从应用启动看Activity的创建过程
从应用启动看Activity的创建过程
Kobe_Gong_5 发表于2年前
从应用启动看Activity的创建过程
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/*
*Acitivity的创建过程:
*应用程序的入口为ActivityThread的main函数。
*在main函数中:
*/
public static void main(String[] args) {
SamplingProfilerIntegration.start();

// CloseGuard defaults to true and can be quite spammy. We
        // disable it here, but selectively enable it later (via
        // StrictMode) on debug builds, but using DropBox, not logs.
        CloseGuard.setEnabled(false);


//为当前的User初始化一个用户目录,以及一些环境变量
        Environment.initForCurrentUser();


        // Set the reporter for event logging in libcore
        EventLogger.setReporter(new EventLoggingReporter());


        Security.addProvider(new AndroidKeyStoreProvider());


        // Make sure TrustedCertificateStore looks in the right place for CA certificates
        final File configDir = Environment.getUserConfigDirectory(UserHandle.myUserId());
        TrustedCertificateStore.setDefaultUserDirectory(configDir);


        Process.setArgV0("<pre-initialized>");


        Looper.prepareMainLooper();


//创建了一个AcitivityThread,
        ActivityThread thread = new ActivityThread();
        thread.attach(false);


        if (sMainThreadHandler == null) {
            sMainThreadHandler = thread.getHandler();
        }


        AsyncTask.init();


        if (false) {
            Looper.myLooper().setMessageLogging(new
                    LogPrinter(Log.DEBUG, "ActivityThread"));
        }


        Looper.loop();


        throw new RuntimeException("Main thread loop unexpectedly exited");
    }
private void attach(boolean system) {
        //将当前的ActivityThread对象赋值给ActivityThread的静态变量sCurrentActivityThread
        sCurrentActivityThread = this;
        mSystemThread = system;//system=false
        if (!system) {
            ViewRootImpl.addFirstDrawHandler(new Runnable() {
                @Override
                public void run() {
                    ensureJitEnabled();
                }
            });
            android.ddm.DdmHandleAppName.setAppName("<pre-initialized>",
                                                    UserHandle.myUserId());
            RuntimeInit.setApplicationObject(mAppThread.asBinder());
            //ActivityManagerNative属于IPC代理类,IPC服务端是ActivityManagerService
            final IActivityManager mgr = ActivityManagerNative.getDefault();
            try {
                /*IPC调用attachApplication,aAppThread是ApplicationThread类型。 ApplicationThread继承于ApplicationThreadNative,ApplicationThreadNative继承于Binder。 Application创建之前的一些工作 */
                mgr.attachApplication(mAppThread);
            } catch (RemoteException ex) {
                // Ignore
            }
            // Watch for getting close to heap limit.
            BinderInternal.addGcWatcher(new Runnable() {
                @Override public void run() {
                    if (!mSomeActivitiesChanged) {
                        return;
                    }
                    Runtime runtime = Runtime.getRuntime();
                    long dalvikMax = runtime.maxMemory();
                    long dalvikUsed = runtime.totalMemory() - runtime.freeMemory();
                    if (dalvikUsed > ((3*dalvikMax)/4)) {
                        if (DEBUG_MEMORY_TRIM) Slog.d(TAG, "Dalvik max=" + (dalvikMax/1024)
                                + " total=" + (runtime.totalMemory()/1024)
                                + " used=" + (dalvikUsed/1024));
                        mSomeActivitiesChanged = false;
                        try {
                            mgr.releaseSomeActivities(mAppThread);
                        } catch (RemoteException e) {
                        }
                    }
                }
            });
        } else {
            //由于system为false,所以此处不执行

            android.ddm.DdmHandleAppName.setAppName("system_process",
                    UserHandle.myUserId());
            try {
                //接下来是创建ContextImpl,Application,调用Application的onCreate
                mInstrumentation = new Instrumentation();
                ContextImpl context = ContextImpl.createAppContext(
                        this, getSystemContext().mPackageInfo);
                mInitialApplication = context.mPackageInfo.makeApplication(true, null);
                mInitialApplication.onCreate();
            } catch (Exception e) {
                throw new RuntimeException(
                        "Unable to instantiate Application():" + e.toString(), e);
            }
        }

