iOS系统原生二维码条形码扫描

　本文讲述如何用系统自带的东东实现二维码扫描的功能:点击当前页面的某个按钮，创建扫描VIEW。细心的小伙伴可以发现 title被改变了，返回按钮被隐藏了。这个代码自己写就行了，与本文关系不大。。。绿色的线会上下跑，不要担心:D

实现效果如下：

　　1.在工程中添加框架AVFoundation.framework

　　2.声明代理：AVCaptureMetadataOutputObjectsDelegate 。 define 几个东东用来画框、画线：

#define SCANVIEW_EdgeTop 40.0
#define SCANVIEW_EdgeLeft 50.0
#define TINTCOLOR_ALPHA 0.2 //浅色透明度
#define DARKCOLOR_ALPHA 0.5 //深色透明度
#define VIEW_WIDTH [UIScreen mainScreen].bounds.size.width
#define VIEW_HEIGHT [UIScreen mainScreen].bounds.size.height

　　3.声明以下属性：

    AVCaptureSession * session;//输入输出的中间桥梁
    UIView *AVCapView;//此 view 用来放置扫描框、取消按钮、说明 label
    UIView *_QrCodeline;//上下移动绿色的线条
    NSTimer *_timer;

　　4.在某个方法中（我是点击扫描按钮）创建扫描界面，开始扫描：

 //创建一个 view 来放置扫描区域、说明 label、取消按钮
    UIView *tempView = [[UIView alloc]initWithFrame:CGRectMake(, , , [UIScreen mainScreen].bounds.size.height )];
    AVCapView = tempView;
    AVCapView.backgroundColor = [UIColor colorWithRed:.f/ green:.f/ blue:.f/ alpha:];

    UIButton *cancelBtn = [[UIButton alloc]initWithFrame:CGRectMake(, [UIScreen mainScreen].bounds.size.height - , , )];
    UILabel *label = [[UILabel alloc]initWithFrame:CGRectMake(, , , )];
    label.numberOfLines = ;
    label.text = @"小提示：将条形码或二维码对准上方区域中心即可";
    label.textColor = [UIColor grayColor];
    [cancelBtn setTitle:@"取消" forState: UIControlStateNormal];
    [cancelBtn setTitleColor:[UIColor grayColor] forState:UIControlStateNormal];
    [cancelBtn addTarget:self action:@selector(touchAVCancelBtn) forControlEvents:UIControlEventTouchUpInside];
    [AVCapView addSubview:label];
    [AVCapView addSubview:cancelBtn];
    [self.view addSubview:AVCapView];

    //画上边框
    UIView *topView = [[UIView alloc] initWithFrame:CGRectMake(SCANVIEW_EdgeLeft, SCANVIEW_EdgeTop, VIEW_WIDTH-  * SCANVIEW_EdgeLeft, )];
    topView.backgroundColor = [UIColor whiteColor];
    [AVCapView addSubview:topView];

    //画左边框
    UIView *leftView = [[UIView alloc] initWithFrame:CGRectMake(SCANVIEW_EdgeLeft, SCANVIEW_EdgeTop , ,VIEW_WIDTH -  * SCANVIEW_EdgeLeft )];
    leftView.backgroundColor = [UIColor whiteColor];
    [AVCapView addSubview:leftView];

    //画右边框
    UIView *rightView = [[UIView alloc] initWithFrame:CGRectMake(SCANVIEW_EdgeLeft + VIEW_WIDTH-  * SCANVIEW_EdgeLeft, SCANVIEW_EdgeTop , ,VIEW_WIDTH -  * SCANVIEW_EdgeLeft + )];
    rightView.backgroundColor = [UIColor whiteColor];
    [AVCapView addSubview:rightView];

    //画下边框
    UIView *downView = [[UIView alloc] initWithFrame:CGRectMake(SCANVIEW_EdgeLeft, SCANVIEW_EdgeTop + VIEW_WIDTH-  * SCANVIEW_EdgeLeft,VIEW_WIDTH -  * SCANVIEW_EdgeLeft , )];
    downView.backgroundColor = [UIColor whiteColor];
    [AVCapView addSubview:downView];

    //画中间的基准线
    _QrCodeline = [[UIView alloc] initWithFrame:CGRectMake(SCANVIEW_EdgeLeft + , SCANVIEW_EdgeTop, VIEW_WIDTH-  * SCANVIEW_EdgeLeft - , )];
    _QrCodeline.backgroundColor = [UIColor greenColor];
    [AVCapView addSubview:_QrCodeline];

