Step 28. ActivityStack.realStartActivityLocked

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

        
                
  1. publicclassActivityStack{
    2.             
    3.             
  3. ......
    4.             
    5.             
  5. finalbooleanrealStartActivityLocked(ActivityRecordr,
    6.             
  6. ProcessRecordapp,booleanandResume,booleancheckConfig)
    7.             
  7. throwsRemoteException{
    8.             
    9.             
  9. ......
    10.             
    11.             
  11. r.app=app;
    12.             
    13.             
  13. ......
    14.             
    15.             
  15. intidx=app.activities.indexOf(r);
    16.             
  16. if(idx<0){
    17.             
  17. app.activities.add(r);
    18.             
  18. }
    19.             
    20.             
  20. ......
    21.             
    22.             
  22. try{
    23.             
  23. ......
    24.             
    25.             
  25. List<ResultInfo>results=null;
    26.             
  26. List<Intent>newIntents=null;
    27.             
  27. if(andResume){
    28.             
  28. results=r.results;
    29.             
  29. newIntents=r.newIntents;
    30.             
  30. }
    31.             
    32.             
  32. ......
    33.             
    34.             
  34. app.thread.scheduleLaunchActivity(newIntent(r.intent),r,
    35.             
  35. System.identityHashCode(r),
    36.             
  36. r.info,r.icicle,results,newIntents,!andResume,
    37.             
  37. mService.isNextTransitionForward());
    38.             
    39.             
  39. ......
    40.             
    41.             
  41. }catch(RemoteExceptione){
    42.             
  42. ......
    43.             
  43. }
    44.             
    45.             
  45. ......
    46.             
    47.             
  47. returntrue;
    48.             
  48. }
    49.             
    50.             
  50. ......
    51.             
    52.             
  52. }
    53.

这里最终通过app.thread进入到ApplicationThreadProxy的scheduleLaunchActivity函数中，注意，这里的第二个参数r，是一个ActivityRecord类型的Binder对象，用来作来这个Activity的token值。

Step 29.ApplicationThreadProxy.scheduleLaunchActivity
这个函数定义在frameworks/base/core/java/android/app/ApplicationThreadNative.java文件中：

        
                
  1. classApplicationThreadProxyimplementsIApplicationThread{
    2.             
    3.             
  3. ......
    4.             
    5.             
  5. publicfinalvoidscheduleLaunchActivity(Intentintent,IBindertoken,intident,
    6.             
  6. ActivityInfoinfo,Bundlestate,List<ResultInfo>pendingResults,
    7.             
  7. List<Intent>pendingNewIntents,booleannotResumed,booleanisForward)
    8.             
  8. throwsRemoteException{
    9.             
  9. Parceldata=Parcel.obtain();
    10.             
  10. data.writeInterfaceToken(IApplicationThread.descriptor);
    11.             
  11. intent.writeToParcel(data,0);
    12.             
  12. data.writeStrongBinder(token);
    13.             
  13. data.writeInt(ident);
    14.             
  14. info.writeToParcel(data,0);
    15.             
  15. data.writeBundle(state);
    16.             
  16. data.writeTypedList(pendingResults);
    17.             
  17. data.writeTypedList(pendingNewIntents);
    18.             
  18. data.writeInt(notResumed?1:0);
    19.             
  19. data.writeInt(isForward?1:0);
    20.             
  20. mRemote.transact(SCHEDULE_LAUNCH_ACTIVITY_TRANSACTION,data,null,
    21.             
  21. IBinder.FLAG_ONEWAY);
    22.             
  22. data.recycle();
    23.             
  23. }
    24.             
    25.             
  25. ......
    26.             
    27.             
  27. }
    28.

这个函数最终通过Binder驱动程序进入到ApplicationThread的scheduleLaunchActivity函数中。

Step 30.ApplicationThread.scheduleLaunchActivity
这个函数定义在frameworks/base/core/java/android/app/ActivityThread.java文件中：

        
                
