From 81962923142cc535be7d3af569bee8185370236e Mon Sep 17 00:00:00 2001 From: Omooo <869759698@qq.com> Date: Mon, 23 Mar 2020 17:28:39 +0800 Subject: [PATCH] =?UTF-8?q?Create=20Activity=20=E7=9A=84=E5=90=AF=E5=8A=A8?= =?UTF-8?q?=E6=B5=81=E7=A8=8B.md?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- .../Activity 的启动流程.md | 203 ++++++++++++++++++ 1 file changed, 203 insertions(+) create mode 100644 blogs/Android/Framework/Interview/应用进程相关/Activity 的启动流程.md diff --git a/blogs/Android/Framework/Interview/应用进程相关/Activity 的启动流程.md b/blogs/Android/Framework/Interview/应用进程相关/Activity 的启动流程.md new file mode 100644 index 0000000..3271c67 --- /dev/null +++ b/blogs/Android/Framework/Interview/应用进程相关/Activity 的启动流程.md @@ -0,0 +1,203 @@ +--- +说说 Activity 的启动流程 +--- + +1. 启动 Activity 会经历哪些生命周期回调 +2. 冷启动大致流程，涉及哪些组件，通信过程是怎么样的？ +3. Activity 启动过程中，生命周期回调的原理？ + +#### 启动流程 + +```java +startActivity -> +ActivityManagerNative.getDefault().startActivity -> +mRemote.transact(START_ACTIVITY_TRANSACTION, data, reply, 0); + +@Override +public boolean onTransact(int code, Parcel data, Parcel reply, int flags) { + switch(code) { + case START_ACTIVITY_TRANSACTION: { + startActivity(app, callingPackage, intent, ...); + } + } +} +``` + +```java +// AMS +void startSpecialActivityLocked(ActivityRecord r, ...) { + // 查询组件对应的进程是否已经启动 + ProcessRecord app = mService.getProcessRecordLocked(r.processName, ...); + if(app!=null&&app.thread!=null){ + realStartActivity(r, app, ...); + return; + } + // 启动进程 + mService.startProcessLocked(r.processName, ...); +} +``` + +```java +private final void startProcessLocked(ProcessRecord app) { + // 进程启动完成后，执行的入口函数的 Java 类 + if(entryPoint == null) entryPoint = "android.app.ActivityThread"; + Process.ProcessStartResult startResult = Process.start(entryPoint, ); + + synchronized(mPidsSelfLocked) { + mPidsSelfLocked.put(startResult.pid, app); + Message msg = mHandle.obtainMessage(PROC_START_TIMEOUT_MSG); + msg.obj = app; + mHandle.sendMessageDelayed(msg, PROC_START_TIMEOUT); + } +} +``` + +```java +public static final ProcessStartResult start(final String processClass, ){ + return startViaZygote(processClass,); +} +``` + +```java +ProcessStartResult startViaZygote(final String processClass, ){ + return zygoteSendArgsAndGetResult( + openZygoteSocketIfNeeded(abi), argsForZygote); +} +``` + +```java +boolean runOnce() { + // 读取 Zygote 发送过来的参数列表 + String[] args = readArgumentList(); + // 创建应用进程 + int pid = Zygote.forkAndSpecialize(...); + if(pid == 0) { + // 子进程，执行 ActivityThread#main 函数 + handleChildProc(...); + return true; + } else { + // 父进程把 pid 通过 Socket 在写回去 + return handlePArentProc(pid, ...); + } +} +``` + +```java +// ActivityThread +public static void main(String[] args) { + Looper.prepareMainLooper(); + + ActivityThread thread = new ActivityThread(); + thread.attach(false); + + Looper.loop(); + + throw new RuntimeException(""); +} +``` + +```java +private void attach(boolean system) { + IActivityManager mgr = ActivityManagerNative.getDefault(); + mgr.attachApplication(mAppThread); +} +``` + +```java +boolean attachApplicationLocked(IApplicationThread thread, ...) { + ProcessRecord app = mPidsSelfLocked.get(pid); + // IPC 调用，回到应用进程 + thread.bindApplication(...); + // 以下处理挂起的应用组件 + mStackSupervisor.attachApplicationLocked(app); + mServices.attachApplicationLocked(app, processName); + sendPendingBroadcastsLocked(app); +} +``` + +```java +boolean attachApplicationLocked(ProcessRecord app) { + // stack: mFocusedStack， + ActivityRecord hr = stack.topRunningActivityLocked(null); + realStartActivityLocked(hr, app, true, true); +} +``` + +```java +final boolean realStartActivityLocked(ActivityRecord r, ) { + // ProcessRecord.ApplicationThread.scheduleLaunchActivity + app.thread.scheduleLaunchActivity(new Intent(r.intent), ...); +} +``` + +```java +@Override +public final void scheduleLaunchActivity(Intent intent, IBinder token, ){ + ActivityClientRecord r = new ActivityClientRecord(); + // mH,sendMessage，丢到主线程的 Handler + sendMessage(H.LAUNCH_ACTIVITY, r); +} +``` + +```java +// 主线程处理 +final ActivityClientRecord r = (ActivityClientRecord)msg.obj; +// 生成 LoadedApk 对象 +r.packageInfo = getPackageInfoNoCheck(...); +handleLaunchActivity(r, null); +``` + +```java +private void handleLaunchActivity(ActivityClientRecord r, ...) { + Activity a = performLaunchActivity(r, customIntent); + if(a!=null) { + handleResumeActivity(r.token, false, ...); + } +} +``` + +```java +private Activity performLaunchActivity(ActivityClientRecord r, ...) { + Activity activity = mInstrumentation.newActivity(...); + Application app = r.packageInfo.makeApplication(false, mInstrumentation); + Context appContext = createBaseContextForActivity(r, activity); + // activity.attach + activity.attach(appContext, ...); + // activity.onCreate + mInstrumentation.callActivityOnCreate(activity, r.state); + // activity.onStart + activity.performStart(); + return activity; +} +``` + +```java +final void handleResumeActivity(IBinder token) { + ActivityClientRecord r = performResumeActivity(...); + //... +} +``` + +**总结** + +1. 创建 Activity 对象 + + 首先通过 ClassLoder 加载 LoadedApk 里的类生成 Activity 对象 + +2. 准备好 Application + + Application 在应用进程启动时就已经创建好了，这一步直接拿即可 + +3. 创建 ContextImpl + +4. attach 上下文 + +5. 生命周期回调 + +![Activity 启动流程](/Users/omooo/Downloads/Activity 启动流程.png) + +#### 说说 Activity 的启动流程 + +1. 启动 Activity 要向 AMS 发起 binder 调用 +2. Activity 所在进程是怎么启动的？ +3. 应用 Activity 的生命周期回调原理 \ No newline at end of file