Flutter插件中获取Activity

前言

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1、最近在做 Flutter 插件开发时，需要判断是否为折叠屏。

2、折叠屏的监听需要用到 Activity，故写下了这篇博客。

1、Flutter 低版本

在低版本的 Flutter 中可以通过 registerWith(Registrar registrar) 方法获取
Android 原生端代码:

package com.jiangxr.flutter_plugin

import android.app.Activity
import android.widget.Toast
import io.flutter.plugin.common.MethodCall
import io.flutter.plugin.common.MethodChannel
import io.flutter.plugin.common.MethodChannel.*
import io.flutter.plugin.common.PluginRegistry.Registrar

class JPlugin(registrar: Registrar) : MethodCallHandler {

  private var activity: Activity? = null

  init {
    activity = registrar.activity()
  }

  fun registerWith(registrar: Registrar) {
    val channel = MethodChannel(registrar.messenger(), "jiang_plugin")
    channel.setMethodCallHandler(JPlugin(registrar))
  }

  override fun onMethodCall(call: MethodCall, result: Result) {
    when (call.method) {
      "getPlatformVersion" -> {
        result.success("Android ${android.os.Build.VERSION.RELEASE}")
      }
      "showToast" -> {
        Toast.makeText(activity, "Flutter 调用 Android 原生端 Toast", Toast.LENGTH_SHORT).show()
      }
      else -> {
        result.notImplemented()
      }
    }
  }
}

Flutter 端的代码：

import 'dart:async';

import 'package:flutter/services.dart';

class FlutterPlugin {
  static const MethodChannel _channel = MethodChannel('jiang_plugin');

  static Future<String?> get platformVersion async {
    final String? version = await _channel.invokeMethod('getPlatformVersion');
    return version;
  }

  static Future<void> get showToast async {
    await _channel.invokeMethod('showToast');
  }
}

在 Flutter 中调用的时候直接使用 await FlutterPluginDemo.showToast(); 即可

2、Flutter 高版本

在 Flutter 高版本中直接通过实现 ActivityAware 接口拿到 Activity
由于涉及隐私，这里只写了关键代码，代码如下：

package com.jiangxr.flutter_plugin

import android.app.Activity
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 java.lang.ref.WeakReference

class XPlugin : MethodCallHandler, ActivityAware {

  private var mActivity: WeakReference<Activity>? = null

  override fun onMethodCall(call: MethodCall, result: Result) {
    TODO("Not yet implemented")
  }

  override fun onAttachedToActivity(binding: ActivityPluginBinding) {
    mActivity = WeakReference(binding.activity)
  }

  override fun onDetachedFromActivityForConfigChanges() {
    TODO("Not yet implemented")
  }

  override fun onReattachedToActivityForConfigChanges(binding: ActivityPluginBinding) {
    TODO("Not yet implemented")
  }

  override fun onDetachedFromActivity() {
    mActivity = null;
  }
}