Plugin does not work headless (fix included)

[mootw]

Hi,

This plugin has issues when launching in headless mode using background_fetch plugin.

Here is the fix for the issue

All plugin developers need to guard themselves against the case where an App can launch Headless, where registrar.activity() == null.

Relevant error logs:
07-04 14:56:31.110 10430 10430 E AndroidRuntime: FATAL EXCEPTION: main 07-04 14:56:31.110 10430 10430 E AndroidRuntime: Process: com.noaimgames.shadowweather, PID: 10430 07-04 14:56:31.110 10430 10430 E AndroidRuntime: java.lang.RuntimeException: java.lang.IllegalStateException: registrar.activity() must not be null 07-04 14:56:31.110 10430 10430 E AndroidRuntime: at android.app.job.JobServiceEngine$JobHandler.handleMessage(JobServiceEngine.java:112) 07-04 14:56:31.110 10430 10430 E AndroidRuntime: at android.os.Handler.dispatchMessage(Handler.java:106) 07-04 14:56:31.110 10430 10430 E AndroidRuntime: at android.os.Looper.loop(Looper.java:214) 07-04 14:56:31.110 10430 10430 E AndroidRuntime: at android.app.ActivityThread.main(ActivityThread.java:7032) 07-04 14:56:31.110 10430 10430 E AndroidRuntime: at java.lang.reflect.Method.invoke(Native Method) 07-04 14:56:31.110 10430 10430 E AndroidRuntime: at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:494) 07-04 14:56:31.110 10430 10430 E AndroidRuntime: at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:965) 07-04 14:56:31.110 10430 10430 E AndroidRuntime: Caused by: java.lang.IllegalStateException: registrar.activity() must not be null 07-04 14:56:31.110 10430 10430 E AndroidRuntime: at com.builttoroam.devicecalendar.DeviceCalendarPlugin$Companion.registerWith(DeviceCalendarPlugin.kt:50) 07-04 14:56:31.110 10430 10430 E AndroidRuntime: at com.builttoroam.devicecalendar.DeviceCalendarPlugin.registerWith(Unknown Source:2) 07-04 14:56:31.110 10430 10430 E AndroidRuntime: at io.flutter.plugins.GeneratedPluginRegistrant.registerWith(GeneratedPluginRegistrant.java:35) 07-04 14:56:31.110 10430 10430 E AndroidRuntime: at com.noaimgames.shadowweather.Application.registerWith(Application.java:17) 07-04 14:56:31.110 10430 10430 E AndroidRuntime: at com.transistorsoft.flutter.backgroundfetch.HeadlessTask.initFlutterView(HeadlessTask.java:133) 07-04 14:56:31.110 10430 10430 E AndroidRuntime: at com.transistorsoft.flutter.backgroundfetch.HeadlessTask.<init>(HeadlessTask.java:47) 07-04 14:56:31.110 10430 10430 E AndroidRuntime: at com.transistorsoft.flutter.backgroundfetch.HeadlessJobService.onStartJob(HeadlessJobService.java:38) 07-04 14:56:31.110 10430 10430 E AndroidRuntime: at android.app.job.JobService$1.onStartJob(JobService.java:62) 07-04 14:56:31.110 10430 10430 E AndroidRuntime: at android.app.job.JobServiceEngine$JobHandler.handleMessage(JobServiceEngine.java:108) 07-04 14:56:31.110 10430 10430 E AndroidRuntime: ... 6 more 07-04 14:57:20.079 17712 17712 E AndroidRuntime: FATAL EXCEPTION: main 07-04 14:57:20.079 17712 17712 E AndroidRuntime: Process: com.noaimgames.shadowweather, PID: 17712 07-04 14:57:20.079 17712 17712 E AndroidRuntime: java.lang.RuntimeException: java.lang.IllegalStateException: registrar.activity() must not be null 07-04 14:57:20.079 17712 17712 E AndroidRuntime: at android.app.job.JobServiceEngine$JobHandler.handleMessage(JobServiceEngine.java:112) 07-04 14:57:20.079 17712 17712 E AndroidRuntime: at android.os.Handler.dispatchMessage(Handler.java:106) 07-04 14:57:20.079 17712 17712 E AndroidRuntime: at android.os.Looper.loop(Looper.java:214) 07-04 14:57:20.079 17712 17712 E AndroidRuntime: at android.app.ActivityThread.main(ActivityThread.java:7032) 07-04 14:57:20.079 17712 17712 E AndroidRuntime: at java.lang.reflect.Method.invoke(Native Method) 07-04 14:57:20.079 17712 17712 E AndroidRuntime: at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:494) 07-04 14:57:20.079 17712 17712 E AndroidRuntime: at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:965) 07-04 14:57:20.079 17712 17712 E AndroidRuntime: Caused by: java.lang.IllegalStateException: registrar.activity() must not be null 07-04 14:57:20.079 17712 17712 E AndroidRuntime: at com.builttoroam.devicecalendar.DeviceCalendarPlugin$Companion.registerWith(DeviceCalendarPlugin.kt:50) 07-04 14:57:20.079 17712 17712 E AndroidRuntime: at com.builttoroam.devicecalendar.DeviceCalendarPlugin.registerWith(Unknown Source:2) 07-04 14:57:20.079 17712 17712 E AndroidRuntime: at io.flutter.plugins.GeneratedPluginRegistrant.registerWith(GeneratedPluginRegistrant.java:35) 07-04 14:57:20.079 17712 17712 E AndroidRuntime: at com.noaimgames.shadowweather.Application.registerWith(Application.java:17) 07-04 14:57:20.079 17712 17712 E AndroidRuntime: at com.transistorsoft.flutter.backgroundfetch.HeadlessTask.initFlutterView(HeadlessTask.java:133) 07-04 14:57:20.079 17712 17712 E AndroidRuntime: at com.transistorsoft.flutter.backgroundfetch.HeadlessTask.<init>(HeadlessTask.java:47) 07-04 14:57:20.079 17712 17712 E AndroidRuntime: at com.transistorsoft.flutter.backgroundfetch.HeadlessJobService.onStartJob(HeadlessJobService.java:38) 07-04 14:57:20.079 17712 17712 E AndroidRuntime: at android.app.job.JobService$1.onStartJob(JobService.java:62) 07-04 14:57:20.079 17712 17712 E AndroidRuntime: at android.app.job.JobServiceEngine$JobHandler.handleMessage(JobServiceEngine.java:108) 07-04 14:57:20.079 17712 17712 E AndroidRuntime: ... 6 more

