Android4.4.4启动Activity源码记录

//本文主要是自己记录流程使用

1、Activity中的startActivity()方法

@Override    public void startActivity(Intent intent) {        startActivity(intent, null);    }

@Override    public void startActivity(Intent intent, Bundle options) {        if (options != null) {            startActivityForResult(intent, -1, options);        } else {            // Note we want to go through this call for compatibility with            // applications that may have overridden the method.            startActivityForResult(intent, -1);        }    }

public void startActivityForResult(Intent intent, int requestCode) {        startActivityForResult(intent, requestCode, null);    }

public void startActivityForResult(Intent intent, int requestCode, Bundle options) {        if (mParent == null) {//现在走的是这里            Instrumentation.ActivityResult ar =                mInstrumentation.execStartActivity(//执行主要是在Instrumentation类这里                    this, mMainThread.getApplicationThread(), mToken, this,                    intent, requestCode, options);            if (ar != null) {                mMainThread.sendActivityResult(                    mToken, mEmbeddedID, requestCode, ar.getResultCode(),                    ar.getResultData());            }            if (requestCode >= 0) {                // If this start is requesting a result, we can avoid making                // the activity visible until the result is received.  Setting                // this code during onCreate(Bundle savedInstanceState) or onResume() will keep the                // activity hidden during this time, to avoid flickering.                // This can only be done when a result is requested because                // that guarantees we will get information back when the                // activity is finished, no matter what happens to it.                mStartedActivity = true;            }            final View decor = mWindow != null ? mWindow.peekDecorView() : null;            if (decor != null) {                decor.cancelPendingInputEvents();            }            // TODO Consider clearing/flushing other event sources and events for child windows.        } else {            if (options != null) {                mParent.startActivityFromChild(this, intent, requestCode, options);            } else {                // Note we want to go through this method for compatibility with                // existing applications that may have overridden it.                mParent.startActivityFromChild(this, intent, requestCode);            }        }    }

2、Instrumentation类

public ActivityResult execStartActivity(            Context who, IBinder contextThread, IBinder token, Activity target,            Intent intent, int requestCode, Bundle options) {        IApplicationThread whoThread = (IApplicationThread) contextThread;        if (mActivityMonitors != null) {            synchronized (mSync) {                final int N = mActivityMonitors.size();                for (int i=0; i<N; i++) {                    final ActivityMonitor am = mActivityMonitors.get(i);                    if (am.match(who, null, intent)) {                        am.mHits++;                        if (am.isBlocking()) {                            return requestCode >= 0 ? am.getResult() : null;                        }                        break;                    }                }            }        }        try {            intent.migrateExtraStreamToClipData();            intent.prepareToLeaveProcess();            int result = ActivityManagerNative.getDefault()//主要是在这里执行，这里主要是在whoThread中执行的                .startActivity(whoThread, who.getBasePackageName(), intent,                        intent.resolveTypeIfNeeded(who.getContentResolver()),                        token, target != null ? target.mEmbeddedID : null,                        requestCode, 0, null, null, options);            checkStartActivityResult(result, intent);        } catch (RemoteException e) {        }        return null;    }

3、ActivityManagerNative类

 public int startActivity(IApplicationThread caller, String callingPackage, Intent intent,            String resolvedType, IBinder resultTo, String resultWho, int requestCode,            int startFlags, String profileFile,            ParcelFileDescriptor profileFd, Bundle options) throws RemoteException {        Parcel data = Parcel.obtain();        Parcel reply = Parcel.obtain();        data.writeInterfaceToken(IActivityManager.descriptor);        data.writeStrongBinder(caller != null ? caller.asBinder() : null);        data.writeString(callingPackage);        intent.writeToParcel(data, 0);        data.writeString(resolvedType);        data.writeStrongBinder(resultTo);        data.writeString(resultWho);        data.writeInt(requestCode);        data.writeInt(startFlags);        data.writeString(profileFile);        if (profileFd != null) {            data.writeInt(1);            profileFd.writeToParcel(data, Parcelable.PARCELABLE_WRITE_RETURN_VALUE);        } else {            data.writeInt(0);        }        if (options != null) {            data.writeInt(1);            options.writeToParcel(data, 0);        } else {            data.writeInt(0);        }        mRemote.transact(START_ACTIVITY_TRANSACTION, data, reply, 0);        reply.readException();        int result = reply.readInt();        reply.recycle();        data.recycle();        return result;    }    public int startActivityAsUser(IApplicationThread caller, //主要是这里IApplicationThread

String callingPackage, Intent intent,            String resolvedType, IBinder resultTo, String resultWho, int requestCode,            int startFlags, String profileFile,            ParcelFileDescriptor profileFd, Bundle options, int userId) throws RemoteException {        Parcel data = Parcel.obtain();        Parcel reply = Parcel.obtain();        data.writeInterfaceToken(IActivityManager.descriptor);        data.writeStrongBinder(caller != null ? caller.asBinder() : null);        data.writeString(callingPackage);        intent.writeToParcel(data, 0);        data.writeString(resolvedType);        data.writeStrongBinder(resultTo);        data.writeString(resultWho);        data.writeInt(requestCode);        data.writeInt(startFlags);        data.writeString(profileFile);        if (profileFd != null) {            data.writeInt(1);            profileFd.writeToParcel(data, Parcelable.PARCELABLE_WRITE_RETURN_VALUE);        } else {            data.writeInt(0);        }        if (options != null) {            data.writeInt(1);            options.writeToParcel(data, 0);        } else {            data.writeInt(0);        }        data.writeInt(userId);        mRemote.transact(START_ACTIVITY_AS_USER_TRANSACTION, data, reply, 0);        reply.readException();        int result = reply.readInt();        reply.recycle();        data.recycle();        return result;    }

