简介
Flutter与原生之间的通信依赖灵活的消息传递方式：
- 应用的Flutter部分通过平台通道（platform channel）将消息发送到其应用程序的所在的宿主（iOS或Android）应用（原生应用）。
- 宿主监听平台通道，并接收该消息。然后它会调用该平台的API，并将响应发送回客户端，即应用程序的Flutter部分。
- MethodChannel // Flutter与原生方法相互调用，用于方法掉用
- BasicMessageChannel // Flutter与原生相互发送消息，用于数据传递
- EventChannel // 原生发送消息，Flutter接收，用于数据流通信
可以传递的数据结构
Dart | Android | iOS |
null | null | nil(NSNull when nested) |
bool | Java.lang.Boolean | NSNumber numberWithBool: |
int | Java.lang.Integer | NSNumber numberWithInt: |
int, if 32 bits not enough | Java.lang.Long | NSNumber numberWithLong: |
int, if 64 bits not enough | Java.lang.BigInteger | FlutterStandardBigInteger |
double | Java.lang.Double | NSNumber numberWithDouble |
String | java.lang.String | NSString |
Unit8List | byte[] | FlutterStandardTypedData typedDataWithBytes: |
Int32List | int[] | FlutterStandardTypedData typedDataWithInt32: |
Int64List | long[] | FlutterStandardTypedData typedDataWithInt64: |
Float64List | double[] | FlutterStandardTypedData typedDataWithFloat64: |
List | Java.util.ArrayList | NSArray |
Map | Java.util.HashMap | NSDictionary |
MethodChannel（互相调用方法）
Android调用Flutter方法：
Android:
- 初始化MethodChannel
//初始化，传递1. flutterView（MainActivity中getFlutter获取），2. name常量，Flutter中使用同名常量
MethodChannel methodChannel = new MethodChannel(flutterView, “testflutter”);
- 调用Flutter方法
通过MethodChannel调用invokeMethod("方法名","传递参数",[Flutter返回参数回调，非必须]);
Flutter:
- 初始化MethodChannel
static const methodChannel = const MethodChannel('testflutter');
复制代码- 添加处理方法到MethodChannel
methodChannel.setMethodCallHandler(_addNativeMethod);
- 处理android调用的方法，根据方法名
Flutter调用Android方法：
Android：
- 初始化MethodChannel，并添加自定义plugin
MethodChannel methodChannel = new MethodChannel(flutterView, METHOD_CHANNEL);
methodChannel.setMethodCallHandler(plugin);
- 自定义的plugin实现MethodChannel.MethodCallHandler接口的onMethodCall方法
@Override
public void onMethodCall(MethodCall methodCall, MethodChannel.Result result) {
// Flutter调用Native的方法
if (methodCall.method.equals("getBatteryLevel")) {
int batteryLevel = getBatteryLevel();
if (batteryLevel != -1) {
result.success(batteryLevel);
} else {
result.error("UNAVALIABLE", "battery level unavaliable", null);
}
} else {
result.notImplemented();
}
}
//在onMethodCall中监听Flutter调用什么名字的方法（此处getBatterLevel），通过result返回方法的执行结果。
Flutter：
- 初始化MethodChannel
static const methodChannel = const MethodChannel('testflutter');
复制代码- 调用Android的方法，接收返回数据
//方法通道的方法是异步的
Future<Null> _getBatteryLevel() async {
String batteryLevel;
try {
final int result = await methodChannel.invokeMethod('getBatteryLevel');
batteryLevel = 'Battery level $result .';
} on PlatformException catch (e) {
batteryLevel = 'Battery level unknown ${e.message}';
}
setState(() {
_batteryLevel = batteryLevel;
});
}
BasicMessageChannel（互相发送消息）
Android给Flutter发消息：
Android：
- 初始化BasicMethodChannel
BasicMessageChannel messageChannel =
new BasicMessageChannel<>(flutterView,
"messageChannel", StandardMessageCodec.INSTANCE);
复制代码- 调用发送消息的方法
private void sendMessageToFlutter() {
if (this.mBasicMessageChannel != null) {
this.mBasicMessageChannel.send("Message From Native");
}
}
Flutter：
- 初始化BasicMessageChannel
static const basicMessageChannel = BasicMessageChannel('messageChannel', StandardMessageCodec());
复制代码- 添加接收信息处理方法
void _listenMessageFromNative() {
basicMessageChannel.setMessageHandler(_receiveMessageFromNative);
}
- 处理接收的数据
//Flutter接收Native发来的消息
Future<dynamic> _receiveMessageFromNative(Object result) async {
setState(() {
_messageFromNative = result.toString();
});
}
Flutter给Android发消息：
Android：
- 初始化BasicMessageChannel并添加plugin给handler
BasicMessageChannel messageChannel = new BasicMessageChannel<>(flutterView, "messageChannel", StandardMessageCodec.INSTANCE);
messageChannel.setMessageHandler(plugin);
- plugin实现BasicMessageChannel.MessageHandler接口的onMessage方法，处理接收到的信息
@Override
public void onMessage(Object o, BasicMessageChannel.Reply reply) {
Toast.makeText(mContext, o.toString(), Toast.LENGTH_LONG).show();
reply.reply(o.toString()+" back from native");
}
//reply返回数据给Flutter
Flutter：
- 初始化BasicMessageChannel
static const basicMessageChannel =
BasicMessageChannel('messageChannel', StandardMessageCodec());
- 发送消息给Android并接收返回数据
EventChannel（原生发送消息，Flutter接收）
Android：
- 初始化EventChannel并添加plugin给handler
