详解Flutter 调用 Android Native 的2种方

Flutter 调用 Android Native 的方法，是通过MethodChannel的方式来实现的。

Android端：

实现方式一：

• 创建一个Class，实现FlutterPlugin 和 MethodCallHandler 接口
• 重写onAttachedToEngine()，onDetachedFromEngine()，onMethodCall() 这3个方法
• onMethodCall方法中，通过自定义的METHOD_NAME，来响应Flutter中，invokeMethod对Native的通信
• 在io.flutter.plugins包下的GeneratedPluginRegistrant添加代码 flutterEngine.getPlugins().add(SpeechPlugin1.Companion.getINSTANCE());

代码如下：

/**
 *      todo Flutter 调用 Android Native 的方法 2
 *              1、创建一个Class，实现FlutterPlugin和MethodCallHandler接口
 *              2、重写onAttachedToEngine()，onDetachedFromEngine()，onMethodCall()
 *              3、onMethodCall中，通过自定义的METHOD_NAME，来响应Flutter中，invokeMethod对Native的通信，
 *              4、在io.flutter.plugins包下的GeneratedPluginRegistrant添加代码 flutterEngine.getPlugins().add(SpeechPlugin1.Companion.getINSTANCE());
 */
class SpeechPlugin1:MethodChannel.MethodCallHandler,FlutterPlugin {

    private var methodChannel: MethodChannel? = null
    private var context:Context ?= null

    companion object{
        private const val CHANNEL_NAME = "speech_plugin"
        val INSTANCE : SpeechPlugin1 by lazy (mode = LazyThreadSafetyMode.SYNCHRONIZED){
            SpeechPlugin1()
        }
    }

    override fun onAttachedToEngine(binding: FlutterPlugin.FlutterPluginBinding) {
        methodChannel = MethodChannel(binding.binaryMessenger,CHANNEL_NAME)
        context= binding.applicationContext
        methodChannel?.setMethodCallHandler(this)
    }

    override fun onDetachedFromEngine(binding: FlutterPlugin.FlutterPluginBinding) {
        methodChannel?.setMethodCallHandler(null)
        methodChannel = null
    }
    @SuppressLint("SimpleDateFormat")
    override fun onMethodCall(call: MethodCall, result: MethodChannel.Result) {
        when(call.method){
            "android_time" -> result.success(SimpleDateFormat("yyyy-MM-dd hh:mm:ss").format(System.currentTimeMillis()))
            "toast" -> {
                if (call.hasArgument("msg") && !TextUtils.isEmpty(call.argument<String>("msg"))) {
                    Toast.makeText(context, call.argument<String>("msg"), Toast.LENGTH_LONG).show()
                } else {
                    Toast.makeText(context, "msg 不能为空", Toast.LENGTH_SHORT).show()
                }

            }
            else ->result.notImplemented()
        }
    }
   

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实现方式二：

在继承了FlutterActivity的MainActivity类中重写configureFlutterEngine方法

class MainActivity: FlutterActivity() {

    private lateinit var speechPlugin: SpeechPlugin2
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

    }

    override fun configureFlutterEngine(flutterEngine: FlutterEngine) {
        super.configureFlutterEngine(flutterEngine)
        speechPlugin = SpeechPlugin2(this)
        //通过MethodChannel与原生通信
        val methodChannel = MethodChannel(flutterEngine.dartExecutor, "speech_plugin")
        methodChannel.setMethodCallHandler(speechPlugin)
    }

class SpeechPlugin2(private val context: Context) : MethodChannel.MethodCallHandler {

    @SuppressLint("SimpleDateFormat")
    override fun onMethodCall(call: MethodCall, result: MethodChannel.Result) {
        when(call.method){
            "android_time" -> result.success(SimpleDateFormat("yyyy-MM-dd hh:mm:ss").format(System.currentTimeMillis()))
            "toast" -> {
                if (call.hasArgument("msg") && !TextUtils.isEmpty(call.argument<String>("msg"))) {
                    Toast.makeText(context, call.argument<String>("msg"), Toast.LENGTH_LONG).show()
                } else {
                    Toast.makeText(context, "msg 不能为空", Toast.LENGTH_SHORT).show()
                }
            }
            else ->result.notImplemented()
        }
    }
}

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，

class SpeechPlugin {
  //一定要和android native端一致
  static const String METHOD_NAME = "speech_plugin";  
  //定义与Native进行交互的MethodChannel,Android与Ios通用
  static const MethodChannel _methodChannel = MethodChannel(METHOD_NAME);

  //通过安卓获取当前时间
  static Future<String> getAndroidTime() async {
    //通过MethodChannel对象的invokeMethod()方法调用原生方法
    var time = await _methodChannel.invokeMethod("android_time");
    return Future.value(time);
  }

  //显示安卓土司
  static showAndroidToast(String message) async {
    try{
      await _methodChannel.invokeMethod("toast",{"msg":message});
    } on PlatformException catch(e){ //使用 catch on 捕获不同类型的错误
      // handle PlatformException
      print(e.toString());
    }
  }
}

 //获取到android端的系统时间后，再传递给android端。用android端的吐司显示出来
  void _showAndridToast(SearchViewModel model) {
   SpeechPlugin.getAndroidTime().then((message) {
     SpeechPlugin.showAndroidToast(message);
   });

  }