Flutter 混合開發系列 包含如下：
- 嵌入原生View-Android
- 嵌入原生View-iOS
- 與原生通信-MethodChannel
- 與原生通信-BasicMessageChannel
- 與原生通信-EventChannel
- 添加 Flutter 到 Android Activity
- 添加 Flutter 到 Android Fragment
- 添加 Flutter 到 iOS
每個工作日分享一篇，歡迎關注、點贊及轉發。
iOS View
建議使用 Xcode 進行開發，在 Android Studio 左側 project tab下選中 ios 目錄下任意一個文件，右上角會出現 Open iOS module in Xcode ，
點擊即可打開，打開后如下：
在Runner 目錄下創建 iOS View，此 View 繼承 FlutterPlatformView ，返回一個簡單的 UILabel ：
import Foundation
import Flutter
class MyFlutterView: NSObject,FlutterPlatformView {
let label = UILabel()
init(_ frame: CGRect,viewID: Int64,args :Any?,messenger :FlutterBinaryMessenger) {
label.text = "我是 iOS View"
}
func view() -> UIView {
return label
}
}
- getView ：返回iOS View
注冊PlatformView
創建 MyFlutterViewFactory：
import Foundation
import Flutter
class MyFlutterViewFactory: NSObject,FlutterPlatformViewFactory {
var messenger:FlutterBinaryMessenger
init(messenger:FlutterBinaryMessenger) {
self.messenger = messenger
super.init()
}
func create(withFrame frame: CGRect, viewIdentifier viewId: Int64, arguments args: Any?) -> FlutterPlatformView {
return MyFlutterView(frame,viewID: viewId,args: args,messenger: messenger)
}
func createArgsCodec() -> FlutterMessageCodec & NSObjectProtocol {
return FlutterStandardMessageCodec.sharedInstance()
}
}
在 AppDelegate 中注冊：
import UIKit
import Flutter
@UIApplicationMain
@objc class AppDelegate: FlutterAppDelegate {
override func application(
_ application: UIApplication,
didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?
) -> Bool {
GeneratedPluginRegistrant.register(with: self)
let registrar:FlutterPluginRegistrar = self.registrar(forPlugin: "plugins.flutter.io/custom_platform_view_plugin")!
let factory = MyFlutterViewFactory(messenger: registrar.messenger())
registrar.register(factory, withId: "plugins.flutter.io/custom_platform_view")
return super.application(application, didFinishLaunchingWithOptions: launchOptions)
}
}
記住 plugins.flutter.io/custom_platform_view ，這個字符串在 Flutter 中需要與其保持一致。
嵌入Flutter
在 Flutter 中調用
class PlatformViewDemo extends StatelessWidget {
@override
Widget build(BuildContext context) {
Widget platformView() {
if (defaultTargetPlatform == TargetPlatform.android) {
return AndroidView(
viewType: 'plugins.flutter.io/custom_platform_view',
onPlatformViewCreated: (viewId) {
print('viewId:$viewId');
platforms
.add(MethodChannel('com.flutter.guide.MyFlutterView_$viewId'));
},
creationParams: {'text': 'Flutter傳給AndroidTextView的參數'},
creationParamsCodec: StandardMessageCodec(),
);
}else if(defaultTargetPlatform == TargetPlatform.iOS){
return UiKitView(
viewType: 'plugins.flutter.io/custom_platform_view',
);
}
}
return Scaffold(
appBar: AppBar(),
body: Center(
child: platformView(),
),
);
}
}
上面嵌入的是 iOS View，因此通過 defaultTargetPlatform == TargetPlatform.iOS 判斷當前平台加載，在 iOS 上運行效果：
設置初始化參數
Flutter 端修改如下：
UiKitView(
viewType: 'plugins.flutter.io/custom_platform_view',
creationParams: {'text': 'Flutter傳給IOSTextView的參數'},
creationParamsCodec: StandardMessageCodec(),
)
- creationParams ：傳遞的參數，插件可以將此參數傳遞給 AndroidView 的構造函數。
- creationParamsCodec ：將 creationParams 編碼后再發送給平台側，它應該與傳遞給構造函數的編解碼器匹配。值的范圍：
- StandardMessageCodec
- JSONMessageCodec
- StringCodec
- BinaryCodec
修改 MyFlutterView ：
import Foundation
