From 9c5b453330331e7ec5d038e7b95c5645954e6ac6 Mon Sep 17 00:00:00 2001
From: Ben Konyi <bkonyi@google.com>
Date: Wed, 8 Jan 2020 12:50:10 -0800
Subject: [PATCH] [android_alarm_manager] Fixed issue where callback lookup was
 failing in the background (#2453)

If callback lookup was attempted before Flutter was initialized, the
callback cache would not yet be populated resulting in a failed callback
lookup.
---
 packages/android_alarm_manager/CHANGELOG.md     |  4 ++++
 .../FlutterBackgroundExecutor.java              | 17 +++++++++++------
 packages/android_alarm_manager/pubspec.yaml     |  2 +-
 3 files changed, 16 insertions(+), 7 deletions(-)

diff --git a/packages/android_alarm_manager/CHANGELOG.md b/packages/android_alarm_manager/CHANGELOG.md
index 1a744c969407..32fdb76c0b16 100644
--- a/packages/android_alarm_manager/CHANGELOG.md
+++ b/packages/android_alarm_manager/CHANGELOG.md
@@ -1,3 +1,7 @@
+## 0.4.5+3
+
+* Fixed issue where callback lookup would fail while running in the background.
+
 ## 0.4.5+2
 
 * Remove the deprecated `author:` field from pubspec.yaml
diff --git a/packages/android_alarm_manager/android/src/main/java/io/flutter/plugins/androidalarmmanager/FlutterBackgroundExecutor.java b/packages/android_alarm_manager/android/src/main/java/io/flutter/plugins/androidalarmmanager/FlutterBackgroundExecutor.java
index c7eebc2332bf..4e755c315528 100644
--- a/packages/android_alarm_manager/android/src/main/java/io/flutter/plugins/androidalarmmanager/FlutterBackgroundExecutor.java
+++ b/packages/android_alarm_manager/android/src/main/java/io/flutter/plugins/androidalarmmanager/FlutterBackgroundExecutor.java
@@ -151,17 +151,22 @@ public void startBackgroundIsolate(Context context, long callbackHandle) {
       return;
     }
 
-    FlutterCallbackInformation flutterCallback =
-        FlutterCallbackInformation.lookupCallbackInformation(callbackHandle);
-    if (flutterCallback == null) {
-      Log.e(TAG, "Fatal: failed to find callback");
-      return;
-    }
     Log.i(TAG, "Starting AlarmService...");
     String appBundlePath = FlutterMain.findAppBundlePath(context);
     AssetManager assets = context.getAssets();
     if (appBundlePath != null && !isRunning()) {
       backgroundFlutterEngine = new FlutterEngine(context);
+
+      // We need to create an instance of `FlutterEngine` before looking up the
+      // callback. If we don't, the callback cache won't be initialized and the
+      // lookup will fail.
+      FlutterCallbackInformation flutterCallback =
+          FlutterCallbackInformation.lookupCallbackInformation(callbackHandle);
+      if (flutterCallback == null) {
+        Log.e(TAG, "Fatal: failed to find callback");
+        return;
+      }
+
       DartExecutor executor = backgroundFlutterEngine.getDartExecutor();
       initializeMethodChannel(executor);
       DartCallback dartCallback = new DartCallback(assets, appBundlePath, flutterCallback);
diff --git a/packages/android_alarm_manager/pubspec.yaml b/packages/android_alarm_manager/pubspec.yaml
index 4852a3a73110..c0fc46e2d3f0 100644
--- a/packages/android_alarm_manager/pubspec.yaml
+++ b/packages/android_alarm_manager/pubspec.yaml
@@ -1,7 +1,7 @@
 name: android_alarm_manager
 description: Flutter plugin for accessing the Android AlarmManager service, and
   running Dart code in the background when alarms fire.
-version: 0.4.5+2
+version: 0.4.5+3
 homepage: https://github.com/flutter/plugins/tree/master/packages/android_alarm_manager
 
 dependencies: