How create NSLayoutConstraint when scrolling UITableView - ios

Question

I have UITableView on SingleView. Table view have constraint left 0, right 0, bottom 0, top 520. I need change top 520 to the 0 when scrolling up, and when scrolling bottom return 520. How can make it.
How change NSLayoutConstraint from scroll in -
- (void)scrollViewDidScroll:(UIScrollView *)scrollView
I was trying to implement the so-but failed
- (void)scrollViewDidScroll:(UIScrollView *)scrollView{
if (scrollView.tag == 1){
if (scrollView.contentOffset.y < pointNow.y) {
self.heightLogTabTableView.constant = 0;
[UIView animateWithDuration:0.5f animations:^{
[self.view layoutIfNeeded];
}];
}else if (scrollView.contentOffset.y > pointNow.y) {
self.heightLogTabTableView.constant = 520;
[UIView animateWithDuration:0.5f animations:^{
[self.view layoutIfNeeded];
}];
}
}
}

Answer 1

Replace [self.view layoutIfNeeded]; in your code by-- [_tableView beginUpdates]; and [_tableView endUpdates];. Also modify your variable pointNow as follows.
#import "ViewController.h"
#interface ViewController (UIScrollViewDelegate){
}
#end
#implementation ViewController
CGPoint pointNow;
- (void)viewDidLoad{
[super viewDidLoad];
pointNow = CGPointMake(0, 0);
}
- (void)scrollViewDidScroll:(UIScrollView *)scrollView{
if (scrollView.contentOffset.y < pointNow.y) {
self.heightLogTabTableView.constant = 0;
[UIView animateWithDuration:0.5f animations:^{
[_tableView beginUpdates];
[_tableView endUpdates];
}];
}else if (scrollView.contentOffset.y > pointNow.y) {
self.heightLogTabTableView.constant = 520;
[UIView animateWithDuration:0.5f animations:^{
[_tableView beginUpdates];
[_tableView endUpdates];
}];
}
pointNow = scrollView.contentOffset;
}
#end

Answer 2

Try the setNeedsUpdateConstraints method right after you change the constraint constant. Like:
[self.tableView setNeedsUpdateConstraints];
Update -
If I understood you correctly, this is what you are looking for I think :
-(void)scrollViewWillEndDragging:(UIScrollView *)scrollView withVelocity:(CGPoint)velocity targetContentOffset:(inout CGPoint *)targetContentOffset{
if(self.heightLogTabTableView.contentOffset.y<0){
//it means table view is pulled down like refresh
}
else if(self.heightLogTabTableView.contentOffset.y >= 0) {
//it means table view is being scrolled up
}
}
Hope this helps you.

Answer 3

This single line of code will solve your issue with all top,bottom,left, right constraints to Zero
[self.tableView setContentInset:UIEdgeInsetsMake(520, 0, 0, 0)];

Answer 4

Please try this and it will help you....
-(void)scrollViewWillEndDragging:(UIScrollView *)scrollView withVelocity:(CGPoint)velocity targetContentOffset:(inout CGPoint *)targetContentOffset
{
if (scrollView.tag != 1)
{
return;
}
if(self.heightLogTabTableView.contentOffset.y<0)
{
self.heightLogTabTableView.constant = 0;
[UIView animateWithDuration:0.5f animations:^{
[self.view layoutIfNeeded];
}];
}
else
{
self.heightLogTabTableView.constant = 520;
[UIView animateWithDuration:0.5f animations:^{
[self.view layoutIfNeeded];
}];
}
}

Answer 5

i add global varible CGFloat in my .h file "#property (nonatomic) CGFloat lastScrollOffset;"
- (void)scrollViewDidScroll:(UIScrollView *)scrollView{
if (scrollView.tag == 1){
if (scrollView.contentOffset.y > _lastScrollOffset) {
self.heightLogTabTableView.constant = 0;
[UIView animateWithDuration:0.5f animations:^{
[self.view layoutIfNeeded];
}];
} else if (scrollView.contentOffset.y < _lastScrollOffset) {
self.heightLogTabTableView.constant = self.informationTask.frame.size.height;
[UIView animateWithDuration:0.5f animations:^{
[self.view layoutIfNeeded];
}];
}
_lastScrollOffset = scrollView.contentOffset.y;
}
else if (scrollView.tag == 2){
if (scrollView.contentOffset.y > _lastScrollOffset) {
self.heightCommentTabTableView.constant = 0;
[UIView animateWithDuration:0.5f animations:^{
[self.view layoutIfNeeded];
self.typeCommentView.hidden = NO;
}];
} else if (scrollView.contentOffset.y < _lastScrollOffset) {
self.heightCommentTabTableView.constant = self.informationTask.frame.size.height + 220;
[UIView animateWithDuration:0.5f animations:^{
[self.view layoutIfNeeded];
self.typeCommentView.hidden = YES;
}];
}
}
}