發生觸摸事件時，UIImageView跳轉

Question

好的，基本上該代碼當前執行的操作是根據用戶拖動圖像的位置沿Y軸上下拖動圖像，然后圖像返回其原始位置。 我的問題是，如果有人不直接觸摸UIImageView的中心並開始拖動它，將會搖晃（非常不平滑）。 每當有人觸摸UIImageView並開始拖動UIImageView的位置時，都會有些微晃動，直接進入觸摸事件的中心。

我在考慮使用動畫只是將其移動到需要圖像的位置，還是還有其他方法？

如果這不是一種有效的方式，我深表歉意。 我對IOS世界還很陌生。

這是我所擁有的：

-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
    //Gets location of UIImageView.
    self.originalFrame = self.foregroundImage.frame;
}
//This method is used for moving the UIImageView along the y axis depending on touch events.
-(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
    UITouch *touch = [[event allTouches] anyObject];
    if([touch view]==self.foregroundImage) {
        CGPoint location = [touch locationInView:self.view];
        location.x=self.foregroundImage.center.x;
        self.foregroundImage.center=location;
    }
}
//This method sets the UIImageView back to its original position.
-(void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
    CGRect newFrame = self.foregroundImage.frame;
    newFrame.origin.y = self.originalFrame.origin.y;
    [UIView animateWithDuration:1.1 animations:^{
        self.foregroundImage.frame = newFrame;
    }];
}

Answer 1

您還需要將相對於父視圖的第一個位置保存在touchesBegan中。 然后，您可以使用它通過前一個位置和新位置之間的差異來更改框架。 請參見以下代碼。

- (void) touchesBegan: (NSSet*)   touches
            withEvent: (UIEvent*) event
{
  if (touches.count == 1)
  {
    UITouch* touch = [touches anyObject];
    self.touchLocation = [touch locationInView: self.view];
  }
}

- (void) touchesMoved: (NSSet*)   touches
            withEvent: (UIEvent*) event
{
  if (touches.count == 1)
  {
    UITouch* touch = [touches anyObject];
    CGPoint newTouchLocation = [touch locationInView: self.view];

    if (touch.view == self.foregroundImage)
    {
      /* Determine the difference between the last touch locations */
      CGFloat deltaX = newTouchLocation.x - self.touchLocation.x;
      CGFloat deltaY = newTouchLocation.y - self.touchLocation.y;

      /* Offset the foreground image */
      self.foregroundImage.center
        = CGPointMake(self.foregroundImage.center.x + deltaX,
                      self.foregroundImage.center.y + deltaY);
    }

    /* Keep track of the new touch location */
    self.touchLocation = newTouchLocation;
  }
}