Q:

Cannot find symbol @NonNull when adding Pushe plugin

I want to install Pushe plugin for flutter, but I'm having this error:
I even add this line to the native imports:
import android.support.annotation. NonNull;
but get the same exception. 
What can I do to solve this problem? 
Here is my stacktrace:
Launching lib\main.dart on Android SDK built for x86 in debug mode...
Initializing gradle...
Resolving dependencies...
Running Gradle task 'assembleDebug'...
C:\Users\Elyas\AppData\Roaming\Pub\Cache\hosted\pub.dartlang.org\pushe-1.0.0\android\src\main\java\co\ronash\pushe\flutter\PushePlugin.java:49: error: cannot find symbol
    public void onMethodCall(@NonNull MethodCall call, @NonNull Result result) {
                              ^
  symbol:   class NonNull
  location: class PushePlugin
C:\Users\Elyas\AppData\Roaming\Pub\Cache\hosted\pub.dartlang.org\pushe-1.0.0\android\src\main\java\co\ronash\pushe\flutter\PushePlugin.java:49: error: cannot find symbol
    public void onMethodCall(@NonNull MethodCall call, @NonNull Result result) {
                                                        ^
  symbol:   class NonNull
  location: class PushePlugin
C:\Users\Elyas\AppData\Roaming\Pub\Cache\hosted\pub.dartlang.org\pushe-1.0.0\android\src\main\java\co\ronash\pushe\flutter\PusheApplication.java:28: error: cannot find symbol
            public void onNotificationReceived(@NonNull final NotificationData notificationData) {
                                                ^
  symbol: class NonNull
C:\Users\Elyas\AppData\Roaming\Pub\Cache\hosted\pub.dartlang.org\pushe-1.0.0\android\src\main\java\co\ronash\pushe\flutter\PusheApplication.java:35: error: cannot find symbol
            public void onNotificationClicked(@NonNull final NotificationData notificationData) {
                                               ^
  symbol: class NonNull
C:\Users\Elyas\AppData\Roaming\Pub\Cache\hosted\pub.dartlang.org\pushe-1.0.0\android\src\main\java\co\ronash\pushe\flutter\PusheApplication.java:42: error: cannot find symbol
            public void onNotificationButtonClicked(@NonNull final NotificationData notificationData,
                                                     ^
  symbol: class NonNull
C:\Users\Elyas\AppData\Roaming\Pub\Cache\hosted\pub.dartlang.org\pushe-1.0.0\android\src\main\java\co\ronash\pushe\flutter\PusheApplication.java:43: error: cannot find symbol
                                                    @NonNull final NotificationButtonData notificationButtonData) {
                                                     ^
  symbol: class NonNull
C:\Users\Elyas\AppData\Roaming\Pub\Cache\hosted\pub.dartlang.org\pushe-1.0.0\android\src\main\java\co\ronash\pushe\flutter\PusheApplication.java:51: error: cannot find symbol
            public void onCustomContentReceived(@NonNull final JSONObject jsonObject) {
                                                 ^
  symbol: class NonNull
C:\Users\Elyas\AppData\Roaming\Pub\Cache\hosted\pub.dartlang.org\pushe-1.0.0\android\src\main\java\co\ronash\pushe\flutter\PusheApplication.java:58: error: cannot find symbol
            public void onNotificationDismissed(@NonNull final NotificationData notificationData) {
                                                 ^
  symbol: class NonNull
8 errors

FAILURE: Build failed with an exception. 

* What went wrong:
Execution failed for task ':pushe:compileDebugJavaWithJavac'. 
> Compilation failed; see the compiler error output for details. 

* Try:
Run with --stacktrace option to get the stack trace.  Run with --info or --debug option to get more log output.  Run with --scan to get full insights. 

* Get more help at https://help.gradle.org

BUILD FAILED in 16s
Finished with error: Gradle task assembleDebug failed with exit code 1

A:

According to Pushe's Github repo, this issue's been fixed as of version 1.0.1. 

https://github.com/pusheco/pushe-flutter/releases

Version 1.0.0 or lower is not fully compatible with the AndroidX artifacts since Flutter does not touch plugin's codes and does not migrate them.