原文地址 https://juejin.cn/post/7212432799848579133
启动Activty触发点为Activity中的startActivity。
Activity startActivity ->
Instrumentation --> execStartActivity
try {
intent.migrateExtraStreamToClipData(who);
intent.prepareToLeaveProcess(who);
//
int result = android.app.ActivityTaskManager.getService().startActivity(whoThread,
who.getBasePackageName(), who.getAttributionTag(), intent,
intent.resolveTypeIfNeeded(who.getContentResolver()), token,
target != null ? target.mEmbeddedID : null, requestCode, 0, null, options);
checkStartActivityResult(result, intent);
} catch (RemoteException e) {
throw new RuntimeException("Failure from system", e);
}
/** @hide */
public static IActivityTaskManager getService() {
//通过aidl接口获取ActivityTaskManagerService操作对象
return IActivityTaskManagerSingleton.get();
}
通过aidl接口得到ActivityTaskManagerService的对象(简称ATMS),activity启动原来是ams管理的,在android10之后增加了ATMS,将原来AMS中的部分代码移动了此类中。
Instrumentation中调用了execStartActivity之后,最终调用了ATMS中的startActivityAsUser()方法。
@Override
public final int startActivity(IApplicationThread caller, String callingPackage,
String callingFeatureId, Intent intent, String resolvedType, IBinder resultTo,
String resultWho, int requestCode, int startFlags, ProfilerInfo profilerInfo,
Bundle bOptions) {
return startActivityAsUser(caller, callingPackage, callingFeatureId, intent, resolvedType,
resultTo, resultWho, requestCode, startFlags, profilerInfo, bOptions,
UserHandle.getCallingUserId());
}
private int startActivityAsUser(IApplicationThread caller, String callingPackage,
@Nullable String callingFeatureId, Intent intent, String resolvedType,
IBinder resultTo, String resultWho, int requestCode, int startFlags,
ProfilerInfo profilerInfo, Bundle bOptions, int userId, boolean validateIncomingUser) {
assertPackageMatchesCallingUid(callingPackage);
enforceNotIsolatedCaller("startActivityAsUser");
userId = getActivityStartController().checkTargetUser(userId, validateIncomingUser,
Binder.getCallingPid(), Binder.getCallingUid(), "startActivityAsUser");
// TODO: Switch to user app stacks here.
//通过ActivityStartController最终调用到了ActivityStarter中的execute方法。
return getActivityStartController().obtainStarter(intent, "startActivityAsUser")
.setCaller(caller)
.setCallingPackage(callingPackage)
.setCallingFeatureId(callingFeatureId)
.setResolvedType(resolvedType)
.setResultTo(resultTo)
.setResultWho(resultWho)
.setRequestCode(requestCode)
.setStartFlags(startFlags)
.setProfilerInfo(profilerInfo)
.setActivityOptions(bOptions)
.setUserId(userId)
.execute();
}
通过ActivityStartController最终调用到了ActivityStarter中的execute方法。
execute方法方法调用:startActivityInner---> deliverToCurrentTopIfNeeded
RootWindowContainer-->resumeFocusedStacksTopActivities
ActivityStack-->resumeTopActivityUncheckedLocked-->resumeTopActivityInnerLocked
在resumeTopActivityInnerLocked末尾处调用了ActivityStackSupervisor中的startSpecificActivity方法。
ActivityStackSupervisor--->startSpecificActivity 代码如下:
void startSpecificActivity(ActivityRecord r, boolean andResume, boolean checkConfig) {
// Is this activity's application already running?
final WindowProcessController wpc =
mService.getProcessController(r.processName, r.info.applicationInfo.uid);
boolean knownToBeDead = false;
if (wpc != null && wpc.hasThread()) {
try {
realStartActivityLocked(r, wpc, andResume, checkConfig);
return;
} catch (RemoteException e) {
Slog.w(TAG, "Exception when starting activity "
+ r.intent.getComponent().flattenToShortString(), e);
}
// If a dead object exception was thrown -- fall through to
// restart the application.
