android内核剖析-----activity启动流程

主要类 :ActivityThread(一个应用的启动入口) ActivityServiceManager(负责所有activity的管理)

每个应用的启动都会产生一条ActivityThread线程     负责维护该应用

当ActivityThread接收到ActivityServiceManager发送而来的启动activity的信息时

调用 scheduleLaunchActivity

 public final void scheduleLaunchActivity(Intent intent, IBinder token, int ident,                ActivityInfo info, Bundle state, List<ResultInfo> pendingResults,                List<Intent> pendingNewIntents, boolean notResumed, boolean isForward) {            ActivityClientRecord r = new ActivityClientRecord();            r.token = token;            r.ident = ident;            r.intent = intent;            r.activityInfo = info;            r.state = state;            r.pendingResults = pendingResults;            r.pendingIntents = pendingNewIntents;            r.startsNotResumed = notResumed;            r.isForward = isForward;            queueOrSendMessage(H.LAUNCH_ACTIVITY, r);        }

然后通过handler发送一条异步处理请求 在handleMessage中处理了请求

 public void handleMessage(Message msg) {            if (DEBUG_MESSAGES) Slog.v(TAG, ">>> handling: " + msg.what);            switch (msg.what) {                case LAUNCH_ACTIVITY: {                    ActivityClientRecord r = (ActivityClientRecord)msg.obj;                    r.packageInfo = getPackageInfoNoCheck(                            r.activityInfo.applicationInfo);                    handleLaunchActivity(r, null);                } break;......}

handleLaunchActivity:

 private final void handleLaunchActivity(ActivityClientRecord r, Intent customIntent) {        // If we are getting ready to gc after going to the background, well        // we are back active so skip it.        unscheduleGcIdler();        if (localLOGV) Slog.v(            TAG, "Handling launch of " + r);        Activity a = performLaunchActivity(r, customIntent);        if (a != null) {            r.createdConfig = new Configuration(mConfiguration);            Bundle oldState = r.state;            handleResumeActivity(r.token, false, r.isForward);            if (!r.activity.mFinished && r.startsNotResumed) {                // The activity manager actually wants this one to start out                // paused, because it needs to be visible but isn't in the                // foreground.  We accomplish this by going through the                // normal startup (because activities expect to go through                // onResume() the first time they run, before their window                // is displayed), and then pausing it.  However, in this case                // we do -not- need to do the full pause cycle (of freezing                // and such) because the activity manager assumes it can just                // retain the current state it has.                try {                    r.activity.mCalled = false;                    mInstrumentation.callActivityOnPause(r.activity);                    // We need to keep around the original state, in case                    // we need to be created again.                    r.state = oldState;                    if (!r.activity.mCalled) {                        throw new SuperNotCalledException(                            "Activity " + r.intent.getComponent().toShortString() +                            " did not call through to super.onPause()");                    }                } catch (SuperNotCalledException e) {                    throw e;                } catch (Exception e) {                    if (!mInstrumentation.onException(r.activity, e)) {                        throw new RuntimeException(                                "Unable to pause activity "                                + r.intent.getComponent().toShortString()                                + ": " + e.toString(), e);                    }                }                r.paused = true;            }        } else {            // If there was an error, for any reason, tell the activity            // manager to stop us.            try {                ActivityManagerNative.getDefault()                    .finishActivity(r.token, Activity.RESULT_CANCELED, null);            } catch (RemoteException ex) {            }        }    }

