I would like to reproduce UIScrollView's flick-to-scroll behavior, but I don't want to use (or can't use) that class. What can I do?
Okay, I've answered this by implementing my own library that captures the dynamics of UIScrollView.
What’s useful about my code is that it is independent of coordinate system, animation rate, and particular UI classes that you're using. It can easily be nested in a custom view class of your choosing.
The iPhone’s default flick-to-scroll behavior is interesting. If you hold your finger down for a long time and move it in a variety of directions, you’ll see that only the very last direction is used to compute the scrolling motion.
If you try to build this code yourself, however, you’ll quickly discover that simply using the last two points to compute the direction of motion isn’t going to cut it. Instead, my code keeps a short history of touches and uses linear interpolation to determine where the touch “would have been” some small amount of time ago. This interpolated point is used as the basis for computing the motion vector. This leads to a very pleasing interaction.
The code is available on github, here: http://gist.github.com/100855. It is released under the BSD license.
So what about UIScrollView did not work for you? That class is pretty flexible...
Dave, I see you've answerd your own question with some code but, doesn't setting the following give you what you need:
myScrollView.bounces = YES;
myScrollView.pagingEnabled = YES;
myScrollView.directionalLockEnabled = YES;
Specifically, it sounds like you have reimplemented directionLockEnabled. Maybe understanding why you can't use UIScrollView is the more interesting problem :-)
This is cool! I've used it in an app where my scrollable view is one day's worth of graphical data in a range from 1902-2037, so a UIScrollView would not be efficient.
Related
I have an infinite scrollview in which I add images as the user scrolls. Those images have varying heights and I've been trying to come up with the best way of finding a clear space inside the current bounds of the view that would allow me to add the image view.
Is there anything built-in that would make my search more efficient?
The problem is I want the images to be sort of glued to one another with no blank space between them. Making the search through 320x480 pixels tends to be quite a CPU hog. Does anyone know an efficient method to do it?
Thanks!
It seems that you're scrolling this thing vertically (you mentioned varying image heights).
There's nothing built in to UIScrollView that will do this for you. You'll have to track your UIImageView subviews manually. You could simply maintain the max y coordinate occupied by you images as you add them.
You might consider using UITableView instead, and implementing a very customized tableView:heightForRowAtIndexPath: in your delegate. You would probably need to do something special with the actual cells as well, but it would seem to make your job a little easier.
Also, for what it's worth, you might find a way to avoid making your solution infinite. Be careful about your memory footprint! iOS will shut your app off if things get out of hand.
UPDATE
Ok, now I understand what you're going for. I had imagined that you were presenting photographs or something rectangular like that. If I were trying to cover a scroll view with UILeafs (wah wah) I would take a statistical approach. I would 'paint' leaves randomly along horizontal/vertical strips as the user scrolls. Perhaps that's what you're doing already? Whatever you're doing I think it looks good.
Now I guess that the reason you're asking is to prevent the little random white spots that show through - is that right? If I may suggest a different solution: try to color the background of your scroll view to something earthy that looks good if it shows through here and there.
Also, it occurred to me that you could use a larger template image -- something that already has a nice distribution of leaves -- with transparency all along the outside outline of the leaves but nowhere else. Then you could tile these, but with overlap, so that the alpha just shows through to the leaves below. You could have a number of these images so that it doesn't look obvious. This would take away all of the uncertainty and make your retiling very efficient.
Also, consider learning about CoreAnimation (CALayer in particular) and CoreGraphics/Quartz 2D ). Proper use of these libraries will probably yield great improvements in rendering speed.
UPDATE 2:
If your images are all 150px wide, then split your scrollview into columns and add/remove based on those (as discussed in chat).
Good luck!
I am currently working on an app, which includes a paint function. It actually doesn't work that bad, but the problem is, that the refresh-rate or the frequency of the calls for the touchesMoved-method is too bad.
If you move the fingers fast over the screen, the lines get many edges and it doesn't look that good. So i thought about increasing the call-frequency for this method. Would that be a good and even possible solution for my problem?
Maybe you can help me with my problem. Thank you in advance.
Think about this approach: Look at Adobe's Ideas App on the AppStore. If touchesEnd, work with NSBezierPath to get a smoother look without edges. You basically store the points in touchesMoved in an array? So you got the points to insert in the Bezier Path functions. You have a edgy look while drawing but after releasing it looks kind of smooth. I did so in one of my projects and result is fairly okay.
(But there are many other approaches to build a drawing application.)
Demo App from Apple: Click here
I am not a newbie to Cocos2D but I am building quite an advanced HUD with several sliding and overlapping CCLayer and CCMenu/CCMenuItemImage objects.
They are all responding to touches correctly in turn. However when things overlap, it seems the buttons underneath take priority over the things on the top, no matter what order I add them to the world.
Indeed, even implementing the registerWithTouchDispatcher method and returning YES/NO ccTouchBegan:withEvent: seems not to have the correct effect. It also appears that ccTouchBegan:withEvent: is then called on all buttons/menus in the world rather than just those underneath the touch.
I'd really like advice on a reliable way to detect and consume a touch on an object that is top most in the view without anything else hearing about the touch.
Thanks in advance!
How about this commit for develop branch of cocos2d-iphone?
v1.0.0-rc3 or earlier doesn't have the mechanism for touch priority. This commit seems to implement it.
Why can't you use tags? I'm not sure at the moment how to check z order but I would personally probably just use tags.
How can I integrate a Scrollwheel into my application?
I'm currently using Sliders but have found them to be sometimes difficult to control exactly (for example with a linear scale from 0% to 100%). I guess they weren't designed for that purpose and are meant to be used for cases where not pitch perfect control is ok (Volume Control and the likes). However, I really need an exact way of inputting data (other than TextFields, they won't work in my case).
I figured that a Scrollwheel kind of UI Element would be perfect for me. Are there any opensourced Scrollwheels available that would fit my needs?
Horizontal, just like Sliders
Variable Start and End Values
Variable Scale
Small in height
Pretty :)
I tried using the Picker but that didn't work for me since it shows it's values inside of it, which makes it both big and not pretty to look at when used multiple times inside of one View.
If there's nothing available that fulfills my needs (described above) could someone please give me a hint on how to start effectively with creating such a UI element? Thanks!
I've finally found something which fits my needs :)
OBSlider, a subclass of UISlider which allows variable scrubbing speeds – it imitates the behavior seen while scrubbing in iPod.app.
Fulfills all my needs:
Horizontal
Variable Start and End Values
Variable Scale
Small in height
Pretty :)
I am new to iPhone programming, so I think part of the problem is that I don't know what I really want to google to find my answer. I am looking for a method that allows a user to draw a line on the screen. There is no guarantee that it will be straight, it can be curved or whatever. I was thinking that I could create some small square image, and then as they draw, place them into a NSset. But I am not really sure how to communicate each new object up to the view. Up to this point, I've just been messing around with objects I put on the view and then assign movement to those, this is my first jump into on-the-fly object creation.
It might be that I just need to jump into a class/object type or even a tutorial, any guidance would be great.
Thanks!
Are you asking how to create a 'paint' type application? There's an apple example for that:
http://developer.apple.com/iphone/library/samplecode/GLPaint/Introduction/Intro.html
This question is relevant, but might be too complex when you're just starting out:
Improving Finger Painting Performance
If you're a bit more specific about what problem your app is to solve you might get some more specific answers.