razvan razvan - 1 month ago 27
iOS Question

Get device signal strength

I am trying to get the signal strength in dBm for the carrier, wifi, 3g, and 4g.

I am currently using this code to get the carrier's and wifi from the status bar and I would like to know if there is another way or a better way? Also how could I get it for 3g and 4g?

UIApplication *app = [UIApplication sharedApplication];
NSArray *subviews = [[[app valueForKey:@"statusBar"] valueForKey:@"foregroundView"] subviews];
NSString *dataNetworkItemView = nil;
NSString *wifiNetworkItemView = nil;

for (id subview in subviews) {
if([subview isKindOfClass:[NSClassFromString(@"UIStatusBarSignalStrengthItemView") class]]) {
dataNetworkItemView = subview;
}
if([subview isKindOfClass:[NSClassFromString(@"UIStatusBarDataNetworkItemView") class]]) {
wifiNetworkItemView = subview;
}
}

int carrierSignalStrength = [[dataNetworkItemView valueForKey:@"signalStrengthRaw"] intValue];
int wifiSignalStrength = [[wifiNetworkItemView valueForKey:@"wifiStrengthRaw"] intValue];


It doesn't matter if any methods I use are private or not.

JAL JAL
Answer

Use CoreTelephony and CTTelephonyCenter observers:

#include <CoreTelephony/CoreTelephony.h>

// Event handler
static void SignalStrengthDidChange(CFNotificationCenterRef center, void *observer, CFStringRef name, const void *object, CFDictionaryRef userInfo)
{
    long int raw = 0;
    long int graded = 0;
    long int bars = 0;

    CTIndicatorsGetSignalStrength(&raw, &graded, &bars);

    printf("Signal strength changed! Raw: %li, graded: %li bars: %li\n", raw, graded, bars);
    // Prints something like:
    // Signal strength changed! Raw: -96, graded: 27 bars: 3
}

Register the handler in another function:

// Register as a listener to the kCTIndicatorsSignalStrengthNotification notification to be notified when the signal strength changed.
CTTelephonyCenterAddObserver(CTTelephonyCenterGetDefault(), NULL, SignalStrengthDidChange, kCTIndicatorsSignalStrengthNotification, NULL, CFNotificationSuspensionBehaviorCoalesce);

// Get the initial strength.
SignalStrengthDidChange();

CFRunLoopRun();

Adapted from the iPhone Dev Wiki article on CTIndicators.

These methods are no longer in any iOS SDKs greater than 8.4 (?) I believe. To access them, create a new header with to extern the functions and constants:

#include <CoreFoundation/CoreFoundation.h>

#if __cplusplus
extern "C" {
#endif

#pragma mark - API

    /* This API is a mimic of CFNotificationCenter. */

    CFNotificationCenterRef CTTelephonyCenterGetDefault();
    void CTTelephonyCenterAddObserver(CFNotificationCenterRef center, const void *observer, CFNotificationCallback callBack, CFStringRef name, const void *object, CFNotificationSuspensionBehavior suspensionBehavior);
    void CTTelephonyCenterRemoveObserver(CFNotificationCenterRef center, const void *observer, CFStringRef name, const void *object);
    void CTTelephonyCenterRemoveEveryObserver(CFNotificationCenterRef center, const void *observer);

    void CTIndicatorsGetSignalStrength(long int *raw, long int *graded, long int *bars);

#pragma mark - Definitions

    /* For use with the CoreTelephony notification system. */
    extern CFStringRef kCTIndicatorsSignalStrengthNotification;

#if __cplusplus
}
#endif
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