在颤振插件中获取活动参考

Question

我在创建flutter插件时，插件类默认有两个方法：

override fun onAttachedToEngine(flutterPluginBinding: FlutterPlugin.FlutterPluginBinding)

和

fun registerWith(registrar: Registrar)

文件上的评论说： It is encouraged to share logic between onAttachedToEngine and registerWith to keep them functionally equivalent. Only one of onAttachedToEngine or registerWith will be called depending on the user's project. onAttachedToEngine or registerWith must both be defined in the same class.

现在，我需要从这里开始另一个活动，activity.startActivityForResult()。 可以使用registrar.activity() 获得对registerWith(registrar: Registrar) 中活动的引用。如何在方法onAttachedToEngine(flutterPluginBinding: FlutterPlugin.FlutterPluginBinding) 中做到这一点？

Answer 1

通过实现 ActivityAware 接口

https://www.codenong.com/jseb7df49fdfb1/

package com.example.fluttertoast

import android.app.Activity
import android.content.Context
import android.widget.Toast
import androidx.annotation.NonNull;

import io.flutter.embedding.engine.plugins.FlutterPlugin
import io.flutter.embedding.engine.plugins.activity.ActivityAware
import io.flutter.embedding.engine.plugins.activity.ActivityPluginBinding
import io.flutter.plugin.common.MethodCall
import io.flutter.plugin.common.MethodChannel
import io.flutter.plugin.common.MethodChannel.MethodCallHandler
import io.flutter.plugin.common.MethodChannel.Result
import io.flutter.plugin.common.PluginRegistry.Registrar

/** FluttertoastPlugin */
class FluttertoastPlugin: FlutterPlugin, MethodCallHandler, ActivityAware {
  private lateinit var channel : MethodChannel
  private lateinit var activity:Activity
  private lateinit var context: Context

  override fun onAttachedToEngine(@NonNull flutterPluginBinding: FlutterPlugin.FlutterPluginBinding) {
    channel = MethodChannel(flutterPluginBinding.flutterEngine.dartExecutor, "fluttertoast")
    channel.setMethodCallHandler(this)
    this.context = flutterPluginBinding.applicationContext
  }

  companion object {
    @JvmStatic
    fun registerWith(registrar: Registrar) {
      val channel = MethodChannel(registrar.messenger(), "fluttertoast")
      channel.setMethodCallHandler(FluttertoastPlugin())
    }
  }

  override fun onMethodCall(@NonNull call: MethodCall, @NonNull result: Result) {
    if (call.method == "getPlatformVersion") {
      Toast.makeText(activity,"Hello!",Toast.LENGTH_SHORT).show()
      result.success("Android ${android.os.Build.VERSION.RELEASE}")
    } else {
      result.notImplemented()
    }
  }

  override fun onDetachedFromEngine(@NonNull binding: FlutterPlugin.FlutterPluginBinding) {
    channel.setMethodCallHandler(null)
  }
  override fun onDetachedFromActivity() {}
  override fun onReattachedToActivityForConfigChanges(binding: ActivityPluginBinding) {
    onAttachedToActivity(binding)
  }
  override fun onAttachedToActivity(binding: ActivityPluginBinding) {
    this.activity = binding.activity
  }
  override fun onDetachedFromActivityForConfigChanges() {}
}

Answer 2

注意：

您可以通过实现 ActivityAware 接口来获取对活动的引用但是如果您在 onAttachToEngine() 方法中 setMethodCallHandler(...) 将永远不会调用 onAttachToActivity() 并且您将永远无法访问活动

看看下面的例子

什么不起作用： 在下面的例子中，onAttachToActivity() 永远不会被调用

class AndroidLongTaskPlugin : FlutterPlugin, ActivityAware {
  private var activity: FlutterActivity? = null

  

  override fun onAttachedToEngine(@NonNull flutterPluginBinding: FlutterPlugin.FlutterPluginBinding) {
    //activity is null here 
    //also onAttachToActivity will never be called because we are calling setMethodHandler here
    channel = MethodChannel(binaryMessenger, CHANNEL_NAME)
    channel.setMethodCallHandler { call, result ->
        //our code
    }

  }

  override fun onDetachedFromEngine(@NonNull binding: FlutterPlugin.FlutterPluginBinding) {
    channel?.setMethodCallHandler(null)
  }

  override fun onAttachedToActivity(binding: ActivityPluginBinding) {
    activity = binding.activity as FlutterActivity
  }

  //rest of the methods
}

这是一个工作示例：

class MyPlugin : FlutterPlugin, ActivityAware {
  private var activity: FlutterActivity? = null
  private var binaryMessenger: BinaryMessenger? = null

  override fun onAttachedToEngine(@NonNull flutterPluginBinding: FlutterPlugin.FlutterPluginBinding) {
    binaryMessenger = flutterPluginBinding.binaryMessenger
  }

  override fun onDetachedFromEngine(@NonNull binding: FlutterPlugin.FlutterPluginBinding) {
    Log.d("DART/NATIVE", "onDetachedFromEngine")
    channel?.setMethodCallHandler(null)
  }

  override fun onAttachedToActivity(binding: ActivityPluginBinding) {
    Log.d("DART/NATIVE", "onAttachedToActivity")
    activity = binding.activity as FlutterActivity
    //here we have access to activity
    //also make sure to setMethodCallHandler here
    channel.setMethodCallHandler { call, result ->
        //our code
    }
  }

  //rest of the methods
}

Answer 3

找到解决方案here。
实现ActivityAware，其方法之一是

 override fun onAttachedToActivity(binding: ActivityPluginBinding) {
    this.activity = binding.activity;
  }