how to draw Arc in viewdidload method in iPhone - iphone

i try to draw arc in view i use this code.
- (void)viewDidLoad
{
[super viewDidLoad];
CGRect rect = CGRectMake(0,0,340,480);
UIView *ui = [[UIView alloc] initWithFrame:rect];
[self.view addSubview:ui];
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextAddArc(context, 50, 50, 20, 0, 30, 0);
//set the fill or stroke color
CGContextSetRGBFillColor(context, 0.5, 0.5, 0.5, 1.0);
CGContextSetRGBStrokeColor(context, 0.5, 0.5, 0.5, 1.0);
//fill or draw the path
CGContextDrawPath(context, kCGPathStroke);
CGContextDrawPath(context, kCGPathFill);
}
if possible to draw arc in viewdidload method kindly guide me.

Your views should be drawing when requested (e.g. in drawRect:), rather than your view controllers drawing when loaded.
So what you may want to try is creating a UIView subclass and moving the drawing code to its drawRect:.
Very briefly:
#interface MONView : UIView
#end
#implementation MONView
- (void)drawRect:(CGRect)frame
{
CGContextRef context = UIGraphicsGetCurrentContext();
<-- now draw here -->
}
#end
- (void)viewDidLoad
{
[super viewDidLoad];
CGRect rect = CGRectMake(0,0,340,480);
UIView * ui = [[MONView alloc] initWithFrame:rect];
[self.view addSubview:ui];
[ui release];
}

It is not possible to draw an arc in view Did Load.
What you need to do is:-
1.)Add a file of type UIView(lets say ArcView.h and ArcView.m)in your project
2.)In ArcView.m file implement - (void)drawRect:(CGRect)rect method
3.)In this method you need to write your logic of drawing an arc or whatever you want to draw)
4.)Now the ViewController in which you have to show your arc lets say(ArcViewController is the file in which you want to show your arc)
5.)In ArcViewController.m file you need to do following steps:-
a.)#import "ArcView.h"
b.)Whenever you want to show your arc view do:-
ArcView *vw = [[ArcView alloc] initWithFrame:*your required frame where you want to show arc*];
vw.backgroundColor=[UIColor redColor];
[self.view addSubview:vw];
[vw release];
After that you will see your arc coming on your screen.

Related

Getting the CGContextRef from a subview

I'm using UIGraphicsGetCurrentContext() to create a gradient background for a UI element, but I guess I misunderstood where the drawing was taking place. I wanted the drawing to take place on a subview, but instead it's happening in the view itself.
I think the problem is that when I use UIGraphicsGetCurrentContext(), I'm getting a CGContextRef of the view, so that's where the drawing is taking place. What I want to do is have the drawing take place on the subview, so that I can fade it in and out with other related subviews. Can this be done, or do I need to create another UIView subclass just for the background layer?
Here's a simplification of the code I'm using and my goal is to be able to fade in and out the background gradient in topBar while leaving the InterfaceControlsView view visible.
#implementation InterfaceControlsView
- (id)initWithFrame:(CGRect)frame
{
topBar = [[UIView alloc] initWithFrame:CGRectMake(0.0, 20.0, self.frame.size.width, 45.0)];
/* etc. */
}
- (void)drawRect:(CGRect)rect {
CGContextRef context = UIGraphicsGetCurrentContext();
CGRect rect = topBar.frame; // topBar is a subview
CGContextSaveGState(context);
CGContextAddRect(context, rect);
CGContextClip(context);
CGContextDrawLinearGradient(context, gradient, startPoint, endPoint, 0);
CGContextRestoreGState(context);
/* etc. */
}
#end
To create gradient bg for subviews, you dont need to create subclass, use gradiant layers.
Hope this helps
CALayer *layer = _button.layer;
layer.borderWidth = 1.0f;
layer.borderColor = [UIColor lightGrayColor].CGColor;
CAGradientLayer *gLayer = [CAGradientLayer layer];
[gLayer setName:#"gradient"];
gLayer.frame = layer.bounds;
gLayer.colors = [NSArray arrayWithObjects:
(id)[UIColor colorWithRed:26.0/255.0 green:94.0/255.0 blue:74.0/255.0 alpha:1.0].CGColor,
(id)[UIColor colorWithRed:23.0/255.0 green:59.0/255.0 blue:37.0/255.0 alpha:1.0].CGColor,
nil];
[layer addSublayer:gLayer];

