从 swift 或 objective-c 向 js 发送事件

Question

>我创建了以下类(精简版)，这里是对完整文件的引用 https://github.com/cotyembry/CastRemoteNative/blob/7e74dbc56f037cc61241f6ece24a94d8c52abb32/root/ios/CastRemoteNative/NativeMethods.swift

@objc(NativeMethods)
class NativeMethods: RCTEventEmitter {
@objc(sendEventToJSFromJS)
func sendEventToJSFromJS {
self.emitEvent(eventName: "test", body: "bodyTestString")
}
func emitEvent(eventName: String: body: Any) {
self.sendEvent(withName: eventName, body: body)
}
}

这工作得很好，当我调用emitEvent方法时，它会触发我的 javascript 代码中的回调侦听器，如下所示，它是来自 https://github.com/cotyembry/CastRemoteNative/blob/7e74dbc56f037cc61241f6ece24a94d8c52abb32/root/js/Components/ChromecastDevicesModal.js

从JavaScript方面

import {
NativeModules,
NativeEventEmitter
} from 'react-native'
//here I bring in the swift class to use inside javascript
var NativeMethods = NativeModules.NativeMethods;
//create an event emitter to use to listen for the native events when they occur
this.eventEmitter = new NativeEventEmitter(NativeMethods);
//listen for the event once it sends
this.subscription = this.eventEmitter.addListener('test', (body) => { console.log('in test event listener callback', body)});
NativeMethods.sendEventToJSFromJS() //call the native method written in swift

我只是在javascript中按下按钮时调用了sendEventToJSFromJS方法

同样，这是有效的，并且console.log('in test event listener callback', body)代码在javascript端工作并运行

我的问题，这不起作用：

如果我在定义类后在 swift 文件中执行以下操作，这将不起作用：

var nativeMethodsInstance = nativeMethods()
nativeMethodsInstance.sendEventToJSFromSwift()

为什么？因为抛出以下错误：

Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'bridge is not set. This is probably because you've explicitly synthesized the bridge in NativeMethods, even though it's inherited from RCTEventEmitter.'

那么，在创建 NativeMethodsinstance时，与不创建 NativeMethods 有什么区别？

有关其他信息：

当我在 .h 和 .m 文件中而不是在 .swift 文件中编写这些相同的代码片段时，Objective-C 得到相同的桥接未设置问题

我找到了本机代码中打印错误消息的位置，但它只有变量

_bridge

并正在检查它是否nil

此错误来自的文件是：

RCTEventEmitter.h
RCTEventEmitter.c

以下是RCTEventEmitter.c的完整片段

- (void)sendEventWithName:(NSString *)eventName body:(id)body
{

RCTAssert(_bridge != nil, @"bridge is not set. This is probably because you've "
"explicitly synthesized the bridge in %@, even though it's inherited "
"from RCTEventEmitter.", [self class]);
if (RCT_DEBUG && ![[self supportedEvents] containsObject:eventName]) {
RCTLogError(@"`%@` is not a supported event type for %@. Supported events are: `%@`",
eventName, [self class], [[self supportedEvents] componentsJoinedByString:@"`, `"]);
}
if (_listenerCount > 0) {
[_bridge enqueueJSCall:@"RCTDeviceEventEmitter"
method:@"emit"
args:body ? @[eventName, body] : @[eventName]
completion:NULL];
} else {
RCTLogWarn(@"Sending `%@` with no listeners registered.", eventName);
}
}

这个_bridge值在哪里设置以及如何设置，以便我可以知道，在失败的情况下如何设置它

我也在RCTEventEmitter.h中找到了以下内容

@property (nonatomic, weak) RCTBridge *bridge;

在给出的错误中，它提到桥是在RCTEventEmitter中继承的，那么这可能是bridge属性的weak部分的问题吗？

还是我需要改变我的策略来做这一切？

我知道这可能与我没有完全理解

有关

@synthesize bridge = _bridge;

部分代码和混合的所有语言都没有多大帮助，哈哈......

