flutter plugin之路：flutter与原生交互传值O

上一篇flutter plugin之路：flutter与原生交互传值OC/java版(一)说道如何使用flutter调用原生api传值(值的传递流程这样：flutter->原生->flutter,flutter调用原生方法，此时flutter可以传一个参数给原生，然后原生接受flutter的调用后，再返回一个值给flutter)，这一篇说的是原生如何主动传值给flutter

实现流程

flutter通过标识监听指定的通道->原生通过这个通道向flutter发送信息->flutter通过监听这个通道获取原生发送的信息

实现目标，原生每1秒调用一次方法，自增数值，然后传到flutter，再由flutter进行显示

本demo的github地址：https://github.com/iBinbro/flutterstudy
（补充了安卓java版，以OC为例作为分析，安卓java同理不做叙述了）

一、flutter端的实现

1.创建TwoCommunicate类(statefulwidget)
2.flutter注册监听通道
3.声明两个方法用于处理接收到的数据以及异常错误
4.执行监听
5.build方法实现布局，将返回的数据显示出来

import 'package:flutter/material.dart';
import 'dart:async';
import 'package:flutter/services.dart';

class TwoCommunicate extends StatefulWidget {
  @override
  _TwoCommunicateState createState() => _TwoCommunicateState();
}

class _TwoCommunicateState extends State<TwoCommunicate> {

  //****************原生主动调用flutter****************//
  //存放原生传给flutter的值
  String _nativeToFlutterString = '';

  //注册监听原生通道
  EventChannel eventChannel = EventChannel('https://www.jianshu.com/p/7dbbd3b4ce32');

  //监听到数据后用于处理数据的方法，这个函数是用于处理接收到原生传进来的数据的，可自行定义
  void _receiveFromeNative(Object para){
    print(para);
    setState(() {
      _nativeToFlutterString = para.toString();
    });
  }

  //原生返回错误信息
  void _fromNativeError(Object error){
    print(error);
  }

  @override
  void initState() {
    // TODO: implement initState
    //实现通道的监听，并传入两个带有参数的函数用于监听到数据后 对数据进行处理
    eventChannel.receiveBroadcastStream().listen(_receiveFromeNative, onError: _fromNativeError);
    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('text'),
      ),
      body: Container(
        padding: EdgeInsets.all(32.0),
        child: Center(
          child: Column(
            children: <Widget>[
              //显示原生传过来的值
              MaterialButton(
                color: Colors.green,
                child: Text(_nativeToFlutterString),
                onPressed: () {
                },
              )
            ],
          ),
        ),
      ),
    );
  }
}

二、原生端iOS OC的实现,

先运行下工程，避免打开ios工程缺少文件，然后在工程目录进入ios文件夹，打开Runner.xcworkspace，使用xcode进行原生代码的编写

#include "AppDelegate.h"
#include "GeneratedPluginRegistrant.h"

//遵循代理方法
@interface AppDelegate()<FlutterStreamHandler>

@end

@implementation AppDelegate{
    /// 用于主动传值给flutter的桥梁.
    FlutterEventSink _eventSink;
    NSInteger _nativeCount;
}

- (BOOL)application:(UIApplication *)application
    didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    
    __weak __typeof(self) weakself = self;
    
    FlutterViewController *controller = (FlutterViewController *)self.window.rootViewController;
    
    /**********原生主动传值给flutter-Start**********/
    _nativeCount = 0;
    
    NSLog(@"原生实现 原生传值给flutter的通道标识");
    FlutterEventChannel *eventChannel = [FlutterEventChannel eventChannelWithName:@"https://www.jianshu.com/p/7dbbd3b4ce32" binaryMessenger:controller];
    //设置代理
    [eventChannel setStreamHandler:self];
    
    /**********原生主动传值给flutter-End**********/
    
    
    
  [GeneratedPluginRegistrant registerWithRegistry:self];
  // Override point for customization after application launch.
  return [super application:application didFinishLaunchingWithOptions:launchOptions];
}

/**********原生主动传值给flutter-Start**********/
//flutter开始进行监听，并在此方法传入 原生主动传值给flutter的桥梁 event
- (FlutterError *)onListenWithArguments:(id)arguments eventSink:(FlutterEventSink)events{
    NSLog(@"flutter开始进行监听，并在此方法传入 原生主动传值给flutter的桥梁 event");
    _eventSink = events;
    
    [self repeatAddNativeCount];
    
    return nil;
}

//翻了下官方文档 Invoked when the last listener is deregistered from the Stream associated to this channel on the Flutter side. 大致意思是stream关联的这个通道监听器取消后调用,找了下flutter的dart代码，没取消监听的方法 后面再说吧 待解
- (FlutterError *)onCancelWithArguments:(id)arguments{
    _eventSink = nil;
    return nil;
}

- (void)repeatAddNativeCount{
    NSLog(@"重复传值执行");
    _nativeCount++;
    //通过桥梁传值
    if (_eventSink) {
        _eventSink(@(_nativeCount));
    }
    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(1 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
        [self repeatAddNativeCount];
    });
}

/**********原生主动传值给flutter-Start**********/

@end

效果图

image.png