实现长按识别webview中的二维码

@property (nonatomic,copy) NSString *imgURL;   UIWebView *_web;   NSInteger _gesState;- (void)webViewDidFinishLoad:(UIWebView *)webView{    [MBProgressHUD hideHUD];    //实现图片长按识别功能    static NSString* const kTouchJavaScriptString=    @"document.ontouchstart=function(event){\    x=event.targetTouches[0].clientX;\    y=event.targetTouches[0].clientY;\    document.location=\"myweb:touch:start:\"+x+\":\"+y;};\    document.ontouchmove=function(event){\    x=event.targetTouches[0].clientX;\    y=event.targetTouches[0].clientY;\    document.location=\"myweb:touch:move:\"+x+\":\"+y;};\    document.ontouchcancel=function(event){\    document.location=\"myweb:touch:cancel\";};\    document.ontouchend=function(event){\    document.location=\"myweb:touch:end\";};";    [webView stringByEvaluatingJavaScriptFromString:kTouchJavaScriptString];//注入js方法}- (BOOL)webView:(UIWebView *)webView shouldStartLoadWithRequest:(NSURLRequest *)request navigationType:(UIWebViewNavigationType)navigationType{    // add by zcj 实现图片长按识别功能    NSString *requestString =  request.URL.absoluteString;    NSArray *components = [requestString componentsSeparatedByString:@":"];    if ([components count] > 1 && [(NSString *)[components objectAtIndex:0]                                   isEqualToString:@"myweb"]) {        if([(NSString *)[components objectAtIndex:1] isEqualToString:@"touch"])        {            //NSLog(@"you are touching!");            if ([(NSString *)[components objectAtIndex:2] isEqualToString:@"start"])            {                _gesState = UIGestureRecognizerStateBegan;                float ptX  =[[components objectAtIndex:3]floatValue];                float ptY =[[components objectAtIndex:4]floatValue];                NSString *js = [NSString stringWithFormat:@"document.elementFromPoint(%f, %f).tagName", ptX, ptY];                NSString * tagName = [_web stringByEvaluatingJavaScriptFromString:js];                if ([tagName isEqualToString:@"IMG"]) {                    self.imgURL = [NSString stringWithFormat:@"document.elementFromPoint(%f, %f).src", ptX, ptY];                }                if (self.imgURL) {                    [self performSelector:@selector(handleLongTouch) withObject:nil afterDelay:1.0];                }            }            else if ([(NSString *)[components objectAtIndex:2] isEqualToString:@"move"])            {                _gesState = UIGestureRecognizerStateChanged;            }        }        else if ([(NSString*)[components objectAtIndex:2]isEqualToString:@"end"]) {            _gesState = UIGestureRecognizerStateEnded;        }    }// ]end    return YES;}- (void)handleLongTouch {    if (self.imgURL && _gesState == UIGestureRecognizerStateBegan) {        UIAlertController *alertController = [UIAlertController alertControllerWithTitle:nil message:nil preferredStyle:UIAlertControllerStyleActionSheet];        NSString *urlToSave = [_web stringByEvaluatingJavaScriptFromString:self.imgURL];        NSData* data = [NSData dataWithContentsOfURL:[NSURL URLWithString:urlToSave]];        UIImage* image = [UIImage imageWithData:data];        NSDictionary *options = [[NSDictionary alloc] initWithObjectsAndKeys:                                 @"CIDetectorAccuracy", @"CIDetectorAccuracyHigh",nil];        CIDetector *detector = nil;        if ([[UIDevice currentDevice].systemVersion floatValue] >= 8.0)            detector = [CIDetector detectorOfType:CIDetectorTypeQRCode                                          context:nil                                          options:options];        NSArray *features = [detector featuresInImage:[CIImage imageWithCGImage:image.CGImage]] ;        // 识别图中二维码        UIAlertAction *judgeCode = [UIAlertAction actionWithTitle:@"识别图中二维码" style:UIAlertActionStyleDefault handler:^(UIAlertAction * _Nonnull action) {            CIQRCodeFeature *feature = [features objectAtIndex:0];            NSString *scannedResult = feature.messageString;            if ([[UIApplication sharedApplication] canOpenURL:[NSURL URLWithString:scannedResult]]){                [[UIApplication sharedApplication] openURL:[NSURL URLWithString:scannedResult]];            }else{                [MBProgressHUD showError:@"无法识别的网址"];            }        }];        // 保存图片到手机        UIAlertAction *saveImage = [UIAlertAction actionWithTitle:@"保存到手机" style:UIAlertActionStyleDefault handler:^(UIAlertAction * _Nonnull action) {            UIImageWriteToSavedPhotosAlbum(image, self, @selector(image:didFinishSavingWithError:contextInfo:), nil);        }];        // 取消        UIAlertAction *cancell = [UIAlertAction actionWithTitle:@"取消" style:UIAlertActionStyleCancel handler:^(UIAlertAction * _Nonnull action) {        }];        if (features.count >= 1) {            [alertController addAction:judgeCode];        }        [alertController addAction:saveImage];        [alertController addAction:cancell];        [self presentViewController:alertController animated:YES completion:nil];    }}