这两天用到了二维码扫描功能，网上第三方框架是有，但是想弄清楚其原理，就自己用了系统原生的方法，其中部分地方有点坑，就记录下来，权当下次使用提醒。
二维码扫描
不多说，上代码：
#import //引用AVFoundation框架
@interface ViewController () //遵守AVCaptureMetadataOutputObjectsDelegate协议
@property ( strong , nonatomic ) AVCaptureDevice * device; //捕获设备，默认后置摄像头
@property ( strong , nonatomic ) AVCaptureDeviceInput * input; //输入设备
@property ( strong , nonatomic ) AVCaptureMetadataOutput * output;//输出设备，需要指定他的输出类型及扫描范围
@property ( strong , nonatomic ) AVCaptureSession * session; //AVFoundation框架捕获类的中心枢纽，协调输入输出设备以获得数据
@property ( strong , nonatomic ) AVCaptureVideoPreviewLayer * previewLayer;//展示捕获图像的图层，是CALayer的子类
@property (nonatomic,strong)UIView *scanView;定位扫描框在哪个位置
初始化对象：
- (AVCaptureDevice *)device
{
if (_device == nil) {
// 设置AVCaptureDevice的类型为Video类型
_device = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
}
return _device;
}
- (AVCaptureDeviceInput *)input
{
if (_input == nil) {
//输入设备初始化
_input = [AVCaptureDeviceInput deviceInputWithDevice:self.device error:nil];
}
return _input;
}
这里设置输出设备要注意rectOfInterest属性的设置，一般默认是CGRect(x: 0, y: 0, width: 1, height: 1),全屏都能读取的，但是读取速度较慢。注意rectOfInterest属性的传人的是比例。比例是根据扫描容器的尺寸比上屏幕尺寸（注意要计算的时候要计算导航栏高度，有的话需减去）。
参照的是横屏左上角的比例，而不是竖屏。所以我们再设置的时候要调整方向如下面所示。
- (AVCaptureMetadataOutput *)output
{
if (_output == nil) {
//初始化输出设备
_output = [[AVCaptureMetadataOutput alloc] init];
// 1.获取屏幕的frame
CGRect viewRect = self.view.frame;
// 2.获取扫描容器的frame
CGRect containerRect = self.scanView.frame;
CGFloat x = containerRect.origin.y / viewRect.size.height;
CGFloat y = containerRect.origin.x / viewRect.size.width;
CGFloat width = containerRect.size.height / viewRect.size.height;
CGFloat height = containerRect.size.width / viewRect.size.width;
//rectOfInterest属性设置设备的扫描范围
_output.rectOfInterest = CGRectMake(x, y, width, height);
}
return _output;
}
网上还有一种是根据AVCaptureInputPortFormatDescriptionDidChangeNotification通知设置的，也是可行的，自选一种即可。
__weak typeof(self) weakSelf = self;
[[NSNotificationCenter defaultCenter]addObserverForName:AVCaptureInputPortFormatDescriptionDidChangeNotification
object:nil
queue:[NSOperationQueue mainQueue]
usingBlock:^(NSNotification * _Nonnull note) {
if (weakSelf){
//调整扫描区域
AVCaptureMetadataOutput *output = weakSelf.session.outputs.firstObject;
output.rectOfInterest = [weakSelf.previewLayer metadataOutputRectOfInterestForRect:weakSelf.scanView.frame];
}
}];
下面初始化AVCaptureSession和AVCaptureVideoPreviewLayer:
- (AVCaptureSession *)session
{
if (_session == nil) {
_session = [[AVCaptureSession alloc] init];
}
return _session;
}
- (AVCaptureVideoPreviewLayer *)previewLayer
{
if (_previewLayer == nil) {
//负责图像渲染出来
_previewLayer = [AVCaptureVideoPreviewLayer layerWithSession:self.session];
self.previewLayer.videoGravity = AVLayerVideoGravityResizeAspectFill;
}
return _previewLayer;
}
接着我们再viewDidLoad中初始化并启动扫描
- (void)viewDidLoad {
[super viewDidLoad];
CGFloat kScreen_Width = [UIScreen mainScreen].bounds.size.width;
//定位扫描框在屏幕正中央，并且宽高为200的正方形
self.scanView = [[UIView alloc]initWithFrame:CGRectMake((kScreen_Width-200)/2, (self.view.frame.size.height-200)/2, 200, 200)];
[self.view addSubview:self.scanView];
//设置扫描界面（包括扫描界面之外的部分置灰，扫描边框等的设置）,后面设置
TNWCameraScanView *clearView = [[TNWCameraScanView alloc]initWithFrame:self.view.frame];
