UIPanGestureRecognizer gets stuck before moving after image is idle for a bit
So I'm making a simple iPhone app that lets you move / scale images that have been imported in a view. I'm using UIGestureRecognizers with @paulsolt 's code below to accomplish this. It works great. The only problem I'm having is when I go to move an object after not having touched the screen or performed any other actions for a while, there is a slight hiccup before it starts moving smoothly.
Does anyone know how to fix this problem?
- (void)addGestureRecognizersToView:(UIView *)theView {
theView.userInteractionEnabled = YES; // Enable user interaction
UIPanGestureRecognizer *panGesture = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(handlePanGesture:)];
[panGesture setMaximumNumberOfTouches:2];
[panGesture setDelegate:self];
[theView addGestureRecognizer:panGesture];
[panGesture release];
UIPinchGestureRecognizer *pinchGesture = [[UIPinchGestureRecognizer alloc] initWithTarget:self action:@selector(handlePinchGesture:)];
[theView addGestureRecognizer:pinchGesture];
[pinchGesture release];
}
- (void)handlePinchGesture:(UIPinchGestureRecognizer *)gestureRecognizer {
if([gestureRecognizer state] == UIGestureRecognizerStateBegan) {
// Reset the last scale, necessary if there are multiple objects with different scales
lastScale = [gestureRecognizer scale];
}
if ([gestureRecognizer state] == UIGestureRecognizerStateBegan ||
[gestureRecognizer state] == UIGestureRecognizerStateChanged) {
CGFloat currentScale = [[[gestureRecognizer view].layer valueForKeyPath:@"transform.scale"] floatValue];
// Constants to adjust the max/min values of zoom
const CGFloat kMaxScale = 1.5;
const CGFloat kMinScale = 1.0;
const CGFloat kSpeed = 0.75;
CGFloat newScale = 1 - (lastScale - [gestureRecogn开发者_开发百科izer scale]) * (kSpeed);
newScale = MIN(newScale, kMaxScale / currentScale);
newScale = MAX(newScale, kMinScale / currentScale);
CGAffineTransform transform = CGAffineTransformScale([[gestureRecognizer view] transform], newScale, newScale);
[gestureRecognizer view].transform = transform;
lastScale = [gestureRecognizer scale]; // Store the previous scale factor for the next pinch gesture call
}
}
- (void)handlePanGesture:(UIPanGestureRecognizer *)gestureRecognizer {
UIView *myView = [gestureRecognizer view];
CGPoint translate = [gestureRecognizer translationInView:[myView superview]];
if ([gestureRecognizer state] == UIGestureRecognizerStateChanged || [gestureRecognizer state] == UIGestureRecognizerStateChanged) {
[myView setCenter:CGPointMake(myView.center.x + translate.x, myView.center.y + translate.y)];
[gestureRecognizer setTranslation:CGPointZero inView:[myView superview]];
}
}
Maybe because you do this [panGesture setMaximumNumberOfTouches:2];
, it has to ensure that the current action is not pinching before moving your view?
This is happening when the imagepicker selects a photo taken by the iPhone camera. For other images it seems to work fine. Not sure how to fix this.
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