Is there a way to resize a QGraphicsItem to a fixed size?
I know it can be done with scale(float, float), but that seems like a bad direction to go when wanting to resize the item with mouse event. Is there a way to change the boundingRect() so that the Item will then fit the new size?
Thanks
May be too late.
But probably my code at Github PGraphicsItem.py helps you.
I derived my own GraphicsItem class from QtGui.QGraphicsItem.
There I set the size/scale in the paint method which you need to override.
The scaling factors I get from PGraphicsView.py where I subclassed QtGui.QGraphicsView. It holds a method wheelEvent which calculates scaling factors from mouse wheel increments.
EDIT:
In the PGraphicsView.py its the method adjustMarkerSize that recalculates the items to a fixed pixel size.
I do not no if that fits exactly to the question.
Related
I ran into this problem, I have 27 UIView's laying on top of each other, with exactly the same frame, visually they are laying next to each other, visual respresentation:
So the frame for all of them is the big yellow square. They get masked using a CAShapeLayer (the colored triangles). I add a UIPanGesture to all of them (not sure this is the best way to do it), and I want to determine on which one the user panned. Of course (obviously), only the top one is accessible, and always is the view in the UIPanGesture. How do I determine on which one of the UIView's the finger was panning? A for loop seems expensive too.. Or am I approaching this wrong?
This is the code for creating all of them and handling the pan gesture:
Gist to code
Sender to tag is always 27 though, of course... No clue how to solve this one guys! Anyone a clue?
Figure it out!
I moved everything into a custom UIView, where in draw rect I draw all the triangles using CAShapeLayers, add a UIPanGesture to it self, and in the gesture handler you can check in a for loop with CGPathContainsPoint if that layer contains the gesture point!
Solution code snippet
Hope this helps someone!
OK, this might seem very simple but I've been struggling for too long, so I decided to ask for some help.
Basical, I've got a container NSView.
The contents are (from left to right):
an NSSegmentedControl
an NSTextField
an NSSegmentedControl
And they are all aligned horizontally (= they're in the same "line").
What I'm trying to do is:
Fixed width for the first element, and fixed on the left
resizeable textfield
Fixed width for the last element, and fixed on the right
I guess it's pretty self-explanatory.
And here are my autoresizing settings for the 3 views:
View 1
View 2
View 3
And here's the issue: the whole resizing works fine. Until the textfield is resized at such a point where it is collapsed. When the superview/container is resized at a normal size again, the whole design is messed up (with the textfield overflowing the container and lots of such weird issue).
What's going on? Any suggestions?
Note: I got it to work with Auto Layout (merely setting "Auto Layout" and "Add(ing) missing constraints"), but I most definitely want to avoid it since the performance impact is huge -- the overall design is rather complicated, with lots of nesting, so let's stick to the old-fashioned way. :-)
The old springs-and-struts model using autoresizing masks is based on proportional distribution of the change in size based on the current sizes of the subviews being resized. Once any subview gets to zero size, it goes haywire. Either there's division by zero or multiplication by zero and you get bogus results. This is a long-standing issue with the system.
You must set minimum window size to prevent that from happening.
Auto layout is the solution to that and many other limitations of the old model, for all of its flaws.
I want to place a series of images in a UIView... I want to be able to change each image's color using three different .png files (red,yellow,green) as a status indicator. Other than actually drawing the rectangle and filling it, is there an easier way?
Research effort: I have Googled and looked through SO and found nothing dealing with this.
There are lots of ways you can do this. I think the easiest way would be to pragmatically add UIViews as subviews to your main view, or to your parent UIView.
You can set the frame of your views as well as the background color. See this link
adding uiview as a subview to the main view
You can also use images, but since it is a plain solid color, its a lot of extra storage space, etc. to use images when you can programatically render a color.
If it is a series of rectangles, you can store UIViews in some kind of data structure so it is easier to dynamically change the color at runtime. If you aren't moving them around, then init there frames/geometry so they are in the correct location, then access them as members of an array or something similar.
If you want to add gradients to images, this is the best thing I have found:
Gradients on UIView and UILabels On iPhone
I figured it out... I took a UIButton, changed the Type to "Custom", sized it (32 x 32) and programmatically changed the the image depending on circumstances.