[self.view addSubview:clearView];
[self startScan];
}
- (void)startScan
{
// 1.判断输入能否添加到会话中
if (![self.session canAddInput:self.input]) return;
[self.session addInput:self.input];
// 2.判断输出能够添加到会话中
if (![self.session canAddOutput:self.output]) return;
[self.session addOutput:self.output];
// 4.设置输出能够解析的数据类型
// 注意点: 设置数据类型一定要在输出对象添加到会话之后才能设置
//设置availableMetadataObjectTypes为二维码、条形码等均可扫描，如果想只扫描二维码可设置为
// [self.output setMetadataObjectTypes:@[AVMetadataObjectTypeQRCode]];
self.output.metadataObjectTypes = self.output.availableMetadataObjectTypes;
// 5.设置监听监听输出解析到的数据
[self.output setMetadataObjectsDelegate:self queue:dispatch_get_main_queue()];
// 6.添加预览图层
[self.view.layer insertSublayer:self.previewLayer atIndex:0];
self.previewLayer.frame = self.view.bounds;
// 8.开始扫描
[self.session startRunning];
}
下面是接收扫描结果的代理AVCaptureMetadataOutputObjectsDelegate:
- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputMetadataObjects:(NSArray *)metadataObjects fromConnection:(AVCaptureConnection *)connection
{
[self.session stopRunning]; //停止扫描
//我们捕获的对象可能不是AVMetadataMachineReadableCodeObject类，所以要先判断，不然会崩溃
if (![[metadataObjects lastObject] isKindOfClass:[AVMetadataMachineReadableCodeObject class]]) {
[self.session startRunning];
return;
}
// id 类型不能点语法,所以要先去取出数组中对象
AVMetadataMachineReadableCodeObject *object = [metadataObjects lastObject];
if ( object.stringValue == nil ){
[self.session startRunning];
}
上面就是常用的二维码扫描部分的代码，我们下面再简单的看下它扫描框之外界面的设置（包括扫描界面之外的部分置灰，扫描边框等）。具体样式你们可以自己调整添加。
扫描框
@interface TNWCameraScanView : UIView
- (instancetype)initWithFrame:(CGRect)frame;
@end
#import "TNWCameraScanView.h"
@interface TNWCameraScanView()
{
CGFloat sceenHeight;
NSTimer *timer;
CGRect scanRect;
CGFloat kScreen_Width;
CGFloat kScreen_Height;
}
@property (nonatomic,assign)CGFloat lineWidth;
@property (nonatomic,assign)CGFloat height;
@property (nonatomic,strong)UIColor *lineColor;
@property (nonatomic, assign)CGFloat scanTime;
@end
@implementation TNWCameraScanView
- (instancetype)initWithFrame:(CGRect)frame{
if (self = [super initWithFrame:frame]) {
self.backgroundColor = [UIColor clearColor]; // 清空背景色，否则为黑
sceenHeight =self.frame.size.height;
_height = 200; // 宽高200的正方形
_lineWidth = 2; // 扫描框4个脚的宽度
_lineColor = [UIColor greenColor]; // 扫描框4个脚的颜色
_scanTime = 3; //扫描线的时间间隔设置
kScreen_Width = [UIScreen mainScreen].bounds.size.width;
kScreen_Height = [UIScreen mainScreen].bounds.size.height;
[self scanLineMove];
//定时，多少秒扫描线刷新一次
timer = [NSTimer scheduledTimerWithTimeInterval:_scanTime target:self selector:@selector(scanLineMove) userInfo:nil repeats:YES];
}
return self;
}
- (void)scanLineMove{
UIView *line = [[UIView alloc]initWithFrame:CGRectMake((kScreen_Width-_height)/2, (sceenHeight-_height)/2, _height, 1)];
line.backgroundColor = [UIColor greenColor];
[self addSubview:line];
[UIView animateWithDuration:_scanTime animations:^{
line.frame = CGRectMake((kScreen_Width-_height)/2, (sceenHeight+_height)/2, _height, 0.5);
} completion:^(BOOL finished) {
[line removeFromSuperview];
}];
}
-(void)drawRect:(CGRect)rect{
CGFloat bottomHeight = (sceenHeight-_height)/2;
CGFloat leftWidth = (kScreen_Width-_height)/2;