        // add dropbox logging to libcore
        DropBox.setReporter(new DropBoxReporter());

        ViewRootImpl.addConfigCallback(new ComponentCallbacks2() {
            @Override
            public void onConfigurationChanged(Configuration newConfig) {
                synchronized (mResourcesManager) {
                    // We need to apply this change to the resources
                    // immediately, because upon returning the view
                    // hierarchy will be informed about it.
                    if (mResourcesManager.applyConfigurationToResourcesLocked(newConfig, null)) {
                        // This actually changed the resources! Tell
                        // everyone about it.
                        if (mPendingConfiguration == null ||
                                mPendingConfiguration.isOtherSeqNewer(newConfig)) {
                            mPendingConfiguration = newConfig;

                            sendMessage(H.CONFIGURATION_CHANGED, newConfig);
                        }
                    }
                }
            }
            @Override
            public void onLowMemory() {
            }
            @Override
            public void onTrimMemory(int level) {
            }
        });
    }

//在ActivityManagerService.java中:
    @Override
    public final void attachApplication(IApplicationThread thread) {
        synchronized (this) {
            int callingPid = Binder.getCallingPid();
            final long origId = Binder.clearCallingIdentity();
            attachApplicationLocked(thread, callingPid);
            Binder.restoreCallingIdentity(origId);
        }
    }



    private final boolean attachApplicationLocked(IApplicationThread thread,
            int pid) {

        // Find the application record that is being attached... either via
        // the pid if we are running in multiple processes, or just pull the
        // next app record if we are emulating process with anonymous threads.
        ProcessRecord app;
        if (pid != MY_PID && pid >= 0) {
            synchronized (mPidsSelfLocked) {
                app = mPidsSelfLocked.get(pid);
            }
        } else {
            app = null;
        }

        if (app == null) {
            Slog.w(TAG, "No pending application record for pid " + pid
                    + " (IApplicationThread " + thread + "); dropping process");
            EventLog.writeEvent(EventLogTags.AM_DROP_PROCESS, pid);
            if (pid > 0 && pid != MY_PID) {
                Process.killProcessQuiet(pid);
                //TODO: Process.killProcessGroup(app.info.uid, pid);
            } else {
                try {
                    thread.scheduleExit();
                } catch (Exception e) {
                    // Ignore exceptions.
                }
            }
            return false;
        }

        //此处省去部分代码
       ......


        boolean badApp = false;
        boolean didSomething = false;

        // See if the top visible activity is waiting to run in this process...
        if (normalMode) {
            try {

                if (mStackSupervisor.attachApplicationLocked(app)) {
                    didSomething = true;
                }
            } catch (Exception e) {
                Slog.wtf(TAG, "Exception thrown launching activities in " + app, e);
                badApp = true;
            }
        }


        //此处省去部分代码
       ......


        return true;
    }


     boolean attachApplicationLocked(ProcessRecord app) throws RemoteException {
        final String processName = app.processName;
        boolean didSomething = false;
        for (int displayNdx = mActivityDisplays.size() - 1; displayNdx >= 0; --displayNdx) {
            ArrayList<ActivityStack> stacks = mActivityDisplays.valueAt(displayNdx).mStacks;
            for (int stackNdx = stacks.size() - 1; stackNdx >= 0; --stackNdx) {
                final ActivityStack stack = stacks.get(stackNdx);
                if (!isFrontStack(stack)) {
                    continue;
                }
                ActivityRecord hr = stack.topRunningActivityLocked(null);
                if (hr != null) {
                    if (hr.app == null && app.uid == hr.info.applicationInfo.uid
                            && processName.equals(hr.processName)) {
                        try {
                            if (realStartActivityLocked(hr, app, true, true)) {
                                didSomething = true;
                            }
                        } catch (RemoteException e) {
                            Slog.w(TAG, "Exception in new application when starting activity "
                                  + hr.intent.getComponent().flattenToShortString(), e);
                            throw e;
                        }
                    }
                }
            }
        }
        if (!didSomething) {
            ensureActivitiesVisibleLocked(null, 0);
        }
        return didSomething;
    }


    final boolean realStartActivityLocked(ActivityRecord r,
            ProcessRecord app, boolean andResume, boolean checkConfig)
            throws RemoteException {

        r.startFreezingScreenLocked(app, 0);
        if (false) Slog.d(TAG, "realStartActivity: setting app visibility true");
        mWindowManager.setAppVisibility(r.appToken, true);

       ......


