I've created a 200x200 circle in a custom UIView. I am using the following script to move the view object around the screen on the iPad.
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
UITouch *touch = [touches anyObject];
CGPoint currentPoint = [touch locationInView:self.view];
if([touch view] == newShape)
{
newShape.center = currentPoint;
}
[self.view setNeedsDisplay];
}
Everything works fine, I can move the circle anywhere on the screen. However, if I don't touch dead center on the circle object, it jumps slightly. By reading the code, this is quite obvious because newShape.center is being set to wherever the touch happens and ultimately snapping quickly to that position.
I'm looking for a way to move an object without snapping to the touch position. I'm thinking I would use xy coordinates to achieve this, but I'm not sure how to implement it.
Thanks!
Declare CGPoint prevPos; in .h file.
Here my view is _rectView.
-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
UITouch *touch = [touches anyObject];
CGPoint currentPoint = [touch locationInView:self.view];
prevPos = currentPoint;
}
-(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
UITouch *touch = [touches anyObject];
CGPoint currentPoint = [touch locationInView:self.view];
if([touch view] == _rectView)
{
float delX = currentPoint.x - prevPos.x;
float delY = currentPoint.y - prevPos.y;
CGPoint np = CGPointMake(_rectView.frame.origin.x+delX, _rectView.frame.origin.y+delY);
//_rect.center = np;
CGRect fr = _rectView.frame;
fr.origin = np;
_rectView.frame = fr;
}
//[self.view setNeedsDisplay];
prevPos = currentPoint;
}
Use the above code. You will not get that 'jump' effect.
An obvious way to do it is to store the offset of the touch from the shape's center in -touchesBegan:withEvent: and apply the offset in -touchesMoved:withEvent:.
Related
-(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
UITouch *touch = [[event touchesForView:self.view] anyObject];
CGPoint point = [touch locationInView:self.view];
basketView.center = CGPointMake(point.x, point.y);
}
I currently have this code that works to allow the user to move an image around with their finger. However, if I wanted to add multiple moveable images to the screen (say I also wanted to be able to move UIImages basketView2 and basketView3), how would I alter the code to allow for this?
you just need to modify your code as below
UITouch *touch = [[event touchesForView:self.view] anyObject];
CGPoint point = [touch locationInView:self.view];
UIImageView *currentView=(UIImageView *)touch.view;
currentView.center = CGPointMake(point.x, point.y);
I'm working on an image editing app. Right now I have the app built so a user can choose a photo from their library or take a photo with the camera. I also have another view (a picker view) that has other images a user can choose from. By selecting one of the images the app takes the user back to the main photo.
I want the user to be able to touch anywhere on screen and add the image they selected.
What is the best way to approach this?
touchesBegan? touchesMoved? UITapGestureRecognizer?
If anyone knows of any sample code or can give me a general idea of how to approach this that would be great!
EDIT:
Now I am able to see the coordinates and that my UIImage is getting the image I select from my Picker. But the image is not being displayed on the screen when I tap. Can someone help me troubleshoot my code please:
-(void)drawRect:(CGRect)rect
{
CGRect currentRect = CGRectMake(touchPoint.x, touchPoint.y, 30.0, 30.0);
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextFillRect(context, currentRect);
}
-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
UITouch * touch = [touches anyObject];
touchPoint = [touch locationInView:imageView];
NSLog(#"%f", touchPoint.x);
NSLog(#"%f", touchPoint.y);
if (touchPoint.x > -1 && touchPoint.y > -1)
{
stampedImage = _imagePicker.selectedImage;
//[stampedImage drawAtPoint:touchPoint];
[_stampedImageView setFrame:CGRectMake(touchPoint.x, touchPoint.y, 30.0, 30.0)];
[_stampedImageView setImage:stampedImage];
[imageView addSubview:_stampedImageView];
NSLog(#"Stamped Image = %#", stampedImage);
//[self.view setNeedsDisplay];
}
}
For an example of my NSLogs I am seeing:
162.500000
236.000000
Stamped Image = <UIImage: 0xe68a7d0>
Thanks!
In your ViewController, user the method "-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event" to get the X and Y coordinate of where a touch happened. Here is some sample code that shows how to get the x and y of the touch
-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
/* Detect touch anywhere */
UITouch *touch = [touches anyObject];
CGPoint touchPoint = [touch locationInView:self.view];
NSLog(#"%f", touchPoint.x); // The x coordinate of the touch
NSLog(#"%f", touchPoint.y); // The y coordinate of the touch
}
Once you have this x and y data, you can set the image that the user selected or shot with the built in camera to appear at those coordinates.
EDIT:
I think the issue MIGHT lie in how you create you UIImage view. Instead of this:
-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
UITouch * touch = [touches anyObject];
touchPoint = [touch locationInView:imageView];
CGRect myImageRect = CGRectMake(touchPoint.x, touchPoint.y, 20.0f, 20.0f);
UIImageView * myImage = [[UIImageView alloc] initWithFrame:myImageRect];
[myImage setImage:_stampedImageView.image];
myImage.opaque = YES;
[imageView addSubview:myImage];
[myImage release];
}
Try this:
-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
UITouch * touch = [touches anyObject];
touchPoint = [touch locationInView:imageView];
myImage = [[UIImageView alloc] initWithImage:_stampedImageView.image];
[imageView addSubview:myImage];
[myImage release];
}
If this does not work, try checking if "_stampedImageView.image == nil". If this is true, Your UIImage may not have been created properly.
