在flatter中集成firebase通知时，我们创建了推荐的java类和编译器，演示如下：

Launching lib\main.dart on SM G935T in debug mode...
Running Gradle task 'assembleDebug'...                                  
Running Gradle task 'assembleDebug'... Done                        24.6s
√ Built build\app\outputs\flutter-apk\app-debug.apk.
E/AndroidRuntime(29186): FATAL EXCEPTION: main
E/AndroidRuntime(29186): Process: com.example.FcmDemoProject, PID: 29186
E/AndroidRuntime(29186): java.lang.RuntimeException: Unable to instantiate application com.example.FcmDemoProject.Application: java.lang.ClassNotFoundException: Didn't find class "com.example.FcmDemoProject.Application" on path: DexPathList[[zip file "/data/app/com.example.FcmDemoProject-Nl0VYF4f8q17yd1t4aifZg==/base.apk"],nativeLibraryDirectories=[/data/app/com.example.FcmDemoProject-Nl0VYF4f8q17yd1t4aifZg==/lib/arm64, /data/app/com.example.FcmDemoProject-Nl0VYF4f8q17yd1t4aifZg==/base.apk!/lib/arm64-v8a, /system/lib64, /system/vendor/lib64]]
E/AndroidRuntime(29186):        at android.app.LoadedApk.makeApplication(LoadedApk.java:979)
E/AndroidRuntime(29186):        at android.app.ActivityThread.handleBindApplication(ActivityThread.java:6036)
E/AndroidRuntime(29186):        at android.app.ActivityThread.-wrap1(Unknown Source:0)
E/AndroidRuntime(29186):        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1764)
E/AndroidRuntime(29186):        at android.os.Handler.dispatchMessage(Handler.java:105)
E/AndroidRuntime(29186):        at android.os.Looper.loop(Looper.java:164)
E/AndroidRuntime(29186):        at android.app.ActivityThread.main(ActivityThread.java:6944)
E/AndroidRuntime(29186):        at java.lang.reflect.Method.invoke(Native Method)
E/AndroidRuntime(29186):        at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:327)
E/AndroidRuntime(29186):        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1374)
E/AndroidRuntime(29186): Caused by: java.lang.ClassNotFoundException: Didn't find class "com.example.FcmDemoProject.Application" on path: DexPathList[[zip file "/data/app/com.example.FcmDemoProject-Nl0VYF4f8q17yd1t4aifZg==/base.apk"],nativeLibraryDirectories=[/data/app/com.example.FcmDemoProject-Nl0VYF4f8q17yd1t4aifZg==/lib/arm64, /data/app/com.example.FcmDemoProject-Nl0VYF4f8q17yd1t4aifZg==/base.apk!/lib/arm64-v8a, /system/lib64, /system/vendor/lib64]]
E/AndroidRuntime(29186):        at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:93)
E/AndroidRuntime(29186):        at java.lang.ClassLoader.loadClass(ClassLoader.java:379)
E/AndroidRuntime(29186):        at java.lang.ClassLoader.loadClass(ClassLoader.java:312)
E/AndroidRuntime(29186):        at android.app.Instrumentation.newApplication(Instrumentation.java:1093)
E/AndroidRuntime(29186):        at android.app.LoadedApk.makeApplication(LoadedApk.java:973)
E/AndroidRuntime(29186):        ... 9 more