android Q activity启动流程

调用者进程

Activity.java

    public void startActivityForResult(@RequiresPermission Intent intent, int requestCode,
            @Nullable Bundle options) {
        if (mParent == null) {
            options = transferSpringboardActivityOptions(options);
            Instrumentation.ActivityResult ar =
                mInstrumentation.execStartActivity(
                    this, mMainThread.getApplicationThread(), mToken, this,
                    intent, requestCode, options);
        ...
    }

Instrumentation.java

    public ActivityResult execStartActivity(
            Context who, IBinder contextThread, IBinder token, Activity target,
            Intent intent, int requestCode, Bundle options) {
        ...
        try {
            intent.migrateExtraStreamToClipData();
            intent.prepareToLeaveProcess(who);
            int result = ActivityManager.getService()
                .startActivity(whoThread, who.getBasePackageName(), intent,
                        intent.resolveTypeIfNeeded(who.getContentResolver()),
                        token, target != null ? target.mEmbeddedID : null,
                        requestCode, 0, null, options);
            checkStartActivityResult(result, intent);
        } catch (RemoteException e) {
            throw new RuntimeException("Failure from system", e);
        }
        return null;
    }

ActivityManager.getService()得到的是ActivityManagerService的binder client

系统进程

ActivityManagerService.java

    @Override
    public final int startActivity(IApplicationThread caller, String callingPackage,
            Intent intent, String resolvedType, IBinder resultTo, String resultWho, int requestCode,
            int startFlags, ProfilerInfo profilerInfo, Bundle bOptions) {
        return startActivityAsUser(caller, callingPackage, intent, resolvedType, resultTo,
                resultWho, requestCode, startFlags, profilerInfo, bOptions,
                UserHandle.getCallingUserId());
    }
	
	public final int startActivityAsUser(IApplicationThread caller, String callingPackage,
            Intent intent, String resolvedType, IBinder resultTo, String resultWho, int requestCode,
            int startFlags, ProfilerInfo profilerInfo, Bundle bOptions, int userId,
            boolean validateIncomingUser) {
        enforceNotIsolatedCaller("startActivity");

        userId = mActivityStartController.checkTargetUser(userId, validateIncomingUser,
                Binder.getCallingPid(), Binder.getCallingUid(), "startActivityAsUser");

        // TODO: Switch to user app stacks here.
        return mActivityStartController.obtainStarter(intent, "startActivityAsUser")
                .setCaller(caller)
                .setCallingPackage(callingPackage)
                .setResolvedType(resolvedType)
                .setResultTo(resultTo)
                .setResultWho(resultWho)
                .setRequestCode(requestCode)
                .setStartFlags(startFlags)
                .setProfilerInfo(profilerInfo)
                .setActivityOptions(bOptions)
                .setMayWait(userId)
                .execute();

    }

ActivityStartController.java

    /**
     * @return A starter to configure and execute starting an activity. It is valid until after
     *         {@link ActivityStarter#execute} is invoked. At that point, the starter should be
     *         considered invalid and no longer modified or used.
     */
    ActivityStarter obtainStarter(Intent intent, String reason) {
        return mFactory.obtain().setIntent(intent).setReason(reason);
    }

Factory是ActivityStarter的内部接口，默认实现类是ActivityStarter的内部类DefaultFactory

ActivityStarter.java

    static class DefaultFactory implements Factory {
        ...
        @Override
        public ActivityStarter obtain() {
            ActivityStarter starter = mStarterPool.acquire();

            if (starter == null) {
                starter = new ActivityStarter(mController, mService, mSupervisor, mInterceptor);
            }

            return starter;
        }
        ...
    }
	
	interface Factory {
        /**
         * Sets the {@link ActivityStartController} to be passed to {@link ActivityStarter}.
         */
        void setController(ActivityStartController controller);

        /**
         * Generates an {@link ActivityStarter} that is ready to handle a new start request.
         * @param controller The {@link ActivityStartController} which the starter who will own
         *                   this instance.
         * @return an {@link ActivityStarter}
         */
        ActivityStarter obtain();

