IOS開發基礎知識--碎片48

1：Assertion failure in dequeueReusableCellWithIdentifier:forIndexPath: 

static NSString *CellIdentifier = @"Cell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier 
                                     forIndexPath:indexPath];

上面是在IOS9以下一直報閃退；後來改成下麵解決：

static NSString *CellIdentifier = @"Cell";
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];

   if (cell==nil) {
      cell = [[UITableViewCell alloc]initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:CellIdentifier];
    }

2:CoreTelephony框架不是私有庫

私有框架的目錄為：
/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS.sdk/System/Library/PrivateFrameworks/

可以看出CoreTelephony框架是在frameworks內而不是PrivateFrameworks，所以它是可以放心使用的。網上之所以有說CoreTelephony是私有庫，是因為在iOS6的時候是私有框架，後來蘋果又給公開了;

3:如何獲取電話狀態

a:首先要導入CoreTelephony框架：

@import CoreTelephony;

b:然後聲明一個CTCallCenter變數：

@interface ViewController () {  
CTCallCenter *center_;   //為了避免形成retain cycle而聲明的一個變數，指向接收通話中心對象
}  
@end

然後監聽電話狀態：

- (void) aboutCall{   
    //獲取電話接入信息
callCenter.callEventHandler = ^(CTCall *call){
    if ([call.callState isEqualToString:CTCallStateDisconnected]){
        NSLog(@"Call has been disconnected");

    }else if ([call.callState isEqualToString:CTCallStateConnected]){
        NSLog(@"Call has just been connected");

    }else if([call.callState isEqualToString:CTCallStateIncoming]){
        NSLog(@"Call is incoming");

    }else if ([call.callState isEqualToString:CTCallStateDialing]){
        NSLog(@"call is dialing");

    }else{
        NSLog(@"Nothing is done");
    }
};
}

還可以獲取運營商信息：

- (void)getCarrierInfo{
// 獲取運營商信息
CTTelephonyNetworkInfo *info = [[CTTelephonyNetworkInfo alloc] init];
CTCarrier *carrier = info.subscriberCellularProvider;
NSLog(@"carrier:%@", [carrier description]);

// 如果運營商變化將更新運營商輸出
info.subscriberCellularProviderDidUpdateNotifier = ^(CTCarrier *carrier) {
    NSLog(@"carrier:%@", [carrier description]);
};

// 輸出手機的數據業務信息
NSLog(@"Radio Access Technology:%@", info.currentRadioAccessTechnology);
}

當然這樣在真機進行測試，以下為輸出信息：

2015-12-29 16:34:14.525 RWBLEManagerDemo[1489:543655] carrier:CTCarrier (0x134e065c0) {
Carrier name: [中國移動]
Mobile Country Code: [460]
Mobile Network Code:[07]
ISO Country Code:[cn]
Allows VOIP? [YES]
}
2015-12-29 16:34:14.526 RWBLEManagerDemo[1489:543655] Radio Access Technology:CTRadioAccessTechnologyHSDPA