Getting iPhone's battery level

Question

I have a simple question. How do I get iPhone's battery level?

[UIDevice currentDevice] batteryLevel]

Simple enough? However there is a little catch - I can't use UIKit. Here is what I wrote so far, but I don't think it works:

    // notification port
IONotificationPortRef nport = IONotificationPortCreate(kIOMasterPortDefault);

CFRunLoopAddSource(CFRunLoopGetCurrent(), IONotificationPortGetRunLoopSource(nport), kCFRunLoopDefaultMode);

CFMutableDictionaryRef matching = IOServiceMatching("IOPMPowerSource");

kern_return_t kr = IOServiceAddMatchingNotification(nport, kIOFirstMatchNotification, matching, (IOServiceMatchingCallback)power, self, &powerIterator);

NSLog(@"Kernel said %d",kr);

power((void*)nport,powerIterator);

I'm still pretty sure you have to rely on IOKit in order to retrieve battery level. My application does not use UIKit as it is a low-level application in which UIKit cannot be used. Here are the frameworks I am using :

alt text http://img837.imageshack.us/img837/1829/screenshot20100718at211.png

Answer 1

A while ago I wrote a program called iox that is similar to ioreg, except it makes it easier for me to translate back to IOKit calls. When I run that on my laptop, I see the following with a battery level.

AppleSmartBattery - IOService:/AppleACPIPlatformExpert/SMB0/AppleECSMBusController/AppleSmartBatteryManager/AppleSmartBattery
        CurrentCapacity = 11678
        FullyCharged = YES
        DesignCapacity = 13000
        MaxCapacity = 11910
        ...

In code, that is

IOServiceNameMatching( "AppleSmartBattery" );

I have no idea if the name would be the same on iOS, but I would try either finding a program like ioreg that you can run on the iPhone, or writing something simple to log the equivalent.

ioreg is part of IOKitTools and it should just compile on iPhone.

Edit:

CFMutableDictionaryRef matching , properties = NULL;
io_registry_entry_t entry = 0;
matching = IOServiceMatching( "IOPMPowerSource" );
//matching = IOServiceNameMatching( "AppleSmartBattery" );
entry = IOServiceGetMatchingService( kIOMasterPortDefault , matching );
IORegistryEntryCreateCFProperties( entry , &properties , NULL , 0 );
NSLog( @"%@" , properties );
CFRelease( properties );
IOObjectRelease( entry );

Add some safety checks. Once you figure out the specific properties you want, you can get them directly instead of using IORegistryEntryCreateCFProperties to get them all at once.

IOKit represents everything as a big tree. IOPMPowerSource may not directly have the attributes you want, in which case you would need to iterate through the children. Using something like ioreg can tell you what you are looking for before you start coding.