Adding shadow to a UINavigationControllerer

I'm trying to add shadow to a UINavigationController. My have is based on NavController and i'm trying to add a shadow like in game centers. I have this so far. It works n a UINavigationnBar but i'm trying to get it to work throughout the entire app.
CGColorRef darkColor = [[UIColor blackColor] colorWithAlphaComponent:.5f].CGColor;
CGColorRef lightColor = [UIColor clearColor].CGColor;
CAGradientLayer *newShadow = [[[CAGradientLayer alloc] init] autorelease];
newShadow.frame = CGRectMake(0, 44, 320, 10);
newShadow.colors = [NSArray arrayWithObjects:(id)darkColor, (id)lightColor, nil];
CALayer *superlayer = self.newShadow.superlayer;
[self.newShadow removeFromSuperlayer];
[superlayer addSublayer:self.newShadow];
[self.navigationBar.layer addSublayer:superlayer];
It works directly on a UINavigationBar but applying to a NavigationController project it fails. It builds but won't add the shadow. Any ideas?
EDIT:
I have been trying different approaches to this. I successfully created the gradient by using a shape.
#implementation UINavigationBar (UINavigationBarCategory)
- (void)drawRect:(CGRect)rect {
UIImage *backgroundImage;
backgroundImage = [UIImage imageNamed:#"nav.png"];
[backgroundImage drawInRect:CGRectMake(0, 0, self.frame.size.width, self.frame.size.height)];
CGContextRef context = UIGraphicsGetCurrentContext();
CGColorSpaceRef myColorspace = CGColorSpaceCreateDeviceRGB();
size_t num_locations = 2;
CGFloat locations[2] = { 1.0, 0.0 };
CGFloat components[8] = { 1.0, 1.0, 1.0, 1.0, 0.0, 0.0, 0.0, 0.5 };
CGGradientRef myGradient = CGGradientCreateWithColorComponents(myColorspace, components, locations, num_locations);
CGPoint myStartPoint, myEndPoint;
myStartPoint.x = 0.0;
myStartPoint.y = 0.0;
myEndPoint.x = 0.0;
myEndPoint.y = 54.0;
CGContextDrawLinearGradient (context, myGradient, myStartPoint, myEndPoint, 1);
}
I can't get the gradient below the UINavigationBar and its overlaying the image. I can't seem to get this to work. What i'm trying to do is add the same shadow Game Center has. I have tried a few different ways. All I need to do here is get this to lie underneath the UINavigationBar allowing the image to be on top and have a little part of the shadow lie on top on the UITableView so when you scroll up its above the UITableView. If you fire up Game Center you'll see exactly what i'm talking about.
I believe you should add it to the
UINavigationController.view.layer
As the UINavigationController he is not a UIView child.
if already you did so, an other way to effect the navigationbar, consistently all over the app is to use the UINavigationBarCategory:
you sould pace this at the end of your delegate - after the #end
#implementation UINavigationBar (UINavigationBarCategory)
- (void)drawRect:(CGRect)rect {
//implement your design
}
#end
EDIT
in this link you can find basic info on how to draw the bar:
An iPhone Graphics Drawing Tutorial using Quartz 2D
and here you can find how to add a shadow:adding shadow with quartz 2d
Good luck
You could subclass UIView and use your existing code to draw the shadow by overriding -drawRect:. Then wherever its needed, create it and add it to the view of the navigation controller.
Consider this example
CGFloat screenWidth = [UIScreen mainScreen].applicationFrame.size.width;
ShadowView *shadowView = [[ShadowView alloc] initWithFrame:CGRectMake(0.0f, 0.0f, screenWidth, 20.0f)];
[self.navigationController.view insertSubview:shadowView atIndex:0];
By adding it to the view of the navigationController at index 0, you're effectively overlaying it on top of whatever the view controller is displaying. You could further improve this by checking for the scale of the main screen to appropriately calculate the height of the shadow view so that it will appear correctly on all devices regardless of having a retina display.

drawRect: isn't working

I want to place some "handles" on a UIView I have on-screen.
So, I'm creating more UIViews, one at each corner of the UIView's frame rectangle, and I simply want to draw a circle that "fills" the rectangle that is the frame of the "handle" UIView.
Here's what I mean:
How I create the "HandleView":
CGPoint upperLeft = CGPointMake([[self viewToMove] frame].origin.x - 5, [[self viewToMove] frame].origin.y - 5);
HandleView *uL = [[HandleView alloc] initWithFrame:CGRectMake(upperLeft.x, upperLeft.y, 10, 10)];
[self setUpperLeftHandle:uL];
[uL release];
[[self view] addSubview:[self upperLeftHandle]];
drawRect: for HandleView:
- (void)drawRect:(CGRect)rect {
// Drawing code
CGContextRef context = UIGraphicsGetCurrentContext();
[[UIColor orangeColor] set];
CGContextFillEllipseInRect(context, [self frame]);
}
What I'm getting is just a set of black rectangles where I place the HandleViews. I'm not sure why they're black, but I can change the color by changing the [HandleView backgroundColor] property. I cannot, though, get anything to DRAW on this view. Calling setNeedsDisplay doesn't seem to make any difference.
Also, the drawRect: method IS being called, so there's a problem with the code there, probably not anywhere else.
It's been a while since I've messed with custom drawing, but I don't remember it being this hard.
What am I missing?
Thanks!!!
Update:
Modified code to this:
- (id)initWithFrame:(CGRect)frame {
if ((self = [super initWithFrame:frame])) {
// Initialization code
[self setBackgroundColor:[UIColor clearColor]];
}
return self;
}
- (void)drawRect:(CGRect)rect {
// Drawing code
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSetRGBFillColor(context, 100, 100, 100, 1.0);
CGContextFillEllipseInRect(context, rect);
}
Now, I see the circle, but only where it overlays another view. Where it's just sitting on top of the "background" UIView, I get nothing I can see. Also, even though the color is (100, 100, 100), it shows up white/light-light-gray.
What's the deal?
This might work:
- (void)drawRect:(CGRect)rect {
// Drawing code
[[UIColor orangeColor] setFill];
[[UIBezierPath bezierPathWithOvalInRect:rect] fill];
}
The problem is with the following line:
CGContextFillEllipseInRect(context, [self frame]);
You need to change this to the following:
CGContextFillEllipseInRect(context, [self bounds]);
Origin of frame is the left-top corner location of view in the parent. So, it can be any value within the limits of the size of parent view.
So, while drawing with frame, you will be offsetting Fillellipse rect location which happens to be beyond the visible rect of the handle view.
Hence, you were not able to see anything.
As for the color showing up as white, it's because CGContextSetRGBFillColor() expects values from 0.0 to 1.0 for the color component values (not 0-255). So, by passing 100, you were effectively passing 1.0, which was creating a white color.