CGContextRef ctx = UIGraphicsGetCurrentContext();
//设置4个方向的灰度值，透明度为0.5，可自行调整。
CGContextSetRGBFillColor(ctx, 0, 0, 0, 0.5);
CGContextFillRect(ctx, CGRectMake(0, 0, kScreen_Width, bottomHeight));
CGContextStrokePath(ctx);
CGContextFillRect(ctx, CGRectMake(0,bottomHeight, leftWidth, _height));
CGContextStrokePath(ctx);
CGContextFillRect(ctx, CGRectMake((kScreen_Width+_height)/2, bottomHeight, leftWidth, _height));
CGContextStrokePath(ctx);
CGContextFillRect(ctx, CGRectMake(0,(sceenHeight+_height)/2, kScreen_Width, bottomHeight));
CGContextStrokePath(ctx);
//扫描框4个脚的设置
CGContextSetLineWidth(ctx, _lineWidth);
CGContextSetStrokeColorWithColor(ctx, _lineColor.CGColor);
//左上角
CGContextMoveToPoint(ctx, leftWidth, bottomHeight+30);
CGContextAddLineToPoint(ctx, leftWidth, bottomHeight);
CGContextAddLineToPoint(ctx, leftWidth+30, bottomHeight);
CGContextStrokePath(ctx);
//右上角
CGContextMoveToPoint(ctx, (kScreen_Width+_height)/2-30, bottomHeight);
CGContextAddLineToPoint(ctx, (kScreen_Width+_height)/2, bottomHeight);
CGContextAddLineToPoint(ctx, (kScreen_Width+_height)/2, bottomHeight+30);
CGContextStrokePath(ctx);
//左下角
CGContextMoveToPoint(ctx, leftWidth, (sceenHeight+_height)/2-30);
CGContextAddLineToPoint(ctx, leftWidth, (sceenHeight+_height)/2);
CGContextAddLineToPoint(ctx, leftWidth+30, (sceenHeight+_height)/2);
CGContextStrokePath(ctx);
//右下角
CGContextMoveToPoint(ctx, (kScreen_Width+_height)/2-30, (sceenHeight+_height)/2);
CGContextAddLineToPoint(ctx, (kScreen_Width+_height)/2, (sceenHeight+_height)/2);
CGContextAddLineToPoint(ctx, (kScreen_Width+_height)/2, (sceenHeight+_height)/2-30);
CGContextStrokePath(ctx);
设置扫描框4个边的颜色和线框。
// CGContextSetStrokeColorWithColor(ctx, [UIColor whiteColor].CGColor);
// CGContextSet_lineWidth(ctx, 1);
// CGContextAddRect(ctx, CGRectMake(leftWidth, bottomHeight, height, height));
// CGContextStrokePath(ctx);
scanRect = CGRectMake(leftWidth, bottomHeight, _height, _height);
}
- (void)dealloc{
//清除计时器
[timer invalidate];
timer = nil;
}
扫描相册中的二维码
再说一下关于扫描相册中的二维码部分，使用CIDetector进行图片解析，比较简单。
- (void)choicePhoto{
//调用相册
UIImagePickerController *imagePicker = [[UIImagePickerController alloc]init];
//UIImagePickerControllerSourceTypePhotoLibrary为相册
imagePicker.sourceType = UIImagePickerControllerSourceTypePhotoLibrary;
//设置代理UIImagePickerControllerDelegate和UINavigationControllerDelegate
imagePicker.delegate = self;
[self presentViewController:imagePicker animated:YES completion:nil];
}
//选中图片的回调
-(void)imagePickerController:(UIImagePickerController*)picker didFinishPickingMediaWithInfo:(NSDictionary *)info
{
//取出选中的图片
UIImage *pickImage = info[UIImagePickerControllerOriginalImage];
NSData *imageData = UIImagePNGRepresentation(pickImage);
CIImage *ciImage = [CIImage imageWithData:imageData];
//创建探测器
//CIDetectorTypeQRCode表示二维码，这里选择CIDetectorAccuracyLow识别速度快
CIDetector *detector = [CIDetector detectorOfType:CIDetectorTypeQRCode context:nil options:@{CIDetectorAccuracy: CIDetectorAccuracyLow}];
NSArray *feature = [detector featuresInImage:ciImage];
//取出探测到的数据
for (CIQRCodeFeature *result in feature) {
NSString *content = result.messageString;// 这个就是我们想要的值
}
[self dismissViewControllerAnimated:YES completion:nil];
}
常用的二维码或条形码就是这些吧，后续再进行补充。