最近公司项目需要实现一个类似qq扫一扫功能，该功能主要分为三个部分：扫一扫、扫描相册中二维码图片、开灯（我的二维码不是主要功能）
1.扫一扫
iOS7以后，AVFoundation.framework框架支持扫一扫功能，详细代码，可以参考/p/6b7d54b3f88b
但该博客中的代码只能简单的实现扫一扫功能，周围的背景并不是半透明的。
通过以下代码可以实现中间透明，旁边半透明的效果
-(void)setupBgView{self.view.backgroundColor = [UIColor blackColor];//绘制扫一扫背景，中间透明，旁边半透明UIGraphicsBeginImageContext(self.view.frame.size);CGContextRef ctx = UIGraphicsGetCurrentContext();CGContextSetRGBFillColor(ctx, 0,0,0,0.5);CGRect drawRect =CGRectMake(0, 0, Screen_Width, Screen_height);//draw the transparent layerCGContextFillRect(ctx, drawRect);//clear the center rect of the layerdrawRect = self.scanBg.frame;CGContextClearRect(ctx, drawRect);UIImage* returnimage = UIGraphicsGetImageFromCurrentImageContext();UIImageView * img = [[UIImageView alloc] initWithImage:returnimage];[self.view addSubview:img];UIGraphicsEndImageContext();}
但以上代码仍然存在一点小问题：这张背景图片是直接盖在最上层，导致扫一扫界面上的图片和文字效果不好（左图）。
只需将背景图片移到视图的最上层即可（右图）：
[self.view addSubview:img];[self.view sendSubviewToBack:img];
2.扫描相册中二维码图片
在网上寻找了很久，发现AVFoundation.framework框架并不支持扫描相册中二维码图片功能。
于是，开始寻找支持扫描相册中二维码图片的第三方类库，目前只有ZBar和ZXingObjC支持，而前者很久没更新，故而选择后者。
通过以下代码可以实现点击相册，选择图片，获取图片中的二维码信息。
- (IBAction)clickPhotoAlbum:(id)sender {UIImagePickerController *picker = [[UIImagePickerController alloc] init];picker.allowsEditing = YES;picker.delegate = self;picker.sourceType = UIImagePickerControllerSourceTypePhotoLibrary;[self presentViewController:picker animated:YES completion:^{}];}#pragma mark - UIImagePickerControllerDelegate- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info{UIImage *image = [info objectForKey:@"UIImagePickerControllerEditedImage"];[self dismissViewControllerAnimated:YES completion:^{[self getURLWithImage:image];}];}-(void)getURLWithImage:(UIImage *)img{UIImage *loadImage= img;CGImageRef imageToDecode = loadImage.CGImage;ZXLuminanceSource *source = [[ZXCGImageLuminanceSource alloc] initWithCGImage:imageToDecode];ZXBinaryBitmap *bitmap = [ZXBinaryBitmap binaryBitmapWithBinarizer:[ZXHybridBinarizer binarizerWithSource:source]];NSError *error = nil;ZXDecodeHints *hints = [ZXDecodeHints hints];ZXMultiFormatReader *reader = [ZXMultiFormatReader reader];ZXResult *result = [reader decode:bitmaphints:hintserror:&error];if (result) {// The coded result as a string. The raw data can be accessed with// result.rawBytes and result.length.NSString *contents = result.text;NSLog(@"contents =%@",contents);UIAlertView *alter = [[UIAlertView alloc] initWithTitle:@"解析成功" message:contents delegate:nil cancelButtonTitle:@"确定" otherButtonTitles: nil];[alter show];} else {UIAlertView *alter1 = [[UIAlertView alloc] initWithTitle:@"解析失败" message:nil delegate:nil cancelButtonTitle:@"确定" otherButtonTitles: nil];[alter1 show];}}
但，以上代码存在一点小问题，跳转到相册后，选择一张图片，这张图片是可编辑的状态
picker.allowsEditing = YES;
改为
picker.allowsEditing = NO;
结果，闪退。调试发现跳转到以下代码，image为空。
UIImage *image = [info objectForKey:@"UIImagePickerControllerEditedImage"];
打印info，发现info中还有UIImagePickerControllerOriginalImage，将image该为UIImagePickerControllerOriginalImage即可。
UIImage *image = [info objectForKey:@"UIImagePickerControllerOriginalImage"];
3.开灯
这里的开灯其实就是打开手电筒，手电筒也是基于AVFoundation.framework框架，通过以下代码可以实现开灯和关灯功能。
- (IBAction)clickLight:(id)sender {AVCaptureDevice *device = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];if ([device hasTorch]) {[device lockForConfiguration:nil];if(isLedOn){//关灯[device setTorchMode: AVCaptureTorchModeOff];}else{//开灯[device setTorchMode: AVCaptureTorchModeOn];}[device unlockForConfiguration];}isLedOn = !isLedOn;}
但是，光有以上代码是不够的，在离开扫一扫界面时，如果没有关闭手电筒，手电筒一直会是开启的状态。这时，需要添加以下代码，在离开页面时，关闭手电筒。
-(void)viewWillDisappear:(BOOL)animated{AVCaptureDevice *device = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];if ([device hasTorch]) {[device lockForConfiguration:nil];[device setTorchMode: AVCaptureTorchModeOff];[device unlockForConfiguration];}isLedOn = NO;}
以上三部分代码，即可完成类似qq扫一扫功能。