4、IApplicationThread类

void scheduleLaunchActivity(Intent intent, IBinder token, int ident,            ActivityInfo info, Configuration curConfig, CompatibilityInfo compatInfo,            int procState, Bundle state, List<ResultInfo> pendingResults,    List<Intent> pendingNewIntents, boolean notResumed, boolean isForward,    String profileName, ParcelFileDescriptor profileFd, boolean autoStopProfiler)    throws RemoteException;

该方法是个接口，具体的实现类是ActivityThread中的内部类ApplicationThread
5、ActivityThread类

 public final void scheduleLaunchActivity(Intent intent, IBinder token, int ident,                ActivityInfo info, Configuration curConfig, CompatibilityInfo compatInfo,                int procState, Bundle state, List<ResultInfo> pendingResults,                List<Intent> pendingNewIntents, boolean notResumed, boolean isForward,                String profileName, ParcelFileDescriptor profileFd, boolean autoStopProfiler) {            updateProcessState(procState, false);            ActivityClientRecord r = new ActivityClientRecord();            r.token = token;            r.ident = ident;            r.intent = intent;            r.activityInfo = info;            r.compatInfo = compatInfo;            r.state = state;            r.pendingResults = pendingResults;            r.pendingIntents = pendingNewIntents;            r.startsNotResumed = notResumed;            r.isForward = isForward;            r.profileFile = profileName;            r.profileFd = profileFd;            r.autoStopProfiler = autoStopProfiler;            updatePendingConfiguration(curConfig);            sendMessage(H.LAUNCH_ACTIVITY, r);//主要看这里        }

6、H中的部分代码

public void handleMessage(Message msg) {            if (DEBUG_MESSAGES) Slog.v(TAG, ">>> handling: " + codeToString(msg.what));            switch (msg.what) {                case LAUNCH_ACTIVITY: {                    Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "activityStart");                    ActivityClientRecord r = (ActivityClientRecord)msg.obj;                    r.packageInfo = getPackageInfoNoCheck(                            r.activityInfo.applicationInfo, r.compatInfo);                    handleLaunchActivity(r, null);//主要是这里                    Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);                } break;        }}

7、handleLaunchActivity(r,null)方法;

private 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 (r.profileFd != null) {            mProfiler.setProfiler(r.profileFile, r.profileFd);            mProfiler.startProfiling();            mProfiler.autoStopProfiler = r.autoStopProfiler;        }        // Make sure we are running with the most recent config.        handleConfigurationChanged(null, null);        if (localLOGV) Slog.v(            TAG, "Handling launch of " + r);        Activity a = performLaunchActivity(r, customIntent);//重点在这里，Activity实例化，并且会回调onCreate();        if (a != null) {            r.createdConfig = new Configuration(mConfiguration);            Bundle oldState = r.state;            handleResumeActivity(r.token, false, r.isForward,//这里回调resume()的方法                    !r.activity.mFinished && !r.startsNotResumed);            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.  But we only do this                    // for pre-Honeycomb apps, which always save their state                    // when pausing, so we can not have them save their state                    // when restarting from a paused state.  For HC and later,                    // we want to (and can) let the state be saved as the normal                    // part of stopping the activity.                    if (r.isPreHoneycomb()) {                        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) {                // Ignore            }        }    }

8、performLaunchActivity()这个方法

private 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, r.compatInfo,                    Context.CONTEXT_INCLUDE_CODE);        }//首先从intent中解析出目标activity的启动参数          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 {

    //用ClassLoader（类加载器）将目标activity的类通过类名加载进来并调用newInstance来实例化一个对象

    //其实就是通过Activity的无参构造方法来new一个对象，对象就是在这里new出来的。            java.lang.ClassLoader cl = r.packageInfo.getClassLoader();            activity = mInstrumentation.newActivity(                    cl, component.getClassName(), r.intent);            StrictMode.incrementExpectedActivityCount(activity.getClass());            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) {                Context appContext = createBaseContextForActivity(r, activity);                CharSequence title = r.activityInfo.loadLabel(appContext.getPackageManager());                Configuration config = new Configuration(mCompatConfiguration);                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.lastNonConfigurationInstances, config);                if (customIntent != null) {                    activity.mIntent = customIntent;                }                r.lastNonConfigurationInstances = null;                activity.mStartedActivity = false;                int theme = r.activityInfo.getThemeResource();                if (theme != 0) {                    activity.setTheme(theme);                }                activity.mCalled = false;

//目标activity的onCreate被调用了，到此为止，Activity被启动了，接下来的流程就是Activity的生命周期了，

//其生命周期的各种状态的切换由ApplicationThread内部来完成                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)) {                if (e instanceof InflateException) {                    Log.e(TAG, "Failed to inflate", e);                    String pkg = null;                    if (r.packageInfo != null && !TextUtils.isEmpty(r.packageInfo.getPackageName())) {                        pkg = r.packageInfo.getPackageName();                    }                    Intent intent = new Intent(Intent.ACTION_APP_LAUNCH_FAILURE,                            (pkg != null)? Uri.fromParts("package", pkg, null) : null);                    getSystemContext().sendBroadcast(intent);                }                throw new RuntimeException(                    "Unable to start activity " + component                    + ": " + e.toString(), e);            }        }        return activity;    }

====完结，参照大神任玉刚====