I just noticed something weird in the UIView's class reference. Under alpha it states:
This value affects only the current view and does not affect any of its embedded subviews.
But as you most certainly know, that is not the case. If you change the alpha of a superview all subviews also apply the new alpha.
Is it a mistake in the documentation or am I misunderstanding it?
This value affects only the current view and does not affect any of its embedded subviews.
I understand this as:
Changing the alpha value on a view will not change the alpha value on any subviews. As in, whilst the subviews will appear to have changed their alpha, their .alpha property value will not change when the superview's .alpha is changed.
Related
I have two UITableViews. One of the tables is working fine but the UILabels in the other table is blurry. I have tried changing their color programmatically. It can change the color ex: black to green but the blurry issue still remains.
This is my hierarchy of this particular view
How can I make the text clear like the first table?
You might have changed the alpha value of any of the superviews of UITableView. If you changed a view's alpha value, it affects all the subview's alpha
Set shouldRasterize = false on the CGLayer of the view containing the UILabel.
And
Your label is blurry because the frame is using floating numbers.
To force integers value for your frame just do :
[loadingText setFrame:CGRectIntegral(loadingText.frame)];
Is it possible in some way to receive and respond to touch events from a UIView that is not visible. I tried -- as well as read from the Apple docs -- that simply setting 'hidden' will not work. I'm looking for an alternative to achieve the same effect.
A hidden view disappears from its window and does not receive input events. It remains in its superview’s list of subviews, however, and participates in autoresizing as usual. Hiding a view with subviews has the effect of hiding those subviews and any view descendants they might have. This effect is implicit and does not alter the hidden state of the receiver’s descendants.
if a view has set userInteractionEnabled to YES it will be touchable when hidden. Try to experiment with UIButton for example.
Make it transparent, not hidden (with alpha set to 0). If that doesn't work, make it nearly transparent (alpha set to 0.1).
I have a viewController with three subviews.
Also I use AutoLayout and size classes.
These views are animated and change location and size.
After the animations I update a label but the whole view is redrawn so each view is in their initial position and size. This shouldn't happen.
As in Apple developer reference that says:
"The default content mode of the UILabel class is
UIViewContentModeRedraw. This mode causes the view to redraw its
contents every time its bounding rectangle changes. You can change
this mode by modifying the inherited contentMode property of the
class."
It doesn't seem clear to me how to modify the -contentMode- in order to update that label and leave the view -as is-. Can anyone give me a clue?
Thanks in advance.
It sounds like you may be using autolayout to lay out your view (e.g., via constraints in IB), but then you're manipulating your views' frames directly for your animations - is this the case? If so, you should instead be animating the constant values of your constraints, or possibly the transforms of your subviews.
If you manipulate frames directly in a view which uses autolayout, your changes will be over-written the next time the system lays out your view (e.g. after a label's text changes).
You have 3 options to overcome your issue -
Stop using AutoLayout in your Storyboard/Xib.
Not a great solution
Animate changes to the transform property of your subviews. e.g. myView.transform = CGAffineTransformMakeScale(2.0,2.0);
Useful for presentation and dismissal animations, but mixing AutoLayout and transforms has some issues pre-iOS 8.0
Add IBOutlets for the constraints you need to change in your animations. Animate changes to the constant values of those constraints.
Most robust approach but can lead to a lot of properties and code for complex animations
Try contentMode = UIViewContentModeCenter. This should prevent the redraw you're seeing. Although that may not be the contentMode you want.
Option 2 is to use CATextLayer to draw the label. It will resize very nicely with animation, but it's a lot more work to set up.
I'm having trouble figuring out how much I can adjust the imageView property of a UIButton. In the docs, it says:
Although this property is read-only, its own properties are read/write. Use these properties to configure the appearance and behavior of the button’s view.
I'm hoping to perform a transition where I shrink the size of the button in an animation, and I'd like the button's image to also shrink accordingly. However, I find that I have no control over the size of that image. If I modify either the frame or the bounds of UIButton's imageView property, nothing seems to happen. The image seems to want to retain it's standard dimensions. Changing autolayout properties on the imageView or contentMode properties on the button don't seem to help either.
In fact, the only thing that seems to work at all is to use UIEdgeInsetsMake to "squish" the image from all sides, but that isn't animatable.
I'd prefer not to use the backgroundImage property either, since I'm already using that to style the button in the first place.
You could add an own UIImageView as subview to the UIButton instead of using the "embedded" imageView.
You can set the frame of "your" image view as usually relative to the surrounding UIButton. You will have full control on it's position and you will also be able to animate it.
In my example, I have 3 views: one red view containing two white views. I change the red container view's alpha to 0.3 and this happens (look at the image, the current result).
By seeing this, I can only assume (tell me if I'm wrong) that setting a view's alpha will also set all of its subviews' alphas. My question is : is there a way to simply tell the red view to act as a whole so that setting its alpha would give something that looks like the wanted result (in the image)?
This is what it looks like without any alpha :
To elaborate on Mark's answer: If you set UIViewGroupOpacity in the Info.plist, it will change the behavior for all views in your app, if you are interested in only fixing the rendering of this particular view, you could also use this snippet:
redContainerView.layer.shouldRasterize = YES;
// No setting rasterizationScale, will cause blurry images on retina.
redContainerView.layer.rasterizationScale = [[UIScreen mainScreen] scale];
The iOS alpha property is inherited by its subviews. If we are setting alpha 0.3 for red view then both subview will have the alpha = 0.3. There is no way to stop subviews from inheriting their alpha value from their superview.
The solution might be to set the colour of the red view with an alpha of 0.3. The color property will not be inherited by its subview.
[redView setBackgroundColor:[UIColor colorWithHue:238.0f/255.0f saturation:24.0f/255.0f brightness:24.0f/255.0f alpha:0.3]];
Check out the possible UIKit keys for Info.plist, specifically UIViewGroupOpacity.
UIViewGroupOpacity (Boolean - iOS) specifies whether Core Animation
sublayers inherit the opacity of their superlayer.
Info.plist UIKit Keys