[button setImage:<#(UIImage *)#> forState:<#(UIControlState)#>]
Thanks to both of you for getting the thought process running... :D
i want my app to be able to track a person when he moves 2 dimensionally upwards. I already have a vertical scroll view, and it works, but when i press a button i want it to track a little stick figure as he walks vertically, how can i control this? i thought of setting the scrollview.contentoffset to a certain position, but it just changes it one time when i want it to change it fluidly. i suppose i could make a timer that updates the contentOffSet every like .001 seconds or something, but i thought there maybe a better way.
Also, while i was searching the UIScrollView's methods, one of them was an isTracking method, which is a boolean, and I'm assuming it returns yes if the scrollview is tracking something, so given that i assume there is a feature in scrollview so that you can track things. Also, if to track things you have to use some other framework thing that would be helpful to know too
THANKYOU FOR ANY HELP!
The property tracking tells if the scroll view is currently tracking the user's movement. So that definitely won't help you out. (See David H's post for a better explanation for what the property indicates.)
However, you could use setContentOffset:animated: and set animated to YES. That results in a smooth transition to the new content offset.
Instead of calculating a reasonable content offset you might find it easier to specify an area that contains the stick figure. If so use scrollRectToVisible:animated:. Obviously animated should be set to YES.
1) don't use contentOffset = x;, use "- (void)setContentOffset:(CGPoint)contentOffset animated:(BOOL)animated". Experiment how often you need to send this message, but I'm guessing you can do it no more than 10 times a second and get nice results.
2) isTracking means the user has their finger on the scrollView but has not started dragging it. By testing "isTracking" and "isDragging" you can determine if the user is fiddling with your scrollView or not.
I'm trying to draw a graph that is indefinitely large horizontally, and the same height as the screen. I've added a UIScrollView, and a subclass of a UIView within it, which implements the -drawRect: method. In the simulator, everything works fine, but on the device, it can't seem to draw the graph after it reaches a certain size.
I'm already caching pretty much everything I can, and basically only calling CGContextAddLineToPoint in the -drawRect: section. I'm only drawing what's visible on the screen. I have a delegate to the UIScrollView which listens for -scrollViewDidScroll: which then tells the graph to redraw itself ([graphView setNeedsDisplay]).
I found one method that tells me to override the +layerClass method and return [CATiledLayer class]. This does allow the graph to actually draw on the device, but it functions very poorly. It's incredibly slow to actually draw, and the fade in that occurs is undesirable.
Any suggestions?
Well, here's my answer: I basically did something similar to how the UITableView works with cells: I have an NSMutableSet of GraphView objects which store unused graphs. When a section of the scroll view becomes visible, I take a graph view from that set (or make a new one if the set is empty). It already had a scrollX property to determine which part of it was supposed to draw. I set the scrollX property to the correct value and, instead of using the screen width, I gave it an arbitrary width to draw. When it goes out of the scroll view, it is removed from the UIScrollView and added to the set.
I wonder though if I really even need to remove them when they go outof the view? It may be prudent to try leaving them in and remove the ones not on screen only if I get a low memory warning? This might get rid of the pause whenever it needs to redraw a section of graph that hasn't changed.
My saving grace here was that my GraphView already was set up to draw only a portion of the graph. All I needed to do then was just make more than one of them.
I think this is a limitation of the iPhone graphics hardware. Through experimentation, I have seen that the iPhone will refuse to draw a frame that is bigger than 2000 pixels in either height or width. It probably has something to do with limited size for frame buffers in hardware.
Watch the 2011 WWDC session video entitled "Session 104 - Advanced Scroll View Techniques".
Thanks, that's helpful. One question -- what did you use for the contentSize of the UIScrollView? Does UIScrollView tolerate large content sizes (over 2000 px) as long as you're not creating buffers to fill the entire space in your content view? Or are you keeping the UIScrollView a constant size (say, 2 screen widths) and resting the UIScrollView contentOffset property each time you draw (using scrollX instead of the contentOffset to store your position)?
I think I answered my own question (the latter seems like a better alternative), heh, but I'll go ahead and post this in case other people need clarification.