knownToBeDead = true;
}
r.notifyUnknownVisibilityLaunchedForKeyguardTransition();
final boolean isTop = andResume && r.isTopRunningActivity();
mService.startProcessAsync(r, knownToBeDead, isTop, isTop ? "top-activity" : "activity");
}
此处,如果有app进程,则直接调用realStartActivityLocked方法。
如果没有进程,则去启动进程,我们进入mService.startProcessAsync() 代码,进行跟踪。
ActivityTaskManagerService-->startProcessAsync
方法中调用了这个方法:ActivityManagerInternal::startProcess,这个接口直接回调到了AMS中的startProcess。
ActivityManagerService-->startProcess--> startProcessLocked
ProcessList-->startProcessLocked-->startProcessLocked
final String entryPoint = "android.app.ActivityThread"; 这个值很关键
startProcessLocked方法继续往下。
startProcessLocked-->startProcess-->startProcess()-->createAppZygoteForProcessIfNeeded
创建AppZygote对象,保存到zygote集合中,并返回此对象。
创建appzygote对象之后,直接调用start方法。
此时来到了ZygoteProcess类中的start方法。
ZygoteProcess-->start()-->startViaZygote()
start方法调用后会根据传入的processClass参数进行创建新的进程然后调用该进程的main方法,在start函数reture之后创建出来的进程不受影响,继续运行。
进入到startViaZygote方法之内。
调用zygoteSendArgsAndGetResult,注意入参,会检查是否需要建立socket链接进行通信。
进入openZygoteSocketIfNeeded方法,最终调用connect方法。
/**
* @hide for internal use only
*/
public static final int SOCKET_BUFFER_SIZE = 256;
先是创建一个LocalSocket,然后connect链接,并设置了传输buffer字节限制,SOCKET_BUFFER_SIZE=256.
socket链接之后,我们回到zygoteSendArgsAndGetResult,进入该方法中。
进入到 attemptUsapSendArgsAndGetResult 方法中,写入消息:
前面传入的 final String entryPoint = "android.app.ActivityThread" 值就是processClass,被socket发送了出去。
Zygote查看接收方法,如果调用进程的main方法的。
zygote初始化的时候会开启一个无限循环,一直读取发送过来的值。
ZygoteInit -->main()
ZygoteServer --> runSelectLoop()
进入到processOneCommand方法中,继续调用 handleChildProc 方法,最后调用Zygote中的 childZygoteInit 方法。
ZygoteServer --> runSelectLoop()
ZygoteConnection --> processOneCommand()--> handleChildProc()
processOneCommand的方法如下:
readArgumentList就是读取localSocket发送过来的值。(android.app.ActivityThread 这个processClass字符参数就被发送到了这里)
ZygoteInit --> childZygoteInit()
/**
* The main function called when starting a child zygote process. This is used as an alternative
* to zygoteInit(), which skips calling into initialization routines that start the Binder
* threadpool.
*/
static final Runnable childZygoteInit(
int targetSdkVersion, String[] argv, ClassLoader classLoader) {
RuntimeInit.Arguments args = new RuntimeInit.Arguments(argv);
return RuntimeInit.findStaticMain(args.startClass, args.startArgs, classLoader);
}
RuntimeInit-->findStaticMain() 通过反射调用class的main方法。
传递进来的className是ActivityThread,所以此处反射的就是ActivityThread的main方法,我们直接进入其中看下代码。
ActivityThread.main()
代码如下:
public static void main(String[] args) {
……………………
Looper.prepareMainLooper();
// Find the value for {@link #PROC_START_SEQ_IDENT} if provided on the command line.
// It will be in the format "seq=114"
long startSeq = 0;
if (args != null) {
for (int i = args.length - 1; i >= 0; --i) {
if (args[i] != null && args[i].startsWith(PROC_START_SEQ_IDENT)) {
startSeq = Long.parseLong(
args[i].substring(PROC_START_SEQ_IDENT.length()));
}
}
}
ActivityThread thread = new ActivityThread();
thread.attach(false, startSeq);
…………………
// End of event ActivityThreadMain.
