android - 为什么我的调用堆栈说我有 2 个电源正在运行？

Question

我开始为 FCM 实现后台消息，他们要求我制作自己的 Kotlin 应用程序。但是自从我这样做以来，我的调用堆栈中似乎有 2 个主要功能。

这怎么可能？如果我运行一个空项目，它的调用堆栈中有 0 个主电源？
我添加了 Application.kt

package HERE_I_HAVE_MY_PACKAGE_NAME

import io.flutter.app.FlutterApplication
import io.flutter.plugin.common.PluginRegistry
import io.flutter.plugin.common.PluginRegistry.PluginRegistrantCallback
import io.flutter.plugins.firebasemessaging.FlutterFirebaseMessagingService

public class Application: FlutterApplication(), PluginRegistrantCallback {
  override fun onCreate() {
    super.onCreate()
    FlutterFirebaseMessagingService.setPluginRegistrant(this)
  }

  override fun registerWith(registry: PluginRegistry) {
    FirebaseCloudMessagingPluginRegistrant.registerWith(registry)
  }
}

和 FirebaseCloudMessagingPluginRegistrant.kt

package HERE_I_HAVE_MY_PACKAGE_NAME

import io.flutter.plugin.common.PluginRegistry
import io.flutter.plugins.firebasemessaging.FirebaseMessagingPlugin

class FirebaseCloudMessagingPluginRegistrant {
  companion object {
    fun registerWith(registry: PluginRegistry) {
      if (alreadyRegisteredWith(registry)) {
        return;
      }
      FirebaseMessagingPlugin.registerWith(registry.registrarFor("io.flutter.plugins.firebasemessaging.FirebaseMessagingPlugin"))
    }

    fun alreadyRegisteredWith(registry: PluginRegistry): Boolean {
      val key = FirebaseCloudMessagingPluginRegistrant::class.java.name
      if (registry.hasPlugin(key)) {
        return true
      }
      registry.registrarFor(key)
      return false
    }
  }
}

这是我的 AndroidManifest.xml

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.company_name.app_name">
    <uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
    <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
    <uses-permission android:name="android.permission.READ_CONTACTS" />
    <uses-permission android:name="android.permission.WAKE_LOCK" />
    <!-- io.flutter.app.FlutterApplication is an android.app.Application that
         calls FlutterMain.startInitialization(this); in its onCreate method.
         In most cases you can leave this as-is, but you if you want to provide
         additional functionality it is fine to subclass or reimplement
         FlutterApplication and put your custom class here. -->
    <application
        android:name=".Application"
        android:label="App Name"
        android:icon="@mipmap/ic_launcher">
        <activity
            android:name=".MainActivity"
            android:launchMode="singleTop"
            android:theme="@style/LaunchTheme"
            android:configChanges="orientation|keyboardHidden|keyboard|screenSize|smallestScreenSize|locale|layoutDirection|fontScale|screenLayout|density|uiMode"
            android:hardwareAccelerated="true"
            android:windowSoftInputMode="adjustResize">
            <intent-filter>
                <action android:name="android.intent.action.MAIN"/>
                <category android:name="android.intent.category.LAUNCHER"/>
            </intent-filter>
            <intent-filter>
                <action android:name="FLUTTER_NOTIFICATION_CLICK" />
                <category android:name="android.intent.category.DEFAULT" />
            </intent-filter>
        </activity>
        <activity
        android:name="com.yalantis.ucrop.UCropActivity"
        android:screenOrientation="portrait"
        android:theme="@style/Theme.AppCompat.Light.NoActionBar"/>
        <!-- Don't delete the meta-data below.
             This is used by the Flutter tool to generate GeneratedPluginRegistrant.java -->
        <meta-data
            android:name="flutterEmbedding"
            android:value="2" />
        <meta-data
            android:name="com.google.firebase.messaging.default_notification_channel_id"
            android:value="@string/default_notification_channel_id"/>  
    </application>
</manifest>

Answer 1

如果您标记您的 main功能为 async ，或您的main函数调用另一个标有 async 的函数，它将 fork 来处理事件队列或微任务队列，这实际上是使它能够await一个 future不阻塞线程并返回到 await 之后离开的位置关键字。