having some issues getting my head around resizing UIViews and drawing in drawRect. Currently I am performing some custom drawing in a UIView in the drawRect. Now I want to resize the frame but keep the drawing inside the same. Using a UISlider I have:
- (IBAction)changeSize:(id)sender {
//where 20,20 is the original frame position and 72*72 the original size
CGRect newFrame = CGRectMake(20, 20, 72*self.slider2.value, 72*self.slider2.value);
self.square.frame = newFrame;
}
The frame is growing but the contents inside are also getting stretched with it. What am I doing wrong? Any pointers on this would be great. Thanks
self.contentMode = UIViewContentModeRedraw;
This will cause view to redraw itself when bounds change.
UIView contains a boolean property named autoresizesSubviews. So check out the current value and try setting it to false
self.square.autoresizesSubviews = NO;
Related
I am applying shadow to a UITableViewCell using CALayer.
Here's my code:
- (void)addShadowToView:(UIView *)view
{
// shadow
view.layer.shadowColor = [[UIColor colorWithWhite:0.0f alpha:0.1f] CGColor];
view.layer.shadowOpacity = 1.0f;
view.layer.shadowOffset = CGSizeMake(0.0f, 3.0f);
view.layer.shadowRadius = 6.0f;
CGRect shadowFrame = view.layer.bounds;
CGPathRef shadowPath = [UIBezierPath bezierPathWithRect:shadowFrame].CGPath;
view.layer.shadowPath = shadowPath;
}
The issue is that for some tableviewcells, the shadow does not span the entire width of the cell. For some cells it would be correct, for others it would be faulty. I do notice that the rotation of the device also affects it, and reloading of the tableview data sometimes solves it.
What is the best way to mitigate this issue (and with that I don't mean to reload the whole tableview on each rotation etc.)?
Example bottom of cell where shadow is correctly applied:
Bottom of cell in same tableview after scrolling down (shadow only applied for first 75% of width):
Edit: I have noticed the issue is caused from these lines of code:
CGRect shadowFrame = view.layer.bounds;
CGPathRef shadowPath = [UIBezierPath bezierPathWithRect:shadowFrame].CGPath;
view.layer.shadowPath = shadowPath;
If I leave them out, everything is fine. But I've been told there is certain performance benefit when using this. Somehow the shadow is not correctly applied to new dimensions after rotating..
You can override the setter for you're cell's frame and call addShadowToView:. You can optimize this more by storing your cell's size and only updating the shadow path when the size changes for example:
#property (nonatomic, assign) CGSize size;
And
- (void) setFrame:(CGRect)frame
{
[super setFrame:frame];
// Need to check make sure this subview has been initialized
if(self.subviewThatNeedsShadow != nil && !CGSizeEqualToSize(self.size,_frame.size)
{
[self addShadowToView: self.subviewThatNeedsShadow];
}
}
The easiest solution is to add the shadow to the UITableViewCell's contentView (vs the layer for the cell's backing view). Since the cell's bounds change on scroll, if you add the shadow to the root view then you would have to update the shadow's path on each scroll event which would be costly and not necessary.
You're definitely correct re: the performance hit by not explicitly setting the shadowPath though. If you don't have any animated content within the cell, I'd also recommend rasterizing it to further improve performance.
EDIT: You must also ensure that when you set the shadow path that the contentView's bounds are in their 'final' position. If the size of the cell is later modified, this will result in the contentView's bounds changing and thus an incorrect shadowPath. The solution to this is to update the path in the UITableViewCell's -layoutSubviews method.
Here the concern is not the parent view frame where your working here concern is its sublayer and its size which should be changed when layout changes. You can override the below method which will help you to setup correct frame on layout changing.
public override void LayoutSublayersOfLayer(CALayer layer)
{
base.LayoutSublayersOfLayer(layer);
if (layer.Name == "gradient")
{
layer.Frame = view.Layer.Frame;
}
}
In above code view is the where you added sublayer. If you are playing with multiple layers in same view than you can use the identifier name property to work on particular layer.
Thanks for #beyowulf's answer gave me clues in override UIView frame get and set
In my case, I would like to make shadow stick with the other subview in subclass tableView cell.
Swift 5
// TargetView old size
var lastSize: CGSize = .zero
// Override frame in subclass tableView cell
override var frame: CGRect {
get {
super.frame
}
set {
super.frame = newValue
if targetView != nil {
// Compared targetView size with old one.
if lastSize != targetView.frame.size {
/* Update the other subview's shadow path or layer frame here */
lastSize = targetView.frame.size
}
}
}
}
It works for me.
I know that it works if I change the view's frame via the changing of a layer's transform (in this case it simply takes a view with all the subviews and works with it as if it is a single image). It is not good enough for me to use it because:
It is too hard to calculate the appropriate position;
I use HMLauncherView which has some logic based on frames not
transforms.
I tried a lot of ways described here but it seems they are all for autolayout because none of them works. Depending on the type of the autoresizing mask some elements jump to their destination position and some of them are not affected at all or affected via strange ways.
How to solve such issue? Are there ways to solve this via an autoresizing mask?
EDITED
Animation code (the same result is for setting of center/bounds):
[UIView animateWithDuration:0.3 animations:^{
lastLauncherIcon.layer.transform = CATransform3DIdentity;
CGRect r = self.bounds;
r.origin.y = MAX(0, MIN(self.scrollView.contentOffset.y, self.scrollView.contentSize.height - self.bounds.size.height));
launcherIcon.frame = r;
} completion:^(BOOL finished) {
...
