Is there a way for Interface Builder to render IBDesignable views which don't override drawRect:
Objective CXcodeSwiftInterface BuilderObjective C Problem Overview
I very rarely override drawRect in my UIView subclasses, usually preferring to set layer.contents
with pre-rendering images and often employing multiple sublayers or subviews and manipulating these based on input parameters. Is there a way for IB to render these more complex view stacks?
Objective C Solutions
Solution 1 - Objective C
Thanks, @zisoft for the clueing me in on prepareForInterfaceBuilder
. There a few nuances with Interface Builder's render cycle which were the source of my issues and are worth noting...
- Confirmed: You don't need to use
-drawRect
.
Setting images on UIButton control states works. Arbitrary layer stacks seem to work if a few things are kept in mind...
- IB uses
initWithFrame:
..not initWithCoder
. awakeFromNib
is also NOT called.
init...
is only called once per session
I.e. once per re-compile whenever you make a change in the file. When you change IBInspectable properties, init is NOT called again. However...
prepareForInterfaceBuilder
is called on every property change
It's like having KVO on all your IBInspectables as well as other built-in properties. You can test this yourself by having the your _setup
method called, first only from your init..
method. Changing an IBInspectable will have no effect. Then add the call as well to prepareForInterfaceBuilder
. Whahla! Note, your runtime code will probably need some additional KVO since it won't be calling the prepareForIB
method. More on this below...
init...
is too soon to draw, set layer content, etc.
At least with my UIButton
subclass, calling [self setImage:img forState:UIControlStateNormal]
has no effect in IB. You need to call it from prepareForInterfaceBuilder
or via a KVO hook.
- When IB fails to render, it doesn't blank our your component but rather keeps the last successful version.
Can be confusing at times when you are making changes that have no effect. Check the build logs.
Tip: Keep Activity Monitor nearby
I get hangs all the time on a couple different support processes and they take the whole machine down with them. Apply Force Quit
liberally.
(UPDATE: This hasn't really been true since XCode6 came out of beta. It seldom hangs anymore)
UPDATE
- 6.3.1 seems to not like KVO in the IB version. Now you seem to need a flag to catch Interface Builder and not set up the KVOs. This is ok as the
prepareForInterfaceBuilder
method effectively KVOs all theIBInspectable
properties. It's unfortunate that this behaviour isn't mirrored somehow at runtime thus requiring the manual KVO. See the updated sample code below.
UIButton subclass example
Below is some example code of a working IBDesignable UIButton
subclass. Note, UPDATE: See point 8 above.prepareForInterfaceBuilder
isn't actually required as KVO listens for changes to our relevant properties and triggers a redraw.
IB_DESIGNABLE
@interface SBR_InstrumentLeftHUDBigButton : UIButton
@property (nonatomic, strong) IBInspectable NSString *topText;
@property (nonatomic) IBInspectable CGFloat topTextSize;
@property (nonatomic, strong) IBInspectable NSString *bottomText;
@property (nonatomic) IBInspectable CGFloat bottomTextSize;
@property (nonatomic, strong) IBInspectable UIColor *borderColor;
@property (nonatomic, strong) IBInspectable UIColor *textColor;
@end
@implementation HUDBigButton
{
BOOL _isInterfaceBuilder;
}
- (id)initWithCoder:(NSCoder *)aDecoder
{
self = [super initWithCoder:aDecoder];
if (self) {
[self _setup];
}
return self;
}
//---------------------------------------------------------------------
- (id)initWithFrame:(CGRect)frame
{
self = [super initWithFrame:frame];
if (self) {
[self _setup];
}
return self;
}
//---------------------------------------------------------------------
- (void)_setup
{
// Defaults.
_topTextSize = 11.5;
_bottomTextSize = 18;
_borderColor = UIColor.whiteColor;
_textColor = UIColor.whiteColor;
}
//---------------------------------------------------------------------
- (void)prepareForInterfaceBuilder
{
[super prepareForInterfaceBuilder];
_isInterfaceBuilder = YES;
[self _render];
}
//---------------------------------------------------------------------
- (void)awakeFromNib
{
[super awakeFromNib];
if (!_isInterfaceBuilder) { // shouldn't be required but jic...
// KVO to update the visuals
@weakify(self);
[self
bk_addObserverForKeyPaths:@[@"topText",
@"topTextSize",
@"bottomText",
@"bottomTextSize",
@"borderColor",
@"textColor"]
task:^(id obj, NSDictionary *keyPath) {
@strongify(self);
[self _render];
}];
}
}
//---------------------------------------------------------------------
- (void)dealloc
{
if (!_isInterfaceBuilder) {
[self bk_removeAllBlockObservers];
}
}
//---------------------------------------------------------------------
- (void)_render
{
UIImage *img = [SBR_Drawing imageOfHUDButtonWithFrame:self.bounds
edgeColor:_borderColor
buttonTextColor:_textColor
topText:_topText
topTextSize:_topTextSize
bottomText:_bottomText
bottomTextSize:_bottomTextSize];
[self setImage:img forState:UIControlStateNormal];
}
@end
Solution 2 - Objective C
This answer is related to overriding drawRect, but maybe it can give some ideas:
I have a custom UIView class which has complex drawings in drawRect. You have to take care about references which are not available during design time, i.e. UIApplication. For that, I override prepareForInterfaceBuilder
where I set a boolean flag which I use in drawRect to distinguish between runtime and design time:
@IBDesignable class myView: UIView {
// Flag for InterfaceBuilder
var isInterfaceBuilder: Bool = false
override init(frame: CGRect) {
super.init(frame: frame)
// Initialization code
}
required init(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
}
override func prepareForInterfaceBuilder() {
self.isInterfaceBuilder = true
}
override func drawRect(rect: CGRect)
{
// rounded cornders
self.layer.cornerRadius = 10
self.layer.masksToBounds = true
// your drawing stuff here
if !self.isInterfaceBuilder {
// code for runtime
...
