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.
Related
I have taken a UiView subclass but it's background color is not changing
This class I am using these method
- (id)initWithFrame:(CGRect)frame
{
self = [super initWithFrame:CGRectMake(50, 80, 200, 200)];
if (self)
{
// Initialization code
}
return self;
}
- (void)drawRect:(CGRect)rect{
CGContextRef context = UIGraphicsGetCurrentContext();
[[UIColor darkGrayColor]setFill];
CGContextClearRect(context, rect);
CGContextSetLineWidth(context, 2.0);
CGContextBeginPath(context);
CGContextSetStrokeColorWithColor(context, [UIColor orangeColor].CGColor);
CGContextMoveToPoint(context, 1, 1);
CGContextAddLineToPoint(context, 100, 100);
CGContextStrokePath(context); // and draw
}
I am calling this class to main view controller
Newclass *obj =[[Newsclass alloc]init];
obj.backgroundColor =[UIColor redColor];
[self.view addsubview :obj];
but background color by default show black color. It is not changing
if i implemented background-color code init with frame method or
draw rect method than not changing.
if i code it
- (id)initWithCoder:(NSCoder*)aDecoder
than it's method not called
please suggest me UIview subclass black background color how to change
First of all, you should do the color part in UIView file.
if (self = [super initWithFrame:CGRectMake(220,60, 100, 300)])
{
self.backgroundColor =[UIColor greenColor];
}
how ever you don't need to do in this case... ;)
it will definitely change your background color. But what happens next is that Draw rect method is called ,your color is no more visible as the draw rect method draws a view above it (whatever you draw in that method).
- (void)drawRect:(CGRect)rect
{
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSetStrokeColorWithColor(context, [UIColor blueColor].CGColor);
CGRect rectangle = CGRectMake(0,0,200,300);
CGContextSetFillColorWithColor(context, [UIColor redColor].CGColor);
CGContextFillRect(context, rectangle);
}
You just cannot directly set the background color of cgcontext, you have to fill that context with color.
please make sure that you replace rectangle by rectangular frame of your view. It works like a charm for me.
I've created a subview of UIView to make some drawings - the drawings work fine in the drawRect method of my subclass, however, I cannot change the background color of the view. A little googling tells me I haven't set the frame for the view, but I'm not entirely sure how to do this. I tried two things:
I create the view in Storyboard and add it to my view controller, then declare it as a property in the header file and link them up. I synthesize the property at the top of the implementation file and in the viewDidLoad method, I add:
[myView setBackgroundColor: [UIColor whiteColor]];
The view's background is still black.
I also tried:
ViewSubclass *v = [[ViewSubclass alloc] initWithFrame: self.view.frame];
v.backgroundColor = [UIColor whiteColor];
myView = v;
To no avail.
What am I doing wrong?
UPDATE: This is the code I use to draw in the view, in case there's something going on there!
- (void)drawRect:(CGRect)rect {
CGFloat height = self.bounds.size.height;
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextClearRect(context, rect);
CGContextSetFillColorWithColor(context, [UIColor grayColor].CGColor);
CGFloat barWidth = 30;
int count = 0;
for (NSNumber *num in samples) {
CGFloat x = count * (barWidth + 10);
CGRect barRect = CGRectMake(x, height - ([num floatValue] * height), barWidth, [num floatValue] * height);
CGContextAddRect(context, barRect);
count++;
}
CGContextFillPath(context);
}
It just creates a set of bars in the screen, of different heights.
CGContextClearRect From the docs:
If the provided context is a window or bitmap context, Quartz
effectively clears the rectangle. For other context types, Quartz
fills the rectangle in a device-dependent manner. However, you should
not use this function in contexts other than window or bitmap
contexts.
It might be that this clearing clears your entire view with no regard to the background color you set
I can t add comments due my low lvl, but the question springs to mind, have you added to your UIView to viewcontroller?
like
[self.view addSubview:v];
EDIT:
I'm sorry I had understood that the second option was added to the view that pragmatically.
