cordova-plugin-run-in-background/src/ios/APPBackgroundMode.m

/*
    Copyright 2013-2017 appPlant GmbH

    Licensed to the Apache Software Foundation (ASF) under one
    or more contributor license agreements.  See the NOTICE file
    distributed with this work for additional information
    regarding copyright ownership.  The ASF licenses this file
    to you under the Apache License, Version 2.0 (the
    "License"); you may not use this file except in compliance
    with the License.  You may obtain a copy of the License at

     http://www.apache.org/licenses/LICENSE-2.0

    Unless required by applicable law or agreed to in writing,
    software distributed under the License is distributed on an
    "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
    KIND, either express or implied.  See the License for the
    specific language governing permissions and limitations
    under the License.
*/

#import "APPBackgroundMode.h"

@implementation APPBackgroundMode

NSString *const kAPPBackgroundJsNamespace = @"cordova.plugins.backgroundMode";
NSString *const kAPPBackgroundEventActivate = @"activate";
NSString *const kAPPBackgroundEventDeactivate = @"deactivate";
NSString *const kAPPBackgroundEventFailure = @"failure";

#pragma mark -
#pragma mark Initialization

/**
 * Initialize the plugin.
 */
- (void) pluginInitialize
{
    [self disable:NULL];
    [self configureAudioPlayer];
    [self configureAudioSession];
    [self observeLifeCycle];
}

/**
 * Register the listener for pause and resume events.
 */
- (void) observeLifeCycle
{
    NSNotificationCenter* listener = [NSNotificationCenter defaultCenter];

    if (UIApplicationDidEnterBackgroundNotification && UIApplicationWillEnterForegroundNotification) {

        [listener addObserver:self
                     selector:@selector(keepAwake)
                         name:UIApplicationDidEnterBackgroundNotification
                       object:nil];

        [listener addObserver:self
                     selector:@selector(stopKeepingAwake)
                         name:UIApplicationWillEnterForegroundNotification
                       object:nil];

        [listener addObserver:self
                     selector:@selector(handleAudioSessionInterruption:)
                         name:AVAudioSessionInterruptionNotification
                       object:nil];

    } else {
        [self enable:NULL];
        [self keepAwake];
    }
}

#pragma mark -
#pragma mark Interface

/**
 * Enable the mode to stay awake
 * when switching to background for the next time.
 */
- (void) enable:(CDVInvokedUrlCommand*)command
{
    enabled = YES;
}

/**
 * Disable the background mode
 * and stop being active in background.
 */
- (void) disable:(CDVInvokedUrlCommand*)command
{
    enabled = NO;

    [self stopKeepingAwake];
}

#pragma mark -
#pragma mark Core

/**
 * Keep the app awake.
 */
- (void) keepAwake
{
    if (enabled) {
        [audioPlayer play];
        [self fireEvent:kAPPBackgroundEventActivate withParams:NULL];
    }
}

/**
 * Let the app going to sleep.
 */
- (void) stopKeepingAwake
{

    if (TARGET_IPHONE_SIMULATOR) {
        NSLog(@"BackgroundMode: On simulator apps never pause in background!");
    }

    if (audioPlayer.isPlaying) {
        [self fireEvent:kAPPBackgroundEventDeactivate withParams:NULL];
    }

    [audioPlayer pause];
}

/**
 * Configure the audio player.
 */
- (void) configureAudioPlayer
{
    NSString* path = [[NSBundle mainBundle]
                      pathForResource:@"appbeep" ofType:@"wav"];

    NSURL* url = [NSURL fileURLWithPath:path];


    audioPlayer = [[AVAudioPlayer alloc]
                   initWithContentsOfURL:url error:NULL];

    audioPlayer.volume        = 0;
    audioPlayer.numberOfLoops = -1;
};

/**
 * Configure the audio session.
 */
- (void) configureAudioSession
{
    AVAudioSession* session = [AVAudioSession
                               sharedInstance];

    // Don't activate the audio session yet
    [session setActive:NO error:NULL];

    // Play music even in background and dont stop playing music
    // even another app starts playing sound
    [session setCategory:AVAudioSessionCategoryPlayback
             withOptions:AVAudioSessionCategoryOptionMixWithOthers
                   error:NULL];

    // Active the audio session
    [session setActive:YES error:NULL];
};

#pragma mark -
#pragma mark Helper

/**
 * Restart playing sound when interrupted by phone calls.
 */
- (void) handleAudioSessionInterruption:(NSNotification*)notification
{
    [self fireEvent:kAPPBackgroundEventDeactivate withParams:NULL];
    [self keepAwake];
}

/**
 * Method to fire an event with some parameters in the browser.
 */
- (void) fireEvent:(NSString*)event withParams:(NSString*)params
{
    NSString* active = [event isEqualToString:kAPPBackgroundEventActivate] ? @"true" : @"false";

    NSString* flag = [NSString stringWithFormat:@"%@._isActive=%@;",
                      kAPPBackgroundJsNamespace, active];

    NSString* depFn = [NSString stringWithFormat:@"%@.on%@(%@);",
                       kAPPBackgroundJsNamespace, event, params];
    
    NSString* fn = [NSString stringWithFormat:@"%@.fireEvent('%@',%@);",
                    kAPPBackgroundJsNamespace, event, params];

    NSString* js = [NSString stringWithFormat:@"%@%@%@", flag, depFn, fn];

    [self.commandDelegate evalJs:js];
}

@end