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
Looper.loop();
throw new RuntimeException("Main thread loop unexpectedly exited");
}
ActivityThread --> main()-->attach(false)
注意此处的attach传入的参数是false,不是true,我们不要看到下面的 createAppContext中创建context逻辑里面去了。
IActivityManager --> attachApplication(); 此类是aidl接口,让ActivityThread和AMS直接通信。
ActivityManageService--> attachApplication() 这个方法很长,大约四百多行,我们直接搜索参数thread使用的地方,找到了thread.bindApplication();
ActivityThread-->bindApplication() -->sendMessage(H.BIND_APPLICATION, data)-->handleBindApplication()
图片中红色箭头处是创建applicatio的流程:
LoadedApk-->makeApplication()
Instumentation--> newApplication()
Application --> attach()-->attachBaseContext()
ContextWrapper -->attachBaseContext()
此刻的Application创建好之后,并没有发现执行application的onCreate方法,所以我们需要回到ActtivityThread中的当前代码节点继续往下看。
try {
//创建application
app = data.info.makeApplication(data.restrictedBackupMode, null);
if (!data.restrictedBackupMode) {
if (!ArrayUtils.isEmpty(data.providers)) {
//初始化contentProvider
installContentProviders(app, data.providers);
}
}
try {
mInstrumentation.onCreate(data.instrumentationArgs);
}
catch (Exception e) {
throw new RuntimeException(
"Exception thrown in onCreate() of "
+ data.instrumentationName + ": " + e.toString(), e);
}
try {
//回调application的onCreate方法
mInstrumentation.callApplicationOnCreate(app);
} catch (Exception e) {
if (!mInstrumentation.onException(app, e)) {
throw new RuntimeException(
"Unable to create application " + app.getClass().getName()
+ ": " + e.toString(), e);
}
}
} finally {
// If the app targets < O-MR1, or doesn't change the thread policy
// during startup, clobber the policy to maintain behavior of b/36951662
if (data.appInfo.targetSdkVersion < Build.VERSION_CODES.O_MR1
|| StrictMode.getThreadPolicy().equals(writesAllowedPolicy)) {
StrictMode.setThreadPolicy(savedPolicy);
}
}
我们进入到callApplicationOnCreate方法中,代码如下:
/**
* Perform calling of the application's {@link Application#onCreate}
* method. The default implementation simply calls through to that method.
*
* <p>Note: This method will be called immediately after {@link #onCreate(Bundle)}.
* Often instrumentation tests start their test thread in onCreate(); you
* need to be careful of races between these. (Well between it and
* everything else, but let's start here.)
*
* @param app The application being created.
*/
public void callApplicationOnCreate(Application app) {
app.onCreate();
}
该方法直接执行了Application的onCreate方法,此时我们的程序已经算启动了。
前面流程先回顾一下
activity通过startActivity时,最终会调用到ActivityStackSupervisor--->startSpecificActivity() ,进程如果不存在,则去启动,如果进程存在,则会执行realStartActivityLocked()方法。
而在该方法中,我们刚刚是看的进程未启动的流程,所以这个地方它是如何又回调的这个地方来的呢?我们回到ActivityManagerService中的thread.bindApplication()代码节点继续往下走。
图片中红框一 调用了ATMS中的attachApplication() 方法。
红框二处是绑定服务的流程,先略过。
进入到ATMS中的attachApplication方法。
ATMS-->attachApplication();
RootWindowContainer --> attachApplication() -- startActivityForAttachedApplicationIfNeeded();
进入到startActivityForAttachedApplicationIfNeede方法中。
private boolean startActivityForAttachedApplicationIfNeeded(ActivityRecord r,
WindowProcessController app, ActivityRecord top) {
if (r.finishing || !r.okToShowLocked() || !r.visibleIgnoringKeyguard || r.app != null
|| app.mUid != r.info.applicationInfo.uid || !app.mName.equals(r.processName)) {
return false;
}
try {
//此处回调了ActivityStackSupervisor中的realStartActivityLocked方法。
if (mStackSupervisor.realStartActivityLocked(r, app,
top == r && r.isFocusable() /*andResume*/, true /*checkConfig*/)) {
mTmpBoolean = true;
}
} catch (RemoteException e) {
Slog.w(TAG, "Exception in new application when starting activity "
+ top.intent.getComponent().flattenToShortString(), e);
mTmpRemoteException = e;
return true;
}
return false;
}
此处回调了ActivityStackSupervisor中的realStartActivityLocked方法。
ActivityStackSupervisor --> realStartActivityLocked();
这个地方就和前面形成了闭环,即启动activity时,先检查进程是否存在,如果存在,直接启动activity;如果不存在,去创建进程,进程创建成功后,再次启动activity。
我们进入到realStartActivityLocked 看看activity是怎么启动的,它的生命周期又是如何回调的。
// Create activity launch transaction.
