编辑:有人建议这篇文章是 duplicate ,情况并非如此,因为黑条最初并不存在,仿射变换无法解决该问题。
我在 iPad Air 2 上运行此程序,目标是 iOS 8。
我有一个 UIImagePickerController
,其 showsCameraControls
属性设置为 NO
。当以横向方式启动应用程序然后放大时,会发生以下情况(所有图像均未裁剪):
出现黑条,可以通过将设备方向更改为纵向(这也会显示黑条)然后将其更改回来来消除黑条。
更改为纵向后:
返回横向(+放大):
奇怪的是,返回横向后,缩放 slider 在缩放过程中不再可见。当最初从纵向开始时,首先进行缩放,直到变为横向,此时会出现一个黑条,当返回纵向时,该黑条会保留。
将 showsCameraControls
设置为 YES
时,不会发生这种情况。
我怎样才能摆脱这个问题?
更新:Apple 声称已在 iOS 9 中修复了此问题。
最佳答案
我找到了一种方法来解决由于缺乏更好的理解而标记为错误的问题(苹果提供的示例也会发生这种情况)。
对我来说,解决方案是通过向覆盖 View 添加 UIPinchGestureRecognizer
来进行手动缩放。然后, Controller 必须实现缩放回调,这将消除上述现象。
@implementation CameraViewController
{
CGFloat _lastScale; //< the current zoom scale before update
}
- (void)viewDidLoad
{
[super viewDidLoad];
self.imagePicker = [[UIImagePickerController alloc] init];
self.imagePicker.delegate = self;
self.imagePicker.sourceType = UIImagePickerControllerSourceTypeCamera;
self.imagePicker.allowsEditing = NO;
self.imagePicker.showsCameraControls = NO;
[[NSBundle mainBundle] loadNibNamed:@"CameraOverlay" owner:self options:nil];
UIPinchGestureRecognizer *pinchRec = [[UIPinchGestureRecognizer alloc] initWithTarget:self action:@selector(zoom:)];
[self.overlayView addGestureRecognizer:pinchRec];
self.imagePicker.cameraOverlayView = self.overlayView;
_lastScale = 1.;
}
- (void)zoom:(UIPinchGestureRecognizer *) sender
{
// reset scale when pinch has ended so that future scalings are applied cumulatively and the zoom does not jump back (not sure I understand this)
if([sender state] == UIGestureRecognizerStateEnded)
{
_lastScale = 1.0;
return;
}
CGFloat scale = 1.0 - (_lastScale - sender.scale); // sender.scale gives current distance of fingers compared to initial distance. We want a value to scale the current transform with, so diff between previous scale and new scale is what must be used to stretch the current transform
CGAffineTransform currentTransform = self.imagePicker.cameraViewTransform;
CGAffineTransform newTransform = CGAffineTransformScale (currentTransform, scale, scale); // stretch current transform by amount given by sender
newTransform.a = MAX(newTransform.a, 1.); // it should be impossible to make preview smaller than screen (or initial size)
newTransform.d = MAX(newTransform.d, 1.);
self.imagePicker.cameraViewTransform = newTransform;
_lastScale = sender.scale;
}
@end
关于ios - UIImagePickerController 在缩放时显示黑条 – 这是 iOS 中的错误吗?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/30288950/