Are you adding the view in the header file? If so you might need to be sure the frame's coordinates are visible and that the view is on top, also make the new view slightly smaller to see if it is actually being created:
UIView *myView = [[UIView alloc] initWithFrame:CGRectMake(0,0,100,100)];
[self.view addSubview: myView];
[self.view bringSubviewToFront:myView];
You can also change the main view background color to see if the new view is actually being created. For example:
[self.view setBackgroundColor:[UIColor grayColor]];
If the color is changing for your main view then the problem is that your new view is not being or brought to the front. Let us know how it goes!
At the point where do
[myView setBackgroundColor: [UIColor whiteColor]];
check to see if myView is not nil in the debugger
simply I am beginner in developing on ipad and I need to draw rectangle at point x,y with width and height when i clicked or touched button .
I searched on google but i didn't find anything working in button handler
Create rectangleButton in viewDidLoad method and write -(void)rectangleButtonSelected method in your ViewController.m. And also create class RectangleView of UIView.
-(void)rectangleButtonSelected{
RectangleView *temp = [[RectangleView alloc] initWithFrame:CGRectMake(0, 0, 60, 40)];
temp.center = CGPointMake(arc4random()%100, arc4random()%200);
NSLog(#"The Main center Point : %f %f",temp.center.x,temp.center.y);
[self.view addSubview:temp];
}
Implement - (void)drawRect:(CGRect)rect method in RectanglerView.m
- (void)drawRect:(CGRect)rect
{
// Drawing code
context =UIGraphicsGetCurrentContext();
CGContextSetRGBStrokeColor(context, 1.0, 1.0, 1.0, 1.0);
// And draw with a blue fill color
CGContextSetRGBFillColor(context, 0.0, 0.0, 1.0, 1.0);
// Draw them with a 2.0 stroke width so they are a bit more visible.
CGContextSetLineWidth(context, 2.0);
CGContextAddRect(context, self.bounds);
CGContextStrokePath(context);
// Close the path
CGContextClosePath(context);
// Fill & stroke the path
CGContextDrawPath(context, kCGPathFillStroke);
}
I hope it will be helpful to you
You actually need to do this with state. There's only one place you're allowed to do drawing, and that's in drawRect:. So, when the user clicks the button, you need to set some instance variable, like _isShowingRectangle or something, then call setNeedsDisplay on your custom UIView where you're doing your drawing.
Then, in your custom view's drawRect:, you can check if that state variable is set, and draw (or not draw) the rectangle. The code for drawing depends on which graphics layer you're using, but it's probably going to be something like
CGContextRef ctxt = UIGraphicsGetCurrentContext();
CGContextSetStrokeColorWithColor(ctxt,[[UIColor blackColor] CGColor]);
CGContextSetLineWidth(ctxt,3.0);
CGContextStrokeRect(ctxt,CGRectMake(10,20,100,50));
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.
I am trying to get a transparent background in CG but it keeps coming out black.
I have the following code:
- (id)initWithFrame:(CGRect)frame {
if ((self = [super initWithFrame:frame])) {
DLog(#">>> Alloc: DrawingCanvas [0x%X]", (unsigned int)self);
[self setOpaque:NO];
[self setBackgroundColor:[UIColor clearColor]];
}
return self;
}
- (void) drawRect:(CGRect)rect
{
CGContextRef context = UIGraphicsGetCurrentContext();
CGRect frame = rect;
int counter = 3;
CGContextClearRect(context, frame);
CGContextSetFillColorWithColor(context, [UIColor clearColor].CGColor);
CGContextFillRect(context, frame);
}
How do I get this code to show a transparent background?
With that setup and as long as you don't set clearsContextBeforeDrawing to NO, the background should already be transparent when your drawRect: method is called. Remove the CGContextClearRect and other drawing calls.
You could simply remove these lines :
CGContextClearRect(context, frame);
CGContextSetFillColorWithColor(context, [UIColor clearColor].CGColor);
CGContextFillRect(context, frame);
As long as you have set opaque to NO and clearColor as backgroundColor everything should be fine.
Be careful when drawing since your other drawing code may fill the background entirely (take care of [path fill] things in a non-clipped context).
I had this same problem and the solution was to set the backgroundColor property of the UIView which I was drawing in, from the parent view's class. I didn't need any code to clear the background in the UIView's class where the drawing happens.
myDrawingView.backgroundColor = [UIColor clearColor];