Flutter - 处理页面路由跳转（Dart -> Na

背景

最近一直在考虑Flutter如何处理由原生页面处理后返回的结果，比如：startActivityForResult，需要处理的结果必须在onActivityResult方法处理，但是Dart代码中又要接收到该值。经过多番查看资料，终于找到了相应的办法。

相关代码

1. 创建一个插件库，编写一个叫RouterPlugin的项目。注意代码中的几个重要的接口：PluginRegistry.ActivityResultListener，该类需要实现onActivityResult方法，用于处理相应的返回处理。

2. 插件类中保存MethodCall、Result的实例，用于处理相关的结果。

   class RouterPlugin private constructor(private val registrar: Registrar) : MethodCallHandler, PluginRegistry.ActivityResultListener {
   
       companion object {
   
           @JvmStatic
           private val TAG = RouterPlugin::class.java.simpleName
   
           @JvmStatic
           fun registerWith(registrar: Registrar): Unit {
               val instance = RouterPlugin(registrar)
               val channel = MethodChannel(registrar.messenger(), "router_plugin")
               registrar.addActivityResultListener(instance)
               channel.setMethodCallHandler(instance)
           }
   
       }
   
       private var methodCall: MethodCall? = null
       private var pendingResult: Result? = null
       private var requestCode: Int = 0
   
       override fun onMethodCall(call: MethodCall, result: Result): Unit {
           if (this.pendingResult != null) {
               Log.e(TAG, "RouterPlugin is already active.")
               return
           }
           val activity = registrar.activity()
           if (activity == null) {
               Log.e(TAG, "RouterPlugin requires a foreground activity.")
               return
           }
           this.methodCall = call
           this.pendingResult = result
           val activityClassName = if (!call.hasArgument("activity")) null else call.argument<String>("activity")
           if (activityClassName.isNullOrEmpty()) {
               Log.e(TAG, "RouterPlugin requires a activity class name.")
               return
           }
           val arguments = if (!call.hasArgument("arguments")) null else call.argument<Map<String, Any>?>("arguments")
           when (call.method) {
               "startActivity" -> {
                   activity.startActivity(getActivityIntent(activity, activityClassName!!, arguments))
                   result.success(null)
                   this.methodCall = null
                   this.pendingResult = null
               }
               "startActivityForResult" -> {
                   val requestCode = if (!call.hasArgument("requestCode")) -1 else call.argument("requestCode")
                   if (requestCode == -1) {
                       Log.e(TAG, "RequestCode cannot be null")
                       return
                   }
                   this.requestCode = requestCode
                   activity.startActivityForResult(getActivityIntent(activity, activityClassName!!, arguments), requestCode)
               }
           }
       }
   
       override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?): Boolean {
           if (requestCode == this.requestCode) {
               if (resultCode == Activity.RESULT_OK) {
                   val ret: MutableMap<String, Any> = mutableMapOf()
                   data?.extras?.keySet()?.forEach {
                       ret[it] = data.extras[it]
                   }
                   println("---------->信息：$ret")
                   this.pendingResult?.success(if (ret.isEmpty()) null else ret)
               }
               this.methodCall = null
               this.pendingResult = null
               this.requestCode = 0
               return true
           }
           return false
       }
   
       private fun getActivityIntent(context: Context, activityClassName: String, params: Map<String, Any>? = null): Intent {
           val intent = Intent(context, Class.forName(activityClassName))
           with(intent) {
               params?.forEach { key, value ->
                   when (value) {
                       is Char -> putExtra(key, value)
                       is Short -> putExtra(key, value)
                       is Int -> putExtra(key, value)
                       is Long -> putExtra(key, value)
                       is Float -> putExtra(key, value)
                       is Double -> putExtra(key, value)
                       is Boolean -> putExtra(key, value)
                       is String -> putExtra(key, value)
                       is CharArray -> putExtra(key, value)
                       is ShortArray -> putExtra(key, value)
                       is IntArray -> putExtra(key, value)
                       is LongArray -> putExtra(key, value)
                       is FloatArray -> putExtra(key, value)
                       is DoubleArray -> putExtra(key, value)
                       is BooleanArray -> putExtra(key, value)
                       is Parcelable -> putExtra(key, value)
                       else -> putExtra(key, Gson().toJson(value)) //复杂类型会被转换成JSON-String
                   }
               }
           }
           return intent
       }
   
   }
   

3. 对应的dart代码[RouterPlugin.dart]

   class RouterPlugin {
   
     static const MethodChannel _channel =
     const MethodChannel('router_plugin');
   
     static void startActivity(String activityClassName,
         [Map<String, dynamic> arguments]) =>
         _channel.invokeMethod("startActivity", {
           "activity": activityClassName,
           "arguments": arguments
         });
   
     static Future<dynamic> startActivityForResult(String activityClassName, int requestCode,
         [Map<String, dynamic> arguments]) =>
         _channel.invokeMethod("startActivityForResult", {
           "activity": activityClassName,
           "requestCode": requestCode,
           "arguments": arguments
         });
   
   }
   

4. 主项目添加一个Activity，叫做HeloActivity，并编写以下代码

   class HeloActivity : AppCompatActivity() {
   
       override fun onCreate(savedInstanceState: Bundle?) {
           super.onCreate(savedInstanceState)
           setContentView(R.layout.activity_helo)
       }
   
       override fun onKeyDown(keyCode: Int, event: KeyEvent?): Boolean {
           if (keyCode == KeyEvent.KEYCODE_BACK && event?.action == KeyEvent.ACTION_DOWN) {
               val data = Intent()
               data.putExtra("name", "谢尔顿")
               data.putExtra("age", 8)
               setResult(Activity.RESULT_OK, data)
               this.finish()
               return true
           }
           return super.onKeyDown(keyCode, event)
       }
   
   }
   

5. 测试代码[main.dart]

   void main() => runApp(new MyApp());
   
   class MyApp extends StatelessWidget {
     @override
     Widget build(BuildContext context) {
       return new MaterialApp(
         title: 'Flutter Demo',
         theme: new ThemeData(
           primarySwatch: Colors.blue,
         ),
         home: new MyHomePage(title: 'Flutter Demo Home Page'),
       );
     }
   }
   
   class MyHomePage extends StatefulWidget {
     MyHomePage({Key key, this.title}) : super(key: key);
   
     final String title;
   
     @override
     _MyHomePageState createState() => new _MyHomePageState();
   }
   
   class _MyHomePageState extends State<MyHomePage> {
   
     String backMessage; //返回信息
   
     _incrementCounter() async {
       var value = await RouterPlugin.startActivityForResult(
           "com.mrper.flutterapp.HeloActivity", 200); //启动一个原生页面
       setState(() {
         backMessage = value.toString();
       });
     }
   
     @override
     Widget build(BuildContext context) {
       return new Scaffold(
         appBar: new AppBar(
           title: new Text(widget.title),
         ),
         body: new Center(
           child: new Column(
             mainAxisAlignment: MainAxisAlignment.center,
             children: <Widget>[
               new Text(
                 '接收startActivityForResult返回的信息:',
               ),
               new Text(
                 '$backMessage',
                 style: Theme.of(context).textTheme.display1,
               ),
             ],
           ),
         ),
         floatingActionButton: new FloatingActionButton(
           onPressed: _incrementCounter,
           tooltip: 'Increment',
           child: new Icon(Icons.add),
         ),
       );
     }
   }
   

结语

现目前能从Flutter跳转到原生UI了，但是如何从原生UI跳转到Flutter的UI，现目前也还没找到相应的策略，纠结!

​