[Timer] EventDispatcher sendDeviceEventWithName only called once.

[mintuz]

Hello, I think the EventDispatcher sendDeviceEventWithName has a bug in which the EventDispatcher sendDeviceEventWithName is only called once initially until you close the app down to the background and then reopen it. Once you open it the Events seem to be triggered as expected.

I have created a native bridge to a library located https://github.com/omergul123/Discovery It's also worth pointing out that the library works fine whilst not in a React Native project.

My bridge looks like this

//
//  DiscoveryManager.m
//  DiscoveryExample
//
//  Created by Adam Bulmer on 07/05/2015.
//  Copyright (c) 2015 Adam Bulmer All rights reserved.
//

#import <Foundation/Foundation.h>
#import "DiscoveryManager.h"

@implementation DiscoveryManager

  @synthesize bridge = _bridge;

  RCT_EXPORT_MODULE()

  RCT_EXPORT_METHOD(startAdvertising:(NSString *)uuidString
                    username:(NSString*)username) {

    NSMutableArray *usernameArrays = [[NSMutableArray alloc] init];
    NSLog(@"startAdvertising called");

    // create our App UUID.
    CBUUID *uuid = [CBUUID UUIDWithString:uuidString];

    // start Discovery API
    self.discovery = [[Discovery alloc] initWithAppUUID:uuid username:username usersBlock:^(NSArray *users, BOOL usersChanged) {

      NSLog(@"users found in ObjC - %@", users);

      // Hacky
      for (BLEUser *user in users) {
        [usernameArrays addObject:user.username];
      }

      [self.bridge.eventDispatcher sendDeviceEventWithName:@"FoundUsers" body:@{@"users":usernameArrays}];
    }];
  }

@end

The Javascript component looks like this.

var React = require('react-native');
var LoginView = require('./App/views/Login.ios.js');
var AuthStore = require('./App/stores/AuthStore.ios.js');
var DiscoveryManager = require('NativeModules').DiscoveryManager;

const APP_UUID = '6969EFE7-C07E-4497-95E7-105C01152421';

var {
  View, 
  DeviceEventEmitter, 
  AlertIOS
} = React;

var App = React.createClass({
  getInitialState: function() {

    return {
      loggedIn: false
    };
  },
  onAuthChange: function(authObj) {

    this.setState({loggedIn:authObj});
    DiscoveryManager.startAdvertising(APP_UUID, 'mintuz');
  },
  onUsersChange: function(obj) {

    console.log(obj);

    AlertIOS.alert(
      'User Found',
      obj.users[0]
    );
  },
  componentWillMount: function() {

    console.log("will mount");

    AuthStore.listen(this.onAuthChange);
    DeviceEventEmitter.addListener('FoundUsers', this.onUsersChange);
  },
  render: function() {

    if(!this.state.loggedIn){
      return (<LoginView></LoginView>);
    }

    return (<View style={{flexDirection: 'row', height: 100, padding: 20}}>
      <View style={{backgroundColor: 'blue', flex: 0.3}} />
      <View style={{backgroundColor: 'red', flex: 0.5}} />
    </View>);
  }
});

React.AppRegistry.registerComponent('TestAppSpike', () => App);

[mintuz]

To add to this I have found out that the block for Discovery library isn't called multiple times until you close the app and reopen it. It does however work if its not called within a React Native environment. Looking at the Discovery library the only things that I think could be breaking with React Native are the timers and queues that are being set. Any help would be appreciated.

[ide]

RN pauses timers when the app is backgrounded. Not sure why this is -- it probably shouldn't do this at the infrastructure level.

[mintuz]

The timers don't seem to fire until the app is closed and reopened.

[vjeux]

cc @nicklockwood and @a2, this is weird that timers are suppressed

[a2]

I assume this has to do with the way run loops (and run loop modes) work?

[mintuz]

I know NSTimers work without the use of React Native within a standard native app.

[ide]

@a2 that could be part of it since the run loop is driven by the display link. This for sure is part of the problem:

react-native/React/Modules/RCTTiming.m

Line 89 in 4eece85

[[NSNotificationCenter defaultCenter] addObserver:self

    for (NSString *name in @[UIApplicationWillResignActiveNotification,
                             UIApplicationDidEnterBackgroundNotification,
                             UIApplicationWillTerminateNotification]) {

      [[NSNotificationCenter defaultCenter] addObserver:self
                                               selector:@selector(stopTimers)
                                                   name:name
                                                 object:nil];
    }

[a2]

@ide That would definitely do it! 😕

[mintuz]

Any update on this?

[ghost]

Thank you for reporting this issue and appreciate your patience. We've notified the core team for an update on this issue. We're looking for a response within the next 30 days or the issue may be closed.

[mintuz]

Any update on this, sorry for the spam. Just seems to have gone quiet.

[brentvatne]

Hi there! This issue is being closed because it has been inactive for a while.

But don't worry, it will live on with ProductPains! Check out it's new home: https://productpains.com/post/react-native/timer-eventdispatcher-senddeviceeventwithname-only-called-once