drawrect

UIView的layoutSubviews和drawRect

由 只愿长相守 提交于 2019-12-09 12:59:09
UIView的setNeedsDisplay和setNeedsLayout方法。首先两个方法都是 异步 执行的。setNeedsDisplay会调用自动调用drawRect方法，这样可以拿到UIGraphicsGetCurrentContext，就可以画画了。而setNeedsLayout会默认调用layoutSubViews，就可以处理子视图中的一些数据。 综上两个方法都是异步执行的， layoutSubviews方便数据计算，drawRect方便视图重绘 。 先大概看下ios layout机制相关的这几个方法： - (CGSize)sizeThatFits:(CGSize)size - (void)sizeToFit ——————- - (void)layoutSubviews - (void)layoutIfNeeded - (void)setNeedsLayout ——————– - (void)setNeedsDisplay - (void)drawRect 一、 layoutSubviews在以下情况下会被调用： 1、init初始化不会触发layoutSubviews。 2、addSubview会触发layoutSubviews。 3、设置view的Frame会触发layoutSubviews，当然前提是frame的值设置前后发生了变化。 4

IOS中UIView的layoutSubviews和drawRect

由 拈花ヽ惹草 提交于 2019-12-09 12:55:58
UIView的setNeedsDisplay和setNeedsLayout方法。首先两个方法都是 异步 执行的。setNeedsDisplay会调用自动调用drawRect方法，这样可以拿到UIGraphicsGetCurrentContext，就可以画画了。而setNeedsLayout会默认调用layoutSubViews，就可以处理子视图中的一些数据。 综上两个方法都是异步执行的， layoutSubviews方便数据计算，drawRect方便视图重绘 。 先大概看下ios layout机制相关的这几个方法： 1 2 3 - (CGSize)sizeThatFits:(CGSize)size - (void)sizeToFit 1 2 3 4 5 - (void)layoutSubviews - (void)layoutIfNeeded - (void)setNeedsLayout 1 2 3 - (void)setNeedsDisplay - (void)drawRect 一、 layoutSubviews在以下情况下会被调用： 1、init初始化不会触发layoutSubviews。 2、addSubview会触发layoutSubviews。 3、设置view的Frame会触发layoutSubviews，当然前提是frame的值设置前后发生了变化。 4

Why an empty implementation of drawRect: will adversely affect performance during animation

由 梦想与她 提交于 2019-12-09 04:58:56
问题 I am subclassing my UIView class. The Xcode (I am using 4.6.3) auto generated code says, /* // Only override drawRect: if you perform custom drawing. // An empty implementation adversely affects performance during animation. - (void)drawRect:(CGRect)rect { // Drawing code } */ It raised few questions in my mind : 1) Why an empty implementation of drawRect: will cause adverse performance during animation. 2) When should I implement drawRect: . 3) If I am implementing drawRect: then what should

Resizing a rectangle drawn in drawRect

由 牧云@^-^@ 提交于 2019-12-09 03:56:28
问题 I have two UIViews . My aim is to draw the smallest rectangle which contains both these UIView s. I thought to draw a rectangle using the frame which I'll get out of CGRectUnion(view1.frame, view2.frame); But when I move any of the two UIView s, I need to update the frame of the outlining rectangle. I thought I could do this by : 1) Resizing the previously drawn rectangle. (or) 2) Deleting the previously drawn rectangle and drawing a new one. The problem is that, I don't know how to get the

UITabBarItem image created in code doesn’t appear

由 杀马特。学长 韩版系。学妹 提交于 2019-12-08 11:15:00
问题 I create the following View in code, the idea is to use it as an image in UITableViewCell and UITabBarItem : - (void)drawRect:(CGRect)rect { // Fill the background with white CGContextRef context = UIGraphicsGetCurrentContext(); UIColor * whiteColor = [UIColor colorWithRed:1.0 green:1.0 blue:1.0 alpha:1.0]; CGContextSetFillColorWithColor(context, whiteColor.CGColor); CGContextFillRect(context, self.bounds); //// Color Declarations UIColor* fillColor = [UIColor colorWithRed: 1.0 green: 1.0

ViewController and drawRect

由 旧时模样 提交于 2019-12-08 10:12:03
问题 I have a UIViewController and I would like it to call drawRect so i can draw on the view but nothing happens. #import <UIKit/UIKit.h> @interface ViewController : UIViewController { ...code... } @end and the implementation #import "ViewController.h" @implementation ViewController -(void) drawRect:(CGRect) rect { draw a pony } - (void)viewDidLoad { } - (void)didReceiveMemoryWarning { // Releases the view if it doesn't have a superview. [super didReceiveMemoryWarning]; // Release any cached data

Drop Shadow in DrawRect

由 浪尽此生 提交于 2019-12-08 05:38:42
问题 I made this cool pie chart and now I'd like to drop a shadow under it. Is there anyway I can do it with DrawRect ? I'd like to do it right under the pie chart (drawn using DrawRect). Suggestions are welcome 回答1: Have a look at BNPiechart here - http://bynomial.com/blog/?p=104 . The code is open source.You can use it directly.If you do not want to use the library, you can refer the code for creating the shadow. 来源： https://stackoverflow.com/questions/9367727/drop-shadow-in-drawrect

Why is drawRoundRectComplex() not documented in ActionScript?

由 安稳与你 提交于 2019-12-07 14:16:26
问题 In studying actionscript 3's graphics class, I've come across the undocumented drawRoundRectComplex() method. It's a variant of drawRoundRect() but with 8 parameters, the final four being the diameter of each corner (x, y, width, height, top left, top right, bottom left, bottom right). //example var sp:Sprite = new Sprite(); sp.graphics.lineStyle(1, 0x000000); sp.graphics.drawRoundRectComplex(0, 0, 200, 150, 110, 50, 0, 10); addChild(sp); this seems to be a pretty useful method, so i'm just

NSString font size specific to frame width

由 无人久伴 提交于 2019-12-07 11:46:58
问题 I am using drawRect for a text display, calling NSString . I am trying to implement using sizeWithFont to auto resizing font (shrinking) with default font size of 17 and using a loop to reduce the font size by 1 if it does not fit the size of width. Can anyone help me how to implement this? Example would be nice right now I just have the font size set to 17.0 [[self.string displayName] drawAtPoint:CGPointMake(xcoord, ycoord) withFont:[UIFont boldSystemFontOfSize:17.0]]; CGSize size = [[self

iOS 6 view hierarchy nightmare

由 这一生的挚爱 提交于 2019-12-07 06:18:19
问题 I have an app in the app store with nearly 5-star rating, but when iOS 6 came out, some of the views in in the app's main view hierarchy started blinking. This happens on the app that was in the store (I removed it when iOS6 came out) as well as in the simulator. I've spent about 14 hours, trying 100 things, to debug this in Xcode, but can't get any traction on it. Subviews disappear and reappear like there's a gremlin randomly setting the visible property off and on for each of them up to 10
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