【Android 性能优化】应用启动优化 ( 启动白屏问题 | 应用启动时间测量 | 冷启动 | 热启动 | 应用启动时间计算源码分析 )

2020-06-20 08:44:09.821 1266-1305/? I/ActivityTaskManager: Displayed kim.hsl.recyclerview/.MainActivity: +334ms
2020-06-20 08:44:18.457 1266-1305/? I/ActivityTaskManager: Displayed 
com.google.android.permissioncontroller/com.android.packageinstaller.permission.ui.GrantPermissionsActivity: +315ms
2020-06-20 08:44:22.308 1266-1305/? I/ActivityTaskManager: Displayed kim.hsl.cckfa/.MainActivity: +311ms

Microsoft Windows [版本 10.0.18362.900]
(c) 2019 Microsoft Corporation。保留所有权利。

C:\Users\octop>adb shell am start -W kim.hsl.rtmp/kim.hsl.rtmp.MainActivity
Starting: Intent { act=android.intent.action.MAIN cat=[android.intent.category.LAUNCHER] 
cmp=kim.hsl.rtmp/.MainActivity }
Status: ok
LaunchState: COLD
Activity: kim.hsl.rtmp/.MainActivity
TotalTime: 374
WaitTime: 376
Complete

C:\Users\octop>

package kim.hsl.rtmp;
public class MainActivity extends AppCompatActivity {
	//...
}

C:\Users\octop>adb shell am start -W kim.hsl.rtmp/kim.hsl.rtmp.MainActivity
Starting: Intent { act=android.intent.action.MAIN 
cat=[android.intent.category.LAUNCHER] cmp=kim.hsl.rtmp/.MainActivity }
Status: ok
LaunchState: COLD
Activity: kim.hsl.rtmp/.MainActivity
TotalTime: 431
WaitTime: 433
Complete

C:\Users\octop>

IActivityManager.WaitResult result = null;
int res;

// 记录开始时间
final long startTime = SystemClock.uptimeMillis();
if (mWaitOption) {
    // 启动 Activity 
    result = mAm.startActivityAndWait(null, null, intent, mimeType,
                null, null, 0, mStartFlags, profilerInfo, null, mUserId);
    res = result.result;
} else {
    res = mAm.startActivityAsUser(null, null, intent, mimeType,
            null, null, 0, mStartFlags, profilerInfo, null, mUserId);
}
// 记录结束时间
final long endTime = SystemClock.uptimeMillis();

if (mWaitOption && launched) {
    if (result == null) {
        result = new IActivityManager.WaitResult();
        result.who = intent.getComponent();
    }
    System.out.println("Status: " + (result.timeout ? "timeout" : "ok"));
    if (result.who != null) {
        System.out.println("Activity: " + result.who.flattenToShortString());
    }
    if (result.thisTime >= 0) {
        System.out.println("ThisTime: " + result.thisTime);
    }
    if (result.totalTime >= 0) {
        System.out.println("TotalTime: " + result.totalTime);
    }
    System.out.println("WaitTime: " + (endTime-startTime));
    System.out.println("Complete");
}

public void windowsDrawn() {
    synchronized(service) {
        if (displayStartTime != 0) {
        	// 该方法是入口方法
            reportLaunchTimeLocked(SystemClock.uptimeMillis());
        }
        mStackSupervisor.sendWaitingVisibleReportLocked(this);
        startTime = 0;
        finishLaunchTickingLocked();
        if (task != null) {
            task.hasBeenVisible = true;
        }
    }
}

    private void reportLaunchTimeLocked(final long curTime) {
        final ActivityStack stack = task.stack;
        // 这里计算了 APP 启动时间
        final long thisTime = curTime - displayStartTime;
        final long totalTime = stack.mLaunchStartTime != 0
                ? (curTime - stack.mLaunchStartTime) : thisTime;
        if (ActivityManagerService.SHOW_ACTIVITY_START_TIME) {
            Trace.asyncTraceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER, "launching", 0);
            EventLog.writeEvent(EventLogTags.AM_ACTIVITY_LAUNCH_TIME,
                    userId, System.identityHashCode(this), shortComponentName,
                    thisTime, totalTime);
            StringBuilder sb = service.mStringBuilder;
            sb.setLength(0);
            sb.append("Displayed ");
            sb.append(shortComponentName);
            sb.append(": ");
            TimeUtils.formatDuration(thisTime, sb);
            if (thisTime != totalTime) {
                sb.append(" (total ");
                TimeUtils.formatDuration(totalTime, sb);
                sb.append(")");
            }
            Log.i(ActivityManagerService.TAG, sb.toString());
        }
        mStackSupervisor.reportActivityLaunchedLocked(false, this, thisTime, totalTime);
        if (totalTime > 0) {
            //service.mUsageStatsService.noteLaunchTime(realActivity, (int)totalTime);
        }
        displayStartTime = 0;
        stack.mLaunchStartTime = 0;
    }

// 记录开始时间
final long startTime = SystemClock.uptimeMillis();

        if (displayStartTime != 0) {
        	// 该方法是入口方法
            reportLaunchTimeLocked(SystemClock.uptimeMillis());
        }

final ActivityStack stack = task.stack;
final long thisTime = curTime - displayStartTime;

final long totalTime = stack.mLaunchStartTime != 0
        ? (curTime - stack.mLaunchStartTime) : thisTime;