Creating a draggable image view - objective-c

I have been searching the net for a long time and I have not found a concrete way of making an image view draggable. Here is what I have so far:
tempViewController.h
#import <UIKit/UIKit.h>
#import "MyRect.h"
#class UIView;
#interface tempViewController : UIViewController
#property (nonatomic, strong) MyRect *rect1;
#end
tempViewController.m
#import "tempViewController.h"
#interface tempViewController ()
#end
#implementation tempViewController
#synthesize rect1 = _rect1;
- (void)viewDidLoad
{
[super viewDidLoad];
_rect1 = [[MyRect alloc]initWithFrame:CGRectMake(150.0, 100.0, 80, 80)];
[_rect1 setImage:[UIImage imageNamed:#"cloud1.png"]];
[_rect1 setUserInteractionEnabled:YES];
[self.view addSubview:_rect1];
}
- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
-(void) touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
UITouch *touch = [[event allTouches]anyObject];
if([touch view] == _rect1)
{
CGPoint pt = [[touches anyObject] locationInView:_rect1];
NSLog(#"%#",NSStringFromCGPoint(pt));
_rect1.center = pt;
}
}
-(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
UITouch *touch = [[event allTouches]anyObject];
if([touch view] == _rect1)
{
CGPoint pt = [[touches anyObject] locationInView:_rect1];
NSLog(#"%#",NSStringFromCGPoint(pt));
_rect1.center = pt;
}
}
#end
MyRect right now is an empty UIImageView Class.
Dragging the image from a point such as [532,589] on micron moves it to a totally different part of the screen such as [144, 139]

Just attach a UIPanGestureRecognizer to your view. In the recognizer's action, update your view's center based on the “translation” (offset) of the recognizer, then reset the recognizer's translation to zero. Here's an example:
- (void)viewDidLoad {
[super viewDidLoad];
UIView *draggableView = [[UIView alloc] initWithFrame:CGRectMake(150, 100, 80, 80)];
draggableView.userInteractionEnabled = YES;
draggableView.backgroundColor = [UIColor redColor];
[self.view addSubview:draggableView];
UIPanGestureRecognizer *panner = [[UIPanGestureRecognizer alloc]
initWithTarget:self action:#selector(panWasRecognized:)];
[draggableView addGestureRecognizer:panner];
}
- (void)panWasRecognized:(UIPanGestureRecognizer *)panner {
UIView *draggedView = panner.view;
CGPoint offset = [panner translationInView:draggedView.superview];
CGPoint center = draggedView.center;
draggedView.center = CGPointMake(center.x + offset.x, center.y + offset.y);
// Reset translation to zero so on the next `panWasRecognized:` message, the
// translation will just be the additional movement of the touch since now.
[panner setTranslation:CGPointZero inView:draggedView.superview];
}

Don't use -touchesBegan:withEvent: etc.
What you want to use for such "high-level" things are UIGestureRecognizers.
You would add a pan gesture recognizer to your view set a delegate (possibly the view itself), and in the callback move the view by the distance the recognizer moved.
You either remember the initial position and move by the -translationInView each time, or simply move by the translation and then use -setTranslation:inView: to reset the recognizers translation to zero, so on the next call of the delegate method, you will again get the movement since the last call.

Related

how to add 3dtouchforce to UIButton?

I want to measure the touch force when tapping or dragging a button. i have created a UITapGestureRecognizer (for tapping) and added it to myButton like this:
UITapGestureRecognizer *tapRecognizer2 = [[UITapGestureRecognizer alloc] initWithTarget:self action:#selector(buttonPressed:)];
[tapRecognizer2 setNumberOfTapsRequired:1];
[tapRecognizer2 setDelegate:self];
[myButton addGestureRecognizer:tapRecognizer2];
i have created a method called buttonPrssed like this:
-(void)buttonPressed:(id)sender
{
[myButton touchesMoved:touches withEvent:event];
myButton = (UIButton *) sender;
UITouch *touch=[[event touchesForView:myButton] anyObject];
CGFloat force = touch.force;
forceString= [[NSString alloc] initWithFormat:#"%f", force];
NSLog(#"forceString in imagePressed is : %#", forceString);
}
I keep getting zero values (0.0000) for touch. any help or advice would be appreciated. i did a search and found DFContinuousForceTouchGestureRecongnizer sample project but found it too complicated. I use iPhone 6 Plus s that has touch. i can also measure touch when tapping on any other area in the screen but not on buttons using this code:
- (void)touchesMoved:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event
{
[super touchesMoved:touches withEvent:event];
UITouch *touch = [touches anyObject];
//CGFloat maximumPossibleForce = touch.maximumPossibleForce;
CGFloat force = touch.force;
forceString= [[NSString alloc] initWithFormat:#"%f", force];
NSLog(#"forceString is : %#", forceString);
}
You are getting 0.0000 in buttonPressed because the user already lifted his finger when this is called.
You are right, that you need to get the force in the touchesMoved method, but you need to get it in the UIButton's touchesMoved method. Because of that you need to subclass UIButton and override its touchesMoved method:
Header file:
#import <UIKit/UIKit.h>
#interface ForceButton : UIButton
#end
Implementation:
#import "ForceButton.h"
#implementation ForceButton
- (void)touchesMoved:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {
[super touchesMoved:touches withEvent:event];
UITouch *touch = [touches anyObject];
CGFloat force = touch.force;
CGFloat relativeForce = touch.force / touch.maximumPossibleForce;
NSLog(#"force: %f, relative force: %f", force, relativeForce);
}
#end
Also, there is no need to use a UITapGestureRecognizer to detect a single tap on a UIButton. Just use addTarget instead.

