Is there an "accepted" way of performing (pinch) zoom on a view that is not based on UIScrollView?
There's a code sample by Erica Sadun that does the math for treating touch events as scale/rotate/translate transforms that you can probably borrow from. Basically, it sounds like you want to apply a scaling affine transform. This code doesn't include the niceties of "bouncing" the view when you reach the edges of the content, so you'll have to do that yourself.
Full disclosure: I haven't done this in almost a year. It's likely that there are frameworks now that include much more straightforward support for this feature.
If you are working in iPhone OS 3.2 (for the iPad) or iOS 4 for the iPhone 4, you can use the UIPinchGestureRecognizer class to detect pinch gestures.
This code helps to zoom UIImageView without using UIScrollView.
-(void)HandlePinch:(UIPinchGestureRecognizer*)recognizer{
if ([recognizer state] == UIGestureRecognizerStateEnded) {
NSLog(#"=======Scale Applied===========");
if ([recognizer scale]<1.0f) {
[recognizer setScale:1.0f];
}
CGAffineTransform transform = CGAffineTransformMakeScale([recognizer scale], [recognizer scale]);
imgView.transform = transform;
}
}
Related
I have a CALayer and as sublayer to this CALayer i have added an imageLayer which contains an image of resolution 276x183.
I added a UIPanGestureRecognizer to the main view and calculation the coordinates of the CALayer as follows:
- (void)panned:(UIPanGestureRecognizer *)sender{
subLayer.frame=CGRectMake([sender locationInView:self.view].x-138, [sender locationInView:self.view].y-92, 276, 183);
}
in viedDidLoad i have:
subLayer.backgroundColor=[UIColor whiteColor].CGColor;
subLayer.frame=CGRectMake(22, 33, 276, 183);
imageLayer.contents=(id)[UIImage imageNamed:#"A.jpg"].CGImage;
imageLayer.frame=subLayer.bounds;
imageLayer.masksToBounds=YES;
imageLayer.cornerRadius=15.0;
subLayer.shadowColor=[UIColor blackColor].CGColor;
subLayer.cornerRadius=15.0;
subLayer.shadowOpacity=0.8;
subLayer.shadowOffset=CGSizeMake(0, 3);
[subLayer addSublayer:imageLayer];
[self.view.layer addSublayer:subLayer];
It is giving desired output but a bit slow in the simulator. I have not yet tested it in Device. so my question is - Is it OK to move a CALayer containing an image??
Yes, it is OK to move a CALayer containing an image.
If all you want to do with the panning gesture is move the image, then instead of updating the whole frame, you should just update the layer's position property. Like thus:
- (void)panned:(UIPanGestureRecognizer *)sender {
subLayer.position=CGPointMake([sender locationInView:self.view].x, [sender locationInView:self.view].y);
}
Two things:
First, you can't draw ANY conclusions based on the performance of the simulator. Some things on the simulator are an order of magnitude faster than on a device, and other things are significantly slower. Animation is especially a mixed bag.
If you're doing performance-critical work, test it on the device, early and often.
Second, you can certainly animate a layer using a gesture recognizer, but that is an awfully round-about way to do it. Gesture recognizers are designed to work on views, and it's much easier and cleaner to tie the recognizer to a subview rather than a sub layer.
One of the big problems you will have with using a layer is hit-testing. If you let go of your image, then try to drag it some more, you'll have to have the gesture on the containing view, take the gesture coordinates and do hit testing on the layer. Ugh.
Take a look at the gesture based version of the touches sample app from Apple. It shows you how to cleanly move UIView objects around the screen using gestures.
Note that you can create a view that has custom layer content, and drag that around.
In iPhone App I want add functionality to (imageview or webview or other control) zoom in/out an image with pinch gesture.
You can use a UIScrollView for that.
Add a UIImageView to the UIScrollViewand configure the UIScrollView for zooming via its propertys. Check the UIScrollview Class Reference - Zooming and Panning Section
Edit:
Good point by Mike: Check the PhotoScrollersample code by Apple, too
Please refer to this code. I have used it in one of my apps so it works:
- (IBAction)handlePinch:(UIPinchGestureRecognizer *)recognizer {
recognizer.view.transform = CGAffineTransformScale(recognizer.view.transform, recognizer.scale, recognizer.scale);
recognizer.scale = 1;
}
Also don't forget to add Pinch gesture recognizer to your imageView.
Hope this helps.
I had a problem regarding rotation of an image in my code using rotation gesture. After spending some time on SO I got a link to Ray Wenderlich's tutorial on UIGestureRecognizers.
Initially my view was rotating and scaling very fast on corresponding gestures and this link has a nice tutorial on using them properly. However I could not understand why did setting rotation and scale to there normal values 0 and 1 respectively solved the problem.
Here's the link to the tutorial
http://www.raywenderlich.com/6567/uigesturerecognizer-tutorial-in-ios-5-pinches-pans-and-more
UIPinchGestureRecognizer and UIRotationGestureRecognizer is the section I am referring to.
- (IBAction)handlePinch:(UIPinchGestureRecognizer *)recognizer {
recognizer.view.transform = CGAffineTransformScale(recognizer.view.transform, recognizer.scale, recognizer.scale);
recognizer.scale = 1;
}
The code first create a new transform from the recognizer scale and assign it to your view.
After that it reset the scale to 1.
This is actually consider the scaling to the view each time start from 1.
Similar to the rotation, we consider the rotation degree start from 0 every time it called.
