Moving UIView within Parent UIView (UIPanGestureRecognizer) - ios

Question

I am using the following code to move a UIImageView that is present inside of a UIView.
- (IBAction)handlePan:(UIPanGestureRecognizer *)recognizer {
CGPoint translation = [recognizer translationInView:self.view];
recognizer.view.center = CGPointMake(recognizer.view.center.x + translation.x,
recognizer.view.center.y + translation.y);
[recognizer setTranslation:CGPointMake(0, 0) inView:self.view];
}
I would like to make it so that the UIView does not move outside of the parent view. At the minute the image view is able to move across the entire screen.

Answer 1

First get the new frame of your UIImageView and check if it is completely inside its superView using CGRectContainsRect() method. If yes, then set UImageView's frame to new frame.
- (IBAction)handlePan:(UIPanGestureRecognizer *)recognizer {
CGPoint translation = [recognizer translationInView:self.view];
CGRect recognizerFrame = recognizer.view.frame;
recognizerFrame.origin.x += translation.x;
recognizerFrame.origin.y += translation.y;
// Check if UIImageView is completely inside its superView
if (CGRectContainsRect(self.view.bounds, recognizerFrame)) {
recognizer.view.frame = recognizerFrame;
}
// Else check if UIImageView is vertically and/or horizontally outside of its
// superView. If yes, then set UImageView's frame accordingly.
// This is required so that when user pans rapidly then it provides smooth translation.
else {
// Check vertically
if (recognizerFrame.origin.y < self.view.bounds.origin.y) {
recognizerFrame.origin.y = 0;
}
else if (recognizerFrame.origin.y + recognizerFrame.size.height > self.view.bounds.size.height) {
recognizerFrame.origin.y = self.view.bounds.size.height - recognizerFrame.size.height;
}
// Check horizantally
if (recognizerFrame.origin.x < self.view.bounds.origin.x) {
recognizerFrame.origin.x = 0;
}
else if (recognizerFrame.origin.x + recognizerFrame.size.width > self.view.bounds.size.width) {
recognizerFrame.origin.x = self.view.bounds.size.width - recognizerFrame.size.width;
}
}
// Reset translation so that on next pan recognition
// we get correct translation value
[recognizer setTranslation:CGPointMake(0, 0) inView:self.view];
}
Make sure that you pass bounds of superView and frame of UIImageView so that both CGRects are in same coordinate system.

Answer 2

Try with:
- (IBAction)handlePan:(UIPanGestureRecognizer *)recognizer
{
if (gesture.state==UIGestureRecognizerStateChanged || gesture.state == UIGestureRecognizerStateEnded){
UIView *superview = recognizer.view.superview;
CGSize superviewSize = superview.bounds.size;
CGSize thisSize = recognizer.view.size;
CGPoint translation = [recognizer translationInView:self.view];
CGPoint center = CGPointMake(recognizer.view.center.x + translation.x,
recognizer.view.center.y + translation.y);
CGPoint resetTranslation = CGPointMake(translation.x, translation.y);
if(center.x - thisSize.width/2 < 0)
center.x = thisSize.width/2;
else if (center.x + thisSize.width/2 > superviewSize.width)
center.x = superviewSize.width-thisSize.width/2;
else
resetTranslation.x = 0; //Only reset the horizontal translation if the view *did* translate horizontally
if(center.y - thisSize.height/2 < 0)
center.y = thisSize.height/2;
else if(center.y + thisSize.height/2 > superviewSize.height)
center.y = superviewSize.height-thisSize.height/2;
else
resetTranslation.y = 0; //Only reset the vertical translation if the view *did* translate vertically
recognizer.view.center = center;
[recognizer setTranslation:CGPointMake(0, 0) inView:self.view];
}
}
This way it won't ever move outside the parent view bounds and it will just "stick" to the edge if you try to move it out of the bounds!

Answer 3

Swift version of micantox answer
let gesture = UIPanGestureRecognizer(target: self, action: #selector(self.wasDragged(gestureRecognizer:)))
imageView.addGestureRecognizer(gesture)
imageView.isUserInteractionEnabled = true
#objc func wasDragged(gestureRecognizer: UIPanGestureRecognizer) {
if gestureRecognizer.state == UIGestureRecognizerState.changed || gestureRecognizer.state == UIGestureRecognizerState.ended {
let superview = gestureRecognizer.view?.superview
let superviewSize = superview?.bounds.size
let thisSize = gestureRecognizer.view?.frame.size
let translation = gestureRecognizer.translation(in: self.view)
var center = CGPoint(x: gestureRecognizer.view!.center.x + translation.x, y: gestureRecognizer.view!.center.y + translation.y)
var resetTranslation = CGPoint(x: translation.x, y: translation.y)
if center.x - (thisSize?.width)!/2 < 0 {
center.x = (thisSize?.width)!/2
} else if center.x + (thisSize?.width)!/2 > (superviewSize?.width)! {
center.x = (superviewSize?.width)!-(thisSize?.width)!/2
} else {
resetTranslation.x = 0 //Only reset the horizontal translation if the view *did* translate horizontally
}
if center.y - (thisSize?.height)!/2 < 0 {
center.y = (thisSize?.height)!/2
} else if center.y + (thisSize?.height)!/2 > (superviewSize?.height)! {
center.y = (superviewSize?.height)!-(thisSize?.height)!/2
} else {
resetTranslation.y = 0 //Only reset the vertical translation if the view *did* translate vertically
}
gestureRecognizer.view?.center = center
gestureRecognizer.setTranslation(CGPoint(x: 0, y: 0), in: self.view)
}
}

Answer 4

You'll have to set the recognizer.view.center to a new value only if its frame is inside the bounds of its parent view. Use CGRectContainsRect on recognizer.view.superview.bounds and recognizer.view.frame to verify that they are contained.
If you want to allow the image view to move outside its parent view until the center point of the view is outside the parent's bounds, you can use the convertPoint:toView method of UIView and verify that the new CGPoint is not outside your parent's bounds.

Answer 5

if (gesture.state==UIGestureRecognizerStateChanged){
CGPoint translation = [recognizer translationInView:self.view];
CGRect rectToCheck=CGRectMake(yourView.frame.origin.x+translation.x, yourView.frame.origin.y+translation.y, CGRectGetWidth(yourView.frame), CGRectGetHeight(yourView.frame));
if(CGRectContainsRect(self.view.bounds,rectToCheck))// check that the rect that is going to form lies within the bounds of self.view
{
yourView.frame=CGRectMake(yourView.frame.origin.x+translation.x, yourView.frame.origin.y+translation.y, CGRectGetWidth(yourView.frame), CGRectGetHeight(yourView.frame));
}
[gesture setTranslation:CGPointZero yourView]; // important to set this
}
P.S. Use the gesture state block to initiate, pan, remove. i.e. UIGestureRecognizerStateBegan
UIGestureRecognizerStateChanged
UIGestureRecognizerStateEnded