在 viewDidAppear 中无限调用 presentViewController
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【中文标题】在 viewDidAppear 中无限调用 presentViewController【英文标题】:presentViewController called infinitely in viewDidAppear 【发布时间】:2017-12-06 23:47:29 【问题描述】:我正在尝试在我的应用中实现全屏 UIImagePickerController。我无法在viewDidLoad
中显示视图控制器,因为presenting view controllers on detached view controllers is discouraged
。但是,我的viewDidAppear
被无限调用,并且图像选择器控制器被添加,然后在每次调用时从屏幕上掉下来。我尝试分派到主队列,但这并没有解决问题。
- (void)viewDidAppear:(BOOL)animated
[super viewDidAppear:animated];
ipc = [[UIImagePickerController alloc] init];
ipc.delegate = self;
if([UIImagePickerController isSourceTypeAvailable:UIImagePickerControllerSourceTypeCamera])
ipc.sourceType = UIImagePickerControllerSourceTypeCamera;
ipc.showsCameraControls = NO;
CGAffineTransform translate = CGAffineTransformMakeTranslation(0.0, 71.0);
ipc.cameraViewTransform = translate;
CGAffineTransform scale = CGAffineTransformScale(translate, 1.333333, 1.333333);
ipc.cameraViewTransform = scale;
ipc.showsCameraControls = NO;
ipc.tabBarController.tabBar.hidden = YES;
ipc.allowsEditing = NO;
[self presentViewController:ipc animated:YES completion:nil];
#pragma mark - ImagePickerController Delegate
-(void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info
UIImage* theImage = [info objectForKey:UIImagePickerControllerOriginalImage];
if( picker.sourceType == UIImagePickerControllerSourceTypeCamera )
UIImageWriteToSavedPhotosAlbum(theImage, nil, nil, nil);
int height = -1;
if([[NSUserDefaults standardUserDefaults] integerForKey:@"reduce_image"] == 0)
height = 640;
else if ([[NSUserDefaults standardUserDefaults] integerForKey:@"reduce_image"] == 1)
height = 1024;
else
height = 1600;
UIImage* resizedImageForUpload = [UtilityFunctions scaleAndRotateImage:theImage maxResolution:height];
NSData* imageDataForUpload = UIImageJPEGRepresentation(resizedImageForUpload, 1); // reduced image! //
NSString *userDataset = [UtilityFunctions retrieveFromUserDefaults:@"dataset"];
[self didPickImage:imageDataForUpload atLocation:currentLocation
userDataset: userDataset];
[picker dismissViewControllerAnimated:YES completion:nil];
[mLocationManager stopUpdatingLocation];
-(void)imagePickerControllerDidCancel:(UIImagePickerController *)picker
/*navigate to home tab*/
[picker dismissViewControllerAnimated:YES completion:nil];
self.tabBarController.tabBar.hidden = NO;
[self.tabBarController setSelectedIndex:0];
【问题讨论】:
在我看来问题出在代码的其他地方。你在 ipc 的委托方法中做什么? 使用委托方法更新:) 在您的选择器dismissViewControllerAnimated
上设置断点可能会有所帮助。我认为它被意外解雇了。
@mschmidt 你是对的!我关闭了viewWillDisappear
中的图像选择器控制器,这就是让我们进入这个循环的原因!
不相关,但为什么要先创建图像选择器,然后检查源类型是否可用?那是倒退。
【参考方案1】:
您正在关闭图像选择器视图控制器以响应其委托方法被调用,该方法又调用您的 -viewDidAppear:
方法,该方法只是呈现另一个图像选择器视图控制器。您需要以某种方式打破循环,使用您编写的代码,您描述的行为是我所期望的。
一种方法是将ipc
设置为-viewDidLoad
中的UIImagePickerController
实例(仅调用一次),如果它在-viewDidAppear:
中不是nil
,则呈现它,然后nil
它在图像选择器委托方法中显示,下次调用 -viewDidAppear:
时不会重新呈现它。
【讨论】:
在imagePickerControllerDidCancel
和didFinishPickingMediaWithInfo
中取消它?以上是关于在 viewDidAppear 中无限调用 presentViewController的主要内容,如果未能解决你的问题,请参考以下文章
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