iOS

• 导入框架 #import <AVFoundation/AVFoundation.h>
• 设置属性: ViewController 中

@interface ViewController ()

/// 获取设备
@property (nonatomic, strong) AVCaptureDevice *device;
/// 手电筒是否开启
@property (nonatomic,assign) BOOL lightOn;

@end

• 获取硬件以及判断手电筒是否可用:

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    _device = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
    /**
     *  hasTorch :返回YES表名手机上有手电筒
     */
    if (![_device hasTorch]) {
        NSLog(@"手电筒坏了,赶紧换一个iPhone8吧!!!");
        return;
    }
    
}

• 设置开关手电筒的一个方法:clickBtn2:

- (IBAction)clickBtn2:(id)sender {
    
    _lightOn = !_lightOn;
    //根据ligthOn状态判断打开还是关闭
    // torchLevel
    if (_lightOn) {
        //开启手电筒
        [_device lockForConfiguration:nil];
        [_device setTorchMode:AVCaptureTorchModeOn];
        
        // 设置手电筒torchLevel(亮度)数值必须在0~1之间,如果设备过热可能会抛出异常并且不能启动
        // 范围 0 - 1 不能是0,应该是(0,1] 左开右闭区间取值,设置数值以前先lock(lockForConfiguration), 设置完毕后一定unlock(unlockForConfiguration)否则崩溃,解决机子过热或者设置导致的崩溃最好的设置方式@try...@catch...@finally捕获异常防止崩溃
        [_device setTorchModeOnWithLevel:0.01 error:nil];
        [_device unlockForConfiguration];
        
    }else{
        //关闭手电筒
        [_device lockForConfiguration:nil];
        [_device setTorchMode:AVCaptureTorchModeOff];
        [_device unlockForConfiguration];
        
    }
}

• 设置手电筒亮度的一个方法: clickBtn1

/// 设置亮度
- (IBAction)clickBtn1:(id)sender {
    [_device lockForConfiguration:nil];
    [_device setTorchModeOnWithLevel:1 error:nil];
    [_device unlockForConfiguration];
}

注意:
1. 可能由于玩游戏之类原因手机过热导致打开手电筒失败,最终导致崩溃.
2. 设置手电筒的亮度前要 lockForConfiguration
3. 设置手电筒完毕后要 unlockForConfiguration
4. 最好的办法用@try...@catch...@finally捕获异常防止崩溃.