diff --git a/services/core/java/com/android/server/am/ActivityMetricsLogger.java b/services/core/java/com/android/server/am/ActivityMetricsLogger.java
index ff796a54..ebbce02 100644
--- a/services/core/java/com/android/server/am/ActivityMetricsLogger.java
+++ b/services/core/java/com/android/server/am/ActivityMetricsLogger.java
@@ -1,24 +1,36 @@
 package com.android.server.am;
 
+import static android.app.ActivityManager.START_SUCCESS;
+import static android.app.ActivityManager.START_TASK_TO_FRONT;
 import static android.app.ActivityManager.StackId.ASSISTANT_STACK_ID;
 import static android.app.ActivityManager.StackId.DOCKED_STACK_ID;
 import static android.app.ActivityManager.StackId.FREEFORM_WORKSPACE_STACK_ID;
 import static android.app.ActivityManager.StackId.FULLSCREEN_WORKSPACE_STACK_ID;
+import static android.app.ActivityManager.StackId.INVALID_STACK_ID;
 import static android.app.ActivityManager.StackId.PINNED_STACK_ID;
-
+import static android.app.ActivityManagerInternal.APP_TRANSITION_TIMEOUT;
+import static com.android.internal.logging.nano.MetricsProto.MetricsEvent.APP_TRANSITION;
+import static com.android.internal.logging.nano.MetricsProto.MetricsEvent.APP_TRANSITION_ACTIVITY_NAME;
+import static com.android.internal.logging.nano.MetricsProto.MetricsEvent.APP_TRANSITION_DELAY_MS;
+import static com.android.internal.logging.nano.MetricsProto.MetricsEvent.APP_TRANSITION_DEVICE_UPTIME_SECONDS;
+import static com.android.internal.logging.nano.MetricsProto.MetricsEvent.APP_TRANSITION_STARTING_WINDOW_DELAY_MS;
+import static com.android.internal.logging.nano.MetricsProto.MetricsEvent.APP_TRANSITION_WINDOWS_DRAWN_DELAY_MS;
+import static com.android.internal.logging.nano.MetricsProto.MetricsEvent.TYPE_TRANSITION_COLD_LAUNCH;
+import static com.android.internal.logging.nano.MetricsProto.MetricsEvent.TYPE_TRANSITION_HOT_LAUNCH;
+import static com.android.internal.logging.nano.MetricsProto.MetricsEvent.TYPE_TRANSITION_WARM_LAUNCH;
 import static com.android.server.am.ActivityManagerDebugConfig.TAG_AM;
 import static com.android.server.am.ActivityManagerDebugConfig.TAG_WITH_CLASS_NAME;
 import static com.android.server.am.ActivityStack.STACK_INVISIBLE;
 
-import android.annotation.Nullable;
 import android.app.ActivityManager.StackId;
 import android.content.Context;
+import android.metrics.LogMaker;
 import android.os.SystemClock;
 import android.util.Slog;
+import android.util.SparseArray;
+import android.util.SparseIntArray;
 
-import android.metrics.LogMaker;
 import com.android.internal.logging.MetricsLogger;
-import com.android.internal.logging.nano.MetricsProto.MetricsEvent;
 
 import java.util.ArrayList;
 
@@ -48,12 +60,27 @@
     private long mLastLogTimeSecs;
     private final ActivityStackSupervisor mSupervisor;
     private final Context mContext;
+    private final MetricsLogger mMetricsLogger = new MetricsLogger();
 
     private long mCurrentTransitionStartTime = INVALID_START_TIME;
-    private boolean mLoggedWindowsDrawn;
-    private boolean mLoggedStartingWindowDrawn;
+
+    private int mCurrentTransitionDeviceUptime;
+    private int mCurrentTransitionDelayMs;
     private boolean mLoggedTransitionStarting;
 
+    private final SparseArray<StackTransitionInfo> mStackTransitionInfo = new SparseArray<>();
+
+    private final class StackTransitionInfo {
+        private ActivityRecord launchedActivity;
+        private int startResult;
+        private boolean currentTransitionProcessRunning;
+        private int windowsDrawnDelayMs;
+        private int startingWindowDelayMs;
+        private int reason = APP_TRANSITION_TIMEOUT;
+        private boolean loggedWindowsDrawn;
+        private boolean loggedStartingWindowDrawn;
+    }
+
     ActivityMetricsLogger(ActivityStackSupervisor supervisor, Context context) {
         mLastLogTimeSecs = SystemClock.elapsedRealtime() / 1000;
         mSupervisor = supervisor;
@@ -102,7 +129,9 @@
      * activity.
      */
     void notifyActivityLaunching() {
-        mCurrentTransitionStartTime = System.currentTimeMillis();
+        if (!isAnyTransitionActive()) {
+            mCurrentTransitionStartTime = System.currentTimeMillis();
+        }
     }
 
     /**
@@ -118,9 +147,6 @@
                         launchedActivity.appInfo.uid)
                 : null;
         final boolean processRunning = processRecord != null;
-        final String componentName = launchedActivity != null
-                ? launchedActivity.shortComponentName
-                : null;
 