EventChannel eventChannel = new EventChannel(flutterView, EVENT_CHANNEL);
eventChannel.setStreamHandler(plugin);
- plugin实现EventChannel.StreamHandler接口及onListen、onCancel方法
- 在onListen中通过EventChannel.EventShink的实例发消息给Flutter
@Override
public void onListen(Object o, EventChannel.EventSink eventSink) {
BroadcastReceiver chargingBroadcastReceiver = createChargingBroadcaseReceiver(eventSink);
mContext.registerReceiver(chargingBroadcastReceiver,new IntentFilter(Intent.ACTION_BATTERY_CHANGED));
}
@Override
public void onCancel(Object o) {
}
private BroadcastReceiver createChargingBroadcaseReceiver(EventChannel.EventSink eventSink) {
return new BroadcastReceiver() {
@Override
public void onReceive(Context context, Intent intent) {
int status = intent.getIntExtra(BatteryManager.EXTRA_STATUS, -1);
if (status == BatteryManager.BATTERY_STATUS_UNKNOWN) {
eventSink.error("UNAVALIABLE", "charging status is unavailable", null);
} else {
boolean isCharging = status == BatteryManager.BATTERY_STATUS_CHARGING;
eventSink.success(isCharging ? "charging" : "disCharging");
}
}
};
}
Flutter:
- 初始化EventChannel
static const _eventChannel = const EventChannel('charging');
- 添加接收数据方法
void listenNativeEvent() {
_eventChannel.receiveBroadcastStream().listen(_onEvent, onError: _onError);
}
//接收返回的数据
void _onEvent(Object object) {
String s = "Battery is ${object == 'charging' ? '' : 'dis'}Charging";
setState(() {
_batteryStatus = s;
});
}
桥接View给Flutter使用
Android：
- 自定义View，继承自PlatformView
- 实现PlatformViewFactory
public class TextViewFactory extends PlatformViewFactory {
private MessageCodec<Object> messageCodec;
public TextViewFactory(MessageCodec<Object> createArgsCodec) {
super(createArgsCodec);
this.messageCodec = createArgsCodec;
}
@Override
public PlatformView create(Context context, int i, Object o) {
return new MyTextview(context, messageCodec, i, (Map<String, Object>) o);
}
}
- 注册View给Flutter使用
registrar.platformViewRegistry().registerViewFactory("TextView", new TextViewFactory(new StandardMessageCodec()));
//起名叫TextView，给Flutter用做viewType
Flutter:
- 使用桥接的View
AndroidView(
viewType: 'TextView',
creationParams: {'text': 'TTTeeeXXXttt'},
creationParamsCodec: new StandardMessageCodec(),
),//其中creationParams，creationParamsCodec必须同时存在或不存在
以上，正文结束；
官方还有一些其他建议
发布pub使用：
- Hosted packages（发布到pub.dartlang.org）
$flutter packages pub publish --dry-run
$flutter packages pub publish
复制代码在yaml文件和其他dependencies一样使用。
- Git packages（远端）
代码上传到Git，并打一个tag
yaml文件引用
dependencies:
flutter_remote_package:
git:
url: git@gitlab....
ref: 0.0.1 //可以是commit、branch、tag- 本地
在Flutter App根目录下创建plugins文件夹，把插件移动到plugins下。
以上限于在创建工程的时候，使用的是plugins创建的，有时候会在自己的Android或iOS工程内部开发，就不这么方便分离发布了。
dependencies：flutter_plugin_batterylevel:
path: plugins/flutter_plugin_batteryleveldependencies：
flutter_plugin_batterylevel:
path: plugins/flutter_plugin_batterylevel有时候需要到UI thread执行channelMethod，在Android上需要post一个Runnable到Android UI线程。
new Handler(Looper.getMainLooper()).post(new Runnable() {
@Override
public void run(){
// call the desired channel message here.
}
})
- 所谓的“传View”的本质是传递纹理ID，我们只需要明白Flutter是通过Presentation实现了外接纹理，在创建Presentation时，传入FlutterView对应的Context和创建出来的一个虚拟显示屏对象，使得Flutter可以直接通过ID找到并使用Native创建出来的纹理数据。
- 事件处理，从Native传递到Flutter这一阶段Flutter按照自己的规则处理事件，如果AndroidView获取到了事件，事件会被封装成相应的Native端的事件通过方法通道传回Native，Native再处理事件。
对于可能出现的滑动时间冲突，可以参考官方注释：
/// For example, with the following setup vertical drags will not be dispatched to the Android view as the vertical drag gesture is claimed by the parent [GestureDetector].
///
/// GestureDetector(
/// onVerticalDragStart: (DragStartDetails d) {},
/// child: AndroidView(
/// viewType: 'webview',
/// gestureRecognizers: <OneSequenceGestureRecognizer>[],
/// ),
/// )
///
/// To get the [AndroidView] to claim the vertical drag gestures we can pass a vertical drag gesture recognizer in [gestureRecognizers] e.g:
///
/// GestureDetector(
/// onVerticalDragStart: (DragStartDetails d) {},
/// child: SizedBox(
/// width: 200.0,
/// height: 100.0,
/// child: AndroidView(
/// viewType: 'webview',
/// gestureRecognizers: <OneSequenceGestureRecognizer>[new VerticalDragGestureRecognizer()],
/// ),
/// ),
/// )本文章为转载内容，我们尊重原作者对文章享有的著作权。如有内容错误或侵权问题，欢迎原作者联系我们进行内容更正或删除文章。