import Flutter
class MyFlutterView: NSObject,FlutterPlatformView {
let label = UILabel()
init(_ frame: CGRect,viewID: Int64,args :Any?,messenger :FlutterBinaryMessenger) {
super.init()
if(args is NSDictionary){
let dict = args as! NSDictionary
label.text = dict.value(forKey: "text") as! String
}
}
func view() -> UIView {
return label
}
}
最終效果：
Flutter 向 iOS View 發送消息
修改 Flutter 端，創建 MethodChannel 用於通信：
class PlatformViewDemo extends StatefulWidget {
@override
_PlatformViewDemoState createState() => _PlatformViewDemoState();
}
class _PlatformViewDemoState extends State<PlatformViewDemo> {
static const platform =
const MethodChannel('com.flutter.guide.MyFlutterView');
@override
Widget build(BuildContext context) {
Widget platformView() {
if (defaultTargetPlatform == TargetPlatform.android) {
return AndroidView(
viewType: 'plugins.flutter.io/custom_platform_view',
creationParams: {'text': 'Flutter傳給AndroidTextView的參數'},
creationParamsCodec: StandardMessageCodec(),
);
} else if (defaultTargetPlatform == TargetPlatform.iOS) {
return UiKitView(
viewType: 'plugins.flutter.io/custom_platform_view',
creationParams: {'text': 'Flutter傳給IOSTextView的參數'},
creationParamsCodec: StandardMessageCodec(),
);
}
}
return Scaffold(
appBar: AppBar(),
body: Column(children: [
RaisedButton(
child: Text('傳遞參數給原生View'),
onPressed: () {
platform.invokeMethod('setText', {'name': 'laomeng', 'age': 18});
},
),
Expanded(child: platformView()),
]),
);
}
}
在 原生View 中也創建一個 MethodChannel 用於通信：
import Foundation
import Flutter
class MyFlutterView: NSObject,FlutterPlatformView {
let label = UILabel()
init(_ frame: CGRect,viewID: Int64,args :Any?,messenger :FlutterBinaryMessenger) {
super.init()
if(args is NSDictionary){
let dict = args as! NSDictionary
label.text = dict.value(forKey: "text") as! String
}
let methodChannel = FlutterMethodChannel(name: "com.flutter.guide.MyFlutterView", binaryMessenger: messenger)
methodChannel.setMethodCallHandler { (call, result) in
if (call.method == "setText") {
if let dict = call.arguments as? Dictionary<String, Any> {
let name:String = dict["name"] as? String ?? ""
let age:Int = dict["age"] as? Int ?? -1
self.label.text = "hello,\(name),年齡：\(age)"
}
}
}
}
func view() -> UIView {
return label
}
}
Flutter 向 Android View 獲取消息
與上面發送信息不同的是，Flutter 向原生請求數據，原生返回數據到 Flutter 端，修改 MyFlutterView onMethodCall：
import Foundation
import Flutter
class MyFlutterView: NSObject,FlutterPlatformView {
let label = UILabel()
init(_ frame: CGRect,viewID: Int64,args :Any?,messenger :FlutterBinaryMessenger) {
super.init()
if(args is NSDictionary){
let dict = args as! NSDictionary
label.text = dict.value(forKey: "text") as! String
}
let methodChannel = FlutterMethodChannel(name: "com.flutter.guide.MyFlutterView", binaryMessenger: messenger)
methodChannel.setMethodCallHandler { (call, result:FlutterResult) in
if (call.method == "setText") {
if let dict = call.arguments as? Dictionary<String, Any> {
let name:String = dict["name"] as? String ?? ""
let age:Int = dict["age"] as? Int ?? -1
self.label.text = "hello,\(name),年齡：\(age)"
}
}else if (call.method == "getData") {
if let dict = call.arguments as? Dictionary<String, Any> {
let name:String = dict["name"] as? String ?? ""
