在集成掃描二維碼功能時候，我使用的是系統在iOS7.0 之后才支持的掃描二維碼功能類。剛開始創建代碼是這么寫的
1 -(void)setUpCamera 2 { 3 self.device = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo]; 4 5 self.input = [AVCaptureDeviceInput deviceInputWithDevice:self.device error:nil]; 6 7 self.outPut = [[AVCaptureMetadataOutput alloc]init]; 8 self.outPut.metadataObjectTypes = @[AVMetadataObjectTypeQRCode]; 9 [_outPut setMetadataObjectsDelegate:self queue:dispatch_get_main_queue()]; 10 self.session = [[AVCaptureSession alloc]init]; 11 [self.session setSessionPreset:AVCaptureSessionPresetHigh]; 12 if ([self.session canAddInput:self.input]) 13 { 14 [self.session addInput:self.input]; 15 16 } 17 18 if ([self.session canAddOutput:self.outPut]) 19 { 20 [self.session addOutput:self.outPut]; 21 } 22 23 24 _preview =[AVCaptureVideoPreviewLayer layerWithSession:self.session]; 25 _preview.videoGravity = AVLayerVideoGravityResizeAspectFill; 26 _preview.frame =CGRectMake(20,110,280,280); 27 [self.view.layer insertSublayer:self.preview atIndex:0]; 28 29 [self.session startRunning]; 30 }
在其代理類里面
-(void)captureOutput:(AVCaptureOutput *)captureOutput didOutputMetadataObjects:(NSArray *)metadataObjects fromConnection:(AVCaptureConnection *)connection { NSString *stringValue; if ([metadataObjects count] > 0 ) { AVMetadataMachineReadableCodeObject *metadataObject = [metadataObjects objectAtIndex:0]; stringValue = metadataObject.stringValue; } [self.session stopRunning]; [self dismissViewControllerAnimated:YES completion:^{ [timer invalidate]; UIAlertView *alertView = [[UIAlertView alloc]initWithTitle:@"二維碼相關內容" message:stringValue delegate:nil cancelButtonTitle:@"取消" otherButtonTitles:@"確定", nil]; [alertView show]; }]; }
在真機上測試，系統是iOS7.1.1
運行時出現下面的錯誤：
*** Terminating app due to uncaught exception ‘NSInvalidArgumentException’, reason: ‘*** -[AVCaptureMetadataOutput setMetadataObjectTypes:] – unsupported type found. Use -availableMetadataObjectTypes.’
解決不了，上網上搜索也沒有相關的解決方法，最后查找相關文檔並且查看手冊，還是不能夠解決問題，請教一大神，查看系統幫助文檔的 AVMetadataObjectTypes后改變了創建代碼塊-(void)setUpCamera如下；
-(void)setUpCamera { self.device = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo]; self.input = [AVCaptureDeviceInput deviceInputWithDevice:self.device error:nil]; self.outPut = [[AVCaptureMetadataOutput alloc]init]; // self.outPut.metadataObjectTypes = @[AVMetadataObjectTypeQRCode]; // self.outPut.metadataObjectTypes = @[AVMetadataObjectTypeQRCode]; [_outPut setMetadataObjectsDelegate:self queue:dispatch_get_main_queue()]; self.session = [[AVCaptureSession alloc]init]; [self.session setSessionPreset:AVCaptureSessionPresetHigh]; if ([self.session canAddInput:self.input]) { [self.session addInput:self.input]; } if ([self.session canAddOutput:self.outPut]) { [self.session addOutput:self.outPut]; } self.outPut.metadataObjectTypes = [NSArray arrayWithObject:AVMetadataObjectTypeQRCode]; _preview =[AVCaptureVideoPreviewLayer layerWithSession:self.session]; _preview.videoGravity = AVLayerVideoGravityResizeAspectFill; _preview.frame =CGRectMake(20,110,280,280); [self.view.layer insertSublayer:self.preview atIndex:0]; [self.session startRunning]; }
這樣問題就解決了
大神解釋官方文檔的意思大致是：
AVCaptureMetadataOutput類的對象(在本例里是self.outPut),self.outPut的屬性metadataObjectTypes要在AVCaptureSession類對象（本例為self.session)
[self.session addOutput:self.outPut]即添加了AVCaptureMetadataOutput的對象后，方可對其進行設置；