这个问题的解决方案比我预想的要简单得多。以下是我想出了(这是简单的版本,没有所有的花哨的代码):
@interface myViewController {
CGPoint _velocity;
CGFloat _damping;
UIImageView *_myImageView;
}
- (void)viewDidLoad {
_velocity = CGPointZero; // x = 0, y = 0
// Accelerate _myImageView
NSTimer *myTimer = [NSTimer scheduledTimerWithTimeInterval:0.02f // Update frequency
target:self
selector:@selector(slideImageView)
userInfo:nil
repeats:YES];
}
@implementation myViewController
- (void)slideImageView {
// No need to move _myImageView when _velocity = 0
if (_velocity.x > 0 && _velocity.y > 0)
CGPoint position; // The next position
position = _myImageView.center;
position.x += _velocity.x/30;
position.y += _velocity.y/30;
// Damp _velocity with damping factor
_velocity.x *= _damping;
_velocity.y *= _damping;
// Bounce on edges
if (position.x < X_AXIS_MIN_VALUE || position.x > X_AXIS_MAX_VALUE)
_velocity.x = -_velocity.x;
if (position.y < Y_AXIS_MIN_VALUE || position.y > Y_AXIS_MAX_VALUE)
_velocity.y = -_velocity.y;
// Move
_myImageView.center = position;
}
}
// Move been around by implementing touchesBegan: and touchesMoved:
// There are a million tutorials on how to do this.
- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
// Do whatever you need to do and calculate x- and y-axis velocity,
// maybe based on the distance between the last 5 points/time.
CGPoint mySpeed;
mySpeed.x = //the new x speed;
mySpeed.y = //the new y speed
_velocity = mySpeed;
}
@end
上面的代码(+缺少执行),可以在屏幕上拖动一个UIImageView。当你松开手指时,ImageView将继续在屏幕上滑动,如果它们被击中,则会在边缘上弹起。您移动手指的速度越快,ImageView加速的速度就越快(当然,根据您计算速度的方式)。
我希望任何与此类问题斗争的人都会发现它很有用。