final ClientTransaction clientTransaction = ClientTransaction.obtain(
proc.getThread(), r.appToken);
final DisplayContent dc = r.getDisplay().mDisplayContent;
clientTransaction.addCallback(LaunchActivityItem.obtain(new Intent(r.intent),
// Schedule transaction.
mService.getLifecycleManager().scheduleTransaction(clientTransaction);
该方法中调用了ATMS中的getLifecycleManager方法,并最终调用了ClientLifecycleManager.scheduleTransaction()方法,并将ClientTransaction对象当做参数传递了进去。
注意:此处创建了ClientTransaction对象,并addCallBack(). LaunchActivityItem,这个LaunchActivityItem是ClientTransactionItem的子类,后面执行execut方法时会被回调到。
public void schedule() throws RemoteException {
mClient.scheduleTransaction(this);
}
ClientLifecycleManager --> scheduleTransaction()
IApplicationThread --> scheduleTransaction()
ApplicationThread(ActivityThrad的内部类) --> scheduleTransaction()
ClientTransactionHandler(ActivitThread的父类) --> scheduleTransaction()
/** Prepare and schedule transaction for execution. */
void scheduleTransaction(ClientTransaction transaction) {
transaction.preExecute(this);
sendMessage(ActivityThread.H.EXECUTE_TRANSACTION, transaction);
}
ActivityThread的handler中查看该消息。
TransactionExecutor -- > execute() --> executeCallbacks()
ClientTransactionItem --> execute() 调用其父类的execute方法。
LaunchActivityItem --> execute() .
ClientTransactionHandler --> handleLaunchActivity() 它只有一个子类,就是ActivityThread。
ActivityThread --> handleLaunchActivity() --> performLaunchActivity();
performLaunchActivity代码精简如下:
private Activity performLaunchActivity(ActivityClientRecord r, Intent customIntent) {
//反射创建activity类。
ContextImpl appContext = createBaseContextForActivity(r);
Activity activity = null;
try {
java.lang.ClassLoader cl = appContext.getClassLoader();
activity = mInstrumentation.newActivity(
cl, component.getClassName(), r.intent);
StrictMode.incrementExpectedActivityCount(activity.getClass());
r.intent.setExtrasClassLoader(cl);
r.intent.prepareToEnterProcess();
if (r.state != null) {
r.state.setClassLoader(cl);
}
} catch (Exception e) {
if (!mInstrumentation.onException(activity, e)) {
throw new RuntimeException(
"Unable to instantiate activity " + component
+ ": " + e.toString(), e);
}
}
activity.attach(appContext, this, getInstrumentation(), r.token,
r.ident, app, r.intent, r.activityInfo, title, r.parent,
r.embeddedID, r.lastNonConfigurationInstances, config,
r.referrer, r.voiceInteractor, window, r.configCallback,
r.assistToken);
if (activity != null) {
activity.mCalled = false;
//执行Activity的onCreate方法。
if (r.isPersistable()) {
mInstrumentation.callActivityOnCreate(activity, r.state, r.persistentState);
} else {
mInstrumentation.callActivityOnCreate(activity, r.state);
}
}
return activity;
}
其中先是反射创建了activity类,然后attach,最后通过Instumentation回调了Activity的onCreate方法。