通过performLaunchActivity 最后通过反射得到了activity对象

 private final Activity performLaunchActivity(ActivityClientRecord r, Intent customIntent) {        // System.out.println("##### [" + System.currentTimeMillis() + "] ActivityThread.performLaunchActivity(" + r + ")");        ActivityInfo aInfo = r.activityInfo;        if (r.packageInfo == null) {            r.packageInfo = getPackageInfo(aInfo.applicationInfo,                    Context.CONTEXT_INCLUDE_CODE);        }        ComponentName component = r.intent.getComponent();        if (component == null) {            component = r.intent.resolveActivity(                mInitialApplication.getPackageManager());            r.intent.setComponent(component);        }        if (r.activityInfo.targetActivity != null) {            component = new ComponentName(r.activityInfo.packageName,                    r.activityInfo.targetActivity);        }        Activity activity = null;        try {            java.lang.ClassLoader cl = r.packageInfo.getClassLoader();            activity = mInstrumentation.newActivity(                    cl, component.getClassName(), r.intent);            r.intent.setExtrasClassLoader(cl);            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);            }        }        try {            Application app = r.packageInfo.makeApplication(false, mInstrumentation);            if (localLOGV) Slog.v(TAG, "Performing launch of " + r);            if (localLOGV) Slog.v(                    TAG, r + ": app=" + app                    + ", appName=" + app.getPackageName()                    + ", pkg=" + r.packageInfo.getPackageName()                    + ", comp=" + r.intent.getComponent().toShortString()                    + ", dir=" + r.packageInfo.getAppDir());            if (activity != null) {                ContextImpl appContext = new ContextImpl();                appContext.init(r.packageInfo, r.token, this);                appContext.setOuterContext(activity);                CharSequence title = r.activityInfo.loadLabel(appContext.getPackageManager());                Configuration config = new Configuration(mConfiguration);                if (DEBUG_CONFIGURATION) Slog.v(TAG, "Launching activity "                        + r.activityInfo.name + " with config " + config);                activity.attach(appContext, this, getInstrumentation(), r.token,                        r.ident, app, r.intent, r.activityInfo, title, r.parent,                        r.embeddedID, r.lastNonConfigurationInstance,                        r.lastNonConfigurationChildInstances, config);                if (customIntent != null) {                    activity.mIntent = customIntent;                }                r.lastNonConfigurationInstance = null;                r.lastNonConfigurationChildInstances = null;                activity.mStartedActivity = false;                int theme = r.activityInfo.getThemeResource();                if (theme != 0) {                    activity.setTheme(theme);                }                activity.mCalled = false;                mInstrumentation.callActivityOnCreate(activity, r.state);                if (!activity.mCalled) {                    throw new SuperNotCalledException(                        "Activity " + r.intent.getComponent().toShortString() +                        " did not call through to super.onCreate()");                }                r.activity = activity;                r.stopped = true;                if (!r.activity.mFinished) {                    activity.performStart();                    r.stopped = false;                }                if (!r.activity.mFinished) {                    if (r.state != null) {                        mInstrumentation.callActivityOnRestoreInstanceState(activity, r.state);                    }                }                if (!r.activity.mFinished) {                    activity.mCalled = false;                    mInstrumentation.callActivityOnPostCreate(activity, r.state);                    if (!activity.mCalled) {                        throw new SuperNotCalledException(                            "Activity " + r.intent.getComponent().toShortString() +                            " did not call through to super.onPostCreate()");                    }                }            }            r.paused = true;            mActivities.put(r.token, r);        } catch (SuperNotCalledException e) {            throw e;        } catch (Exception e) {            if (!mInstrumentation.onException(activity, e)) {                throw new RuntimeException(                    "Unable to start activity " + component                    + ": " + e.toString(), e);            }        }        return activity;    }

在 performLaunchActivity中执行了

 activity.attach(appContext, this, getInstrumentation(), r.token, ---- attach 额外说明在attach()方法中   把contextImpl对象存进去
                        r.ident, app, r.intent, r.activityInfo, title, r.parent,
                        r.embeddedID, r.lastNonConfigurationInstance,
                        r.lastNonConfigurationChildInstances, config);

mInstrumentation.callActivityOnCreate(activity, r.state); ----onCreate  mInstrumentation内部持有activity对象

activity.performStart();----onstart

if (!r.activity.mFinished) {                    if (r.state != null) {                        mInstrumentation.callActivityOnRestoreInstanceState(activity, r.state);                    }                }

在onPause之后来恢复状态的