如同ZBarViewController有相关方法：
ZBarReaderViewController *reader = [ZBarReaderViewController new];
reader.readerDelegate = self;
reader.videoQuality = UIImagePickerControllerQualityTypeHigh;
reader.supportedOrientationsMask = ZBarOrientationMaskAll;
ZBarImageScanner *scanner = reader.scanner;
[scanner setSymbology:ZBAR_I25 config:ZBAR_CFG_ENABLE to:1];
reader.showsZBarControls =NO;
[self setOverlayPickerView:reader];
[self presentViewController:reader animated:YES completion:nil];
ZBarReaderView有相关的提高聚焦的方法的吗？现在ZBarReaderView在有些机型上很难扫出小型的条形码
ZBarReaderView里面有个属性是AVCaptureSession，吧readonly改成strong，在调用ZBarReaderView的文件里面导入<AVFoundation/AVFoundation.h>，然后就可以这样设置[_readerView.session setSessionPreset:AVCaptureSessionPresetHigh];，这样扫描小型条码就很快了。