         // We consider this a "process switch" if the process of the activity that gets launched
         // didn't have an activity that was in started state. In this case, we assume that lot
@@ -129,7 +155,7 @@
         final boolean processSwitch = processRecord == null
                 || !hasStartedActivity(processRecord, launchedActivity);
 
-        notifyActivityLaunched(resultCode, componentName, processRunning, processSwitch);
+        notifyActivityLaunched(resultCode, launchedActivity, processRunning, processSwitch);
     }
 
     private boolean hasStartedActivity(ProcessRecord record, ActivityRecord launchedActivity) {
@@ -151,92 +177,120 @@
      *
      * @param resultCode one of the ActivityManager.START_* flags, indicating the result of the
      *                   launch
-     * @param componentName the component name of the activity being launched
+     * @param launchedActivity the activity being launched
      * @param processRunning whether the process that will contains the activity is already running
      * @param processSwitch whether the process that will contain the activity didn't have any
      *                      activity that was stopped, i.e. the started activity is "switching"
      *                      processes
      */
-    private void notifyActivityLaunched(int resultCode, @Nullable String componentName,
+    private void notifyActivityLaunched(int resultCode, ActivityRecord launchedActivity,
             boolean processRunning, boolean processSwitch) {
 
-        if (resultCode < 0 || componentName == null || !processSwitch) {
-
-            // Failed to launch or it was not a process switch, so we don't care about the timing.
-            reset();
+        // If we are already in an existing transition, only update the activity name, but not the
+        // other attributes.
+        final int stackId = launchedActivity != null && launchedActivity.getStack() != null
+                ? launchedActivity.getStack().mStackId
+                : INVALID_STACK_ID;
+        final StackTransitionInfo info = mStackTransitionInfo.get(stackId);
+        if (launchedActivity != null && info != null) {
+            info.launchedActivity = launchedActivity;
             return;
         }
 
-        MetricsLogger.action(mContext, MetricsEvent.APP_TRANSITION_COMPONENT_NAME,
-                componentName);
-        MetricsLogger.action(mContext, MetricsEvent.APP_TRANSITION_PROCESS_RUNNING,
-                processRunning);
-        MetricsLogger.action(mContext, MetricsEvent.APP_TRANSITION_DEVICE_UPTIME_SECONDS,
-                (int) (SystemClock.uptimeMillis() / 1000));
+        final boolean otherStacksLaunching = mStackTransitionInfo.size() > 0 && info == null;
+        if ((resultCode < 0 || launchedActivity == null || !processSwitch
+                || stackId == INVALID_STACK_ID) && !otherStacksLaunching) {
 
-        LogMaker builder = new LogMaker(MetricsEvent.APP_TRANSITION);
-        builder.addTaggedData(MetricsEvent.APP_TRANSITION_COMPONENT_NAME, componentName);
-        builder.addTaggedData(MetricsEvent.APP_TRANSITION_PROCESS_RUNNING, processRunning ? 1 : 0);
-        builder.addTaggedData(MetricsEvent.APP_TRANSITION_DEVICE_UPTIME_SECONDS,
-                SystemClock.uptimeMillis() / 1000);
-        MetricsLogger.action(builder);
+            // Failed to launch or it was not a process switch, so we don't care about the timing.
+            reset(true /* abort */);
+            return;
+        } else if (otherStacksLaunching) {
+            // Don't log this stack but continue with the other stacks.
+            return;
+        }
+
+        final StackTransitionInfo newInfo = new StackTransitionInfo();
+        newInfo.launchedActivity = launchedActivity;
+        newInfo.currentTransitionProcessRunning = processRunning;
+        newInfo.startResult = resultCode;
+        mStackTransitionInfo.append(stackId, newInfo);
+        mCurrentTransitionDeviceUptime = (int) (SystemClock.uptimeMillis() / 1000);
     }
 
     /**
      * Notifies the tracker that all windows of the app have been drawn.
      */
-    void notifyWindowsDrawn() {
-        if (!isTransitionActive() || mLoggedWindowsDrawn) {
+    void notifyWindowsDrawn(int stackId) {
+        final StackTransitionInfo info = mStackTransitionInfo.get(stackId);
+        if (info == null || info.loggedWindowsDrawn) {
             return;
         }
-        MetricsLogger.action(mContext, MetricsEvent.APP_TRANSITION_WINDOWS_DRAWN_DELAY_MS,
-                calculateCurrentDelay());
-        mLoggedWindowsDrawn = true;
-        if (mLoggedTransitionStarting) {
-            reset();
+        info.windowsDrawnDelayMs = calculateCurrentDelay();
+        info.loggedWindowsDrawn = true;
+        if (allStacksWindowsDrawn() && mLoggedTransitionStarting) {
+            reset(false /* abort */);
         }
     }
 
     /**
      * Notifies the tracker that the starting window was drawn.
      */
-    void notifyStartingWindowDrawn() {
-        if (!isTransitionActive() || mLoggedStartingWindowDrawn) {
+    void notifyStartingWindowDrawn(int stackId) {
+        final StackTransitionInfo info = mStackTransitionInfo.get(stackId);
+        if (info == null || info.loggedStartingWindowDrawn) {
             return;
         }
-        mLoggedStartingWindowDrawn = true;
-        MetricsLogger.action(mContext, MetricsEvent.APP_TRANSITION_STARTING_WINDOW_DELAY_MS,
-                calculateCurrentDelay());
+        info.loggedStartingWindowDrawn = true;
+        info.startingWindowDelayMs = calculateCurrentDelay();
     }
 