Intrumentation --> callActivityOnCreate(); Activity --> onCreate();
mWindow = new PhoneWindow(this, window, activityConfigCallback);
attach方法就是赋值变量、然后给Activity创建一个视图窗口。
Activity.onCreate()被触发
在触发了Activity的onCreate的方法之后,整个Activity就算启动了,而Activity的启动流程也算是完毕。
Activity的其他生命周期,如start、resume、restart等方法回调是在TransactionExecutor --execute()--> executeLifecycleState().这个和前面的executeCallbacks()触发流程基本差不多,这里就不继续分析了。
avtivity启动后都是在onResume界面才能看到画面,所以我们单独看下onResume的触发流程。
TransactionExecutor-->executeLifecycleState()
ActivityLifecycleItem(父类的方法) --> execute
ResumeActivityItem --> handleResumeActivity()
ActivityThread --> handleResumeActivity();
if (r.activity.mVisibleFromClient) {
r.activity.makeVisible();
}
Activity中的makeVisible方法如下:
void makeVisible() {
if (!mWindowAdded) {
ViewManager wm = getWindowManager();
wm.addView(mDecor, getWindow().getAttributes());
mWindowAdded = true;
}
mDecor.setVisibility(View.VISIBLE);
}
mDecor.setVisibility(View.VISIBLE);
mDecor.setVisibility(View.VISIBLE) 显示界面。
Activity启动全流程汇总
Activity --> startActivity()
Instrumentation ---> execStartActivity
ActivityTaskManagerService --> startActivityAsUser()
ActivityStarter--execute()--> startActivityInner--》deliverToCurrentTopIfNeeded()
RootWindowContainer--》resumeFocusedStacksTopActivities
ActivityStack-->resumeTopActivityUncheckedLocked-->resumeTopActivityInnerLocked
ActivityStackSupervisor--》startSpecificActivity()
startSpecificActivity方法内有两种情况:
1、存在进程,直接做创建activity并启动等流程:ActivityStackSupervisor--》 realStartActivityLocked
2、不存在进程,创建进程,然后再次回调 realStartActivityLocked()。
先看进程没有的流程。
先从zygote发送进程创建的流程开始。
ActivityTaskManagerService-->startProcessAsync
ActivityManagerService-->startProcess--> startProcessLocked()
ProcessList-->startProcessLocked-->startProcessLocked()-->startProcess-->startProcess()-->createAppZygoteForProcessIfNeeded()去创建zygote对象
//在startProcesslocked会判断是否启动了app进程,如果启动了,直接返回,没有则去通过Zygote发送消息的方式启动ActivitThread进程,
ZygoteProcess-->start()-->startViaZygote()--》zygoteSendArgsAndGetResult()
先建立localSocket链接,然后发送消息,去创建ActivitThread,并调用main方法。
另外此处发送的消息是什么要搞清楚?是processClass字段,值是 android.app.ActivityThread
发送消息成功后,我们再看Zygote的接收流程:
从zygote初始化走起。
ZygoteInit -->main()
ZygoteServer --> runSelectLoop() :
runSelectLoop开启无限循环,一直读取localSocket的值。
ZygoteConnection --> processOneCommand()--> handleChildProc()
try {
//一直读取消息,在前面发送“com.app.AcitityThread”消息之后,这里会受到此消息。
args = Zygote.readArgumentList(mSocketReader);
} catch (IOException ex) {
throw new IllegalStateException("IOException on command socket", ex);
}
ZygoteInit --> childZygoteInit()
RuntimeInit-->findStaticMain() 通过反射调用class的main方法。
这里就是Zygote的发送消息、接收消息并创建ActivityThread且执行其main()方法的流程。
查看ActivityThread被创建之后的流程。
ActivityThread.main()
ActivityThread --> main()-->attach(false)
attach传入的是false。
IActivityManager --> attachApplication();