}];
The code of layoutSubviews seems to be extra because I have already tried to subclass UILabel which always jumps to the animation destination position. The investigation showed that the frame of this label is set when I set the view's frame/bounds only. In other cases label's setCenter, setFrame and setBounds are called when you call them directly.
This question is very similar but the suggested solution doesn't work for my case. I also found out I had broken something so the view with transformation doesn't appear on iOS 7.1 (maybe 7.x) but works on 8.3.
In my app that I've been working on for about 6 months now, I've seen a very weird bug in a few places relating to drawing of views. I've built 20+ ios apps, and this is the only project where I've seen anything like this. I must say it has me scratching my head.
Basically a couple of views do not draw until the frame changes, or for a tableview I have, until I scroll it off screen. These views tend to be outside the bounds of their superview that is eventually resized to reveal them (though not always). When the superview is resized the subview is not redrawn.
This happens even with just a simple UITextView in a nib. However, the text view shows up as soon as I scroll the superview which is a UIScrollView (causing a redraw). The bounds/frames are correct and I've checked all views are not hidden and their alpha is 1.0
Is this expected behaviour? Calling setNeedsDisplay and setNeedsLayout does nothing as this just marks the view as needing to be redrawn.
I put together this absolutely terrible hack to force the drawing, and fortunately I only need to use it in about 2 minor places, but I would really love to know what is going on.
This is probably overkill, but I can't waste anymore time on a bug I believe exists in UIView or CALayer.
//Don't use this unless a view really really really really won't draw when it should
- (void)twForceDraw
{
CGAffineTransform transform = self.transform;
CGRect frame = self.frame;
CGRect bounds = self.bounds;
self.transform = CGAffineTransformIdentity;
self.frame = CGRectZero;
self.bounds = CGRectZero;
self.frame = frame;
self.bounds = bounds;
self.transform = transform;
[self setNeedsLayout];
[self setNeedsDisplay];
}
Any thoughts what might be causing this?
I am trying to implement camera zoom using CGAffinetransform. Transform is fine, but when I scale it to a bigger size, it goes out of the frame I have assigned to the AVCaptureVideoPreviewLayer. I tried setting masksToBounds property to YES but it didn't help.
Can I contain it within its frame?
Edit:
What I want is that I can specify a specific area for the camera preview layer, if I apply scaling transform to it, (i.e., frame of preview layer gets expanded), the part of the layer outside of the specified area gets clipped.
You should put the layer you are scaling inside of another layer and mask that one instead (the superlayer). The same thing works with views.
I.e. You have two views / layers: clippingView and scalingView where scalingView is the subview of clippingView and clippingView is the view that actually clips to it's bounds.
[clippingView addSubview:scalingView];
clippingView.clipsToBounds = YES;
or using layers
[clippingLayer addSublayer:scalingLayer];
clippingLayer.masksToBounds = YES;
You guys are all partially right I found but I wanted to clarify.
Lets say we added something like AVCaptureVideoPreviewLayer to the view via [self.view.layer addSublayer:previewLayer]
[self clipsToBounds] does NOTHING until you are telling its primary layer to mask to bounds. [self.view.layer masksToBounds];
Just because your view has a frame and so does its layers DOES NOT MEAN IT HAS BOUNDS. If it doesnt have bounds then there is nothing to mask to. So do this self.view.layer.bounds = self.view.frame;
So heres it all together..keep in mind I did this in my own UIView class so I dont need to call self.view.
previewLayer.bounds = self.frame;
self.layer.bounds = self.frame;
self.layer.masksToBounds = YES;
previewLayer.masksToBounds = YES;
[self setBounds:self.frame];
[self clipsToBounds];
clipsToBounds property of the view to which I am adding the layer should have been set to YES.
I'm trying to move and resize a label, but what happens is the label resizes immediately then moves into position. I first tried simply the commented out lbl.frame line. Next I found this question:
How to animate while resizing UIView
And added all the other code except for the contentMode. This did what I wanted, but the Label's font did not adjust downwards as the label shrunk. ( I tick adjust to fit in xib ). Finally adding the contentMode line gave me the same result as my original frame line - shrink immediately first them animate the move.
lbl.contentMode = UIViewContentModeRedraw;
[UIView animateWithDuration:1.0 delay:0.0
options:(UIViewAnimationOptionAllowUserInteraction)
animations:^{
//lbl.frame = CGRectMake(x, mStartingLine.frame.origin.y+mStartingLine.frame.size.height, 100, 100);
CGRect theBounds = lbl.bounds;
CGPoint theCenter = lbl.center;
theBounds.size.height = 100;
theBounds.size.width = 100;
theCenter.y = mStartingLine.frame.origin.y+mStartingLine.frame.size.height+50;
theCenter.x = x;
lbl.bounds = theBounds;
lbl.center = theCenter;
}
completion:nil
];
I suspect that the auto text resizing feature doesn't work with Core Animation.
What I would suggest doing is to set the label to it's final size (using it's bounds) then apply a transform to it that shrinks it back down to it's starting size. The end effect of those things is that it should stay at the same apparent size.
Finally, use animateWithDuration:animations: to set the view's transform back to the identity transform, so it grows to it's new size.
I don't know what drawing artifacts this will cause - you'll have to try it.