I am trying to draw a circle (small like a dot) at the exact point of a UITouch.
The problem is, when I get the touchPoint from the user touch, I have to then draw the Rect in which to place the circle.
To work out an origin for the Rect, to place it such that, a circle drawn within it will have a centre point at the original touchpoint, I have used Pythagorus' theorem.
However, this approach is not elegant and is not exact.
Is there a better way to do this?
UITouch *touch = obj;
CGPoint touchPoint = [touch locationInView:self.view];
CGContextAddEllipseInRect(context,(CGRectMake ((touchPoint.x - 5.7), (touchPoint.y - 5.7)
, 9.0, 9.0)));
you can do like below
CFFloat radius=10;
UITouch *touch = obj;
CGPoint touchPoint = [touch locationInView:self.view];
CGContextAddEllipseInRect(context,(CGRectMake ((touchPoint.x - radius/2), (touchPoint.y
- radius/2)
, radius, radius)));
I think your approach is fine. What could be more elegant than Pythagorus? As for accuracy, add a few more digits to the constants and you can be more accurate than both the user's sense of his own finger position and the system calculations giving you the centroid of the touch.
What's more, I can't think of a good alternative. (Maybe one: do this with an image view, where the image is a circle, and set the view's anchor point so that it positions in the middle of the touch).
Related
In my app, I allow the user to annotate a photo by adding arrows (custom ArrowView). There can be many arrows added, with various zoom & rotation.
I am trying implement selecting of arrow by touch. Currently, I am iterating & using
CGRectContainsPoint(arrowView.frame, touchPoint)
to decide which arrow to select based on a touch gesture.
But, this does not work well when some of the arrows are big & rotated to 45 degrees (since the frame becomes big).
Question:
I would like to use bounds of the arrow translated to parent co-ordinates instead of frame. How can I get this when scaling & rotation is applied?
Alternatively, is there a better method to solve this selection problem?
This code find the arrow under touchPoint:
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
UITouch *touch = [touches anyObject];
CGPoint touchPoint = [touch locationInView:self.view];
UIView *arrow = [self.view hitTest:touchPoint withEvent:event];
}
I have a UIImageView and I am trying to determine when a drag is performed, how far that drag is from the origin. I currently have this:
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
UITouch *touch = [touches anyObject];
CGPoint location = [touch locationInView:touch.view];
if(CGRectContainsPoint(myimage.frame, location) == 0){
}
else
{ //user didn't tap inside image}
The image itself does not move, but a person can take their finger, click on the image and then drag their finger. I am just trying to determine that drag distance.
If you want to calculate distance, you need to remember the point (store it somewhere) in touchesBegan if the user tapped on your image.
Then in touchesMoved or touchesEnd you will be able to get current point and calculate distance to your original point.
If you need to get distance from UIImageView origin, you can call [touch locationInView:myImage];
And I suggest you to use UIGestureRecognizer class instead of handling touches by yourself. They are simpler to implement.
I have implemented a drag on a sprite object as follows..
-(BOOL)ccTouchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
UITouch * touch = [touches anyObject];
CGPoint location = [[Director sharedDirector] convertCoordinate: [touch locationInView:touch.view]];
[diskSprite setPosition:ccp(location.x , location.y )];
return kEventHandled;
}
but this dragging is not smooth.....
when i drag fast with my thumb the object left from the path.
Thanks
Probably a little bit late but I was searching for a similar thing.
I found this great Tutorial which explained everything:
http://www.raywenderlich.com/2343/how-to-drag-and-drop-sprites-with-cocos2d
- (void)ccTouchMoved:(UITouch *)touch withEvent:(UIEvent *)event {
CGPoint touchLocation = [self convertTouchToNodeSpace:touch];
CGPoint oldTouchLocation = [touch previousLocationInView:touch.view];
oldTouchLocation = [[CCDirector sharedDirector] convertToGL:oldTouchLocation];
oldTouchLocation = [self convertToNodeSpace:oldTouchLocation];
CGPoint translation = ccpSub(touchLocation, oldTouchLocation);
CGPoint newPos = ccpAdd(mySpriteToMove.position, translation);
mySpriteToMove.position = newPos;
}
I had this same issue with my game. Dragging operations appeared jerky. I believe the reason is that touch events aren't generated fast enough to give a smooth appearance.