UIView detecting touches in only one half of the screen

I am currently working on a 3D OpenGLES-based iPhone Game project and I want to have a view that detect touches so I can then rotate my camera according to the touch gestures.
So here I created a TouchPad class that derives from UIView to record the touch gestures.
Once done I have figured out that only half of the screen is effective. The whole left side.
Whenever i touch the right part of the screen it does not call the -[touchesBegan] method
Here is my class definition
#interface TouchPad : UIView
{
CGPoint fingerMove, originalPosition;
}
#property (nonatomic, assign) CGPoint fingerMove;
#end
And here is my class implementation
#import "TouchPad.h"
#implementation TouchPad
#synthesize fingerMove;
- (id)initWithFrame:(CGRect)frame
{
self = [super initWithFrame:frame];
if (self)
fingerMove = CGPointMake(0, 0);
return self;
}
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
std::cout << "called";
UITouch *touch = [touches anyObject];
originalPosition = [touch locationInView:self];
}
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
UITouch *touch = [touches anyObject];
CGPoint currentPosition = [touch locationInView:self];
fingerMove = CGPointMake(currentPosition.x - originalPosition.x,
currentPosition.y - originalPosition.y);
}
- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event;
{
UITouch *touch = [touches anyObject];
originalPosition = [touch locationInView:self];
fingerMove = CGPointMake(0, 0);
}
- (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event
{
fingerMove = CGPointMake(0, 0);
}
#end
And here is how i use it inside my ViewController
- (void)prepareGame
{
game = [[MainGame alloc] init];
[self.view addSubview:game.IrrView];
[game.IrrView release];
rotationPad = [[TouchPad alloc] initWithFrame:CGRectMake(0.0, 0.0,
[[UIScreen mainScreen] bounds].size.width,
[[UIScreen mainScreen] bounds].size.height)];
[self.view addSubview:rotationPad];
[rotationPad release];
}
- (void)runGame
{
[game updateMapPattern];
[game updateCamera :rotationPad.fingerMove];
[game draw];
}
I really want to know how to make the touchPad work in the whole screen and not only the left part of the screen. Maybe there is a conflict with my game view

How to access a class instance from another method

Here's my code:
#import "ViewController.h"
#implementation ViewController
- (void)viewDidLoad
{
[super viewDidLoad];
UIView *view1 = [[UIView alloc] initWithFrame:CGRectMake(50.0, 50.0, 0, 0)];
[self.view addSubview:view1];
}
-(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
UITouch *touch = [[event allTouches] anyObject];
if([touch.view isEqual:self]) {
CGPoint point = [[touches anyObject] locationInView:self];
NSLog(#"%#",NSStringFromCGPoint(point));
self.view1.center = point;
}
}
I want to be able to access the instance "view1" of the class "UIView" from the touchesMoved method.
Thanks in advance!
You can declare local variables as stated in the other answer. However, in my opinion its better to declare private properties in the anonymous category as below:
#import "ViewController.h"
#interface ViewController ()
#property (nonatomic, strong) UIView *view1; // declares view1 as a private property
#end
#implementation ViewController
#synthesize view1 = _view1;
- (void)viewDidLoad
{
[super viewDidLoad];
self.view1 = [[UIView alloc] initWithFrame:CGRectMake(50.0, 50.0, 0, 0)];
[self.view addSubview:self.view1];
}
-(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
UITouch *touch = [[event allTouches] anyObject];
if([touch.view isEqual:self])
{
CGPoint point = [[touches anyObject] locationInView:self];
NSLog(#"%#",NSStringFromCGPoint(point));
self.view1.center = point;
}
}
You can make rect1 an instance variable by placing it in your .h file. You can do something like:
#interface tempViewController : UIViewController
{
myRect *rect1;
}
Then in your .m file you will not have to declare it again.