I have a UIImageView that is an arrow image. I added this view to a parent view with a frame of 500x500 dimensions. I want to rotate the UIImageView so that the arrow is always pointing to the center of its parent when the user touches and moves it around.
I was looking into CGAffineTransform and trigonometry rotations, but I'm having trouble getting started. Can anyone provide some insight?
Thanks!
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
UITouch *touch = [touches anyObject];
CGPoint point = [touch locationInView:self];
pointerView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:#"pointer.png"]];
pointerView.layer.anchorPoint = CGPointMake(0, 0.5);
pointerView.center = point;
[self setPointerRotation];
[self addSubview:pointerView];
[pointerView release];
}
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
UITouch *touch = [touches anyObject];
CGPoint point = [touch locationInView:self];
pointerView.center = point;
[self setPointerRotation];
}
- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
[pointerView removeFromSuperview];
pointerView = nil;
}
- (void)setPointerRotation {
CGAffineTransform transform = // calculate rotation so that pointerView points to the center of the superview
pointerView.transform = transform;
}
I have 2 UIViews (placardView, and PlacardView2) that I would like to constrain them when touched to move horizontally but not vertically using the touchesMoved Method. My thought was to make the Y co-ordinate equal to itself, but I cannot get that to work syntactically in Xcode as I am new to this sort of thing.
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
UITouch *touch = [touches anyObject];
// If the touch was in the placardView, move the placardView to its location
if ([touch view] == placardView) {
CGPoint location = [touch locationInView:self];
placardView.center = location;
placardView.center.y = placardView.center.y;//error is here
return;
}
if ([touch view] == placardView2) {
CGPoint location = [touch locationInView:self];
placardView2.center = location;
placardView2.center.y = placardView2.center.y;//error is here
return;
}
}
You won't change anything by assigning center.y to itself - plus it is already changed by placardView2.center = location; assignment. Instead, you should probably assign just the new x coordinate:
CGPoint placardCenter = placardView2.center;
placardCenter.x = location.x;
placardView2.center = placardCenter;
I was wondering how to draw a CGRect onto an UIImageView. Here is the code I've got but it doesn't seem to be working. Any suggestions? touch1 and touch2 are both CGPoints and point is a CGRect.
-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
UITouch *touch = [touches anyObject];
touch1 = [touch locationInView:self];
touch2 = [touch locationInView:self];
}
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
}
- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
UITouch *touch = [touches anyObject];
touch2 = [touch locationInView:self];
point = CGRectMake(touch2.x, touch2.y, 50, 50);
[self setNeedsDisplay];
}
- (void) drawRect:(CGRect)rect {
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSetLineWidth(context, 2.0);
CGContextSetStrokeColorWithColor(context, [UIColor blackColor].CGColor);
CGContextSetFillColorWithColor(context, pointColor.CGColor);
CGContextAddEllipseInRect(context, point);
CGContextDrawPath(context, kCGPathFillStroke);
}
What do you see actually happening?
A few notes:
You shouldn't be doing this with a UIImageView-- those are specifically intended to be containers for image files. You should just use a subclass of a regular UIView for this.
In your touchesBegan, you know that touch1 and touch2 will always be set to the same thing, right? You don't seem to ever be using touch1.
point is a misleading variable name for something that is a rect.
Your drawRect is not unreasonable. What is pointColor? If you're drawing black-on-black that might be part of the problem.
Listing 3-1 Code that creates an ellipse by applying a transform to a circle
CGContextScaleCTM(context, 1,2);
CGContextBeginPath(context);
CGContextAddArc(context, 0, 0, 25, 0, 2*M_PI, false);
CGContextStrokePath(context);
Lots more example code in the Quartz2d Example
I took your code only, its working for me. Just have look at it. And thanks for your code. In this sample i am drawing a rect.
- (void)drawRect:(CGRect)rect
{
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSetLineWidth(context, 2.0);
CGContextSetStrokeColorWithColor(context, [UIColor blackColor].CGColor);
CGContextSetFillColorWithColor(context, [UIColor redColor].CGColor);
CGContextAddRect(context, rectFrame);
CGContextDrawPath(context, kCGPathFillStroke);
}
-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
UITouch *touch = [touches anyObject];
startPoint = [touch locationInView:self];
rectFrame.origin.x = startPoint.x;
rectFrame.origin.y = startPoint.y;
}
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
UITouch *touch = [touches anyObject];
endPoint = [touch locationInView:self];
rectFrame.size.width = endPoint.y - startPoint.x;
rectFrame.size.height = endPoint.y - startPoint.x;
[self setNeedsDisplay];
}
- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{
UITouch *touch = [touches anyObject];
endPoint = [touch locationInView:self];
rectFrame.size.width = endPoint.y - startPoint.x;
rectFrame.size.height = endPoint.y - startPoint.x;
[self setNeedsDisplay];
}