I am trying use table view on horizontally. I rotated table view using .transform property it only rotates it on the center. Changing the center property undesirable for me.
Can you set arbitrary transformation matrix?
If yes, use one that translate it so center is on origin, then rotate and then translate it back.
Related
I have a view that is slanted as in rotated by an angle. To rotate I used CGAffineTransformMakeRotation. Now I want to animate it going up vertically or in other words in negative y axis relative to the root view for 100 px. But my view needs to know X and Y components of that 100 px in terms of its own X and Y system. I use trigonometry to find those values and its works fine but the problem is that when I animate it using CGAffineTransformTranslate , it moves the view in the X direction first (non animated, jumps) then in Y (animated). How can I make it translate properly in both dimensions together?
From Apple
https://developer.apple.com/library/ios/documentation/WindowsViews/Conceptual/ViewPG_iPhoneOS/WindowsandViews/WindowsandViews.html#//apple_ref/doc/uid/TP40009503-CH2-SW6
https://developer.apple.com/library/ios/documentation/UIKit/Reference/UIView_Class/index.html#//apple_ref/occ/instp/UIView/frame
The value in the center property is always valid, even if scaling or
rotation factors have been added to the view’s transform. The same is
not true for the value in the frame property, which is considered
invalid if the view’s transform is not equal to the identity
transform.
So when you applies non identity transform like rotation the frames becomes invalid. You should not use frame for transformed view. Instead you can use center property for repositioning view.
Say I'm creating an animation, and I want to move the center of a UIView to a certain CGPoint I have. I know what I want the center to be, just the aforementioned CGPoint, and I know the width and height that I want, but when I go to create the frame for my UIView I have no idea what to set for the x and y for the origin.
Should I just be setting 0, 0 or anything really? Does it matter?
Should I just be thinking as setting center as a different method of setting the origin? Makes me wish CGRect had an instantiator with center as an option.
There has been a previous question addressing a somewhat similar question, but it addresses them as three separate entities, rather than how to deal with center when creating the view.
Yes, go ahead and set the initial frame's origin to anything, since subsequently setting the center will effectively move this origin anyway. It is not uncommon to initialise views with a frame of CGRectZero when it is going to be fully configured later.
frame is actually just a calculated property based on the view's center and bounds, and so all three are intrinsically linked when it comes to view layout. The UIView Class Reference has this to say about it:
The geometry of a view is defined by its frame, bounds, and center
properties. The frame defines the origin and dimensions of the view in
the coordinate system of its superview and is commonly used during
layout to adjust the size or position of the view. The center property
can be used to adjust the position of the view without changing its
size. The bounds defines the internal dimensions of the view as it
sees them and is used almost exclusively in custom drawing code. The
size portion of the frame and bounds rectangles are coupled together
so that changing the size of either rectangle updates the size of
both.
Does an affine transform reposition the content within the view or transform the view's output?
In my experiments, it appears to be the latter. If I apply a translation moving the contents off the view the right, I do not appear to be able to draw in the area within the view to the left.
As requested: I would like to be able to create a scrolling view that rotates. Imagine viewing part of a globe viewed parallel to the axis. The content has to rotate with scrolling.
If I use an affine transform, it appears that the view display is transformed, not the content within the view. If I scroll the content to the right using an affine transform, I get a black area to the left visible in the view that I cannot draw in.
I am trying to confirm whether my interpretation of what is happening is correct. If so, I need to try a different approach.
I am rotating the image on slider value -
I am using this code for rotation -
editingView.transform = CGAffineTransformRotate(editingView.transform,sliderVal);
its Rotating properly but if i am trying to move or resize after rotation,The editingView is resizing with unexpected behavior and view disappears from screen.
Please suggest me what i am doing wrong.
Well whenever you rotate a view which is inside a superview, you should preserve the position of the view. If you are not rotating any view across the origin then, you should first translate the view's origin to the superview's origin and then rotate and then again translate back to the original point.
Find the coordinate if the view you want to rotate with respect to its superview, say it (x,y).
Translate the view to the origin as;
view.transform = CGAffineTransformMakeTranslation(x,y)
Rotate the view by some angle, say PI,
view.transform = CGAffineTransformMakeRotation(PI)
After rotation translate back to the original point as;
view.transform = CGAffineTransformMakeTranslation(-x,-y)
And that's it. It should work with all the different rotation.
Have a look at this question.
Since you do not show any code on how you do the move or resizing, I suspect you are not properly concatenating the transforms. Furthermore, after you did the rotation, a translation will possibly work on the rotated coordinate system, therefore leading to unexpected behaviour.
Changing transform value affecting the frame value of UIView. As Apple says:
Warning: If this property is not the identity transform, the value of
the frame property is undefined and therefore should be ignored.
Apple docs
So, if you are moving or resizing your view using frame property, try do this with bounds, center properties
I'm trying to rotate UIImageView for certain degrees with CGAffineTransformMakeRotation() function, but it end with imageView only rotates, but when I moved to another coordinates then imageView stretched or change height and width. I have no clue why this happens.
Here is a code:
double a = atan2(dx,dy);
bowImageView.transform = CGAffineTransformMakeRotation(a);
WHen you apply a transform to a view the geometry changes. If you wish to move that view rotated, the simplest solution is to set the transform back to CGAffineTransformIdentity, move the view and reapply the rotation.
The other way is to work out the movement based on the current rotation.....but I find the first solution easier!