I have a need for rotating UISlider via its superclass property transform, by changing the rotation matrix with:
self.slider.transform = CGAffineTransformMakeRotation(45);
In the documentation for UIView I can see a warning saying:
Warning If this property is not the identity transform, the value of
the frame property is undefined and therefore should be ignored.
So, the question is, how can I rotate a standard UIKit element without messing up frame rect? (By undefined I understand, they mean, totally messed up, not just enlarged enough to contain entire rotated object)
Basically when you set the transform on a view, you will want to set its size and position by using the bounds and center properties. When setting the frame on a view, UIKit will actually set the bounds/center/transform on your view.
So without setting a transform you can set the frame like this.
self.slider.frame = CGRectMake(10, 20, 300, 50);
When using a transform, you would have to do it like this:
self.slider.transform = CGAffineTransformMakeRotation(45);
self.slider.bounds = CGRectMake(0, 0, 300, 50);
self.slider.center = CGRectMake(10, 20, 300, 50);
Related
I have added UIView at some angle. Now at the run time i want to move that view to up (say 20px).
At start
dragView = [[DragbleView alloc] initWithFrame:CGRectMake(10, 200, 200, 90)];
dragView.transform = CGAffineTransformMakeRotation (-0.663247);
At Run Time
NSLog(#"Before : %#",NSStringFromCGRect(dragView.frame));
[dragView setCenter:CGPointMake(dragView.frame.origin.x, dragView.center.y+20)];
NSLog(#"After : %#",NSStringFromCGRect(dragView.frame));
Console O/p
Before : {{3.4947295778412979, 147.97225037436704}, {213.0105408443174, 194.05549925126593}}
After : {{-103.0105408443174, 167.97225037436704}, {213.0105408443174, 194.05549925126593}}
As you can see it goes to the wrong place. How to place above 20 px
If you read the docs on the UIView frame property, they say:
If the transform property is not the identity transform, the value of
this property is undefined and therefore should be ignored.
So you can't change the frame once you've changed your view's transform. It doesn't work any more.
Instead you should use the view's center property, as #GaryRiches suggests in his answer.
It is doing as you have specified. You would get better results using the center point for both the X and Y:
[dragView setCenter:CGPointMake(dragView.center.x, dragView.center.y + 20)];
Also, as noted below. iOS uses 0,0 as top left, so to move something "up" would require subtracting 20 from the dragView.center.y.
To move UP, it requires to minimize Y location values, whereas you are adding.
Try this:
[dragView setCenter:CGPointMake(dragView.frame.origin.x, dragView.center.y - 20)];
I have a problem. I'm working on making a game. As part of my game I need images to be rotated and then moved in the direction of the rotated angle inside a game loop (using an NSTimer). In essence I'm trying to create the effect of launching a projectile. The code works fine when moving in perpendicular directions such as 0, 90, 180, 270, and 360 degrees, but any other angle and the image starts to glitch out. The object on the screen maintains its correct bounds and contents, but the actual displayed image disappears. Does anybody know what the problem is or someway I could get around it? If needed, I can make and post a video of my problem so you can see what I'm talking about.
Here is a sample of the code I'm using. The "background" variable is just a UIImageView:
angle = 60;
background.transform = CGAffineTransformRotate(object.transform, angle*M_PI/180); //converts degrees to radians and rotates the image
background.frame = CGRectMake( background.frame.origin.x + cos(angle*m_PI/180)*32; background.frame.origin.y -sin(angle*M_PI/180)*32, background.frame.size.width, background.frame.size.height); //moves the image in the direction of the angle
For starters, there is a semicolon after the x origin in your CGRect instead of a comma. Was that just a typo?
The UIView documentation for frame states:
Warning: If the transform property is not the identity transform, the
value of this property is undefined and therefore should be ignored.
Changes to this property can be animated. However, if the transform
property contains a non-identity transform, the value of the frame
property is undefined and should not be modified. In that case, you
can reposition the view using the center property and adjust the size
using the bounds property instead.
So there you have it, you should not be trying to change the frame when setting a custom transform. You are only trying to adjust the position of the view anyway so just modify your code to adjust center instead of the origin coordinates.
To change the size, you can use the bounds.
CGRect bounds = myView.bounds;
bounds.size.width = whatever;
bounds.size.height = whatever;
myView.bounds = bounds;
I have created mainView objcet of UIView and added one subview on it. I applied transform on mainView for reducing frame size. But frame of subview of mainView was not reduced. How to reduce the size of this subview.
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
CGFloat widthM=1200.0;
CGFloat heightM=1800.0;
UIView *mainView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, widthM, heightM)];
mainView.backgroundColor = [UIColor colorWithPatternImage:[UIImage imageNamed:#"te.png"]];
[self.view addSubview:mainView];
CGFloat yourDesiredWidth = 250.0;
CGFloat yourDesiredHeight = yourDesiredWidth *heightM/widthM;
CGAffineTransform scalingTransform;
scalingTransform = CGAffineTransformMakeScale(yourDesiredWidth/mainView.frame.size.width, yourDesiredHeight/mainView.frame.size.height);
mainView.transform = scalingTransform;
mainView.center = self.view.center;
NSLog(#"mainView:%#",mainView);
UIView *subMainView= [[UIView alloc] initWithFrame:CGRectMake(100, 100, 1000, 1200)];
subMainView.backgroundColor = [UIColor redColor];
[mainView addSubview:subMainView];
NSLog(#"subMainView:%#",subMainView);
}
NSlog of these views:
mainView:<UIView: 0x8878490; frame = (35 62.5; 250 375); transform = [0.208333, 0, 0, 0.208333, 0, 0]; layer = <CALayer: 0x8879140>>
subMainView:<UIView: 0x887b8c0; frame = (100 100; 1000 1200); layer = <CALayer: 0x887c160>>
Here the width of mainView is 250, the width of subview is 1000. but when i get the output in simulator, subview is occupied correctly, but it's not cross the mainView. How it is possible? How to get frame of subview with respect mainView frame after transformation?
