UIImagePickerController在缩放时显示黑条 - 这是iOS中的错误吗？

Question

修改：有人建议此帖子是duplicate，但事实并非如此，因为黑条最初不存在，仿射转换无法解决问题问题。

我在iPad Air 2上运行它，目标是iOS 8。 我有一个UIImagePickerController，其showsCameraControls属性设置为NO。在横向启动应用程序然后放大时，会发生这种情况（所有图像都是非裁剪的）：

出现一个黑条，可以通过将设备方向更改为纵向（也将显示黑条）然后将其更改回来来消除。

更改为肖像后：

返回风景（+放大）：

奇怪的是，在返回横向后，缩放滑块在缩放过程中不再可见。最初从纵向开始时，首先进行缩放，直到其中一个变为横向，其中出现黑条，当回到纵向时，它会停留。

将showsCameraControls设置为YES时，不会发生这种情况。 我该怎样摆脱这个问题？

更新：Apple声称已在iOS 9中解决此问题。

Answer 1

我找到了一种解决我缺乏更好理解的方法来标记错误的方法（就像苹果提供的样本一样）。

我的解决方案是通过向叠加视图添加UIPinchGestureRecognizer来手动缩放。然后，Controller必须实现缩放回调，以消除上述现象。

@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