        /**
         * Recycles a starter for reuse.
         */
        void recycle(ActivityStarter starter);
    }

execute()依旧是由ActivityStarter实现
ActivityStarter.java

    /**
     * Starts an activity based on the request parameters provided earlier.
     * @return The starter result.
     */
    int execute() {
        try {
            // TODO(b/64750076): Look into passing request directly to these methods to allow
            // for transactional diffs and preprocessing.
            if (mRequest.mayWait) {
                return startActivityMayWait(mRequest.caller, mRequest.callingUid,
                        mRequest.callingPackage, mRequest.intent, mRequest.resolvedType,
                        mRequest.voiceSession, mRequest.voiceInteractor, mRequest.resultTo,
                        mRequest.resultWho, mRequest.requestCode, mRequest.startFlags,
                        mRequest.profilerInfo, mRequest.waitResult, mRequest.globalConfig,
                        mRequest.activityOptions, mRequest.ignoreTargetSecurity, mRequest.userId,
                        mRequest.inTask, mRequest.reason,
                        mRequest.allowPendingRemoteAnimationRegistryLookup);
            } else {
                return startActivity(mRequest.caller, mRequest.intent, mRequest.ephemeralIntent,
                        mRequest.resolvedType, mRequest.activityInfo, mRequest.resolveInfo,
                        mRequest.voiceSession, mRequest.voiceInteractor, mRequest.resultTo,
                        mRequest.resultWho, mRequest.requestCode, mRequest.callingPid,
                        mRequest.callingUid, mRequest.callingPackage, mRequest.realCallingPid,
                        mRequest.realCallingUid, mRequest.startFlags, mRequest.activityOptions,
                        mRequest.ignoreTargetSecurity, mRequest.componentSpecified,
                        mRequest.outActivity, mRequest.inTask, mRequest.reason,
                        mRequest.allowPendingRemoteAnimationRegistryLookup);
            }
        } finally {
            onExecutionComplete();
        }
    }

    private int startActivity(final ActivityRecord r, ActivityRecord sourceRecord,
                IVoiceInteractionSession voiceSession, IVoiceInteractor voiceInteractor,
                int startFlags, boolean doResume, ActivityOptions options, TaskRecord inTask,
                ActivityRecord[] outActivity) {
        int result = START_CANCELED;
        try {
            mService.mWindowManager.deferSurfaceLayout();
            result = startActivityUnchecked(r, sourceRecord, voiceSession, voiceInteractor,
                    startFlags, doResume, options, inTask, outActivity);
        } finally {
            // If we are not able to proceed, disassociate the activity from the task. Leaving an
            // activity in an incomplete state can lead to issues, such as performing operations
            // without a window container.
            final ActivityStack stack = mStartActivity.getStack();
            if (!ActivityManager.isStartResultSuccessful(result) && stack != null) {
                stack.finishActivityLocked(mStartActivity, RESULT_CANCELED,
                        null /* intentResultData */, "startActivity", true /* oomAdj */);
            }
            mService.mWindowManager.continueSurfaceLayout();
        }

        postStartActivityProcessing(r, result, mTargetStack);

        return result;
    }

startActivityUnchecked函数中有非常重的逻辑：

    // Note: This method should only be called from {@link startActivity}.
    private int startActivityUnchecked(final ActivityRecord r, ActivityRecord sourceRecord,
            IVoiceInteractionSession voiceSession, IVoiceInteractor voiceInteractor,
            int startFlags, boolean doResume, ActivityOptions options, TaskRecord inTask,
            ActivityRecord[] outActivity) {
        ...
		// 此时需要重用activity，需要对activity栈做一些清理工作
        if (reusedActivity != null) {
            ... 