            //在此处通过IPC方式调用了ActivityThread的scheduleLaunchActivity,
            //scheduleLaunchActivity方法向主线程消息队列中发送了一个LAUNCH_ACTIVITY的消息。
            app.thread.scheduleLaunchActivity(new Intent(r.intent), r.appToken,
                    System.identityHashCode(r), r.info, new Configuration(mService.mConfiguration),
                    r.compat, r.task.voiceInteractor, app.repProcState, r.icicle, r.persistentState,
                    results, newIntents, !andResume, mService.isNextTransitionForward(),
                    profilerInfo);
    //此处省去部分代码
    ......
        return true;
    }

    //到此在ActivityThread.java.attch()中的mgr.attachApplication(mAppThread);这句代码就执行完了。
    //attach方法执行完后,ActivityThread的Handler就去执行LAUNCH_ACTIVITY的消息了。也就是执行handleLaunchActivity().

    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();
        mSomeActivitiesChanged = true;
        //此处省去部分代码
        ......

        //此处终于创建了Acitivity
        Activity a = performLaunchActivity(r, customIntent);

        if (a != null) {
            r.createdConfig = new Configuration(mConfiguration);
            Bundle oldState = r.state;
            handleResumeActivity(r.token, false, r.isForward,
                    !r.activity.mFinished && !r.startsNotResumed);
            //此处省去部分代码
           .....

        } 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, false);
            } catch (RemoteException ex) {
                // Ignore
            }
        }
    }

    //这里有两个重要的方法。
    //1.performLaunchActivity。
    //2.handleResumeActivity

    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);
        }

        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();

            //此处创建了Activity对象
            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);
            }
        }

        try {
            //创建Application对象
            Application app = r.packageInfo.makeApplication(false, mInstrumentation);


            if (activity != null) {
                Context appContext = createBaseContextForActivity(r, activity);
                CharSequence title = r.activityInfo.loadLabel(appContext.getPackageManager());
                Configuration config = new Configuration(mCompatConfiguration);

                activity.attach(appContext, this, getInstrumentation(), r.token,
                        r.ident, app, r.intent, r.activityInfo, title, r.parent,
                        r.embeddedID, r.lastNonConfigurationInstances, config,
                        r.voiceInteractor);

                if (customIntent != null) {
                    activity.mIntent = customIntent;
                }
                r.lastNonConfigurationInstances = null;
                activity.mStartedActivity = false;

                //在此设置activity的主题
                int theme = r.activityInfo.getThemeResource();
                if (theme != 0) {
                    activity.setTheme(theme);
                }

                activity.mCalled = false;
                //调用Activity的onCreate方法
                if (r.isPersistable()) {
                    mInstrumentation.callActivityOnCreate(activity, r.state, r.persistentState);
                } else {
                    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;
                //调用activity的onStart方法
                if (!r.activity.mFinished) {
                    activity.performStart();
                    r.stopped = false;
                }
                //调用activity的OnRestoreInstanceState方法
                if (!r.activity.mFinished) {
                    if (r.isPersistable()) {
                        if (r.state != null || r.persistentState != null) {
                            mInstrumentation.callActivityOnRestoreInstanceState(activity, r.state,
                                    r.persistentState);
                        }
                    } else if (r.state != null) {
                        mInstrumentation.callActivityOnRestoreInstanceState(activity, r.state);
                    }
                }
                //调用activity的onPostCreate方法
                if (!r.activity.mFinished) {
                    activity.mCalled = false;
                    if (r.isPersistable()) {
                        mInstrumentation.callActivityOnPostCreate(activity, r.state,
                                r.persistentState);
                    } else {
                        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;
    }

