内容

使用平台视图在 Flutter 应用中托管原生 iOS 视图

内容

在 Dart 端
在平台端
组合在一起
性能
组合限制

平台视图允许您在 Flutter 应用中嵌入原生视图，以便您可以从 Dart 中对原生视图应用转换、剪辑和不透明度。

例如，这允许您直接在 Flutter 应用中使用 Android 和 iOS SDK 中的原生 Google Maps。

iOS 仅使用混合合成，这意味着原生 UIView 会附加到视图层次结构中。

要在 iOS 上创建平台视图，请使用以下说明

在 Dart 端，创建一个 Widget 并添加构建实现，如以下步骤所示。

在 Dart 小部件文件中，进行类似于 native_view_example.dart 中所示的更改

添加以下导入

dartimport 'package:flutter/foundation.dart';
import 'package:flutter/services.dart';

实现 build() 方法

dartWidget build(BuildContext context) {
  // This is used in the platform side to register the view.
  const String viewType = '<platform-view-type>';
  // Pass parameters to the platform side.
  final Map<String, dynamic> creationParams = <String, dynamic>{};

  return UiKitView(
    viewType: viewType,
    layoutDirection: TextDirection.ltr,
    creationParams: creationParams,
    creationParamsCodec: const StandardMessageCodec(),
  );
}

有关更多信息，请参阅以下 API 文档：UIKitView。

在平台端，使用 Swift 或 Objective-C

Swift
Objective-C

实现工厂和平台视图。FLNativeViewFactory 创建平台视图，平台视图提供对 UIView 的引用。例如，FLNativeView.swift

swiftimport Flutter
import UIKit

class FLNativeViewFactory: NSObject, FlutterPlatformViewFactory {
    private var messenger: FlutterBinaryMessenger

    init(messenger: FlutterBinaryMessenger) {
        self.messenger = messenger
        super.init()
    }

    func create(
        withFrame frame: CGRect,
        viewIdentifier viewId: Int64,
        arguments args: Any?
    ) -> FlutterPlatformView {
        return FLNativeView(
            frame: frame,
            viewIdentifier: viewId,
            arguments: args,
            binaryMessenger: messenger)
    }

    /// Implementing this method is only necessary when the `arguments` in `createWithFrame` is not `nil`.
    public func createArgsCodec() -> FlutterMessageCodec & NSObjectProtocol {
          return FlutterStandardMessageCodec.sharedInstance()
    }
}

class FLNativeView: NSObject, FlutterPlatformView {
    private var _view: UIView

    init(
        frame: CGRect,
        viewIdentifier viewId: Int64,
        arguments args: Any?,
        binaryMessenger messenger: FlutterBinaryMessenger?
    ) {
        _view = UIView()
        super.init()
        // iOS views can be created here
        createNativeView(view: _view)
    }

    func view() -> UIView {
        return _view
    }

    func createNativeView(view _view: UIView){
        _view.backgroundColor = UIColor.blue
        let nativeLabel = UILabel()
        nativeLabel.text = "Native text from iOS"
        nativeLabel.textColor = UIColor.white
        nativeLabel.textAlignment = .center
        nativeLabel.frame = CGRect(x: 0, y: 0, width: 180, height: 48.0)
        _view.addSubview(nativeLabel)
    }
}

最后，注册平台视图。这可以在应用或插件中完成。

对于应用注册，修改应用的 AppDelegate.swift

swiftimport Flutter
import UIKit

@UIApplicationMain
@objc class AppDelegate: FlutterAppDelegate {
    override func application(
        _ application: UIApplication,
        didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey : Any]?
    ) -> Bool {
        GeneratedPluginRegistrant.register(with: self)

        guard let pluginRegistrar = self.registrar(forPlugin: "plugin-name") else { return false }

        let factory = FLNativeViewFactory(messenger: pluginRegistrar.messenger())
        pluginRegistrar.register(
            factory,
            withId: "<platform-view-type>")
        return super.application(application, didFinishLaunchingWithOptions: launchOptions)
    }
}

对于插件注册，修改插件的主文件（例如，FLPlugin.swift）

swiftimport Flutter
import UIKit

class FLPlugin: NSObject, FlutterPlugin {
    public static func register(with registrar: FlutterPluginRegistrar) {
        let factory = FLNativeViewFactory(messenger: registrar.messenger())
        registrar.register(factory, withId: "<platform-view-type>")
    }
}

在 Objective-C 中，为工厂和平台视图添加头文件。例如，如 FLNativeView.h 中所示

objc#import <Flutter/Flutter.h>

@interface FLNativeViewFactory : NSObject <FlutterPlatformViewFactory>
- (instancetype)initWithMessenger:(NSObject<FlutterBinaryMessenger>*)messenger;
@end