            // This code path leads to delivering a new intent, we want to make sure we schedule it
            // as the first operation, in case the activity will be resumed as a result of later
            // operations.
            if ((mLaunchFlags & FLAG_ACTIVITY_CLEAR_TOP) != 0
                    || isDocumentLaunchesIntoExisting(mLaunchFlags)
                    || isLaunchModeOneOf(LAUNCH_SINGLE_INSTANCE, LAUNCH_SINGLE_TASK)) {
                final TaskRecord task = reusedActivity.getTask();
                // 调用TaskRecord的performClearTaskForReuseLocked逐步清理任务栈中需要重用的activity上的activity
                final ActivityRecord top = task.performClearTaskForReuseLocked(mStartActivity,
                        mLaunchFlags);
                ...
                if (top != null) {
                    if (top.frontOfTask) {
                        // Activity aliases may mean we use different intents for the top activity,
                        // so make sure the task now has the identity of the new intent.
                        top.getTask().setIntent(mStartActivity);
                    }
                    // 调用onNewIntent
                    deliverNewIntent(top);
                }
            }

        boolean newTask = false;
        final TaskRecord taskToAffiliate = (mLaunchTaskBehind && mSourceRecord != null)
                ? mSourceRecord.getTask() : null;

        // 判断是否需要开启新的任务栈
        int result = START_SUCCESS;
        if (mStartActivity.resultTo == null && mInTask == null && !mAddingToTask
                && (mLaunchFlags & FLAG_ACTIVITY_NEW_TASK) != 0) {
            newTask = true;
            result = setTaskFromReuseOrCreateNewTask(taskToAffiliate, topStack);
        } else if (mSourceRecord != null) {
            result = setTaskFromSourceRecord();
        } else if (mInTask != null) {
            result = setTaskFromInTask();
        } else {
            // This not being started from an existing activity, and not part of a new task...
            // just put it in the top task, though these days this case should never happen.
            setTaskToCurrentTopOrCreateNewTask();
        }
        if (result != START_SUCCESS) {
            return result;
        }
        ...
        // 调用ActivityStack的startActivityLocked方法
        mTargetStack.startActivityLocked(mStartActivity, topFocused, newTask, mKeepCurTransition,
                mOptions);
        if (mDoResume) {
            final ActivityRecord topTaskActivity =
                    mStartActivity.getTask().topRunningActivityLocked();
            if (!mTargetStack.isFocusable()
                    || (topTaskActivity != null && topTaskActivity.mTaskOverlay
                    && mStartActivity != topTaskActivity)) {
                // 保证activity可见
                mTargetStack.ensureActivitiesVisibleLocked(null, 0, !PRESERVE_WINDOWS);
                // Go ahead and tell window manager to execute app transition for this activity
 **加粗样式**               // since the app transition will not be triggered through the resume channel.
                mService.mWindowManager.executeAppTransition();
            } else {
                // 保证activity可见并聚焦
                if (mTargetStack.isFocusable() && !mSupervisor.isFocusedStack(mTargetStack)) {
                    mTargetStack.moveToFront("startActivityUnchecked");
                }
				
                mSupervisor.resumeFocusedStackTopActivityLocked(mTargetStack, mStartActivity,
                        mOptions);
            }
        } else if (mStartActivity != null) {
            mSupervisor.mRecentTasks.add(mStartActivity.getTask());
        }
        mSupervisor.updateUserStackLocked(mStartActivity.userId, mTargetStack);

        mSupervisor.handleNonResizableTaskIfNeeded(mStartActivity.getTask(), preferredWindowingMode,
                preferredLaunchDisplayId, mTargetStack);

        return START_SUCCESS;
    }

ActivityStackSupervisor.java

    boolean resumeFocusedStackTopActivityLocked(
            ActivityStack targetStack, ActivityRecord target, ActivityOptions targetOptions) {

        if (!readyToResume()) {
            return false;
        }

        if (targetStack != null && isFocusedStack(targetStack)) {
            return targetStack.resumeTopActivityUncheckedLocked(target, targetOptions);
        }

        final ActivityRecord r = mFocusedStack.topRunningActivityLocked();
        if (r == null || !r.isState(RESUMED)) {
            mFocusedStack.resumeTopActivityUncheckedLocked(null, null);
        } else if (r.isState(RESUMED)) {
            // Kick off any lingering app transitions form the MoveTaskToFront operation.
            mFocusedStack.executeAppTransition(targetOptions);
        }