To solve the problem I smoothed the motion out by running an action on the sprite toward the desired location, instead of setting the position immediately.
I'm not exactly sure what you mean by "the object left from the path". I suppose what you mean is that if you drag your finger over the screen in an arc or circle, that the sprite will "jump" from point to point, instead of follow your finger precisely. Is this correct?
If you want your sprite to follow an exact path, you will have to create a path and then set the sprite to follow it. What you do now is simply set the sprite's position to the touch position, but a "dragged" touch will not create an event for every pixel it touches.
It is fairly easy to create a path for touches received, and code samples can be found here and there. However, if the sprite's speed (in pixels per frame) is too high, you will always see it "jump", even if you use a smooth path.
Example:
You can animate a sprite over a circular path. If you animate this to complete the path in 1 second, you will likely see smooth animation. But if it runs at a high speed, like a full circle in 4 frames, you will just see your sprite at 4 places, not in a smooth circle.
If you wish to 'correct' that, you will need to look into blending, or determine what the maximum speed is for acceptable motion, and slow your sprite down when it's too fast.
I hope that answers your question. If it's not clear, feel free to edit your question, or add a comment to my answer.
look here, what I suggest you to try in such case:
-(void)ccTouchMoved:(UITouch *)touch withEvent:(UIEvent *)event {
if (_binCaptured) {
CGPoint location = [self convertTouchToNodeSpace:touch];
[_sprite stopAllActions];
id move = [CCEaseIn actionWithAction:[CCMoveTo actionWithDuration:0.1 position:ccp(location.x, _sprite.position.y)]];
[_sprite runAction:move];
}
}
And it really work smoothly.
I enjoyed this easy way.
I have drawn a circle on the iphone simulator using quartz 2d with fill. Is there a way by which I can detect a touch event on that circle?
Thanks
Harikant Jammi
If you have a CGPath of that circle, you can obtain a CGPoint of where the user's finger fell inside of touchesBegan and check to see whether it falls within this CGPath using the following code.
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
UITouch *touch = [[event allTouches] anyObject];
CGPoint location = [touch locationInView:self.view];
// Depending on your code, you may need to check a different view than self.view
// You should probably check the docs for the arguments of this function--
// It's been a while since I last used it
if (CGPathContainsPoint(yourCircle, nil, location, nil)) {
// Do something swanky
} else {
// Don't do teh swank
}
}
I haven't tested it, but if the surrounding space around the circle is set to an alpha of 0, then maybe only the circle would accept touches. You'd probably have to turn off isOpaque for the view, and have no background color.
If that doesn't work, then you'll have to process the tap location and write code to see if it is within the circle area or not.
Just put a custom invisible button with 0.0 alpha on that circle, so the button will always be able to detect touch.
Currently I see that a touch event will show me the UIView where the touch occured. But what if I need to detect a touch of some non rectangular shape, like a circle. How would I go about doing something like that ?
Basically I want to do something only if the user touches somewhere within a circular area that's not visible.
Any help/direction is appreciated, TIA!
You would do it like so. Note that 'locationInView' will return the coordinates of the touch with respect to the specified view, so a touch in the top-left corner of a view will return (0,0) regardless of where that view is onscreen.
-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
UITouch *touch = [touches anyObject];
// gets the coordinats of the touch with respect to the specified view.
CGPoint touchPoint = [touch locationInView:self];
// test the coordinates however you wish,
...
}
To test against a sphere you would calculate the distance from the touch point to the center of the sphere, then check whether this was less than the sphere radius.