    // 先让基准线运动一次，避免定时器的时差
    [UIView animateWithDuration:1.2 animations:^{

        _QrCodeline.frame = CGRectMake(SCANVIEW_EdgeLeft + , VIEW_WIDTH -  * SCANVIEW_EdgeLeft + SCANVIEW_EdgeTop , VIEW_WIDTH -  * SCANVIEW_EdgeLeft - , );

    }];

    [self performSelector:@selector(createTimer) withObject:nil afterDelay:0.4];

    AVCaptureDevice * device = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
    //创建输入流
    AVCaptureDeviceInput * input = [AVCaptureDeviceInput deviceInputWithDevice:device error:nil];
    //创建输出流
    AVCaptureMetadataOutput * output = [[AVCaptureMetadataOutput alloc]init];
    //设置代理 在主线程里刷新
    [output setMetadataObjectsDelegate:self queue:dispatch_get_main_queue()];

    //初始化链接对象
    session = [[AVCaptureSession alloc]init];
    //高质量采集率
    [session setSessionPreset:AVCaptureSessionPresetHigh];

    [session addInput:input];
    [session addOutput:output];
    //设置扫码支持的编码格式(如下设置条形码和二维码兼容)
    output.metadataObjectTypes=@[AVMetadataObjectTypeQRCode,AVMetadataObjectTypeEAN13Code, AVMetadataObjectTypeEAN8Code, AVMetadataObjectTypeCode128Code];

    AVCaptureVideoPreviewLayer * layer = [AVCaptureVideoPreviewLayer layerWithSession:session];
    layer.videoGravity=AVLayerVideoGravityResizeAspectFill;
    layer.frame = CGRectMake(SCANVIEW_EdgeLeft, SCANVIEW_EdgeTop, VIEW_WIDTH-  * SCANVIEW_EdgeLeft, );
    [AVCapView.layer insertSublayer:layer atIndex:];
    //开始捕获
    [session startRunning];

　　5.实现定时器、还有基准线的滚动方法

- (void)createTimer
{
    _timer=[NSTimer scheduledTimerWithTimeInterval:1.1 target:self selector:@selector(moveUpAndDownLine) userInfo:nil repeats:YES];
}

- (void)stopTimer
{
    if ([_timer isValid] == YES) {
        [_timer invalidate];
        _timer = nil;
    }

}

// 滚来滚去 :D :D :D
- (void)moveUpAndDownLine
{
    CGFloat YY = _QrCodeline.frame.origin.y;

    if (YY != VIEW_WIDTH -  * SCANVIEW_EdgeLeft + SCANVIEW_EdgeTop ) {
        [UIView animateWithDuration:1.2 animations:^{
            _QrCodeline.frame = CGRectMake(SCANVIEW_EdgeLeft + , VIEW_WIDTH -  * SCANVIEW_EdgeLeft + SCANVIEW_EdgeTop , VIEW_WIDTH -  * SCANVIEW_EdgeLeft - ,);
        }];
    }else {
        [UIView animateWithDuration:1.2 animations:^{
            _QrCodeline.frame = CGRectMake(SCANVIEW_EdgeLeft + , SCANVIEW_EdgeTop, VIEW_WIDTH -  * SCANVIEW_EdgeLeft - ,);
        }];

    }
}

6.扫描成功后，想干嘛干嘛，就在这个代理方法里面实现就行了

-(void)captureOutput:(AVCaptureOutput *)captureOutput didOutputMetadataObjects:(NSArray *)metadataObjects fromConnection:(AVCaptureConnection *)connection{
    if (metadataObjects.count>) {
        //[session stopRunning];
        AVMetadataMachineReadableCodeObject * metadataObject = [metadataObjects objectAtIndex :  ];
        //输出扫描字符串
        NSLog(@"%@",metadataObject.stringValue);
        [session stopRunning];
        [self stopTimer];
        [AVCapView removeFromSuperview];
        .....
    }
}

7.如果用户不想扫描了，点击取消按钮：

- (void)touchAVCancelBtn{
    [session stopRunning];//摄像也要停止
    [self stopTimer];//定时器要停止
    [AVCapView removeFromSuperview];//刚刚创建的 view 要移除

   ...
}