iOS 简单易用的二维码扫描及生成二维码三方控件LFQRCode，可灵活自定义UI

- (void)viewDidLoad {
    [super viewDidLoad];
    
    //扫描有效区（即框内透明区域）
    CGRect interestRect = CGRectMake(20, (self.view.frame.size.height - (self.view.frame.size.width - 40))/2.0f, self.view.frame.size.width - 40, self.view.frame.size.width - 40);
    
    //扫描控件
    _scanView = [[LFQRCodeScanner alloc] initWithFrame:self.view.bounds rectOfInterest:interestRect];
    _scanView.imgLine.image = [UIImage imageNamed:@"line"];
    _scanView.scanFilishBlock = ^(AVMetadataMachineReadableCodeObject *result) {
        NSLog(@"扫描结果：%@",result.stringValue);
    };
    [self.view insertSubview:_scanView atIndex:0];//将扫描view放到底层
}

- (void)viewWillAppear:(BOOL)animated {
    [super viewWillAppear: animated];
    [self.scanView start];
}

- (void)viewDidDisappear:(BOOL)animated {
    [super viewDidDisappear: animated];
    [self.scanView stop];
}