这真的很难，所以任何帮助将不胜感激！ 非常感谢您的时间

这是指向完整项目的链接，当项目历史代码表示我上面问题中的代码时(因为我此后对项目进行了更改)：

https://github.com/cotyembry/CastRemoteNative/tree/7e74dbc56f037cc61241f6ece24a94d8c52abb32

Answer 1

我想通了

警告：此解决方案使用已弃用的方法 react 本机方法 - 我不知道如何"正确"从RCTEventEmitter继承并发送事件......每次我尝试_bridge最终都会被nil

确保 Swift 桥接到 Objective C(如果你使用 swift 将事件发送到 javascript)

不要创建导出的原生模块的实例(无论它们是用 Swift 还是 Objective C 编写的)

让 React Native 的底层实现来做到这一点，对于每个需要发送事件的类，将该特定的 Native Class Objective C 实现代码或 Swift 代码(本机模块)导出到 React-Native。这允许javascript能够侦听事件

var publicBridgeHelperInstance = PublicBridgeHelper()  //instantiate the  the objective c class from inside the .swift file to use later when needing to get a reference to the bridge to send an event to javascript written in react native
@objc(DeviceManager)             //export swift module to objective c
class DeviceManager: NSObject {
@objc(deviceDidComeOnline:)    //expose the function to objective c
public func deviceDidComeOnline(_ device: GCKDevice) {
//imagine this deviceDidComeOnline function gets called from something from the Native code (totally independent of javascript) - honestly this could be called from a native button click as well just to test it works...
//emit an event to a javascript function that is a in react native Component listening for the event like so:
//1. get a reference to the bridge to send an event through from Native to Javascript in React Native (here is where my custom code comes in to get this to actually work)
let rnBridge = publicBridgeHelperInstance.getBridge()  //this gets the bridge that is stored in the AppDelegate.m file that was set from the `rootView.bridge` variable (more on this later)
//(if you want to print the bridge here to make sure it is not `nil` go ahead:
print("rnBridge = (rnBridge)")
//2. actually send the event through the eventDispatcher
rnBridge?.eventDispatcher().sendAppEvent(withName: "test", body: "testBody data!!!")
}
}

放入AppDelegate.h(除了文件中已有的代码)

#import "YourProjectsBridgingHeaderToMakeThisCodeAvailableInSwift.h"  //replace this with your actual header you created when creating a swift file (google it if you dont know how to bridge swift to objective c)
@interface PublicBridgeHelper: NSObject
-(RCTBridge*)getBridge;
@end

放入AppDelegate.m(除了文件中已有的代码)

#import <React/RCTRootView.h>
RCTBridge *rnBridgeFromRootView;
@implementation PublicBridgeHelper    //this is created to SIMPLY return rnBridgeFromRootView defined above over to my Swift class when actually sending the event to javascript that defines a react native Component
-(RCTBridge*)getBridge {
NSLog(@"rnBridgeFromRootView = @%@", rnBridgeFromRootView);
return rnBridgeFromRootView;
}

重要- 还要确保将以下代码行添加到 Objective C .h 的桥接标头中，以使此PublicBridgeHelper定义可用于.swift代码

#import "AppDelegate.h"

最后

现在向您展示如何设置 AppDelegate.m 中使用的 rnBridgeFromRootView 变量(在将事件发送到 javascript 之前返回并在.swift代码中使用)

打开AppDelegate.m并在方法主体中

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions { ... }

在实例化rootView变量的代码行之后包含以下内容

即在可能看起来像的行之后

RCTRootView *rootView = [[RCTRootView alloc] initWithBundleURL:jsCodeLocation moduleName:@"YourProjecNameProbably" initialProperties:nil launchOptions:launchOptions];

加：

rnBridgeFromRootView = rootView.bridge  //set the bridge to  be exposed and returned later and used by the swift class

现在解释一下.swift文件中的publicBridgeHelperInstance.getBridge()部分

publicBridgeHelper是一个目标 c 类的实例，它允许 swift 类能够获取对 react 本机桥接的引用

如果您在阅读本文后仍然无法理解我的答案，我制作了一个视频，您可以在此处观看：

https://www.youtube.com/watch?v=GZj-Vm9cQIg&t=9s