}
}
}
An here is how it looks in InterfaceBuilder:
Solution 3 - Objective C
You do not have to use drawRect, instead you can create your custom interface in a xib file, load it in initWithCoder and initWithFrame and it will be live rendering in IB after adding IBDesignable. Check this short tutorial: https://www.youtube.com/watch?v=L97MdpaF3Xg
Solution 4 - Objective C
I think layoutSubviews is the simplest mechanism.
Here is a (much) simpler example in Swift:
@IBDesignable
class LiveLayers : UIView {
var circle:UIBezierPath {
return UIBezierPath(ovalInRect: self.bounds)
}
var newLayer:CAShapeLayer {
let shape = CAShapeLayer()
self.layer.addSublayer(shape)
return shape
}
lazy var myLayer:CAShapeLayer = self.newLayer
// IBInspectable proeprties here...
@IBInspectable var pathLength:CGFloat = 0.0 { didSet {
self.setNeedsLayout()
}}
override func layoutSubviews() {
myLayer.frame = self.bounds // etc
myLayer.path = self.circle.CGPath
myLayer.strokeEnd = self.pathLength
}
}
I haven't tested this snippet, but have used patterns like this before. Note the use of the lazy property delegating to a computed property to simplify initial configuration.
Solution 5 - Objective C
To elaborate upon Hari Karam Singh's answer, this slideshow explains further:
http://www.splinter.com.au/presentations/ibdesignable/
Then if you aren't seeing your changes show up in Interface Builder, try these menus:
- Xcode->Editor->Automatically Refresh Views
- Xcode->Editor->Refresh All Views
- Xcode->Editor->Debug Selected Views
Unfortunately, debugging my view froze Xcode, but it should work for small projects (YMMV).
Solution 6 - Objective C
In my case, there were two problems:
-
I did not implement
initWithFrame
in custom view: (UsuallyinitWithCoder:
is called when you initialize via IB, but for some reasoninitWithFrame:
is needed forIBDesignable
only. Is not called during runtime when you implement via IB) -
My custom view's nib was loading from
mainBundle
:[NSBundle bundleForClass:[self class]]
was needed.
Solution 7 - Objective C
I believe you can implement prepareForInterfaceBuilder
and do your core animation work in there to get it to show up in IB.
I've done some fancy things with subclasses of UIButton that do their own core animation layer work to draw borders or backgrounds, and they live render in interface builder just fine, so i imagine if you're subclassing UIView directly, then prepareForInterfaceBuilder
is all you'll need to do differently. Keep in mind though that the method is only ever executed by IB
Edited to include code as requested
I have something similar to, but not exactly like this (sorry I can't give you what I really do, but it's a work thing)
class BorderButton: UIButton {
required init(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
commonInit()
}
override init(frame: CGRect) {
super.init(frame: frame)
commonInit()
}
func commonInit(){
layer.borderWidth = 1
layer.borderColor = self.tintColor?.CGColor
layer.cornerRadius = 5
}
override func tintColorDidChange() {
layer.borderColor = self.tintColor?.CGColor
}
override var highlighted: Bool {
willSet {
if(newValue){
layer.backgroundColor = UIColor(white: 100, alpha: 1).CGColor
} else {
layer.backgroundColor = UIColor.clearColor().CGColor
}
}
}
}
I override both initWithCoder
and initWithFrame
because I want to be able to use the component in code or in IB (and as other answers state, you have to implement initWithFrame
to make IB happy.
Then in commonInit
I set up the core animation stuff to draw a border and make it pretty.
I also implement a willSet
for the highlighted variable to change the background color because I hate when buttons draw borders, but don't provide feedback when pressed (i hate it when the pressed button looks like the unpressed button)
Solution 8 - Objective C
Swift 3 macro
#if TARGET_INTERFACE_BUILDER
#else
#endif
and class with function which is called when IB renders storyboard
@IBDesignable
class CustomView: UIView
{
@IBInspectable
public var isCool: Bool = true {
didSet {
#if TARGET_INTERFACE_BUILDER
#else
#endif
}
}
override func prepareForInterfaceBuilder() {
// code
}
}
IBInspectable can be used with types below
Int, CGFloat, Double, String, Bool, CGPoint, CGSize, CGRect, UIColor, UIImage