如何通过触摸和滑动来移动和滑出UIView？

Question

I´m trying to animate a sort of draggable UIView where the behaviour should be something like this:

• Drag along the screen following the touch of the user.
• Detect a swipe touch and drag automatically with an initial speed and a negative acceleration that makes is stop after some time.

Something like moving around a photo and then through it to one side of the screen.

Any tips on this?

Answer 1

A similar question was asked (by me) about 3 weeks ago. Though some of the answers I received were a little off the mark the best advice was: 1- study Apple's MoveMe example for how to touch an object and drag it around. And 2- you "throw" the object by basically comparing the [touch locationInView:self.view] to the [touch previousLocationInView:self.view] in touchesEnded (could also store a reference to first touch in touchesBegan but I find that less helpful as user may pause) using the time stamp of each you can determine the direction of swipe (flick) and rate of speed and use them to send your little UIView flying around. Obviously you want to apply forces ("friction") or whatever to slow it down so it doesn't fly right of your screen...

Answer 2

I am not sure. But may be you can use decelerating property of UIScrollView object. Put your imageView in UIScrollView and use this property. Its a BOOL var and the returned value is YES if user isn't dragging the content but scrolling is still occurring.

Answer 3

Take a look at the MoveMe sample project from Apple (registration may be required). It demonstrates how to have a placard follow a touch as well as transform itself based on different touches.

Essentially, the idea is that you override the UIResponder touch methods to analyze what kind of touch the device received, and then either move the object to follow the user's finger or give it a speed in a direction depending on whether it was a slow drag or a swipe. You can then use Core Animation to animate changes to the object's frame.