ios检测设备摄像头、指南针、录音、陀螺仪的状态

//检查前后摄像头
BOOL cameraAvailable = [UIImagePickerController isCameraDeviceAvailable:UIImagePickerControllerCameraDeviceRear];//前
BOOL frontCameraAvailable = [UIImagePickerController isCameraDeviceAvailable:UIImagePickerControllerCameraDeviceFront];//后

//检查指南针 CoreLocation.framework  <CoreLocation/CoreLocation.h>
BOOL magnetometerAvailbale = [CLLocationManager headingAvailable];

//检查声音支持 AVFoundation.framework <AVFoundation/AVFoundation.h>
AVAudioSession *audioSession = [AVAudioSession sharedInstance];  //返回一个AVAudioSession实例
BOOL audioAvailable = audioSession.inputAvailable;//bool值。获取是否支持

//检查录像支持 MobileCoreServices.framework <MobileCoreServices/MobileCoreServices.h>
- (BOOL)isvideoCameraAvailable
{
    //简单检查所有的可用的媒体资源类型，然后检查返回的数组，如果其中包含了kUTTypeMovie的NSString类型对象，就证明摄像头支持录像
    UIImagePickerController *picker = [[UIImagePickerController alloc]init];
    NSArray *sourceTypes = [UIImagePickerController availableMediaTypesForSourceType:picker.sourceType];//返回所支持的media的类型数组
    [picker release];

    if (![sourceTypes containsObject:(NSString *)kUTTypeMovie]) {//containsObject确定数组中是否包含后面的对象
        return NO;
    }
    return YES;
}
    
//检查陀螺仪可用 CoreMotion.framework <CoreMotion/CoreMotion.h>
- (BOOL) isGyroscopeAvailable
{
#ifdef __IPHONE_4_0//4.0之后才有
    CMMotionManager *motionManager = [[CMMotionManager alloc]init];
    BOOL gyroscopeAvailable = motionManager.gyroAvailable;
    [motionManager release];
    return gyroscopeAvailable;
#else
    return NO;
#endif
}