I have a UIView that a user drags around via setting its center in the touchesMoved: method. When the user lets go, I want the UIView to fall off the screen according to how fast and what direction they were moving it in.
Do I need to somehow create a vector by comparing the UIView's last center point to it's new center point? And subtract a fixed amount to the vector's y value every so often with a NSTimer?
Yes, you will need to a decent amount of physics in calculating
Speed of swipe
Direction of swipe
You will need to use the touchesMoved method along with a timer to track the amount of time for the swipe and also the co-ordinates for the new location of the object. This should be fairly straight forward. Once you are done finding those you can simply add a UIAnimation for the object to move to its new place.
~ A suggestion:
I would suggest that you have a look at Cocos2D and integrate the library with you app. You will not need to implement touch delegate methods and compute things yourself ~ there are libraries for that :) It has a lot of libraries especially for moving objects (or sprites if you wish to call them that way) and you have animation method like easeInEaseOut, etc.. that can be impacted on the moving object. If you are developing a game of some sort, have a look at chipMunk engine in Cocos2D as well.
Related
i need to achieve an animation effect like (the Effects in "Pic Something","Pic Reveal" and so on) in my app.
What i am saying is i need to implement this tasks
Task1: when the user touches one Letter, then it change its frame(current position) to another frame(target position).
Task2:when the user touch the Letter(in Target position), it comes back to its original position again.
this can be clearly understood if u see the sample Apps.
I didn't find out any samples on internet also.
Thanks in Advance..
Take a look at UIView animation and animation blocks in iOS, that's what you need. With them you can create any animation you like. Here's a nice tutorial.
And about the whole system you described - I would create an NSDictionary of UIView positions and attach those to the corresponding tags of UIViews- this way you will always know from which place every UIView came from.
I'm working on an iPad application and that's my problem:
I elaborated an algorithm to know if a point is inside a polygon, in an image. So I need when touching the Image, to know the coordinates of the touched point and then do an action using those coordinates (an NSLog to make the example easy), the problem is that I can't use an IBAction on an UIImageView, and so can't recover the point's coordinates. Thanks for any help
I think at first you have to make polygon which fit to your image. And then you can use touchesBegan:withEvent: to get the coordinate of touch point and judge whether the point is inside of polygon or not.
Here is similar question like yours.
How to get particular touch Area?
I think this is a little difficult work, so maybe you would better use cocos2d library which have collision judgement function.
http://box2d.org/forum/viewtopic.php?f=9&t=7487
But also I think iOS is well constructed for handling touch, so this is beneficial effort for you.
I am trying to program an iPhone app where the user can handwrite. I am using touchesmoved to track the user's finger, but I get between 30 and 50 updates a second. For quick finger movements, this is often no enough to get smooth letters: small letters like i often just get the touches began and then the touches ended points, with no points in between.
I was wondering if I could get better time (and space) resolution by using an NSTimer to query the touch object for its locationInView without waiting for it to call touchesmoved. Anyone knows if this might work?
Thanks.
I'll advise against NSTimer - its better to use CADisplayLink approach. For example, try to use my tiny lib https://github.com/nt9/NTLoop
So I want to have a view (NSView, NSOpenGLView, something CG related?) which basically displays a map. Such as:
http://dump.tanaris4.com/map.png
Obviously that looks horrible, but I did it using an NSView, and it draws SO slow. Clearly not designed for this.
I just need to allow users to click on the individual (x,y) coordinates to make changes, and zoom into a certain area (to see it better).
Should I go the OpenGL route? And if so - any suggestions as to how to get started? (I was able to follow the guide to draw a triangle, so that's good).
I did find this post on zooming in an NSView: How to implement zoom/scale in a Cocoa AppKit-application
My concern is if I'm drawing over 6000 coordinates and the lines connecting them, this isn't efficient at all.
I don't think using OpenGL would be of any good here. The problem does not seem to be the actual painting, but rather the rendering strategy. You would need a scene graph of some kind to dynamically handle level of detail and culling.
Qt has all this packaged in a nice class class QGraphicsScene (see http://doc.qt.nokia.com/latest/qgraphicsscene.html for reference, and http://doc.qt.nokia.com/main-snapshot/demos-chip.html for an example).
Some basic concepts you should consider using:
http://en.wikipedia.org/wiki/Scene_graph
http://en.wikipedia.org/wiki/Quadtree
http://en.wikipedia.org/wiki/Level_of_detail
Try using core graphics for this, really there is so much that could be done. Watch the video Practical Drawing for iOS Developers from WWDC 2011 and it should give an over view of what can be done with CG.
I believe even CoreGraphics will suffice for what you want to achieve, and that should work under a UIView if you draw the rectangle of your view completely under the DrawRect method of your UIView (you must overload this method). Please see the UIView Class Reference. I have a mobile application that logs points on the UIMapKit, kind of like Nike+, and it certainly works well for massive amounts of points/line segments. There is no reason why this simple approach cannot work for you as well.
I want to do some custom drawing in a NSView subclass where should I get started?
As Jarret mentioned the Apple docs are a great place to start. However, some things to bear in mind:
The default coordinate system used with views is the Cartesian coordinate system where the origin is in the bottom left corner of the view. Most often you want the origin to be in the top left corner of the view so this is where you override the isFlipped: method (the default implementation which returns NO), returning YES:
- (BOOL)isFlipped
{
return YES;
}
This "flips" the coordinate system so that the origin becomes in the top left corner, after a vertical flip has taken place. This can make some drawing position calculations easier.
The main things you'll probably want to get started with are things such as:
Filling basic rectangles (using the NSBezierPath class method fillRect:, along with the NSColor class for setting and using colours).
Working with images (using the NSImage class and the drawing methods it provides).
Paths, where you can draw lines and other shapes (with the NSBezierPath class).
You'll also want to take a look into Graphics Contexts at some point, and working with setting attributes (such as the current colour, a shadow etc) on them, used for subsequent drawing operations.
Probably not of immediate concern, but just a side note, that at some point you should take a look at the Optimizing View Drawing section of the View Programming Guide for Cocoa. Drawing operations should be fast, and it amazes me sometimes how little consideration people put into the performance aspects of drawing, when there are some basic things you can do to make your drawing – and therefore application – more efficient, such as only redrawing parts of the view that have actually changed, rather than the entire thing.
Apple's Introduction to Cocoa Drawing Guide is the best place to start. Lots of examples there.
You should start at the beginning.