I know you can mask an image in ios, but can you mask a scrollview? I'm wanting to alpha mask my scrollview so that the content on the ends appears to fade out before it gets clipped by the scrollview. Is something like this possible?
FYI I have already tried work-arounds that "fake" this effect and they don't work due to a dynamic background. I need strict alpha masking on the scrollview if at all possible.
You can fake this effect by laying over an image with alpha over the end of the scrollview. That way the fading effect stays in place, and the scrollView appears to fade out.
You can do this nicely by using layer masking:
create a mask with the appropriate alpha gradient
add the mask to the table
implement the scroll delegate, to reposition the mask to the current viewport when the table gets scrolled.
It is all explained very well here: http://www.cocoanetics.com/2011/08/adding-fading-gradients-to-uitableview/
Could you implement a footer (or last cell) that has the appropriate alpha fade to give you the effect you are looking for?
Related
The apple official photos application have a edit function which you can crop photos. I would like to implement a similar control for cropping photos. I would like to know how to implement the resizing of the crop mask.
The resizing of the crop mask have the following requirements.
The crop mask can only be resizing by dragging edges or corners.
The anchor point of scaling is opposite the the start edge or corner.
The crop mask can have aspect ratio lock.
The crop mask should not go belong a restricted bounds.
I have done the first 3 requirements, but the 4 requirement is troubling me. Consider a case where the crop mask is at its minimal size at the restricted bounds box bottom left corner. Dragging the top edges will make the view scale with anchor point at the bottom left corner. With this strange behaviour, I think my implementation of changing bounds with opposite anchor point cannot have this behaviour. So I think the apple implementation is different from mine. And I would like to know how these behaviour can be achieved.
The question is what procedure have you even taken.
I would suggest this is done with a simple UIScrollView. Your "crop mask" can be the scroll view which may be resized and repositioned by dragging the corners of it. The scroll view must have the "clip subviews" disabled so you may see the content view outside the scroll view (the content view being the actual image).
So this procedure will already save you all the trouble with bounds when scrolling the image. Moving the scroll view will still have a bit of work... Depending on which corner you are dragging you might need to modify the content offset as you seem to have already figured and should give no trouble at all. Then what is left is putting the image into the crop mask when it gets out of bounds which should be done by calling scroll rect to visible for the whole content view frame; if not it can be easily computed manually as well.
You must also override the hit test method so that the scrolling will happen outside the scroll view.
I wonder what the best way to create a horizontal line is?
I have a few labels / text and I would like to add a horizontal line between them. More or less like a when using twitter bootstrap.
Right now I am using a UIview and setting it as 1 in height with a black background color. But I guess this isnt the best way to do it?
That is the way to do it in iOS. UIView is the class which represent something to be shown on the screen. Every UI component is direct or indirect descendant of UIView. So, you should use UIView.
UIView is backed by CALayer to render the content to screen. You could also use CALayer, CAShapeLayer or other layer classes to create a border. But, I would not recommend to use CALayer just to show a border as it is simpler to use UIView with height of 1, on the top of that, you get some nice addition such as autolayout. If you use CALayer, you will have to set frame to layer at appropriate time when the view bounds change. It could also be tricky due to some intrinsic animation within CALayer.
Okay... so I am getting the hang of iOS, have created a UIView with a combination of widgets (buttons, UITableViews) content and some rendering in drawRect.
The rendering is actually to draw a rounded rectangle within the UIView frame, with circular corners. Then I add this view to my main view.
In the rotation animation, I change the position and aspect ratio of my UIView and called a layout method, and was pleased that it would smoothly change its shape and reposition its contents.... EXCEPT: something odd happens to my rendering... they sort of get squished, and my rounded corners are now elliptical/squished (even though the rendering code always makes circles) like the UIView applies a transform after the drawRect, but does;t re-render.
This is a very surprising effect, can someone give me a hint to what may be going on? I want the rendering to be consistent and sensitive to the current rectangle.
EDIT: Added pictures. The UIView onDraw renders framing and headers, and there are two UITableViews as children. It starts up in portrait mode (figure 1) and looks fine. When the parent view rotates I initiate an animation that changes the sizing of the subview to be suitable to landscape. The sub UITableViews resize fine, but the rendering is now squished (Figure 2).
You need to set the contentMode of your UIView to Redraw
How do you add a simple two color gradient as background to a UICollectionView. It should cover the whole background and stay fixed even when scrolling the collection view (horizontally).
All layer based solutions I tried so far had issues regarding not covering the whole screen and covering only the initially visible frame. Bonus points for being animatable and not using images ... ;)
What's the best way to do this?
An easy and fast solution is to set the background color of the UICollectionView to 'clear' and add another UIView with the gradient behind it.
I have a UIScrollView over an image at the bottom of my app that acts as a dock with icons that can be scrolled through horizontally. Instead of the harsh edges of the UIScrollView, I would like the icons to fade out for a more aesthetically pleasing look. Being new to iOS development, I don't know if either of these would be valid options:
Create a faded image to use as an overlay on the scrollview so the
icons only appear through the visible portion.
Actually change the
alpha of the images based on their distance from the center (or from
each edge).
I suspect the first idea would be the most simple, but I'd like to throw this out there for any other ideas.
Note: I did see this tutorial, however that technique assumes that the background is a solid color. If I were to do it programatically, I would probably need to fade the individual images.
You can definitely implement something along the lines of #2. It'd be something similar to what the tutorial describes. The alpha transition however won't be as smooth as using the gradient layer mentioned in the tutorial or using an image since the entire icon would have the same alpha. How much discernible the difference is depends on the size of your icons. Smaller icons, very few will be able to tell the difference. Larger icons the difference would be quite clear.
You'd have to implement the
(void)scrollViewDidScroll:(UIScrollView *)scrollView
method in your scroll view's delegate class. This method will get called every time the scroll view changes the location of its content. In this method you can call its subviews and adjust their alphas as required. To optimize it a bit instead of calling the alpha adjustments on all the elements you can just update the subviews which are still partially/completely visible.
EDIT: to figure out which views to adjust you'll use the contentOffset property of the scrollView that gets passed as a parameter in the above method.