Draw Line in View : Not Drawing

I am trying to draw a line
my Code is this
-(void) drawRect:(CGRect) rect
{
NSLog(#"Reached Draw ARect Function");
CGContextRef ctx = UIGraphicsGetCurrentContext();
CGContextSetLineWidth(ctx, 2.0);
CGContextSetRGBStrokeColor(ctx, 1.0, 2.0, 0, 1);
CGContextMoveToPoint(ctx, 0, 0);
CGContextAddLineToPoint( ctx, 100,100);
CGContextStrokePath(ctx);
}
and i am calling from the viewDidLoad as follows
- (void)viewDidLoad {
[super viewDidLoad];
CGRect k = CGRectMake(1.0, 1.0, 100.0, 200.0);
[self.view drawRect:k];
}
Can any one help me please?
You should subclass a UIView and move your line drawing code to the drawRect: method, like you are doing (just hoping it's for a UIView subclass and not the UIViewController)
- (void)drawRect:(CGRect)rect {
[super drawRect:rect];
// Place your code here
}
You must also make sure you use the UIView subclass in InterfaceBuilder for the view you will be drawing into. You should not have to call this method yourself. If you want to animate something you should call the [view setNeedsDisplay]; to request a redraw of the view.
...and...you should add CGContextBeginPath(ctx); just before you call CGContextMoveToPoint
You can't call drawRect directly.
Instead you call setNeedsDisplay on your UIView, return, and wait for the OS to call the UIView's drawRect with a proper context at some later time.
If there is a need to call
- (void)drawRect:(CGRect)rect
method dynamically while user is dragging a particular view, just place the following code:
[self.view setNeedsDisplay];
then
- (void)drawRect:(CGRect)rect
method will automatically be called

How to make a subview tint a portion of the screen on the iPhone?

I would like to write a UIView subclass that, among other things, colors whatever's underneath it a certain color. This is what I've come up with, but it unfortunately doesn't seem to work correctly:
#import <UIKit/UIKit.h>
#class MyOtherView;
#interface MyView : UIView
{
MyOtherView *subview;
}
#end
#implementation MyView
- (id)initWithFrame:(CGRect)frame
{
if (self = [super initWithFrame:frame]) {
frame.origin.x += 100.0;
frame.origin.y += 100.0;
frame.size.width = frame.size.height = 200.0;
subview = [[MyOtherView alloc] initWithFrame:frame];
[self addSubview:subview];
[subview release];
}
return self;
}
- (void)drawRect:(CGRect)rect
{
// Draw a background to test out on
UIImage *image = [UIImage imageNamed:#"somepic.png"];
[image drawAtPoint:rect.origin];
const CGContextRef ctx = UIGraphicsGetCurrentContext();
[[UIColor blueColor] setFill];
rect.size.width = rect.size.height = 200.0;
CGContextFillRect(ctx, rect);
}
#end
#interface MyOtherView : UIView
#end
#implementation MyOtherView
- (void)drawRect:(CGRect)rect
{
// This should tint "MyView" but it doesn't.
const CGContextRef ctx = UIGraphicsGetCurrentContext();
CGContextSaveGState(ctx);
CGContextSetBlendMode(ctx, kCGBlendModeScreen);
[[UIColor redColor] setFill];
CGContextFillRect(ctx, rect);
CGContextRestoreGState(ctx);
}
#end
I want "MyOtherView" to color "MyView" red where it overlaps, but instead it just draws an opaque red block onto it. However, this seems work fine if I copy the -drawRect: function from "MyOtherView" and append it to the one in "MyView" (this took me quite a headache to finally realize). Anyone know what I'm doing wrong? Is it even possible to do this, or should I be approaching it differently?
I think you're over-thinking this. Overlay one view over the other, and set the alpha of the top view to 0.5. You will also need to set opaque to NO.
If you set the background color of the view appropriately, you won't even need to override drawRect.
Might want to check out this SO question.