判斷是否存在手電筒

@property(nonatomic, readonly) BOOL hasTorch;

檢測(cè)手電筒是否可用

例如：例如設(shè)備過熱,需要降溫。此屬性鍵值可觀測(cè)

@property(nonatomic, readonly, getter=isTorchAvailable) BOOL torchAvailable

檢測(cè)手電筒是否正在使用

@property(nonatomic, readonly, getter=isTorchActive) BOOL torchActive

手電筒模式

@property(nonatomic) AVCaptureTorchMode torchMode;

手電筒模式：打開 關(guān)閉 自動(dòng)

typedef NS_ENUM(NSInteger, AVCaptureTorchMode) {
    AVCaptureTorchModeOff  = 0,
    AVCaptureTorchModeOn   = 1,
    AVCaptureTorchModeAuto = 2,
} NS_AVAILABLE(10_7, 4_0) __TVOS_PROHIBITED;

設(shè)置手電筒亮度[0~1]之間

該值只在AVCaptureTorchModeOn 模式下有效

- (BOOL)setTorchModeOnWithLevel:(float)torchLevel error:(NSError * _Nullable * _Nullable)outError NS_AVAILABLE_IOS(6_0);

更改手電筒模式及亮度的時(shí)候必須先鎖定設(shè)備，修改完后再解鎖，否則崩潰

[device lockForConfiguration:nil];
//設(shè)置閃光燈為自動(dòng)
[device setFlashMode:AVCaptureTorchModeOn];
 [captureDevice setTorchModeOnWithLevel:.2 error:nil];
[device unlockForConfiguration];

檢測(cè)是否支持某種手電筒模式

- (BOOL)isTorchModeSupported:(AVCaptureTorchMode)torchMode;