add android example

example/android/app/build.gradle

@@ -64,4 +64,7 @@ dependencies {
     testImplementation 'junit:junit:4.12'
     androidTestImplementation 'androidx.test:runner:1.1.1'
     androidTestImplementation 'androidx.test.espresso:espresso-core:3.1.1'
+    implementation 'com.google.firebase:firebase-messaging:20.1.2'
 }
+
+apply plugin: 'com.google.gms.google-services'

example/android/app/src/main/AndroidManifest.xml

@@ -7,7 +7,7 @@
          FlutterApplication and put your custom class here. -->
     <uses-permission android:name="android.permission.INTERNET"/>
     <application
-        android:name="io.flutter.app.FlutterApplication"
+        android:name=".Application"
         android:label="example"
         android:icon="@mipmap/ic_launcher">
         <activity
@@ -17,6 +17,10 @@
             android:configChanges="orientation|keyboardHidden|keyboard|screenSize|smallestScreenSize|locale|layoutDirection|fontScale|screenLayout|density|uiMode"
             android:hardwareAccelerated="true"
             android:windowSoftInputMode="adjustResize">
+            <intent-filter>
+                <action android:name="FLUTTER_NOTIFICATION_CLICK" />
+                <category android:name="android.intent.category.DEFAULT" />
+            </intent-filter>
             <intent-filter>
                 <action android:name="android.intent.action.MAIN"/>
                 <category android:name="android.intent.category.LAUNCHER"/>

example/android/app/src/main/kotlin/com/example/example/Application.kt

@@ -0,0 +1,22 @@
+package com.example.example
+
+import io.flutter.app.FlutterApplication
+import io.flutter.plugin.common.PluginRegistry
+import io.flutter.plugin.common.PluginRegistry.PluginRegistrantCallback
+import io.flutter.plugins.GeneratedPluginRegistrant
+import io.flutter.plugins.firebasemessaging.FirebaseMessagingPlugin
+import io.flutter.plugins.firebasemessaging.FlutterFirebaseMessagingService
+import io.flutter.plugins.sharedpreferences.SharedPreferencesPlugin
+
+class Application : FlutterApplication(), PluginRegistrantCallback {
+    override fun onCreate() {
+        super.onCreate()
+        FlutterFirebaseMessagingService.setPluginRegistrant(this)
+    }
+
+    override fun registerWith(registry: PluginRegistry?) {
+        SharedPreferencesPlugin.registerWith(registry?.registrarFor(
+                "io.flutter.plugins.sharedpreferences.SharedPreferencesPlugin"));
+        FirebaseMessagingPlugin.registerWith(registry?.registrarFor("io.flutter.plugins.firebasemessaging.FirebaseMessagingPlugin"))
+    }
+}

example/android/build.gradle

@@ -8,6 +8,7 @@ buildscript {
     dependencies {
         classpath 'com.android.tools.build:gradle:3.5.0'
         classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
+        classpath 'com.google.gms:google-services:4.3.2'
     }
 }