1、首先需要引入AVFoundation.framework框架
2、在 .h文件中添加属性

添加#import <AVFoundation/AVFoundation.h>
@interface LightViewController : UIViewController
{
BOOL isLightOn;
AVCaptureDevice *device;
}

@property BOOL isLightOn;
@end

3. 在 .m 文件中实现
   .m文件

import "LightViewController.h"

@interface LightViewController ()

@end
@implementation LightViewController

@synthesize isLightOn;

• (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
  {
  self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
  if (self) {
  self.navigationItem.title = @"手电筒";
  }
  return self;
  }

4>>

• (void)viewDidLoad
  {
  [super viewDidLoad];
  UIButton *btn = [UIButton buttonWithType:UIButtonTypeRoundedRect];
  [btn setFrame:CGRectMake(80, 150, 100, 80)];
  [btn addTarget:self action:@selector(btnClicked) forControlEvents:UIControlEventTouchUpInside];
  [self.view addSubview:btn];

  //AVCaptureDevice代表抽象的硬件设备
  // 找到一个合适的AVCaptureDevice
  device = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
  if (![device hasTorch]) {//判断是否有闪光灯
  UIAlertView *alter = [[UIAlertView alloc]initWithTitle:@"提示" message:@"当前设备没有闪光灯，不能提供手电筒功能" delegate:nil cancelButtonTitle:@"Cancel" otherButtonTitles:nil, nil];
  [alter show];
  }

  isLightOn = NO;

}

-(void)btnClicked
{
isLightOn = 1-isLightOn;
if (isLightOn) {
[self turnOnLed:YES];
}else{
[self turnOffLed:YES];
}
}

//打开手电筒
-(void) turnOnLed:(bool)update
{
[device lockForConfiguration:nil];
[device setTorchMode:AVCaptureTorchModeOn];
[device unlockForConfiguration];
}

//关闭手电筒
-(void) turnOffLed:(bool)update
{
[device lockForConfiguration:nil];
[device setTorchMode: AVCaptureTorchModeOff];
[device unlockForConfiguration];
}