dart调用android方法,详解Flutter 调用 Android Native 的方法

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("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 {

//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 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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