MMPDeepSleepPreventer.m

//
//  MMPDeepSleepPreventer.m
//  MMPDeepSleepPreventer
//
//  Created by Marco Peluso on 20.08.09.
//  Copyright (c) 2009-2010, Marco Peluso - marcopeluso.com
//  All rights reserved.
// 
//  Redistribution and use in source and binary forms, with or without
//  modification, are permitted provided that the following conditions are met:
// 
//    1. Redistributions of source code must retain the above copyright notice,
//       this list of conditions and the following disclaimer.
// 
//    2. Redistributions in binary form must reproduce the above copyright
//       notice, this list of conditions and the following disclaimer in the
//       documentation and/or other materials provided with the distribution.
// 
//    3. Neither the name of the copyright holders nor the names of its
//       contributors may be used to endorse or promote products derived from
//       this software without specific prior written permission.
// 
//  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
//  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
//  THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
//  PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
//  CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
//  EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
//  PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
//  OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
//  WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
//  OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
//  ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
//

#pragma mark -
#pragma mark Imports

#import "MMPDeepSleepPreventer.h"
#import <AVFoundation/AVFoundation.h>
#import <AudioToolbox/AudioToolbox.h>


#pragma mark -
#pragma mark MMPDeepSleepPreventer Private Interface

@interface MMPDeepSleepPreventer ()

- (void)mmp_playPreventSleepSound;
- (void)mmp_setUpAudioSession;

@end


@implementation MMPDeepSleepPreventer


#pragma mark -
#pragma mark Synthesizes

@synthesize audioPlayer       = audioPlayer_;

#pragma mark -
#pragma mark Creation and Destruction

- (id)init
{
    if ( !(self = [super init]) )
    {
        return nil;
    }

    [self mmp_setUpAudioSession];

    // Set up path to sound file
    NSString *soundFilePath = [[NSBundle mainBundle] pathForResource:@"MMPSilence"
                               ofType:@"wav"];

    NSURL *fileURL = [[NSURL alloc] initFileURLWithPath:soundFilePath];

    // Set up audio player with sound file
    audioPlayer_ = [[AVAudioPlayer alloc] initWithContentsOfURL:fileURL
                    error:nil];
    [fileURL release];

    [self.audioPlayer prepareToPlay];
    // You may want to set this to 0.0 even if your sound file is silent.
    // I don't know exactly, if this affects battery life, but it can't hurt.
    [self.audioPlayer setVolume:0.0];
    //set the infinite loop, stop is triggered by stopPreventSleep method
    [self.audioPlayer setNumberOfLoops:-1];

    return self;
}

- (void)dealloc
{
    [audioPlayer_       release];
    [super dealloc];
}

#pragma mark -
#pragma mark Public Methods

- (void)startPreventSleep
{
    [self mmp_playPreventSleepSound];    
}

- (void)stopPreventSleep
{
    [self.audioPlayer stop];
}

- (BOOL)isPreventingSleep
{
    return [self.audioPlayer isPlaying];
}

#pragma mark -
#pragma mark Private Methods

- (void)mmp_playPreventSleepSound
{
    [self.audioPlayer play];
}

- (void)mmp_setUpAudioSession
{
	// Initialize audio session
	AudioSessionInitialize
	(
		NULL, // Use NULL to use the default (main) run loop.
		NULL, // Use NULL to use the default run loop mode.
		NULL, // A reference to your interruption listener callback function.
		      // See “Responding to Audio Session Interruptions” in Apple's "Audio Session Programming Guide" for a description of how to write
		      // and use an interruption callback function.
		NULL  // Data you intend to be passed to your interruption listener callback function when the audio session object invokes it.
	);
	
	// Activate audio session
	OSStatus activationResult = 0;
	activationResult          = AudioSessionSetActive(true);
	
	if (activationResult)
	{
		MMPDLog(@"AudioSession is active");
	}
	
	// Set up audio session category to kAudioSessionCategory_MediaPlayback.
	// While playing sounds using this session category at least every 10 seconds, the iPhone doesn't go to sleep.
	UInt32 sessionCategory = kAudioSessionCategory_MediaPlayback; // Defines a new variable of type UInt32 and initializes it with the identifier 
	                                                              // for the category you want to apply to the audio session.
	AudioSessionSetProperty
	(
		kAudioSessionProperty_AudioCategory, // The identifier, or key, for the audio session property you want to set.
		sizeof(sessionCategory),             // The size, in bytes, of the property value that you are applying.
		&sessionCategory                     // The category you want to apply to the audio session.
	);
	
	// Set up audio session playback mixing behavior.
	// kAudioSessionCategory_MediaPlayback usually prevents playback mixing, so we allow it here. This way, we don't get in the way of other sound playback in an application.
	// This property has a value of false (0) by default. When the audio session category changes, such as during an interruption, the value of this property reverts to false.
	// To regain mixing behavior you must then set this property again.
	
	// Always check to see if setting this property succeeds or fails, and react appropriately; behavior may change in future releases of iPhone OS.
	OSStatus propertySetError = 0;
	UInt32 allowMixing        = true;
	
	propertySetError = AudioSessionSetProperty
	(
		kAudioSessionProperty_OverrideCategoryMixWithOthers, // The identifier, or key, for the audio session property you want to set.
		sizeof(allowMixing),                                 // The size, in bytes, of the property value that you are applying.
		&allowMixing                                         // The value to apply to the property.
	);
	
	if (propertySetError)
	{
		MMPALog(@"Error setting kAudioSessionProperty_OverrideCategoryMixWithOthers: %d", propertySetError);
	}
}

@end