        return false;
    }

ActivityStack.java

    boolean resumeTopActivityUncheckedLocked(ActivityRecord prev, ActivityOptions options) {
        if (mStackSupervisor.inResumeTopActivity) {
            // Don't even start recursing.
            return false;
        }

        boolean result = false;
        try {
            // Protect against recursion.
            mStackSupervisor.inResumeTopActivity = true;
            result = resumeTopActivityInnerLocked(prev, options);

            final ActivityRecord next = topRunningActivityLocked(true /* focusableOnly */);
            if (next == null || !next.canTurnScreenOn()) {
                checkReadyForSleep();
            }
        } finally {
            mStackSupervisor.inResumeTopActivity = false;
        }

        return result;
    }

resumeTopActivityInnerLocked的核心逻辑如下：

    @GuardedBy("mService")
    private boolean resumeTopActivityInnerLocked(ActivityRecord prev, ActivityOptions options) {
        ...
            ...
				...
                try {
                    final ClientTransaction transaction = ClientTransaction.obtain(next.app.thread,
                            next.appToken);
                    // Deliver all pending results.
                    ArrayList<ResultInfo> a = next.results;
                    if (a != null) {
                        final int N = a.size();
                        if (!next.finishing && N > 0) {
                            if (DEBUG_RESULTS) Slog.v(TAG_RESULTS,
                                    "Delivering results to " + next + ": " + a);
                            transaction.addCallback(ActivityResultItem.obtain(a));
                        }
                    }

                    if (next.newIntents != null) {
                        transaction.addCallback(NewIntentItem.obtain(next.newIntents,
                                false /* andPause */));
                    }

                    // Well the app will no longer be stopped.
                    // Clear app token stopped state in window manager if needed.
                    next.notifyAppResumed(next.stopped);

                    EventLog.writeEvent(EventLogTags.AM_RESUME_ACTIVITY, next.userId,
                            System.identityHashCode(next), next.getTask().taskId,
                            next.shortComponentName);

                    next.sleeping = false;
                    mService.getAppWarningsLocked().onResumeActivity(next);
                    mService.showAskCompatModeDialogLocked(next);
                    next.app.pendingUiClean = true;
                    next.app.forceProcessStateUpTo(mService.mTopProcessState);
                    next.clearOptionsLocked();
                    transaction.setLifecycleStateRequest(
                            ResumeActivityItem.obtain(next.app.repProcState,
                                    mService.isNextTransitionForward()));
                    mService.getLifecycleManager().scheduleTransaction(transaction);

                    if (DEBUG_STATES) Slog.d(TAG_STATES, "resumeTopActivityLocked: Resumed "
                            + next);
                } catch (Exception e) {
                    // Whoops, need to restart this activity!
                    if (DEBUG_STATES) Slog.v(TAG_STATES, "Resume failed; resetting state to "
                            + lastState + ": " + next);
                    next.setState(lastState, "resumeTopActivityInnerLocked");

                    // lastResumedActivity being non-null implies there is a lastStack present.
                    if (lastResumedActivity != null) {
                        lastResumedActivity.setState(RESUMED, "resumeTopActivityInnerLocked");
                    }

                    Slog.i(TAG, "Restarting because process died: " + next);
                    if (!next.hasBeenLaunched) {
                        next.hasBeenLaunched = true;
                    } else  if (SHOW_APP_STARTING_PREVIEW && lastStack != null
                            && lastStack.isTopStackOnDisplay()) {
                        next.showStartingWindow(null /* prev */, false /* newTask */,
                                false /* taskSwitch */);
                    }
                    mStackSupervisor.startSpecificActivityLocked(next, true, false);
                    if (DEBUG_STACK) mStackSupervisor.validateTopActivitiesLocked();
                    return true;
                }
                ...
            ...
        ...
    }

本文地址：https://blog.csdn.net/weixin_40655325/article/details/107924971