Getting the UITouch objects for a UIGestureRecognizer

Is there a way to get the UITouch objects associated with a gesture? UIGestureRecognizer doesn't seem to have any methods for this.
Jay's right... you'll want a subclass. Try this one for size, it's from one of my projects. In DragGestureRecognizer.h:
#interface DragGestureRecognizer : UILongPressGestureRecognizer {
}
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event;
#end
#protocol DragGestureRecognizerDelegate <UIGestureRecognizerDelegate>
- (void) gestureRecognizer:(UIGestureRecognizer *)gr movedWithTouches:(NSSet*)touches andEvent:(UIEvent *)event;
#end
And in DragGestureRecognizer.m:
#import "DragGestureRecognizer.h"
#implementation DragGestureRecognizer
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
[super touchesMoved:touches withEvent:event];
if ([self.delegate respondsToSelector:#selector(gestureRecognizer:movedWithTouches:andEvent:)]) {
[(id)self.delegate gestureRecognizer:self movedWithTouches:touches andEvent:event];
}
}
#end
Of course, you'll need to implement the
- (void) gestureRecognizer:(UIGestureRecognizer *)gr movedWithTouches:(NSSet*)touches andEvent:(UIEvent *)event;
method in your delegate -- for example:
DragGestureRecognizer * gr = [[DragGestureRecognizer alloc] initWithTarget:self action:#selector(pressed:)];
gr.minimumPressDuration = 0.15;
gr.delegate = self;
[self.view addGestureRecognizer:gr];
[gr release];
- (void) gestureRecognizer:(UIGestureRecognizer *)gr movedWithTouches:(NSSet*)touches andEvent:(UIEvent *)event{
UITouch * touch = [touches anyObject];
self.mTouchPoint = [touch locationInView:self.view];
self.mFingerCount = [touches count];
}
If it is just the location you are interested in, you do not have to subclass, you will be notified of location changes of the tap from the UIGestureRecognizer.
Initialize with target:
self.longPressGestureRecognizer = [[[UILongPressGestureRecognizer alloc] initWithTarget: self action: #selector(handleGesture:)] autorelease];
[self.tableView addGestureRecognizer: longPressGestureRecognizer];
Handle UIGestureRecognizerStateChanged to get location changes:
- (void)handleGesture: (UIGestureRecognizer *)theGestureRecognizer {
switch (theGestureRecognizer.state) {
case UIGestureRecognizerStateBegan:
case UIGestureRecognizerStateChanged:
{
CGPoint location = [theGestureRecognizer locationInView: self.tableView];
[self infoForLocation: location];
break;
}
case UIGestureRecognizerStateEnded:
{
NSLog(#"Ended");
break;
}
default:
break;
}
}
If you only need to find out the location of the gesture, you can call either locationInView: or locationOfTouch:inView: on the UIGestureRecognizer object. However if you want to do anything else, then you'll need to subclass.
If you're writing your own UIGestureRecognizer you can get the touch objects overriding:
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
or the equivalent moved, ended or canceled
The Apple docs has lots of info on subclassing
Here is a method to get a long press added to an arbitrary UIView.
This lets you run longpress on any number of UIViews.
In this example I restrict access to the UIView method through tags but you could use isKindOfClass as well.
(From what I found you have to use touchesMoved for LongPress because touchesBegan fires before the LongPress becomes active)
subclass - .h
#import <UIKit/UIKit.h>
#import <UIKit/UIGestureRecognizerSubclass.h>
#interface MyLongPressGestureRecognizer : UILongPressGestureRecognizer
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event;
#property (nonatomic) CGPoint touchPoint;
#property (strong, nonatomic) UIView* touchView;
#end
subclass - .m
#import "MyLongPress.h"
#implementation MyLongPressGestureRecognizer
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event;
{
UITouch * touch = [touches anyObject];
self.touchPoint = [touch locationInView:self.view];
self.touchView = [self.view hitTest:[touch locationInView:self.view] withEvent:event];
}
#pragma mark - Setters
-(void) setTouchPoint:(CGPoint)touchPoint
{
_touchPoint =touchPoint;
}
-(void) setTouchView:(UIView*)touchView
{
_touchView=touchView;
}
#end
viewcontroller - .h
//nothing special here
viewcontroller - .m
#import "ViewController.h"
//LOAD
#import "MyLongPress.h"
#interface ViewController ()
//lOAD
#property (strong, nonatomic) MyLongPressGestureRecognizer* longPressGesture;
#end
#implementation PDViewController
- (void)viewDidLoad
{
[super viewDidLoad];
//LOAD
self.longPressGesture =[[MyLongPressGestureRecognizer alloc] initWithTarget:self action:#selector(longPressHandler:)];
self.longPressGesture.minimumPressDuration = 1.2;
[[self view] addGestureRecognizer:self.longPressGesture];
}
//LOAD
-(void) setLongPressGesture:(MyLongPressGestureRecognizer *)longPressGesture {
_longPressGesture = longPressGesture;
}
- (void)longPressHandler:(MyLongPressGestureRecognizer *)recognizer {
if (self.longPressGesture.touchView.tag >= 100) /* arbitrary method for limiting tap */
{
//code goes here
}
}
Simple and fast:
NSArray *touches = [recognizer valueForKey:#"touches"];
Where recognizer is your UIGestureRecognizer

