【Android】页面启动耗时统计流程梳理

文章基于Android 11

写在前面:

最近的文章都会放流程图,时序图之类的图片,解释下为什么这么做:

图片的好处:

  • 流程清晰,一目了然
  • 很多代码,如同老太太的裹脚布,又臭又长。影响理解,特别当想和别人解释清除一件事时,大量的代码,会搞得大家没耐心。

所以,如果只是浅尝辄止,只要看图即可得到你想要的结论。如果想深入了解,则跟着图片,对照源码梳理一遍流程。因此这篇文章,如果你有自己阅读源码的方式,理解完第一张图,后续的也就不用看了。后面的文章是给想学源码,却不知道怎么学的人,也是我看源码的个人习惯。

正文开始

本文重点

  • 弄清楚Android是如何统计页面启动耗时的
  • 这个时间是如何算出来的

查看Android的日志可以发现这样一条日志

2024-09-25 10:50:20.944 1292-1350 ActivityTaskManager system_process I Displayed xxx包名/.MainActivity: +966ms

那么我们要统计计时,其实只要弄清楚这个日志的时间怎么计算出来的。跟踪源码,全局搜索Displayed发现

ActivityMetricsLogger#logAppDisplayed

java 复制代码
    private void logAppDisplayed(TransitionInfoSnapshot info) {
        if (info.type != TYPE_TRANSITION_WARM_LAUNCH && info.type != TYPE_TRANSITION_COLD_LAUNCH) {
            return;
        }

        EventLog.writeEvent(WM_ACTIVITY_LAUNCH_TIME,
                info.userId, info.activityRecordIdHashCode, info.launchedActivityShortComponentName,
                info.windowsDrawnDelayMs);

        StringBuilder sb = mStringBuilder;
        sb.setLength(0);
        sb.append("Displayed ");
        sb.append(info.launchedActivityShortComponentName);
        sb.append(": ");
        TimeUtils.formatDuration(info.windowsDrawnDelayMs, sb);
        Log.i(TAG, sb.toString());
    }

可以看到重点就是这个时间info.windowsDrawnDelayMs,那么这个数据是怎么来的呢?直接上图(如果看不清楚,下载下来看):

下面是代码分析:整个过程属实无聊。是我自己看源码的一个方法,如果你有自己看源码的方式,后续不看也罢。

as右键find Usages(后续所有的只有一个来源都是这么得到的结论)
TransitionInfoSnapshot#windowsDrawnDelayMs数据的来源只有一个

java 复制代码
		private TransitionInfoSnapshot(TransitionInfo info, ActivityRecord launchedActivity,int windowsFullyDrawnDelayMs) {
			//......
			windowsDrawnDelayMs = info.mWindowsDrawnDelayMs;
			//......
        }

ActivityMetricsLogger#mWindowsDrawnDelayMs

java 复制代码
		/** Elapsed time from when we launch an activity to when its windows are drawn. */
		//直译:从启动 Activity 到绘制其窗口所经过的时间。
        int mWindowsDrawnDelayMs;

查看这个值的写入只有一个地方

ActivityMetricsLogger#notifyWindowsDrawn

java 复制代码
    /**
     * Notifies the tracker that all windows of the app have been drawn.
     *
     * @return Non-null info if the activity was pending to draw, otherwise it might have been set
     *         to invisible (removed from active transition) or it was already drawn.
     */
	TransitionInfoSnapshot notifyWindowsDrawn(@NonNull ActivityRecord r, long timestampNs) {
        if (DEBUG_METRICS) Slog.i(TAG, "notifyWindowsDrawn " + r);

        final TransitionInfo info = getActiveTransitionInfo(r);
        if (info == null || info.allDrawn()) {
            if (DEBUG_METRICS) Slog.i(TAG, "notifyWindowsDrawn no activity to be drawn");
            return null;
        }
        //这里进行赋值
        // Always calculate the delay because the caller may need to know the individual drawn time.
        info.mWindowsDrawnDelayMs = info.calculateDelay(timestampNs);
        info.removePendingDrawActivity(r);
        final TransitionInfoSnapshot infoSnapshot = new TransitionInfoSnapshot(info);
        if (info.mLoggedTransitionStarting && info.allDrawn()) {
            done(false /* abort */, info, "notifyWindowsDrawn - all windows drawn", timestampNs);
        }
        return infoSnapshot;
    }