IActivityManager此类是aidl接口,让ActivityThread和AMS直接通信
ActivityManageService--> attachApplication()
ActivityThread-->bindApplication() -->sendMessage(H.BIND_APPLICATION, data)-->handleBindApplication()
//handleBindApplication执行流程如下:
LoadedApk-->makeApplication()
Instumentation--> newApplication()
Application --> attach()-->attachBaseContext()
ContextWrapper -->attachBaseContext()
application和context都创建完毕之后,继续执行ActivityThread 之后的代码。
ActivityThread-->callApplicationOnCreate()
public void callApplicationOnCreate(Application app) {
app.onCreate();
}
此处执行了Application的onCreate方法,我们的程序已经启动。
进程启动并执行onCreate方法之后,我们回到ATMS继续执行之后的方法。
ATMS-->attachApplication();
RootWindowContainer --> attachApplication() -- startActivityForAttachedApplicationIfNeeded();
ActivityStackSupervisor --> realStartActivityLocked();
调用realStartActivityLocke()d和刚开始点击activity时的流程形成了闭环,即启动进程之后,再去执行启动Activity的流程。
我们现在可以查看realStartActivityLocked()方法之后的流程。
ClientLifecycleManager --> scheduleTransaction()
IApplicationThread --> scheduleTransaction()
ApplicationThread(ActivityThrad的内部类) --> scheduleTransaction()
ClientTransactionHandler(ActivitThread的父类) --> scheduleTransaction()
TransactionExecutor -- > execute() --> executeCallbacks()
ClientTransactionItem --> execute()
LaunchActivityItem --> execute()
ClientTransactionHandler --> handleLaunchActivity()
ClientTransactionHandler它只有一个子类,就是ActivityThread。
ActivityThread --> handleLaunchActivity() --> performLaunchActivity();
performLaunchActivity此处反射创建了activity类,然后attach,最后通过Instumentation回调了Activity的onCreate方法。
Activity.onCreate()被触发
至此Actiivty的启动流程已经完毕。
最后我们再看一下activity显示的流程。
avtivity启动后都是在onResume界面才能看到画面,所以我们单独看下onResume的触发流程。
TransactionExecutor-->executeLifecycleState()
ActivityLifecycleItem(父类的方法) --> execute
ResumeActivityItem --> handleResumeActivity()
ActivityThread --> handleResumeActivity();
if (r.activity.mVisibleFromClient) {
r.activity.makeVisible();
}
void makeVisible() {
if (!mWindowAdded) {
ViewManager wm = getWindowManager();
wm.addView(mDecor, getWindow().getAttributes());
mWindowAdded = true;
}
mDecor.setVisibility(View.VISIBLE);
}
mDecor.setVisibility(View.VISIBLE);
mDecor.setVisibility(View.VISIBLE);这个就是显出view的方法,VISIBLE之后,我们的界面也能看到了。
启动时序总图
总结
Activity启动流程通过startActivity触发,会去检查进程是否启动,如果没有启动进程,会通过Zygote进程通过localSocket发送消息,消息的最关键信息是进程名字:android.app.ActivityThread。
因为zygote开启了无限循环检测,所以能够立马收到消息,并反射创建我们的ActivityThread类,并执行main方法。
ActivityThrad创建之后,会通过AMS中的attachApplication方法,创建Application,最后回到ActivityThread将application绑定context,最后执行Application的onCreate方法,app进程启动。
application启动之后再去启动activity。
启动activity最终会调用ActivityThread中的handleLaunchActivity方法,此方法调用之后会触发activity的onCreate方法,activity启动。
标签:--,app,Activity,ActivityThread,Framework,activity,Android,方法 From: https://www.cnblogs.com/zhanyaowang/p/18293205