i<N; i++) \{ 
44.  PackageParser.Provider p = pkg.providers.get(i); 
45.  p.info.processName = fixProcessName(pkg.applicationInfo.processName, 
46.  p.info.processName, pkg.applicationInfo.uid); 
47.  mProvidersByComponent.put(**new** ComponentName(p.info.packageName, 
48.  p.info.name), p); 
49. 
50.  ...... 
51.  \} 
52. 
53.  N = pkg.services.size(); 
54. **for** (i=0; i<N; i++) \{ 
55.  PackageParser.Service s = pkg.services.get(i); 
56.  s.info.processName = fixProcessName(pkg.applicationInfo.processName, 
57.  s.info.processName, pkg.applicationInfo.uid); 
58.  mServices.addService(s); 
59. 
60.  ...... 
61.  \} 
62. 
63.  N = pkg.receivers.size(); 
64.  r = **null**; 
65. **for** (i=0; i<N; i++) \{ 
66.  PackageParser.Activity a = pkg.receivers.get(i); 
67.  a.info.processName = fixProcessName(pkg.applicationInfo.processName, 
68.  a.info.processName, pkg.applicationInfo.uid); 
69.  mReceivers.addActivity(a, "receiver"); 
70. 
71.  ...... 
72.  \} 
73. 
74.  N = pkg.activities.size(); 
75. **for** (i=0; i<N; i++) \{ 
76.  PackageParser.Activity a = pkg.activities.get(i); 
77.  a.info.processName = fixProcessName(pkg.applicationInfo.processName, 
78.  a.info.processName, pkg.applicationInfo.uid); 
79.  mActivities.addActivity(a, "activity"); 
80. 
81.  ...... 
82.  \} 
83. 
84.  ...... 
85.  \} 
86. 
87.  ...... 
88. 
89. **return** pkg; 
90.  \} 
91. 
92.  ...... 
93. \}

这个函数主要就是把前面解析应用程序得到的package、provider、service、receiver和activity等信息保存在PackageManagerService服务中了。

这样，在Android系统启动的时候安装应用程序的过程就介绍完了，但是，这些应用程序只是相当于在PackageManagerService服务注册好了，如果我们想要在Android桌面上看到这些应用程序，还需要有一个Home应用程序，负责从PackageManagerService服务中把这些安装好的应用程序取出来，并以友好的方式在桌面上展现出来，例如以快捷图标的形式。在Android系统中，负责把系统中已经安装的应用程序在桌面中展现出来的Home应用程序就是Launcher了，在下一篇文章中，我们将介绍Launcher是如何启动的以及它是如何从PackageManagerService服务中把系统中已经安装好的应用程序展现出来的，敬请期待。

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