I created line chart. Now I need to display point on this chart when I tap the screen.
What would be the best method? Do I need to call drawRect method again, draw whole chart with marked point?
I'm thinking about something like transparent layer over the chart UIView.
Can I create another transparent UIView and put it on the position of my chart?
Since all drawing is done in a view's drawRect: you can only optimize your chart's drawing so it can be made to update only a part of it and use setNeedsDisplayInRect: (passing the area where the marker should be).
Or you create another UIView subclass that is layered atop of your chart and that does nothing but drawing the markers on a transparent background. Probably easier and faster to implement. It also would have another benefit:
If you make that view only as big as the bounding box of the marker you could also easily animate it, like fading it in and out. Or letting it rotate a little (to see the effect I have in mind, select the "Help" menu in Mac OS X, type something in the search field like "a", and see the marker next to a menu item move a little around a spot).
You can draw a portion of your view using setNeedsDisplayInRect:.
Related
I am displaying a big image in CATiledLAyer.
Now i want to draw a line between two points where the user touches on that image.
Would that be possible ?? , if so can you outline me the way to accomplish it ??
Thanks,
Ratna
I did something similar for an app a while back. The strategy I used was to place another view on top of the view with the tiles. Then set your self up as a UIScrollViewDelegate and everytime the tiled view scrolls or zooms, recalculate where the overlayed objects need to be. Just read the contentOffset value and the zoomScale and you should have what you need to correctly figure out where your overlay needs to be positioned. You will also have to make sure that touches are correctly reaching the tile view if they have to pass through your overlay view.
So I made a UIView subclass let's called it 'MyView' that simply draws a line inside the DrawRect method.
I then drag a UIImageView in interface builder and put it inside MyView. But now when I run the program it's obscuring the line that I'm drawing. I'm wondering, is there a way for me to draw the line on top of the image that I have dragged into my View?
No, you'll have to reorganise the view hierarchy. CoreGraphics uses a painters model so views behind will always be drawn over by views infront. To solve this you could use a container view that holds your image view and has a transparent view (line drawing view) that sits over the image view.
Another option is to draw the image using core graphics calls in your drawRect method and then draw the line over it.
One way is to have whatever adds MyView to add your UIImageView on top of MyView. It's not ideal (you probably have good reasons for keeping MyView and the UIImageView in a single class) but definitely solves your problem (I recently did this, only, I added it to the keyWindow =)
I would use a CAShapeLayer that has a path representing the line, and insert that layer ahead of the built-in view layer. Then it should draw on top.
My question is very similar to this one Not drawing outside bounds when clipToBounds=NO which received no clear answer.
Basically I have a UIView, and I want to draw a line from the center of it, to the edge of the screen. Calculating where these points are is easy, using [self convertPoint:(CGPoint){0,0} fromView:[self superview]]; (which finds the origin with respect to my view's superview. But when I draw a line from my view's drawRect: it gets clipped at my view's bounds.
Is there a way to draw outside of my view's bounds? I've tried changing the clipsToBounds property, but it doesn't seem to have any effect.
I can't draw my lines from the superview because I need to do this with multiple views and some will be in front of others... figuring out the layer from the superview's drawRect seems like a bad idea.
Similarly, I don't think I can just resize my view's bounds to include the entire screen, because my views need to be dynamically re-sizable... the bounds would have to be HUGE (>20,000 points square) for this to work.
I wouldn't recommend ever drawing outside of a view's bounds. Either your view needs to resize automatically to include your drawing or you need to have transparent overlapping views. Or both. I can't think of a situation that either of these cases wouldn't cover, but I may lack imagination. =)
Likely what is happening currently is that when the super view gets redrawn it tells the super view that it needs redrawn, resulting in erasing the drawing you are doing outside. It's been a while, anyone more knowledgeable can (should!) correct me here if I'm wrong.
I don't know if "Quartz Debug" (from the standard apple developer tools install, /Developer/Applications/Performance Tools/Quartz Debug) works in the simulator, but it's worth a try. It has a mode that will show you when and how often redrawing takes place, with a border and optional delay on the refreshes.
You can do what you are asking, but you need to force redraw your sub-views every time you go outside the sub-view's bounds, meaning that your super-view needs to manually draw it's children inside of it's draw function. Essentially you would be throwing out apple's drawing paradigm and simply causing your sub-views to act like a drawing extension of your main view anyway.
Additionally, if your ranges are so dynamic you may want to consider drawing in percentages of the screen or super-view rather than in points, it may make more sense to code.
I am working with creating a simple iPhone app to show a map and some labels, however the MKMapView likes being centered when I put it in the interface builder.
I am very new to this, so i apologize for my ignorance.
I cannot seem to find a way to move the MKMapView from its centered position. I can scale the edges, however the scaling is mirrored on both sides and it does not let me alter the x and y value manually. I want to move the MKMapView to the top of the screen and have some labels on the bottom, however I don't want any extra space at the top.
Is there any method I can use (either within the Interface Builder OR in the actual Objective C code) which will let me move the MKMapView more freely?
Thank you,
-Serge
It sounds like you're attempting to place it in a bare window. If you want to position it on a portion of the screen somewhere you'll want to place a regular View in the window first (that could just fill the window), then put the MKMapView on that view. You'll be able to move it to wherever you'd like.
I've created a NIB file with some button controls on it, and as a background it has an ImageView which contains a PNG file loaded from my project.
What I want to do is to draw on top of the ImageView - imagine that my UI is a clockface and I want to draw the hands of the clock on top of the background image.
Is it the correct approach to try to subclass the UIImageView and use its DrawRect as when I use the DrawRect of the default view I don't see anything on the screen?
I'm a little lost as I'm finding this particular bit of the documentation hard to follow.
Thanks.
Create a new custom UIView (e.g. named HandsView) that sits on top of your background view (by adding it as a subview of the UIImageView). In the custom view, you can use the drawRect method. Make sure, you clear the context to transparent, so that the background image can be seen below the HandsView.
If you just want to draw turning hands, you can also try to use two fixed UIImageViews with the images of the hands and use the transform property to apply a rotation.