  1. publicfinalclassActivityThread{
    2.             
    3.             
  3. ......
    4.             
    5.             
  5. privatefinalclassApplicationThreadextendsApplicationThreadNative{
    6.             
    7.             
  7. ......
    8.             
    9.             
  9. //weusetokentoidentifythisactivitywithouthavingtosendthe
    10.             
  10. //activityitselfbacktotheactivitymanager.(mattersmorewithipc)
    11.             
  11. publicfinalvoidscheduleLaunchActivity(Intentintent,IBindertoken,intident,
    12.             
  12. ActivityInfoinfo,Bundlestate,List<ResultInfo>pendingResults,
    13.             
  13. List<Intent>pendingNewIntents,booleannotResumed,booleanisForward){
    14.             
  14. ActivityClientRecordr=newActivityClientRecord();
    15.             
    16.             
  16. r.token=token;
    17.             
  17. r.ident=ident;
    18.             
  18. r.intent=intent;
    19.             
  19. r.activityInfo=info;
    20.             
  20. r.state=state;
    21.             
    22.             
  22. r.pendingResults=pendingResults;
    23.             
  23. r.pendingIntents=pendingNewIntents;
    24.             
    25.             
  25. r.startsNotResumed=notResumed;
    26.             
  26. r.isForward=isForward;
    27.             
    28.             
  28. queueOrSendMessage(H.LAUNCH_ACTIVITY,r);
    29.             
  29. }
    30.             
    31.             
  31. ......
    32.             
    33.             
  33. }
    34.             
    35.             
  35. ......
    36.             
  36. }
    37.

函数首先创建一个ActivityClientRecord实例，并且初始化它的成员变量，然后调用ActivityThread类的queueOrSendMessage函数进一步处理。

Step 31.ActivityThread.queueOrSendMessage
这个函数定义在frameworks/base/core/java/android/app/ActivityThread.java文件中：

        
                
  1. publicfinalclassActivityThread{
    2.             
    3.             
  3. ......
    4.             
    5.             
  5. privatefinalclassApplicationThreadextendsApplicationThreadNative{
    6.             
    7.             
  7. ......
    8.             
    9.             
  9. //ifthethreadhasn'tstartedyet,wedon'thavethehandler,sojust
    10.             
  10. //savethemessagesuntilwe'reready.
    11.             
  11. privatefinalvoidqueueOrSendMessage(intwhat,Objectobj){
    12.             
  12. queueOrSendMessage(what,obj,0,0);
    13.             
  13. }
    14.             
    15.             
  15. ......
    16.             
    17.             
  17. privatefinalvoidqueueOrSendMessage(intwhat,Objectobj,intarg1,intarg2){
    18.             
  18. synchronized(this){
    19.             
  19. ......
    20.             
  20. Messagemsg=Message.obtain();
    21.             
  21. msg.what=what;
    22.             
  22. msg.obj=obj;
    23.             
  23. msg.arg1=arg1;
    24.             
  24. msg.arg2=arg2;
    25.             
  25. mH.sendMessage(msg);
    26.             
  26. }
    27.             
  27. }
    28.             
    29.             
  29. ......
    30.             
    31.             
  31. }
    32.             
    33.             
  33. ......
    34.             
  34. }
    35.

函数把消息内容放在msg中，然后通过mH把消息分发出去，这里的成员变量mH我们在前面已经见过，消息分发出去后，最后会调用H类的handleMessage函数。

Step 32. H.handleMessage

这个函数定义在frameworks/base/core/java/android/app/ActivityThread.java文件中：

        
                
  1. publicfinalclassActivityThread{
    2.             
    3.             
  3. ......
    4.             
    5.             
  5. privatefinalclassHextendsHandler{
    6.             
    7.             
  7. ......
    8.             
    9.             
  9. publicvoidhandleMessage(Messagemsg){
    10.             
  10. ......
    11.             
  11. switch(msg.what){
    12.             
  12. caseLAUNCH_ACTIVITY:{
    13.             
  13. ActivityClientRecordr=(ActivityClientRecord)msg.obj;
    14.             
    15.             
  15. r.packageInfo=getPackageInfoNoCheck(
    16.             
  16. r.activityInfo.applicationInfo);
    17.             
  17. handleLaunchActivity(r,null);
    18.             
  18. }break;
    19.             
  19. ......
    20.             
  20. }
    21.             
    22.             
  22. ......
    23.             
    24.             
  24. }
    25.             
    26.             
  26. ......
    27.             
  27. }
    28.

