This tutorial shows how to draw on a graphics context for the view using Quartz 2D:
http://www.techotopia.com/index.php/An_iPhone_Graphics_Drawing_Tutorial_using_Quartz_2D
But I want to draw on a UIButton, not on a view. How can I do that?
Thanks
Draw on UIView . Add the view as subview to your UIButton.
A button IS a UIView. It inherits from UIControl, which inherits from UIView.
So buttons have a drawRect method.
So you can do everything described in the article you linked on a button.
However, buttons are set up to do a lot of things for you, and overriding the drawRect method could make those things not work correctly.
Buttons normally draw a title and a rounded rectangle frame. You can turn that off by setting the button's type to custom.
Custom buttons will draw an image if you install one.
Buttons normally also either draw a highlight over their image, or have a second image to use for the highlighted state. If you want to implement drawRect, you'll need to handle drawing the highlighted state yourself.
In general, you want to avoid using drawRect and use some other technique to get the content you want into your views.
What, exactly, are you trying to do?
Related
I'd like to have a UIView where the user can select each of the four corners and stretch the view by independently moving them.
How would I implement such a view?
To do this, you will need to subclass UIView and handle touch events manually. When you get a touch event, you will have to do some math and then set the frame of the view to the new size. I'd recommend making the background image a stretchable image using stretchableImageWithLeftCap:topCap. It shouldn't actually be that hard.
So I made a UIView subclass let's called it 'MyView' that simply draws a line inside the DrawRect method.
I then drag a UIImageView in interface builder and put it inside MyView. But now when I run the program it's obscuring the line that I'm drawing. I'm wondering, is there a way for me to draw the line on top of the image that I have dragged into my View?
No, you'll have to reorganise the view hierarchy. CoreGraphics uses a painters model so views behind will always be drawn over by views infront. To solve this you could use a container view that holds your image view and has a transparent view (line drawing view) that sits over the image view.
Another option is to draw the image using core graphics calls in your drawRect method and then draw the line over it.
One way is to have whatever adds MyView to add your UIImageView on top of MyView. It's not ideal (you probably have good reasons for keeping MyView and the UIImageView in a single class) but definitely solves your problem (I recently did this, only, I added it to the keyWindow =)
I would use a CAShapeLayer that has a path representing the line, and insert that layer ahead of the built-in view layer. Then it should draw on top.
What's the UI element that is top of that number buttons to display number ? (which is in light blue color)
It looks like a UINavigationBar with a prompt. However, the location of the gloss (which differs from your typical UINavigationBar) and the centering of the numbers (not shown) makes me think it is a custom view.
If you're trying to replicate it, I'd suggest starting with a UIView. Add a UIImageView with appropriate image for the the blue background and a UILabel for the text. Or, instead of the UIImageView, you could draw the background in the UIView's drawRect: method.
I am working on iPhone application development and have come across shadows of UIView.
I know how to show shadows to a UIView but what I am actually interested in is to drop shadow inside the UIView.
Like when I set shadow properties of a UIView the shadow is dropped behind the view. I want it to come over the view so that the view looks as if it is pressed inside.
Example of such view is UITextField with roundedRect styling.
Thanks,
It depends a lot on the final effect you want to achieve.
The easies way would be a custom image with a prebacked shadow as background. This will give the illusion of a recession in the surface of the view. You can then add subviews to it as usual.
Alternatively, you can override the drawRect: method and draw the view as you like there, "inverted drop shadow" included.
I've created a NIB file with some button controls on it, and as a background it has an ImageView which contains a PNG file loaded from my project.
What I want to do is to draw on top of the ImageView - imagine that my UI is a clockface and I want to draw the hands of the clock on top of the background image.
Is it the correct approach to try to subclass the UIImageView and use its DrawRect as when I use the DrawRect of the default view I don't see anything on the screen?
I'm a little lost as I'm finding this particular bit of the documentation hard to follow.
Thanks.
Create a new custom UIView (e.g. named HandsView) that sits on top of your background view (by adding it as a subview of the UIImageView). In the custom view, you can use the drawRect method. Make sure, you clear the context to transparent, so that the background image can be seen below the HandsView.
If you just want to draw turning hands, you can also try to use two fixed UIImageViews with the images of the hands and use the transform property to apply a rotation.