UIKit Dynamics:UITableViewCell内的附件 [英] UIKit Dynamics: Attachment inside UITableViewCell
问题描述
我的表格视图单元格在 UIView
中包含一个圆圈,表示一个值。我想将 UIKit Dynamics
附件行为添加到该圈子中,以便在滚动时滞后一点。
My table view cells contain a circle in an UIView
, indicating a value. I want to add the UIKit Dynamics
attachment behaviour to that circle in order to for it to lag a bit when scrolling.
我不想将单个单元格相互附加,而只是将圆形视图附加到 UITableViewCell
。单元格的其余部分应该像往常一样滚动。
I don't want to attach the individual cells to each other but only the circle view to the UITableViewCell
. The rest of the cell should scroll as usual.
问题: UITableViewCell
的原点始终为(0,0)
。如何在滚动时实际移动的视图中添加圆圈?
Problem: The UITableViewCell
has its origin always at (0, 0)
. How can I add the circle to a view that actually does move when scrolling?
推荐答案
我终于开始工作了。 UITableView
移动每个单元格以及该单元格中包含的所有视图的坐标系。因此,我需要在滚动期间在 UITableViewCell
内手动移动我的视图,同时仍然引用初始锚点。
I finally got it to work. The UITableView
moves the coordinate system of every cell and of all views contained within that cell. Therefor I needed to manually move my view inside the UITableViewCell
during scrolling while still referring to the initial anchor point.
表视图控制器:
- (void)scrollViewDidScroll:(UIScrollView *)scrollView {
BOOL scrollingUp = '\0';
if (self.lastContentOffset > scrollView.contentOffset.y) {
scrollingUp = YES;
}
else if (self.lastContentOffset < scrollView.contentOffset.y) {
scrollingUp = NO;
}
NSInteger offset = 64; // To compensate for the navigation bar.
if (scrollingUp) {
offset = offset - scrollView.contentOffset.y;
}
else {
offset = offset + scrollView.contentOffset.y;
}
// Limit the offset so the views will not disappear during fast scrolling.
if (offset > 10) {
offset = 10;
}
else if (offset < -10) {
offset = -10;
}
// lastContentOffset is an instance variable.
self.lastContentOffset = scrollView.contentOffset.y;
for (UITableViewCell *cell in self.tableView.visibleCells) {
// Use CoreAnimation to prohibit flicker.
[UIView beginAnimations:@"Display notification" context:nil];
[UIView setAnimationDuration:0.5f];
[UIView setAnimationBeginsFromCurrentState:YES];
cell.view.frame = CGRectMake(cell.view.frame.origin.x, offset, cell.view.frame.size.width, cell.view.frame.size.height);
[UIView commitAnimations];
[cell.dynamicAnimator updateItemUsingCurrentState:cell.view];
}
}
表格视图单元格:
-(void)layoutSubviews {
[super layoutSubviews];
// _view is the animated UIView.
UIDynamicItemBehavior *viewBehavior = [[UIDynamicItemBehavior alloc] initWithItems:@[_view]];
viewBehavior.elasticity = 0.9f;
UIAttachmentBehavior *attachmentBehaviorView = [[UIAttachmentBehavior alloc] initWithItem:_view attachedToAnchor:CGPointMake(_anchorView.frame.origin.x + _anchorView.frame.size.width / 2.0f, _anchorView.frame.origin.y + _anchorView.frame.size.height / 2.0f)];
attachmentBehaviorView.damping = 8.0f;
attachmentBehaviorView.frequency = 4.0f;
attachmentBehaviorView.length = 0.0f;
[_dynamicAnimator addBehavior:viewBehavior];
[_dynamicAnimator addBehavior:attachmentBehaviorView];
}
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