objective-c touch-events

I've got a set of Images and would like to know which I have touched. How could I implement that...?
To be more precise:
A "Home-Class" will instantiate a couple of Image-Classes:
Image *myImageView = [[Image alloc] initWithImage:myImage];
The image-class looks something like this:
- (id) initWithImage: (UIImage *) anImage
{
if ((self = [super initWithImage:anImage]))
{
self.userInteractionEnabled = YES;
}
return self;
}
later on, I use these touches-event-methods also in the Image-class:
- (void) touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event{}
- (void) touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event{}
My problem at the moment: the touchesBegan/Ended methods will be fired no matter where I touched the screen, but I would like to find out which of the Images has been touched.....
Whenever you get the touch, you check if that touch happen in between your image area. Here is the example code, lets suppose you have UIImage object called img.
- (void) touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
UITouch *touch = [[event allTouches] anyObject];
CGPoint location = [touch locationInView:self.view];
if (location.x >= img.x && location.x <= img.x && location.y >= img.y && location.y <= img.y) {
// your code here...
}
}
Inside your *.h (interface) file:
#interface MyViewController : UIViewController{
IBOutlet UIImageView *imageViewOne;
IBOutlet UIImageView *imageViewTwo;
UIImageView * alphaImage;
}
-(BOOL)isTouch:(UITouch *)touch WithinBoundsOf:(UIImageView *)imageView;
Place UIImageView components on your *.xib and bind them with 'imageViewOne' and 'imageViewTwo' using the "File's owner".
Go to the *.m (implementation) file and:
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
UITouch *touch = [touches anyObject];
if ([self isTouch:touch WithinBoundsOf:imageViewOne])
{
NSLog(#"Fires first action...");
}
else if([self isTouch:touch WithinBoundsOf:imageViewTwo]){
NSLog(#"Fires second action...");
}
}
//(Optional 01) This is used to reset the transparency of the touched UIImageView
-(void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event{
[alphaImage setAlpha:1.0];
}
-(BOOL)isTouch:(UITouch *)touch WithinBoundsOf:(UIImageView *)imageView{
CGRect _frameRectangle=[imageView frame];
CGFloat _imageTop=_frameRectangle.origin.y;
CGFloat _imageLeft=_frameRectangle.origin.x;
CGFloat _imageRight=_frameRectangle.size.width+_imageLeft;
CGFloat _imageBottom=_frameRectangle.size.height+_imageTop;
CGPoint _touchPoint = [touch locationInView:self.view];
/*NSLog(#"image top %f",_imageTop);
NSLog(#"image bottom %f",_imageBottom);
NSLog(#"image left %f",_imageLeft);
NSLog(#"image right %f",_imageRight);
NSLog(#"touch happens at %f-%f",_touchPoint.x,_touchPoint.y);*/
if(_touchPoint.x>=_imageLeft &&
_touchPoint.x<=_imageRight &&
_touchPoint.y>=_imageTop &&
_touchPoint.y<=_imageBottom){
[imageView setAlpha:0.5];//optional 01 -adds a transparency changing effect
alphaImage=imageView;//optional 01 -marks the UIImageView which deals with the transparency changing effect for the moment.
return YES;
}else{
return NO;
}
}
That's how I handled that. I got the idea having read the post of "itsaboutcode".