PlatformChannel功能简介
PlatformChannel分为BasicMessageChannel、MethodChannel以及EventChannel三种。其各自的主要用途如下：
BasicMessageChannel: 用于传递数据。Flutter与原生项目的资源是不共享的，可以通过BasicMessageChannel来获取Native项目的图标等资源。
MethodChannel: 传递方法调用。Flutter主动调用Native的方法，并获取相应的返回值。比如获取系统电量，发起Toast等调用系统API，可以通过这个来完成。
EventChannel: 传递事件。这里是Native将事件通知到Flutter。比如Flutter需要监听网络情况，这时候MethodChannel就无法胜任这个需求了。EventChannel可以将Flutter的一个监听交给Native，Native去做网络广播的监听，当收到广播后借助EventChannel调用Flutter注册的监听，完成对Flutter的事件通知。
其实可以看到，无论传方法还是传事件，其本质上都是数据的传递，不过上层包的一些逻辑不同而已。
具体实现
1.BasicMessageChannel （可以实现相互传递）
flutter
static const messageChannel = const BasicMessageChannel('samples.flutter.io/message', StandardMessageCodec());
static const messageChannel2 = const BasicMessageChannel('samples.flutter.io/message2', StandardMessageCodec());
Future<String> sendMessage() async {
String reply = await messageChannel.send('发送给Native端的数据');
print('reply: $reply');
return reply;
}
void receiveMessage() {
messageChannel2.setMessageHandler((message) async {
print('message: $message');
return '返回Native端的数据';
});
}
@override
void initState() {
// TODO: implement initState
super.initState();
receiveMessage();
sendMessage();
}
ios
// 初始化定义
FlutterBasicMessageChannel* messageChannel = [FlutterBasicMessageChannel messageChannelWithName:@"samples.flutter.io/message" binaryMessenger:controller];
// 接收消息监听
[messageChannel setMessageHandler:^(id message, FlutterReply callback) {
NSLog(message);
callback(@"返回flutter端的数据");
}];
// 触发事件执行
FlutterViewController* controller = (FlutterViewController*)self.window.rootViewController;
FlutterBasicMessageChannel* messageChannel2 = [FlutterBasicMessageChannel messageChannelWithName:@"samples.flutter.io/message2" binaryMessenger:controller];
// 发送消息
[messageChannel2 sendMessage:(@"发送给flutter的数据") reply:^(id reply) {
NSLog(reply);
}];
2.MethodChannel （ Flutter主动调用Native的方法）
flutter
static const platform = const MethodChannel('samples.flutter.io/battery');
Future<Null> _getBatteryLevel() async {
String batteryLevel;
try {
//关键 platform.invokeMethod('方法名')
final int result = await platform.invokeMethod('getBatteryLevel');
batteryLevel = 'Battery level at $result % .';
} on PlatformException catch (e) {
batteryLevel = "Failed to get battery level: '${e.message}'.";
}
setState(() {
_batteryLevel = batteryLevel;
});
}
// 执行_getBatteryLevel方法
ios
FlutterViewController* controller = (FlutterViewController*)self.window.rootViewController;
FlutterMethodChannel* batteryChannel = [FlutterMethodChannel
methodChannelWithName:@"samples.flutter.io/battery"
binaryMessenger:controller];
[batteryChannel setMethodCallHandler:^(FlutterMethodCall* call, FlutterResult result) {
// TODO
if ([@"getBatteryLevel" isEqualToString:call.method]) {
///Do some thing 做一些事
} else {
result(FlutterMethodNotImplemented);
}
}];
3.FlutterEventChannel （Native将事件通知到Flutter）
flutter
static const EventChannel _eventChannel =
const EventChannel('samples.flutter.io/test');
void _onEvent(Object event) {
print('=======返回的内容: $event');
//Map eventMap = json.decode(event);
// String parts = eventMap['parts'];
// print("===parts==="+parts);
}
void _onError(Object error) {
print('返回的错误');
}
@override
void initState() {
// TODO: implement initState
super.initState();
// 监听开始
_eventChannel.receiveBroadcastStream('123456').listen(_onEvent, onError: _onError);
}
@override
Widget build(BuildContext context) {
print("=======build");
return new Scaffold(
appBar: new AppBar(
title: new Text('TwoPage'),
),
body:ListView(
children: <Widget>[
ListTile(title: Text('1'),),
ListTile(title: Text('2'),),
ListTile(title: Text('3'),),
ListTile(title: Text('4'),),
ListTile(title: Text('5'),),
ListTile(title: Text('6'),),
],
));
}
@override
void dispose() {
super.dispose();
///取消获取登录数据
if (_eventSub != null) _eventSub.cancel();
}
ios
//1.创建控制器
FlutterViewController* controller = [[FlutterViewController alloc]init];
//2.创建事件渠道
FlutterEventChannel* eventChannel = [FlutterEventChannel eventChannelWithName:@"samples.flutter.io/test" binaryMessenger:controller];
//3.设置代理
[eventChannel setStreamHandler:self];
FlutterEventSink eventSink;
#pragma mark - FlutterStreamHandler代理
// // 这个onListen是Flutter端开始监听这个channel时的回调，第二个参数 EventSink是用来传数据的载体。
- (FlutterError* _Nullable)onListenWithArguments:(id _Nullable)arguments
eventSink:(FlutterEventSink)events {
eventSink = events;
// arguments flutter给native的参数
// 回调给flutter， 建议使用实例指向，因为该block可以使用多次
if (events) {
events(@"主动发送通知到flutter");//回调给flutter
}
///可以在此做一些事
NSLog(@"======%@", arguments);
return nil;
}
/// flutter不再接收
- (FlutterError* _Nullable)onCancelWithArguments:(id _Nullable)arguments {
// arguments flutter给native的参数
///可以在此做一些事
eventSink = nil;
return nil;
}
代码执行顺序
//创建完flutterVc 和eventChannel 以后
1.flutter：initState()
2.native：onListenWithArguments
(调用此方法时，先打印方法名，再打印接收的参数arguments，因为执行events会有短暂的延迟，所以会先打印后面的)
3.native： ======12345
4.flutter: =======build
5.flutter: _onEvent
6.flutter: =======返回的内容:主动发送通知到flutter
4.原生跳Flutter页面路由传参
ios setInitialRoute
FlutterViewController *vc = [[FlutterViewController alloc]init];
///初始化路由名称
[vc setInitialRoute:@"myApp"];
FlutterEventChannel *evenChannal = [FlutterEventChannel eventChannelWithName:@"com.jiaparts.flutter_event/plugin" binaryMessenger:vc];
[evenChannal setStreamHandler:self];
[self.navigationController pushViewController:vc animated:YES];
flutter main.dart
window.defaultRouteName获取路由名称
void main() => runApp(_widgetForRoute(window.defaultRouteName));
Widget _widgetForRoute(String route){
return MaterialApp(
home: Scaffold(
resizeToAvoidBottomPadding: false, //输入框抵住键盘 内容不随键盘滚动
body: _ylmPage(route)
));
}
Widget _ylmPage(String routeStr){
switch(routeStr){//接收从原生跳转过来的路由，决定跳转哪个页面
case 'myApp':
return new TwoPage();
default:
return MyApp();
}
}