    //调用了mInstrumentation.newActivity去创建Activity。
    //之后,调用了Activity的attach方法,在其中创建了window,设置了windowManager,
     public Activity newActivity(ClassLoader cl, String className,
            Intent intent)
            throws InstantiationException, IllegalAccessException,
            ClassNotFoundException {
        return (Activity)cl.loadClass(className).newInstance();
    }
    //newActivity方法很简单,通过反射创建Activity。

    //看完了performLaunchActivity。就进入另一个重要的方法handleResumeActivity
    final void handleResumeActivity(IBinder token,
            boolean clearHide, boolean isForward, boolean reallyResume) {
        // If we are getting ready to gc after going to the background, well
        // we are back active so skip it.
        unscheduleGcIdler();
        mSomeActivitiesChanged = true;

        // TODO Push resumeArgs into the activity for consideration
        ActivityClientRecord r = performResumeActivity(token, clearHide);

        if (r != null) {
            final Activity a = r.activity;

            if (localLOGV) Slog.v(
                TAG, "Resume " + r + " started activity: " +
                a.mStartedActivity + ", hideForNow: " + r.hideForNow
                + ", finished: " + a.mFinished);

            final int forwardBit = isForward ?
                    WindowManager.LayoutParams.SOFT_INPUT_IS_FORWARD_NAVIGATION : 0;

            // If the window hasn't yet been added to the window manager,
            // and this guy didn't finish itself or start another activity,
            // then go ahead and add the window.
            boolean willBeVisible = !a.mStartedActivity;
            if (!willBeVisible) {
                try {
                    willBeVisible = ActivityManagerNative.getDefault().willActivityBeVisible(
                            a.getActivityToken());
                } catch (RemoteException e) {
                }
            }
            if (r.window == null && !a.mFinished && willBeVisible) {
                r.window = r.activity.getWindow();
                View decor = r.window.getDecorView();
                decor.setVisibility(View.INVISIBLE);
                ViewManager wm = a.getWindowManager();
                WindowManager.LayoutParams l = r.window.getAttributes();
                a.mDecor = decor;
                l.type = WindowManager.LayoutParams.TYPE_BASE_APPLICATION;
                l.softInputMode |= forwardBit;
                if (a.mVisibleFromClient) {
                    a.mWindowAdded = true;
                    wm.addView(decor, l);
                }

            // If the window has already been added, but during resume
            // we started another activity, then don't yet make the
            // window visible.
            } else if (!willBeVisible) {
                if (localLOGV) Slog.v(
                    TAG, "Launch " + r + " mStartedActivity set");
                r.hideForNow = true;
            }

            // Get rid of anything left hanging around.
            cleanUpPendingRemoveWindows(r);

            // The window is now visible if it has been added, we are not
            // simply finishing, and we are not starting another activity.
            if (!r.activity.mFinished && willBeVisible
                    && r.activity.mDecor != null && !r.hideForNow) {
                if (r.newConfig != null) {
                    if (DEBUG_CONFIGURATION) Slog.v(TAG, "Resuming activity "
                            + r.activityInfo.name + " with newConfig " + r.newConfig);
                    performConfigurationChanged(r.activity, r.newConfig);
                    freeTextLayoutCachesIfNeeded(r.activity.mCurrentConfig.diff(r.newConfig));
                    r.newConfig = null;
                }
                if (localLOGV) Slog.v(TAG, "Resuming " + r + " with isForward="
                        + isForward);
                WindowManager.LayoutParams l = r.window.getAttributes();
                if ((l.softInputMode
                        & WindowManager.LayoutParams.SOFT_INPUT_IS_FORWARD_NAVIGATION)
                        != forwardBit) {
                    l.softInputMode = (l.softInputMode
                            & (~WindowManager.LayoutParams.SOFT_INPUT_IS_FORWARD_NAVIGATION))
                            | forwardBit;
                    if (r.activity.mVisibleFromClient) {
                        ViewManager wm = a.getWindowManager();
                        View decor = r.window.getDecorView();
                        wm.updateViewLayout(decor, l);
                    }
                }
                r.activity.mVisibleFromServer = true;
                mNumVisibleActivities++;
                if (r.activity.mVisibleFromClient) {
                    r.activity.makeVisible();
                }
            }