     /**
      * Notifies the tracker that the app transition is starting.
      *
-     * @param reason The reason why we started it. Must be on of
-     *               ActivityManagerInternal.APP_TRANSITION_* reasons.
+     * @param stackIdReasons A map from stack id to a reason integer, which must be on of
+     *                       ActivityManagerInternal.APP_TRANSITION_* reasons.
      */
-    void notifyTransitionStarting(int reason) {
-        if (!isTransitionActive() || mLoggedTransitionStarting) {
+    void notifyTransitionStarting(SparseIntArray stackIdReasons) {
+        if (!isAnyTransitionActive() || mLoggedTransitionStarting) {
             return;
         }
-        MetricsLogger.action(mContext, MetricsEvent.APP_TRANSITION_REASON, reason);
-        MetricsLogger.action(mContext, MetricsEvent.APP_TRANSITION_DELAY_MS,
-                calculateCurrentDelay());
+        mCurrentTransitionDelayMs = calculateCurrentDelay();
         mLoggedTransitionStarting = true;
-        if (mLoggedWindowsDrawn) {
-            reset();
+        for (int index = stackIdReasons.size() - 1; index >= 0; index--) {
+            final int stackId = stackIdReasons.keyAt(index);
+            final StackTransitionInfo info = mStackTransitionInfo.get(stackId);
+            if (info == null) {
+                continue;
+            }
+            info.reason = stackIdReasons.valueAt(index);
+        }
+        if (allStacksWindowsDrawn()) {
+            reset(false /* abort */);
         }
     }
 
-    private boolean isTransitionActive() {
-        return mCurrentTransitionStartTime != INVALID_START_TIME;
+    private boolean allStacksWindowsDrawn() {
+        for (int index = mStackTransitionInfo.size() - 1; index >= 0; index--) {
+            if (!mStackTransitionInfo.valueAt(index).loggedWindowsDrawn) {
+                return false;
+            }
+        }
+        return true;
     }
 
-    private void reset() {
+    private boolean isAnyTransitionActive() {
+        return mCurrentTransitionStartTime != INVALID_START_TIME
+                && mStackTransitionInfo.size() > 0;
+    }
+
+    private void reset(boolean abort) {
+        if (!abort && isAnyTransitionActive()) {
+            logAppTransitionMultiEvents();
+        }
         mCurrentTransitionStartTime = INVALID_START_TIME;
-        mLoggedWindowsDrawn = false;
+        mCurrentTransitionDelayMs = -1;
         mLoggedTransitionStarting = false;
-        mLoggedStartingWindowDrawn = false;
+        mStackTransitionInfo.clear();
     }
 
     private int calculateCurrentDelay() {
@@ -244,4 +298,41 @@
         // Shouldn't take more than 25 days to launch an app, so int is fine here.
         return (int) (System.currentTimeMillis() - mCurrentTransitionStartTime);
     }
+
+    private void logAppTransitionMultiEvents() {
+        for (int index = mStackTransitionInfo.size() - 1; index >= 0; index--) {
+            final StackTransitionInfo info = mStackTransitionInfo.valueAt(index);
+            final int type = getTransitionType(info);
+            if (type == -1) {
+                return;
+            }
+            final LogMaker builder = new LogMaker(APP_TRANSITION);
+            builder.setPackageName(info.launchedActivity.packageName);
+            builder.addTaggedData(APP_TRANSITION_ACTIVITY_NAME, info.launchedActivity.info.name);
+            builder.setType(type);
+            builder.addTaggedData(APP_TRANSITION_DEVICE_UPTIME_SECONDS,
+                    mCurrentTransitionDeviceUptime);
+            builder.addTaggedData(APP_TRANSITION_DELAY_MS, mCurrentTransitionDelayMs);
+            builder.setSubtype(info.reason);
+            if (info.startingWindowDelayMs != -1) {
+                builder.addTaggedData(APP_TRANSITION_STARTING_WINDOW_DELAY_MS,
+                        info.startingWindowDelayMs);
+            }
+            builder.addTaggedData(APP_TRANSITION_WINDOWS_DRAWN_DELAY_MS, info.windowsDrawnDelayMs);
+            mMetricsLogger.write(builder);
+        }
+    }
+
+    private int getTransitionType(StackTransitionInfo info) {
+        if (info.currentTransitionProcessRunning) {
+            if (info.startResult == START_SUCCESS) {
+                return TYPE_TRANSITION_WARM_LAUNCH;
+            } else if (info.startResult == START_TASK_TO_FRONT) {
+                return TYPE_TRANSITION_HOT_LAUNCH;
+            }
+        } else if (info.startResult == START_SUCCESS) {
+            return TYPE_TRANSITION_COLD_LAUNCH;
+        }
+        return -1;
+    }
 }