I'm drawing a graph on a UIView, which is contained by a UIScrollView so that the user can scroll horizontally to look around the entire graph.
Now I want to zoom the graph when a user pinches in with two fingers, but instead of zooming in a view with the same rate for X and Y direction, I want to zoom only in the X direction by changing the X scale, without changing the Y scale.
I think I have to catch the pinch in/out gesture and redraw the graph, overriding the default zooming behavior.
But is there a way to do this?
I've been having a very difficult time to catch the pinch gesture on the UIScrollView, as it cancels the touches when it starts to scroll. I want the zooming to work even after the UIScrollView cancels the touches. :(
Thanks,
Kura
Although you cannot delete the existing pinch gesture recognizer, you can disable it and then add your own:
// Disable existing recognizer
for (UIGestureRecognizer* recognizer in [_scrollView gestureRecognizers]) {
if ([recognizer isKindOfClass:[UIPinchGestureRecognizer class]]) {
[recognizer setEnabled:NO];
}
}
// Add our own
UIPinchGestureRecognizer* pinchRecognizer =
[[UIPinchGestureRecognizer alloc] initWithTarget:self
action:#selector(pinch:)];
[_scrollView addGestureRecognizer:pinchRecognizer];
[pinchRecognizer release];
Then in
- (void) pinch:(UIPinchGestureRecognizer*)recognizer { .. }
use
[recognizer locationOfTouch:0 inView:..]
[recognizer locationOfTouch:1 inView:..]
to figure out if the user is pinching horizontally or vertically.
You should instead access the gestureRecognizers (defined in UIView), there are several of them being used by the scroll view,
figure out which one is the pinch recognizer and call removeGestureRecognizer: on the scroll view, then create your own and have it do the work, add it back with addGestureRecognizer:.
these are all public API,
the recognizers and what order they are in are not (currently),
so program defensively when accessing them
(this is a perfectly valid way to manipulate UIKit views, and Apple won't/shouldn't have issues with it - though they will not guarantee it works in any future release)
You should be able to subclass UIScrollView and override the touchesBegan: method. Don't call [super touchesBegan:] but instead, adjust the zoom as you like:
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
//Anything you want. Probably you would want to store all the touches
//or their values, so that you can compare them to the touches
//in the touchesEnded: method,
//thus letting you know what the pinch amount was
}
If you like, you can judge whether it's a pinch or not, and if it's not, call the super method, and only handle it yourself for custom pinches.
Edsko & bshirley answers are good, but they don't tell where to place the code.
First, I placed it in viewDidLoad method, but no Pinch Gesture Recognizer was found in the scrollview (maybe because my scrollview is an IBOutlet).
Then I tried in viewWillAppear or viewDidAppear and the UIPinchGestureRecognizer was here.
I am developing an iPad application which is basically a big drawing canvas with a couple of button at the side. (Doesn't sound very original, does it? :P)
No matter how the user holds the device, the canvas should remain in place and should not be rotated. The simplest way to achieve this would be to support just one orientation.
However, I would like the images on the buttons to rotate (like in the iPhone camera app) when the device is rotated. UIPopoverControllers should also use the users current orientation (and not appear sideways).
What is the best way to achieve this?
(I figured I could rotate the canvas back into place with an affineTransform, but I don't think it is ideal.)
Thanks in advance!
Just spouting off an idea (not sure if it would work or not)...
Perhaps you could have your screen controlled by a UIViewController that supports all orientations, but have the canvas be controlled by one that only supports a single orientation (ie, returns NO in its shouldAutorotate... method).
If that doesn't work, I'd probably just go with the affineTransform route.
I discovered a way to do this, similar to what Dave DeLong proposed.
Using a transform worked, but it wasn't ideal. Although the end result (end of the animation) was what I wanted, it would stay show some kind of shaky rotation animation.
Then I found this:
https://developer.apple.com/iphone/library/qa/qa2010/qa1688.html
Which says that a second (or third etc.) UIViewController added to the WINDOW would not receive rotation events, and therefore would never rotate. And that worked!
I created a 'fake' UIViewController with a blank view and added that as the first view controller. This receives the rotation events which I then pass on to the other view controllers that can then choose whether to rotate - the entire view or just button labels.
It is a bit hacky... But I guess the user won't notice.
Using the willRotateToInterfaceOrientation method, you should be able to use some simple logic to swap out the images:
- (void)willRotateToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation duration:(NSTimeInterval)duration
{
[super willRotateToInterfaceOrientation:toInterfaceOrientation duration:duration];
//The following if statement determines if it is an iPad, if it is then the interface orientation is allowed. This line can be taken out to support both iPhones an iPads.
if ([[UIDevice currentDevice] userInterfaceIdiom] == UIUserInterfaceIdiomPad) {
if (toInterfaceOrientation == UIInterfaceOrientationLandscapeRight) {
//Swap images and use animations to make the swap look "smooth"
//NSLog(#"Landscape Right");
} else if (toInterfaceOrientation == UIInterfaceOrientationLandscapeLeft) {
//Swap images and use animations to make the swap look "smooth"
//NSLog(#"Landscape Left");
} else {
//Swap images and use animations to make the swap look "smooth"
//NSLog(#"Portrait");
}
} else {
}
}
To change an image in your interface programmatically:
[myUIImageView setImage:[UIImage imageNamed:#"myImage.png"]];
Also, to make sure the view doesn't auto-rotate use the shouldAutorotateToInterfaceOrientation method to tell your app to stay in portrait.