            if (!r.onlyLocalRequest) {
                r.nextIdle = mNewActivities;
                mNewActivities = r;
                if (localLOGV) Slog.v(
                    TAG, "Scheduling idle handler for " + r);
                Looper.myQueue().addIdleHandler(new Idler());
            }
            r.onlyLocalRequest = false;

            // Tell the activity manager we have resumed.
            if (reallyResume) {
                try {
                    ActivityManagerNative.getDefault().activityResumed(token);
                } catch (RemoteException ex) {
                }
            }

        } else {
            // If an exception was thrown when trying to resume, then
            // just end this activity.
            try {
                ActivityManagerNative.getDefault()
                    .finishActivity(token, Activity.RESULT_CANCELED, null, false);
            } catch (RemoteException ex) {
            }
        }
    }

    //先看看performResumeActivity方法。在此方法中调用activity的生命周期函数onResume。
    public final ActivityClientRecord performResumeActivity(IBinder token,
            boolean clearHide) {
        ActivityClientRecord r = mActivities.get(token);
        if (localLOGV) Slog.v(TAG, "Performing resume of " + r
                + " finished=" + r.activity.mFinished);
        if (r != null && !r.activity.mFinished) {
            if (clearHide) {
                r.hideForNow = false;
                r.activity.mStartedActivity = false;
            }
            try {
                r.activity.mFragments.noteStateNotSaved();
                if (r.pendingIntents != null) {
                    deliverNewIntents(r, r.pendingIntents);
                    r.pendingIntents = null;
                }
                if (r.pendingResults != null) {
                    deliverResults(r, r.pendingResults);
                    r.pendingResults = null;
                }

                //调用onResume方法
                r.activity.performResume();

                EventLog.writeEvent(LOG_ON_RESUME_CALLED,
                        UserHandle.myUserId(), r.activity.getComponentName().getClassName());

                r.paused = false;
                r.stopped = false;
                r.state = null;
                r.persistentState = null;
            } catch (Exception e) {
                if (!mInstrumentation.onException(r.activity, e)) {
                    throw new RuntimeException(
                        "Unable to resume activity "
                        + r.intent.getComponent().toShortString()
                        + ": " + e.toString(), e);
                }
            }
        }
        return r;
    }

    //然后重点就是下面这段代码:
     if (r.window == null && !a.mFinished && willBeVisible) {
                //先拿到window和windowManager对象,这两个对象在上面介绍的Activity的attch方法中创建。
                r.window = r.activity.getWindow();
                View decor = r.window.getDecorView();
                decor.setVisibility(View.INVISIBLE);
                ViewManager wm = a.getWindowManager();
                WindowManager.LayoutParams l = r.window.getAttributes();
                a.mDecor = decor;
                l.type = WindowManager.LayoutParams.TYPE_BASE_APPLICATION;
                l.softInputMode |= forwardBit;
                if (a.mVisibleFromClient) {
                    a.mWindowAdded = true;
                    //windowManager显示decorView,此方法
                    wm.addView(decor, l);
                }

            // If the window has already been added, but during resume
            // we started another activity, then don't yet make the
            // window visible.
            } else if (!willBeVisible) {
                if (localLOGV) Slog.v(
                    TAG, "Launch " + r + " mStartedActivity set");
                r.hideForNow = true;
            }

做个备注:
在ActivityThread.java中:
H是Handler的字类。负责处理Activity的各种操作。
performLaunchActivity中创建了Activity

LoadApk中存储了ActivityThread的引用,还有其他的一些关于该应用的目录等变量。
CompatibilityInfo类保存了应用程序运行的兼容性模式的信息

我们平时在Activity中使用的ContentResolver是ApplicationContentResolver类型的

标签: activity 创建 Android
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