flutter doctor -v
[√] Flutter (Channel stable, v1.5.4-hotfix.2, on Microsoft Windows [Version 10.0.18362.175], locale en-US)
• Flutter version 1.5.4-hotfix.2 at C:\flutter\sdk\flutter
• Framework revision 7a4c33425d (10 weeks ago), 2019-04-29 11:05:24 -0700
• Engine revision 52c7a1e849
• Dart version 2.3.0 (build 2.3.0-dev.0.5 a1668566e5)

[√] Android toolchain - develop for Android devices (Android SDK version 28.0.3)
• Android SDK at C:\Users\Spencer\AppData\Local\Android\sdk
• Android NDK location not configured (optional; useful for native profiling support)
• Platform android-28, build-tools 28.0.3
• Java binary at: C:\Program Files\Android\Android Studio\jre\bin\java
• Java version OpenJDK Runtime Environment (build 1.8.0_152-release-1248-b01)
• All Android licenses accepted.

[√] Android Studio (version 3.3)
• Android Studio at C:\Program Files\Android\Android Studio
• Flutter plugin version 32.0.1
• Dart plugin version 182.5124
• Java version OpenJDK Runtime Environment (build 1.8.0_152-release-1248-b01)

[√] Connected device (1 available)
• SM G973U • RF8M13837GY • android-arm64 • Android 9 (API 28)

• No issues found!

[MaikuB]

Are you able to add a git dependency (see documentation here) that would point to the 101 branch to see if it solves the problem? If it doesn't, would appreciate it if you can provide a sample app to reproduce the issue

[mootw]

I added the branch as a dependency and it solved the problem for me. I did find another issue which I will open a separate ticket for as it is unrelated. Thanks!