以下仅先分析 Activity的启动， 未涉及 App 启动
1. 日志分析
// 先是 start u0调用， 然后再创建 ActivityThread (第一次创建)
07-25 10:55:39.238 D 1879 8353 ActivityTaskManager: startActivityAsUser: callingPid=3746, callingUid=10126, caller=com.android.server.wm.ActivityTaskManagerService.startActivityAsUser:1815 com.android.server.wm.ActivityTaskManagerService.startActivity:1766 android.app.IActivityTaskManager$Stub.onTransact:1244 com.android.server.wm.ActivityTaskManagerService.onTransact:6588 android.os.Binder.execTransactInternal:1316 android.os.Binder.execTransact:1280 <bottom of call stack>
07-25 10:55:39.239 I 1879 8353 ActivityTaskManager: START u0 {act=android.intent.action.MAIN cat=[android.intent.category.LAUNCHER] flg=0x10200000 cmp=com.example.widgettest/.WidgetMainActivity bnds=[543,1172][789,1510]} from uid 10126
// WindowManager 先进行添加Window ?? -> 对的， 但是 不会 回调 App
Activity.onCreate/onResume/onAttachToWindow/onWindowFocusChange，要ActivityThread创建后才会
07-25 10:55:39.252 V 1879 8353 WindowManager: Added starting ActivityRecord{436ab0 u0 com.example.widgettest/.WidgetMainActivity} t23}: startingWindow=null startingView=com.android.server.wm.StartingSurfaceController$StartingSurface@5e76861
07-25 10:55:39.265 D 1879 3586 ActivityManagerPerformance: onActivityResumeLocked() r: com.example.widgettest (ActivityRecord{436ab0 u0 com.example.widgettest/.WidgetMainActivity} t23})
07-25 10:55:39.271 V 1879 4894 WindowManager: addWindow: ActivityRecord{436ab0 u0 com.example.widgettest/.WidgetMainActivity} t23} startingWindow=Window{365c937 u0 Splash Screen com.example.widgettest}
07-25 10:55:39.310 I 3145 3281 ViewRootImpl@94eeaf5[widgettest]: performTraversals params={(0,0)(fillxfill) sim={adjust=pan} ty=APPLICATION_STARTING fmt=TRANSLUCENT wanim=0x1030309
// fork 进程 771, 调用 Java 层的 进程启动及初始化的操作 => 调用 Zygote 是由 ProcessList 发起的？ 需确认
07-25 10:55:39.370 D 1322 1322 Zygote: Forked child process 771
// frameworks/base/services/core/java/com/android/server/am/ProcessList.java
// { private Process.ProcessStartResult startProcess
07-25 10:55:39.370 W 1879 2455 ActivityManager: Slow operation: 98ms so far, now at startProcess: returned from zygote!
// }
// { handleProcessStartedLocked
07-25 10:55:39.370 W 1879 2455 ActivityManager: Slow operation: 98ms so far, now at startProcess: done updating battery stats
07-25 10:55:39.370 W 1879 2455 ActivityManager: Slow operation: 98ms so far, now at startProcess: building log message
07-25 10:55:39.370 I 1879 2455 ActivityManager: Start proc 771:com.example.widgettest/u0a339 for next-top-activity {com.example.widgettest/com.example.widgettest.WidgetMainActivity}
07-25 10:55:39.370 W 1879 2455 ActivityManager: Slow operation: 98ms so far, now at startProcess: starting to update pids map
07-25 10:55:39.371 W 1879 2455 ActivityManager: Slow operation: 98ms so far, now at startProcess: done updating pids map
// handleProcessStartedLocked }
// PID: 771 -> com.example.widgettest (日志右边有注释)
07-25 10:55:39.511 E 771 771 ActivityThread: JustDebugTag main // ActivityThread 主函数入口
07-26 15:47:44.305 E 19988 19988 ActivityThread: java.lang.Exception
07-26 15:47:44.305 E 19988 19988 ActivityThread: at android.app.ActivityThread.main(ActivityThread.java:8708)
07-26 15:47:44.305 E 19988 19988 ActivityThread: at java.lang.reflect.Method.invoke(Native Method)
07-26 15:47:44.305 E 19988 19988 ActivityThread: at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:571) // 反射调用
07-26 15:47:44.305 E 19988 19988 ActivityThread: at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1067) // main 方法
07-25 10:55:39.513 E 771 771 ActivityThread: JustDebugTag ApplicationThread create this=android.app.ActivityThread$ApplicationThread@f54e4a5 // 创建 ApplicationThread 静态变量
07-25 10:55:39.513 E 771 771 ActivityThread: JustDebugTag ActivityThread create this=android.app.ActivityThread@16dd07a // 创建 ActivityThread 实例对象 (先创建了它的静态变量 ApplicationThread)
07-25 10:55:39.513 E 771 771 ActivityThread: JustDebugTag attach system=false
2. 关键点
(1)ActivityThread
应用程序进程 的 主线程，管理、调度和执行Activity，广播，以及ActivityManager 请求的其他操作。
(2)ApplicationThread
AMS/PMS 与 ActivityThread 通信的中间者;
它与AMS/PMS 通过Binder 通信，
与 ActivityThread 通过Handler通信 ( ActivityThread实现了ClientTransactionHandler)
(3)AMS/PMS
大管家，协调各应用、组件的交互需求.
3. 启动 Activity 先决条件
(1) 确保已经启动了App (Zygote fork app进程)，
(2) 创建了 ActivityThread
(3) 创建了 ApplicationThread (在 new ActivityThread 时创建静态变量)， 并将它与 AMS 绑定
(4) AMS/PMS 解析 App 的清单文件，根据 Activity 的属性执行生命周期操作 (通过ApplicationThread 回调到 ActivityThread)
(5) ActivityThread 回调 Activity 的生命周期函数.
下面这个图则是很经典 的：
App Activity 启动框架图.jpg
值得注意的是， 其实 ApplicationThread 是作为 ActivityThread 的内部类实现的
4. ActivityThread 与 AMS 的交互
分两个过程：
(1) ActivityThread.main 函数里创建 ActivityThread 对象，并且创建 ApplicationThread 对象。
然后调用 attach 方法，它里面会调用 AMS.attachApplication, 将自己与 AMS 绑定 （并传递回调接口为 ApplicationThread 对象）
(2) AMS.attachApplication 进行内部处理， 得到应用信息；
然后回调 ApplicationThread.bindApplication(), 将在AMS里得到的应用信息(特别是ApplicationInfo对象 ) 传递给 ActivityThread (Handler)
关键代码如下：
frameworks/base/core/java/android/app/ActivityThread.java
public final class ActivityThread extends ClientTransactionHandler
implements ActivityThreadInternal {
@UnsupportedAppUsage
final ApplicationThread mAppThread = new ApplicationThread();
public static void main(String[] args) {
ActivityThread thread = new ActivityThread();
thread.attach(false, startSeq);
}
@UnsupportedAppUsage
private void attach(boolean system, long startSeq) {
sCurrentActivityThread = this;
final IActivityManager mgr = ActivityManager.getService();
try {
mgr.attachApplication(mAppThread, startSeq);
} catch (RemoteException ex) {
throw ex.rethrowFromSystemServer();
}
private class ApplicationThread extends IApplicationThread.Stub {
public final void bindApplication(String processName, ApplicationInfo appInfo, ..){
AppBindData data = new AppBindData();
data.processName = processName;
data.appInfo = appInfo;
sendMessage(H.BIND_APPLICATION, data);
}
}
class H extends Handler {
public void handleMessage(Message msg) {
if (DEBUG_MESSAGES) Slog.v(TAG, ">>> handling: " + codeToString(msg.what));
switch (msg.what) {
case BIND_APPLICATION:
Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "bindApplication");
AppBindData data = (AppBindData)msg.obj;
handleBindApplication(data);
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
break;
}
@UnsupportedAppUsage
private void handleBindApplication(AppBindData data) {
}
}
frameworks/base/services/core/java/com/android/server/am/ActivityManagerService.java
@Override
public final void attachApplication(IApplicationThread thread, long startSeq) {
if (thread == null) {
throw new SecurityException("Invalid application interface");
}
synchronized (this) {
int callingPid = Binder.getCallingPid();
final int callingUid = Binder.getCallingUid();
final long origId = Binder.clearCallingIdentity();
attachApplicationLocked(thread, callingPid, callingUid, startSeq);
Binder.restoreCallingIdentity(origId);
}
}
@GuardedBy("this")
private boolean attachApplicationLocked(@NonNull IApplicationThread thread,
int pid, int callingUid, long startSeq) {
ProcessRecord app;
if (pid != MY_PID && pid >= 0) {
synchronized (mPidsSelfLocked) {
app = mPidsSelfLocked.get(pid);
}
ApplicationInfo appInfo = instr != null ? instr.mTargetInfo : app.info;
thread.bindApplication(processName, appInfo,
}
5. AMS 里的进程管理
AMS.attachApplication -> attachApplicationLocked -> updateLruProcessLocked
@GuardedBy("this")
final void updateLruProcessLocked(ProcessRecord app, boolean activityChange,
ProcessRecord client) {
mProcessList.updateLruProcessLocked(app, activityChange, client);
}
其中， mProcessList 是 通过 内部类 Injector.getProcessList 去获取的，
而这 Injector 一般是 AMS 创建时同步创建： mInjector = new Injector(systemContext);
也可以在 测试时 由外部 注入的。
/**
* Process management.
*/
final ProcessList mProcessList;
mProcessList = mInjector.getProcessList(this);
ProcessList 是 am 下的一个类， 服务于 AMS, 用于管理所有进程。
frameworks/base/services/core/java/com/android/server/am/ProcessList.java
它里面有实现 startProcess， 响应来自 native 层的创建调用
上面的 Injector 其实也是 AMS 的一个内部类 getProcessList 相当于创建一个 ProcessList
@VisibleForTesting
public static class Injector {
...
private Context mContext;
public Injector(Context context) {
mContext = context;
}
public Context getContext() {
return mContext;
}
/**
* Return the process list instance
*/
public ProcessList getProcessList(ActivityManagerService service) {
return new ProcessList();
}
参考
https://blog.csdn.net/qq_39867049/article/details/130838441
Android App Process 启动流程攻略 - 掘金 (juejin.cn)
(这个讲得很不错)
网友评论