Flutter 调用 Android Native 的方法，是通过MethodChannel的方式来实现的:
在Android端：
- 创建一个Class，实现FlutterPlugin和MethodCallHandler接口
- 重写onAttachedToEngine()，onDetachedFromEngine()，onMethodCall()
- onAttachedToEngine()中，根据自定义的CHANNEL_NAME创建MethodChannel， onDetachedFromEngine中，释放MethodChannel
- onMethodCall中，通过自定义的METHOD_NAME，来响应Flutter中，invokeMethod对Native的通信，代码如下
class MethodChannelPlugin : FlutterPlugin, MethodChannel.MethodCallHandler {
private var methodChannel: MethodChannel? = null
private var mNoteForFlutterListener: NoteForFlutterListener? = null
companion object {
private const val CHANNEL_NAME = "method_channel"
private const val METHOD_NAME = "saveNote"
val instance: MethodChannelPlugin by lazy(mode = LazyThreadSafetyMode.SYNCHRONIZED) {
MethodChannelPlugin()
}
}
override fun onAttachedToEngine(binding: FlutterPlugin.FlutterPluginBinding) {
methodChannel = MethodChannel(binding.binaryMessenger, CHANNEL_NAME)
methodChannel?.setMethodCallHandler(this)
}
override fun onDetachedFromEngine(binding: FlutterPlugin.FlutterPluginBinding) {
methodChannel?.setMethodCallHandler(null)
methodChannel = null
}
override fun onMethodCall(call: MethodCall, result: MethodChannel.Result) {
if (call.method == METHOD_NAME) {
val content = call.argument<String>("content")
mNoteForFlutterListener?.sendData(content!!)
result.success("success")
} else {
result.notImplemented()
}
}
fun setListener(noteForFlutterListener: NoteForFlutterListener) {
mNoteForFlutterListener = noteForFlutterListener
}
在Flutter端：
- 根据Native中定义的METHOD_NAME来创建MethodChannel
- 通过MethodChannel.invokeMethod(METHOD_NAME,params)，参数METHOD_NAME为Native中定义的METHOD_NAME，params为传递的参数，就可以和Native进行通信了，在Native的onMethodCall方法中，通过call.method == METHOD_NAME来确定，Flutter是否调用的是Native中定义的METHOD_NAME的方法，代码如下
class NoteMainFulState extends State<NoteMainFul> {
//flutter 和 native 通信
static const _methodMessageChannel = MethodChannel("method_channel");
TextField textField;
TextEditingController textEditingController;
@override
Widget build(BuildContext context) {
return Scaffold(
body: Container(
margin: EdgeInsets.fromLTRB(20.0, 60.0, 20.0, 20.0),
child: Column(
children: [
Container(
child: Column(
children: [
textField = TextField(
//去掉下划线
decoration: InputDecoration(border: InputBorder.none),
enabled: true,
controller: textEditingController = NoteTextEditingController(),
keyboardType: TextInputType.multiline,
textInputAction: TextInputAction.newline,
maxLines: null,
),
RichText(
text: TextSpan(),
),
],
),
),
Container(
color: Colors.deepPurple,
height: 50,
child: Row(
mainAxisAlignment: MainAxisAlignment.spaceEvenly,
children: [
GestureDetector(
child: Icon(
Icons.forward,
),
onTap: clickOut,
)
],
),
)
],
),
),
);
}
void clickOut() async {
//调用native方法，返回首页
var content = textEditingController.text;
Map<String, dynamic> map = {"content": content};
var result = await _methodMessageChannel.invokeMethod("saveNote", map);
print("result $result");
}
以上就是Flutter 调用 Android Native 的方法的过程，有时间再分析下他们的实现原理
待续....
附，我当前的Flutter版本是 ：
Flutter 1.22.3 • channel stable • https://github.com/flutter/flutter
Framework • revision 8874f21e79 (3 months ago) • 2020-10-29 14:14:35 -0700
Engine • revision a1440ca392
Tools • Dart 2.10.3
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