这里最后调用ActivityThread类的handleLaunchActivity函数进一步处理。

Step 33.ActivityThread.handleLaunchActivity

这个函数定义在frameworks/base/core/java/android/app/ActivityThread.java文件中：

        
                
  1. publicfinalclassActivityThread{
    2.             
    3.             
  3. ......
    4.             
    5.             
  5. privatefinalvoidhandleLaunchActivity(ActivityClientRecordr,IntentcustomIntent){
    6.             
  6. ......
    7.             
    8.             
  8. Activitya=performLaunchActivity(r,customIntent);
    9.             
    10.             
  10. if(a!=null){
    11.             
  11. r.createdConfig=newConfiguration(mConfiguration);
    12.             
  12. BundleoldState=r.state;
    13.             
  13. handleResumeActivity(r.token,false,r.isForward);
    14.             
    15.             
  15. ......
    16.             
  16. }else{
    17.             
  17. ......
    18.             
  18. }
    19.             
  19. }
    20.             
    21.             
  21. ......
    22.             
  22. }
    23.

这里首先调用performLaunchActivity函数来加载这个Activity类，即shy.luo.activity.MainActivity，然后调用它的onCreate函数，最后回到handleLaunchActivity函数时，再调用handleResumeActivity函数来使这个Activity进入Resumed状态，即会调用这个Activity的onResume函数，这是遵循Activity的生命周期的。

Step 34.ActivityThread.performLaunchActivity
这个函数定义在frameworks/base/core/java/android/app/ActivityThread.java文件中：

        
                
  1. publicfinalclassActivityThread{
    2.             
    3.             
  3. ......
    4.             
    5.             
  5. privatefinalActivityperformLaunchActivity(ActivityClientRecordr,IntentcustomIntent){
    6.             
    7.             
  7. ActivityInfoaInfo=r.activityInfo;
    8.             
  8. if(r.packageInfo==null){
    9.             
  9. r.packageInfo=getPackageInfo(aInfo.applicationInfo,
    10.             
  10. Context.CONTEXT_INCLUDE_CODE);
    11.             
  11. }
    12.             
    13.             
  13. ComponentNamecomponent=r.intent.getComponent();
    14.             
  14. if(component==null){
    15.             
  15. component=r.intent.resolveActivity(
    16.             
  16. mInitialApplication.getPackageManager());
    17.             
  17. r.intent.setComponent(component);
    18.             
  18. }
    19.             
    20.             
  20. if(r.activityInfo.targetActivity!=null){
    21.             
  21. component=newComponentName(r.activityInfo.packageName,
    22.             
  22. r.activityInfo.targetActivity);
    23.             
  23. }
    24.             
    25.             
  25. Activityactivity=null;
    26.             
  26. try{
    27.             
  27. java.lang.ClassLoadercl=r.packageInfo.getClassLoader();
    28.             
  28. activity=mInstrumentation.newActivity(
    29.             
  29. cl,component.getClassName(),r.intent);
    30.             
  30. r.intent.setExtrasClassLoader(cl);
    31.             
  31. if(r.state!=null){
    32.             
  32. r.state.setClassLoader(cl);
    33.             
  33. }
    34.             
  34. }catch(Exceptione){
    35.             
  35. ......
    36.             
  36. }
    37.             
    38.             
  38. try{
    39.             
  39. Applicationapp=r.packageInfo.makeApplication(false,mInstrumentation);
    40.             
    41.             
  41. ......
    42.             
    43.             
  43. if(activity!=null){
    44.             
  44. ContextImplappContext=newContextImpl();
    45.             
  45. appContext.init(r.packageInfo,r.token,this);
    46.             
  46. appContext.setOuterContext(activity);
    47.             
  47. CharSequencetitle=r.activityInfo.loadLabel(appContext.getPackageManager());
    48.             
  48. Configurationconfig=newConfiguration(mConfiguration);
    49.             
  49. ......
    50.             
  50. activity.attach(appContext,this,getInstrumentation(),r.token,
    51.             
  51. r.ident,app,r.intent,r.activityInfo,title,r.parent,
    52.             
  52. r.embeddedID,r.lastNonConfigurationInstance,
    53.             
  53. r.lastNonConfigurationChildInstances,config);
    54.             
    55.             
  55. if(customIntent!=null){
    56.             
  56. activity.mIntent=customIntent;
    57.             
  57. }
    58.             
  58. r.lastNonConfigurationInstance=null;
    59.             
  59. r.lastNonConfigurationChildInstances=null;
    60.             
  60. activity.mStartedActivity=false;
    61.             
  61. inttheme=r.activityInfo.getThemeResource();
    62.             
  62. if(theme!=0){
    63.             
  63. activity.setTheme(theme);
    64.             
  64. }
    65.             
    66.             
  66. activity.mCalled=false;
    67.             
  67. mInstrumentation.callActivityOnCreate(activity,r.state);
    68.             
  68. ......
    69.             
  69. r.activity=activity;
    70.             
  70. r.stopped=true;
    71.             
  71. if(!r.activity.mFinished){
    72.             
  72. activity.performStart();
    73.             
  73. r.stopped=false;
    74.             
  74. }
    75.             
  75. if(!r.activity.mFinished){
    76.             
  76. if(r.state!=null){
    77.             
  77. mInstrumentation.callActivityOnRestoreInstanceState(activity,r.state);
    78.             
  78. }
    79.             
  79. }
    80.             
  80. if(!r.activity.mFinished){
    81.             
  81. activity.mCalled=false;
    82.             
  82. mInstrumentation.callActivityOnPostCreate(activity,r.state);
    83.             
  83. if(!activity.mCalled){
    84.             
  84. thrownewSuperNotCalledException(
    85.             
  85. "Activity"+r.intent.getComponent().toShortString()+
    86.             
  86. "didnotcallthroughtosuper.onPostCreate()");
    87.             
  87. }
    88.             
  88. }
    89.             
  89. }
    90.             
  90. r.paused=true;
    91.             
    92.             
  92. mActivities.put(r.token,r);
    93.             
    94.             
  94. }catch(SuperNotCalledExceptione){
    95.             
  95. ......
    96.             
    97.             
  97. }catch(Exceptione){
    98.             
  98. ......
    99.             
  99. }
    100.             
    101.             
  101. returnactivity;
    102.             
  102. }
    103.             
    104.             
  104. ......
    105.             
  105. }
    106.