let age:Int = dict["age"] as? Int ?? -1
result(["name":name,"age":age])
}
}
}
}
func view() -> UIView {
return label
}
}
result() 是返回的數據。
Flutter 端接收數據：
var _data = '獲取數據';
RaisedButton(
child: Text('$_data'),
onPressed: () async {
var result = await platform
.invokeMethod('getData', {'name': 'laomeng', 'age': 18});
setState(() {
_data = '${result['name']},${result['age']}';
});
},
),
解決多個原生View通信沖突問題
當然頁面有3個原生View，
class PlatformViewDemo extends StatefulWidget {
@override
_PlatformViewDemoState createState() => _PlatformViewDemoState();
}
class _PlatformViewDemoState extends State<PlatformViewDemo> {
static const platform =
const MethodChannel('com.flutter.guide.MyFlutterView');
var _data = '獲取數據';
@override
Widget build(BuildContext context) {
Widget platformView() {
if (defaultTargetPlatform == TargetPlatform.android) {
return AndroidView(
viewType: 'plugins.flutter.io/custom_platform_view',
creationParams: {'text': 'Flutter傳給AndroidTextView的參數'},
creationParamsCodec: StandardMessageCodec(),
);
} else if (defaultTargetPlatform == TargetPlatform.iOS) {
return UiKitView(
viewType: 'plugins.flutter.io/custom_platform_view',
creationParams: {'text': 'Flutter傳給IOSTextView的參數'},
creationParamsCodec: StandardMessageCodec(),
);
}
}
return Scaffold(
appBar: AppBar(),
body: Column(children: [
Row(
children: [
RaisedButton(
child: Text('傳遞參數給原生View'),
onPressed: () {
platform
.invokeMethod('setText', {'name': 'laomeng', 'age': 18});
},
),
RaisedButton(
child: Text('$_data'),
onPressed: () async {
var result = await platform
.invokeMethod('getData', {'name': 'laomeng', 'age': 18});
setState(() {
_data = '${result['name']},${result['age']}';
});
},
),
],
),
Expanded(child: Container(color: Colors.red, child: platformView())),
Expanded(child: Container(color: Colors.blue, child: platformView())),
Expanded(child: Container(color: Colors.yellow, child: platformView())),
]),
);
}
}
此時點擊 傳遞參數給原生View 按鈕哪個View會改變內容，實際上只有最后一個會改變。
如何改變指定View的內容？重點是 MethodChannel，只需修改上面3個通道的名稱不相同即可：
- 第一種方法：將一個唯一 id 通過初始化參數傳遞給原生 View，原生 View使用這個id 構建不同名稱的 MethodChannel。
- 第二種方法（推薦）：原生 View 生成時，系統會為其生成唯一id：viewId，使用 viewId 構建不同名稱的 MethodChannel。
原生 View 使用 viewId 構建不同名稱的 MethodChannel：
import Foundation
import Flutter
class MyFlutterView: NSObject,FlutterPlatformView {
let label = UILabel()
init(_ frame: CGRect,viewID: Int64,args :Any?,messenger :FlutterBinaryMessenger) {
super.init()
if(args is NSDictionary){
let dict = args as! NSDictionary
label.text = dict.value(forKey: "text") as! String
}
let methodChannel = FlutterMethodChannel(name: "com.flutter.guide.MyFlutterView_\(viewID)", binaryMessenger: messenger)
methodChannel.setMethodCallHandler { (call, result:FlutterResult) in
...
}
}
func view() -> UIView {
return label
}
}
Flutter 端為每一個原生 View 創建不同的MethodChannel：
var platforms = [];
UiKitView(
viewType: 'plugins.flutter.io/custom_platform_view',
onPlatformViewCreated: (viewId) {
print('viewId:$viewId');
platforms
.add(MethodChannel('com.flutter.guide.MyFlutterView_$viewId'));
},
creationParams: {'text': 'Flutter傳給AndroidTextView的參數'},
creationParamsCodec: StandardMessageCodec(),
)
給第一個發送消息：
platforms[0]
.invokeMethod('setText', {'name': 'laomeng', 'age': 18});
交流
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