@interface FLNativeView : NSObject <FlutterPlatformView>

- (instancetype)initWithFrame:(CGRect)frame
               viewIdentifier:(int64_t)viewId
                    arguments:(id _Nullable)args
              binaryMessenger:(NSObject<FlutterBinaryMessenger>*)messenger;

- (UIView*)view;
@end

实现工厂和平台视图。FLNativeViewFactory 创建平台视图，平台视图提供对 UIView 的引用。例如，FLNativeView.m

objc#import "FLNativeView.h"

@implementation FLNativeViewFactory {
  NSObject<FlutterBinaryMessenger>* _messenger;
}

- (instancetype)initWithMessenger:(NSObject<FlutterBinaryMessenger>*)messenger {
  self = [super init];
  if (self) {
    _messenger = messenger;
  }
  return self;
}

- (NSObject<FlutterPlatformView>*)createWithFrame:(CGRect)frame
                                   viewIdentifier:(int64_t)viewId
                                        arguments:(id _Nullable)args {
  return [[FLNativeView alloc] initWithFrame:frame
                              viewIdentifier:viewId
                                   arguments:args
                             binaryMessenger:_messenger];
}

/// Implementing this method is only necessary when the `arguments` in `createWithFrame` is not `nil`.
- (NSObject<FlutterMessageCodec>*)createArgsCodec {
    return [FlutterStandardMessageCodec sharedInstance];
}

@end

@implementation FLNativeView {
   UIView *_view;
}

- (instancetype)initWithFrame:(CGRect)frame
               viewIdentifier:(int64_t)viewId
                    arguments:(id _Nullable)args
              binaryMessenger:(NSObject<FlutterBinaryMessenger>*)messenger {
  if (self = [super init]) {
    _view = [[UIView alloc] init];
  }
  return self;
}

- (UIView*)view {
  return _view;
}

@end

最后，注册平台视图。这可以在应用或插件中完成。

对于应用注册，修改应用的 AppDelegate.m

objc#import "AppDelegate.h"
#import "FLNativeView.h"
#import "GeneratedPluginRegistrant.h"

@implementation AppDelegate

- (BOOL)application:(UIApplication *)application
    didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
  [GeneratedPluginRegistrant registerWithRegistry:self];

   NSObject<FlutterPluginRegistrar>* registrar =
      [self registrarForPlugin:@"plugin-name"];

  FLNativeViewFactory* factory =
      [[FLNativeViewFactory alloc] initWithMessenger:registrar.messenger];

  [[self registrarForPlugin:@"<plugin-name>"] registerViewFactory:factory
                                                          withId:@"<platform-view-type>"];
  return [super application:application didFinishLaunchingWithOptions:launchOptions];
}

@end

对于插件注册，修改主插件文件（例如，FLPlugin.m）

objc#import <Flutter/Flutter.h>
#import "FLNativeView.h"

@interface FLPlugin : NSObject<FlutterPlugin>
@end

@implementation FLPlugin

+ (void)registerWithRegistrar:(NSObject<FlutterPluginRegistrar>*)registrar {
  FLNativeViewFactory* factory =
      [[FLNativeViewFactory alloc] initWithMessenger:registrar.messenger];
  [registrar registerViewFactory:factory withId:@"<platform-view-type>"];
}

@end

有关更多信息，请参阅以下 API 文档

在 Dart 中实现 build() 方法时，您可以使用 defaultTargetPlatform 检测平台，并决定使用哪个小部件

dartWidget build(BuildContext context) {
  // This is used in the platform side to register the view.
  const String viewType = '<platform-view-type>';
  // Pass parameters to the platform side.
  final Map<String, dynamic> creationParams = <String, dynamic>{};

  switch (defaultTargetPlatform) {
    case TargetPlatform.android:
    // return widget on Android.
    case TargetPlatform.iOS:
    // return widget on iOS.
    case TargetPlatform.macOS:
    // return widget on macOS.
    default:
      throw UnsupportedError('Unsupported platform view');
  }
}

Flutter 中的平台视图存在性能权衡。

对于复杂的情况，有一些技术可以用来缓解性能问题。

例如，您可以在 Dart 中执行动画时使用占位符纹理。换句话说，如果在渲染平台视图时动画缓慢，则考虑对原生视图进行截图并将其渲染为纹理。

组合 iOS 平台视图时存在一些限制。

不支持 ShaderMask 和 ColorFiltered 小部件。
支持 BackdropFilter 小部件，但其使用方式存在一些限制。有关更多详细信息，请查看 iOS 平台视图背景滤镜模糊设计文档。

除非另有说明，否则本网站上的文档反映了 Flutter 的最新稳定版本。页面上次更新于 2024-09-27。查看源代码或报告问题。

在 Dart 端

在平台端

组合在一起

性能

组合限制