函数前面是收集要启动的Activity的相关信息，主要package和component信息：

        
                
  1. ActivityInfoaInfo=r.activityInfo;
    2.             
  2. if(r.packageInfo==null){
    3.             
  3. r.packageInfo=getPackageInfo(aInfo.applicationInfo,
    4.             
  4. Context.CONTEXT_INCLUDE_CODE);
    5.             
  5. }
    6.             
    7.             
  7. ComponentNamecomponent=r.intent.getComponent();
    8.             
  8. if(component==null){
    9.             
  9. component=r.intent.resolveActivity(
    10.             
  10. mInitialApplication.getPackageManager());
    11.             
  11. r.intent.setComponent(component);
    12.             
  12. }
    13.             
    14.             
  14. if(r.activityInfo.targetActivity!=null){
    15.             
  15. component=newComponentName(r.activityInfo.packageName,
    16.             
  16. r.activityInfo.targetActivity);
    17.             
  17. }
    18.

然后通过ClassLoader将shy.luo.activity.MainActivity类加载进来：

        
                
  1. Activityactivity=null;
    2.             
  2. try{
    3.             
  3. java.lang.ClassLoadercl=r.packageInfo.getClassLoader();
    4.             
  4. activity=mInstrumentation.newActivity(
    5.             
  5. cl,component.getClassName(),r.intent);
    6.             
  6. r.intent.setExtrasClassLoader(cl);
    7.             
  7. if(r.state!=null){
    8.             
  8. r.state.setClassLoader(cl);
    9.             
  9. }
    10.             
  10. }catch(Exceptione){
    11.             
  11. ......
    12.             
  12. }
    13.

接下来是创建Application对象，这是根据AndroidManifest.xml配置文件中的Application标签的信息来创建的：

        
                
  1. Applicationapp=r.packageInfo.makeApplication(false,mInstrumentation);
    2.

后面的代码主要创建Activity的上下文信息，并通过attach方法将这些上下文信息设置到MainActivity中去：

        
                
  1. activity.attach(appContext,this,getInstrumentation(),r.token,
    2.             
  2. r.ident,app,r.intent,r.activityInfo,title,r.parent,
    3.             
  3. r.embeddedID,r.lastNonConfigurationInstance,
    4.             
  4. r.lastNonConfigurationChildInstances,config);
    5.

最后还要调用MainActivity的onCreate函数：

        
                
  1. mInstrumentation.callActivityOnCreate(activity,r.state);
    2.

这里不是直接调用MainActivity的onCreate函数，而是通过mInstrumentation的callActivityOnCreate函数来间接调用，前面我们说过，mInstrumentation在这里的作用是监控Activity与系统的交互操作，相当于是系统运行日志。

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