What you're seeing is expected behavior. The frame of an UIView is relative to its parent, so it doesn't change when you apply a transformation to its superview. While the view will appear 'distorted' too, the frame won't reflect the changes since it's still at exact the same position relative to its parent.
However, I assume you would like to get the frame of the view relative to the topmost UIView. In that case UIKit offers these functions:
– [UIView convertPoint:toView:]
– [UIView convertPoint:fromView:]
– [UIView convertRect:toView:]
– [UIView convertRect:fromView:]
I applied these to your example:
CGRect frame = [[self view] convertRect:[subMainView frame] fromView:mainView];
NSLog(#"subMainView:%#", NSStringFromCGRect(frame));
And this is the output:
subMainView:{{55.8333, 83.3333}, {208.333, 250}}
In addition to s1m0n answer, the beautiful thing about applying a transform matrix to your view, is that you can keep reasoning in terms of its original coordinate system (in your case, you can handle subMainView using the non-transformed coordinate system, which is why, even though subMainView's frame is bigger than mainView's transformed frame, it still doesn't cross the parent view, as it gets automatically transformed). This means that when you have a transformed parent view (for example rotated and scaled) and you want to add a subview in a particular point relative to this parent view, you don't have to first keep track of the previous transformations in order to do so.
If you really are interested in knowing the subview's frame in terms of the transformed coordinate system, it will be enough to apply the same transformation to the subview's rectangle with:
CGRect transformedFrame = CGRectApplyAffineTransform(subMainView.frame, mainView.transform);
If you then NSLog this CGRect, you will obtain:
Transformed frame: {{20.8333, 20.8333}, {208.333, 250}}
Which, I believe, are the values that you were looking for. I hope this answers your question!
I am using the following code to rotate and transform an image view:
myImageView.transform = CGAffineTransformMakeRotation(45); // rotation
CGRect frame = myImageView.frame;
frame.origin.x = x_position;
frame.origin.y = y_position;
myImageView.frame = frame; // transformation
tl;dr: The frame is bogus when you have a non-identity transform. Change the center instead.
From the documentation:
Warning If the transform property is not the identity transform, the value of this property is undefined and therefore should be ignored.
When you are setting the transform on the first line and then reading the frame after it is undefined what you actually get back.
// Setting a non-identity transform (1)
myImageView.transform = CGAffineTransformMakeRotation(45);
CGRect frame = myImageView.frame; // At this point the frame is undefined (2)
// You are modifying something which is undefined from now on ...
Also, not only should you not read the frame because it is undefined, you should also not set it.
if the transform property contains a non-identity transform, the value of the frame property is undefined and should not be modified.
The solution to that problem comes in the next sentence of the documentation
In that case, you can reposition the view using the center property and adjust the size using the bounds property instead.
Since you are only changing the position I would suggest that you don't touch the frame and instead read the center of the image view and set it to it's new value. The center is not affected by the transform in the same way as the frame.
CGPoint center = myImageView.center;
center.x = x_center_position; // Note that the `center` is not the same as the frame origin.
center.y = y_center_position; // Note that the `center` is not the same as the frame origin.
myImageView.center = center;
Try to remove autoresizing Mask of ImageView
imageView.autoresizingMask = UIViewAutoresizingNone;
This may solve your problem
My transform does not draw after the frame is redrawn with setFrame.
I'm scaling a view when the orientation changes using setFrame. But this view also needs to change position depending on a BOOL argument: On = up in view, off = down off screen. I use setTransform to adjust the position of the view.
First I draw the view by doing a setFrame. This draws the view 100 points just off screen at the bottom. Then I set a transform (-100 on the ty) to bring it up into the view points (as long as the BOOL is set to TRUE, else the transform is 0 and the view is off screen).
[view setFrame:CGRectMake(0, self.view.bounds.size.height, self.view.bounds.size.width, 100)];
[view setTransform:CGAffineTransformMake(1, 0, 0, 1, 0, -100)]
This works fine, as expected, but when change orientation, and this code is re-run (to re-size the view) the transform does not draw, even though it is Logged as being the transform of the view. In other words the view is just off screen, as if the transform.ty was 0.
Log message before re-draw: view.transform.ty -10.000000
Log message after re-draw: view.transform.ty -10.000000
Any help?
A view's frame is a value that is derived from three fundamental values: bounds, center, and transform. The setter for frame tries to do the right thing by reversing the process, but it can't always work correctly when a non-identity transform is set.
The documentation is pretty clear on this point:
If the transform property is not the identity transform, the value of
this property is undefined and therefore should be ignored.
...
If the transform property contains a non-identity transform, the value
of the frame property is undefined and should not be modified. In that
case, you can reposition the view using the center property and adjust
the size using the bounds property instead.
Since your transform only translates the view, I don't see any reason to use it at all. Just change the origin of the view's frame:
[view setFrame:CGRectMake(0, self.view.bounds.size.height - 100, self.view.bounds.size.width, 100)];