TransitionInfo#calculateDelay

java 复制代码
int calculateDelay(long timestampNs) {
    // Shouldn't take more than 25 days to launch an app, so int is fine here.
    //传入的时间 - 开始过渡的时间
    return (int) TimeUnit.NANOSECONDS.toMillis(timestampNs - mTransitionStartTimeNs);
}

接下来分两部分

  • 开始过渡的时间什么时候赋值
  • 传入的时间是什么时间

开始过渡的时间写入只有一个来源

java 复制代码
        private TransitionInfo(ActivityRecord r, LaunchingState launchingState, int transitionType,
                boolean processRunning, boolean processSwitch) {
            mLaunchingState = launchingState;
            //此处就是赋值的地方
            mTransitionStartTimeNs = launchingState.mCurrentTransitionStartTimeNs;
            //......
        }

查看launchingState.mCurrentTransitionStartTimeNs的赋值

TransitionInfoSnapshot#notifyActivityLaunching

java 复制代码
    private LaunchingState notifyActivityLaunching(Intent intent, @Nullable ActivityRecord caller,
            int callingUid) {
        final long transitionStartTimeNs = SystemClock.elapsedRealtimeNanos();
        //......

        if (existingInfo == null) {
            // Only notify the observer for a new launching event.
            launchObserverNotifyIntentStarted(intent, transitionStartTimeNs);
            final LaunchingState launchingState = new LaunchingState();
            launchingState.mCurrentTransitionStartTimeNs = transitionStartTimeNs;
            return launchingState;
        }
        existingInfo.mLaunchingState.mCurrentTransitionStartTimeNs = transitionStartTimeNs;
        return existingInfo.mLaunchingState;
    }

可以看到是在notifyActivityLaunching方法被调用时的SystemClock.elapsedRealtimeNanos()。继续跟踪这个方法被调用的时机

ActivityStarter#startResolvedActivity

ActivityStartController#doPendingActivityLaunches

ActivityStart#executeRequest

到这里熟悉Activity启动流程的基本也就知道开始过渡时间的来源了。不熟悉的我放一张图,大家看下Activity的启动流程,应该也能明白这个时间大概是什么时候。(为了方便看清楚,只截图了一部分,完整图很大,截图放不下。可私聊我获取)

接下来查看结束时间,即TransitionInfo#calculateDelay传入的时间

再贴一次代码

java 复制代码
    TransitionInfoSnapshot notifyWindowsDrawn(@NonNull ActivityRecord r, long timestampNs) {
        //......
        // Always calculate the delay because the caller may need to know the individual drawn time.
        info.mWindowsDrawnDelayMs = info.calculateDelay(timestampNs);
       //......
    }

ActivityRecord#onWindowsDrawn

java 复制代码
    /** Called when the windows associated app window container are drawn. */
    void onWindowsDrawn(boolean drawn, long timestampNs) {
       //......
        final TransitionInfoSnapshot info = mStackSupervisor
                .getActivityMetricsLogger().notifyWindowsDrawn(this, timestampNs);
        //......
    }

ActivityRecord#updateReportedVisibilityLocked

java 复制代码
    void updateReportedVisibilityLocked() {
        if (nowDrawn != reportedDrawn) {
            onWindowsDrawn(nowDrawn, SystemClock.elapsedRealtimeNanos());
            reportedDrawn = nowDrawn;
        }
    }

至此,结束时间赋值来源分析结束

相关推荐
似霰1 小时前
安卓智能指针sp、wp、RefBase浅析
android·c++·binder
大风起兮云飞扬丶1 小时前
Android——网络请求
android
干一行,爱一行1 小时前
android camera data -> surface 显示
android
断墨先生1 小时前
uniapp—android原生插件开发(3Android真机调试)
android·uni-app
无极程序员3 小时前
PHP常量
android·ide·android studio
萌面小侠Plus4 小时前
Android笔记(三十三):封装设备性能级别判断工具——低端机还是高端机
android·性能优化·kotlin·工具类·低端机
慢慢成长的码农4 小时前
Android Profiler 内存分析
android
大风起兮云飞扬丶4 小时前
Android——多线程、线程通信、handler机制
android
L72564 小时前
Android的Handler
android
清风徐来辽4 小时前
Android HandlerThread 基础
android