Some problems with refresh UICollectionView
Some problems with refresh UICollectionView
Mitchell
发布于 2018-09-30 09:38:42
发布于 2018-09-30 09:38:42
May flash on the screen
- Sometiems you may find your collectionView has a phenomenon of flash when you call
reloadDatawhich is because adding cells is inlayoutSubviewsmethod, aslayoutSubViewswill be called in the next runloop after callreloadData, in this case thevisibleCellsmethod may return nil, so the flash occur.- How to fix it ? You may call
layoutSubViewsmanually as followed:
- How to fix it ? You may call
//BUG:
[self.collectionView reloadData];
//Solution:
[self.collectionView reloadData];
[self.collectionView setNeedsLayout];
[self.collectionView layoutIfNeeded];How to refresh without Animation
- If you partial refresh with UICollectionView like
insert, reload, delete, these methods may have a default animation, here are some ways to remove it:
//One way:
[UIView setAnimationsEnabled:NO];
[collectionView performBatchUpdates:^{
[collectionView reloadItemsAtIndexPaths:indexPaths];
} completion:^(BOOL finished) {
[UIView setAnimationsEnabled:YES];
}];
//Besides:
[UIView animateWithDuration:0 animations:^{
[collectionView performBatchUpdates:^{
[collectionView reloadItemsAtIndexPaths:indexPaths];
} completion:nil];
}];
//In addition:
[UIView performWithoutAnimation:^{
[self.collectionView reloadItemsAtIndexPaths:indexPaths];
}];How to refresh without Animation reference
Asynchronous refresh problem
- If your App contain high-performance rendering requirements with attributes like Weibo or Wechat's message list you may use asynchronous text fresh framework like YYText. You may have the problem with text flash when you call collectionView's
reloadDatamethod github link - Solution: you may replace
reload all data methodwithreload partial data methodas followed:
//insert data:
@try{
[self.collectionView performBatchUpdates:^{
[self.datas insertObjects:items];
[collectionView insertItemsAtIndexPaths:indexPaths];
} completion:^(BOOL finished) {
}];
}
@catch ( NSException * e ) {
[self reloadCollectionView];
}
//reload data:
@try{
[self.collectionView performBatchUpdates:^{
[self.datas replaceItems:items];
[collectionView reloadItemsAtIndexPaths:indexPaths];
} completion:^(BOOL finished) {
}];
}
@catch ( NSException * e ) {
[self reloadCollectionView];
}
//remove data:
@try{
[self.collectionView performBatchUpdates:^{
[self.datas deleteItems:items];
[collectionView deleteItemsAtIndexPaths:indexPaths];
} completion:^(BOOL finished) {
}];
}
@catch ( NSException * e ) {
[self reloadCollectionView];
}- As you can see, using @try-catch syntactic can avoid crashing after refresh failed, once you failed you can call
collectionView realoadDatato refresh all the UICollectionView instead.
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