在iOS上实现瀑布流界面
openkk
12年前
前阵子需要做一个需求,在iPhone上实现瀑布流效果。
第一眼看到这个需求,我想到的两种解决方案分别是:
1. 使用多个UITableView,然后控制它们同时滚动;
2. 使用一个UIScrollView,然后参考UITableView的实现自己做一个符合需求并且以后可以重用的控件。
我首先尝试了第一个方案,并且Google过控制多个UITableView同时滚动的代码,在StackOverflow里面找到一段蛮详细的代码了,不过在复杂的用户操作下,仍然会出现滚动不同步的情况。
最终,我放弃了这个方案。
而第二个方案的关键点就在于参考UITableView实现时,如何重用单元格。
下面是我实现的重用代码:
- (void)onScroll { for (int i = 0; i < self.columns; ++i) { NSUInteger basicVisibleRow = 0; WaterFlowViewCell *cell = nil; CGRect cellRect = CGRectZero; NSMutableArray *singleRectArray = [self.cellRectArray objectAtIndex:i]; NSMutableArray *singleVisibleArray = [self.visibleCells objectAtIndex:i]; if (0 == [singleVisibleArray count]) { // There is no visible cells in current column now, find one. for (int j = 0; j < [singleRectArray count]; ++j) { cellRect = [(NSValue *)[singleRectArray objectAtIndex:j] CGRectValue]; if (![self canRemoveCellForRect:cellRect]) { WFIndexPath *indexPath = [WFIndexPath indexPathForRow:j inColumn:i]; basicVisibleRow = j; cell = [self.waterFlowDataSource waterFlowView:self cellForRowAtIndexPath:indexPath]; // nil ? cell.indexPath = indexPath; cell.frame = cellRect; if (!cell.superview) [self addSubview:cell]; NSLog(@"Cell Info : %@\n", cell); [singleVisibleArray insertObject:cell atIndex:0]; break; } } } else { cell = [singleVisibleArray objectAtIndex:0]; basicVisibleRow = cell.indexPath.row; } // Look back to load visible cells for (int j = basicVisibleRow - 1; j >= 0; --j) { cellRect = [(NSValue *)[singleRectArray objectAtIndex:j] CGRectValue]; if (![self canRemoveCellForRect:cellRect]) { WFIndexPath *indexPath = [WFIndexPath indexPathForRow:j inColumn:i]; if ([self containVisibleCellForIndexPath:indexPath]) { continue ; } cell = [self.waterFlowDataSource waterFlowView:self cellForRowAtIndexPath:indexPath]; // nil ? cell.indexPath = indexPath; cell.frame = cellRect; if (!cell.superview) [self addSubview:cell]; NSLog(@"Cell Info : %@\n", cell); [singleVisibleArray insertObject:cell atIndex:0]; } else { break; } } // Look forward to load visible cells for (int j = basicVisibleRow + 1; j < [singleRectArray count]; ++j) { cellRect = [(NSValue *)[singleRectArray objectAtIndex:j] CGRectValue]; if (![self canRemoveCellForRect:cellRect]) { WFIndexPath *indexPath = [WFIndexPath indexPathForRow:j inColumn:i]; if ([self containVisibleCellForIndexPath:indexPath]) { continue ; } cell = [self.waterFlowDataSource waterFlowView:self cellForRowAtIndexPath:indexPath]; // nil ? cell.indexPath = indexPath; cell.frame = cellRect; if (!cell.superview) [self addSubview:cell]; NSLog(@"Cell Info : %@\n", cell); [singleVisibleArray insertObject:cell atIndex:0]; } else { break; } } // Recycle invisible cells for (int j = 0; j < [singleVisibleArray count]; ++j) { cell = [singleVisibleArray objectAtIndex:j]; if ([self canRemoveCellForRect:cell.frame]) { [cell removeFromSuperview]; [self addReusableCell:cell]; [singleVisibleArray removeObject:cell]; --j; NSLog(@"Removable Cell Info : %@\n", cell); } } } }主要思想就是,1. 找到一个需要展示的Cell;2. 以这个Cell开始,向前、向后推进,为需要展现出来的Cell分配;3. 遍历可见Cell,回收不可见的对象。
最后,把代码稍微做了抽离,弄了个小Demo,放到GitHub:https://github.com/siqin/WaterFlow
转自:http://blog.csdn.net/jasonblog/article/details/7588532