iOS 瀑布流

最新推荐文章于 2018-10-03 20:42:50 发布

原创最新推荐文章于 2018-10-03 20:42:50 发布 · 589 阅读

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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：

 
   01- (void)onScroll  
 
   02{  
 
   03    for (int  i = 0; i < self.columns; ++i) {  
 
   04        NSUInteger basicVisibleRow = 0;  
 
   05        WaterFlowViewCell *cell = nil;  
 
   06        CGRect cellRect = CGRectZero;  
 
   07           
 
   08        NSMutableArray *singleRectArray = [self.cellRectArray objectAtIndex:i];  
 
   09        NSMutableArray *singleVisibleArray = [self.visibleCells objectAtIndex:i];  
 
   10           
 
   11        if (0 == [singleVisibleArray count]) {  
 
   12            // There is no visible cells in current column now, find one.  
 
   13            for (int  j = 0; j < [singleRectArray count]; ++j) {  
 
   14                cellRect = [(NSValue *)[singleRectArray objectAtIndex:j] CGRectValue];  
 
   15                if (![self canRemoveCellForRect:cellRect]) {  
 
   16                    WFIndexPath *indexPath = [WFIndexPath indexPathForRow:j inColumn:i];  
 
   17                    basicVisibleRow = j;  
 
   18                       
 
   19                    cell = [self.waterFlowDataSource waterFlowView:self cellForRowAtIndexPath:indexPath]; // nil ?  
 
   20                    cell.indexPath = indexPath;  
 
   21                    cell.frame = cellRect;  
 
   22                    if (!cell.superview) [self addSubview:cell];  
 
   23                    NSLog(@"Cell Info : %@\n", cell);  
 
   24                       
 
   25                    [singleVisibleArray insertObject:cell atIndex:0];  
 
   26                    break;  
 
   27                }  
 
   28            }  
 
   29        }  else {  
 
   30            cell = [singleVisibleArray objectAtIndex:0];  
 
   31            basicVisibleRow = cell.indexPath.row;  
 
   32        }   
 
   33           
 
   34        // Look back to load visible cells  
 
   35        for (int  j = basicVisibleRow - 1; j >= 0; --j) {  
 
   36            cellRect = [(NSValue *)[singleRectArray objectAtIndex:j] CGRectValue];  
 
   37            if (![self canRemoveCellForRect:cellRect]) {  
 
   38                WFIndexPath *indexPath = [WFIndexPath indexPathForRow:j inColumn:i];  
 
   39                if ([self containVisibleCellForIndexPath:indexPath]) {  
 
   40                    continue ;  
 
   41                }  
 
   42                   
 
   43                cell = [self.waterFlowDataSource waterFlowView:self cellForRowAtIndexPath:indexPath]; // nil ?  
 
   44                cell.indexPath = indexPath;  
 
   45                cell.frame = cellRect;  
 
   46                if (!cell.superview) [self addSubview:cell];  
 
   47                NSLog(@"Cell Info : %@\n", cell);  
 
   48                   
 
   49                [singleVisibleArray insertObject:cell atIndex:0];  
 
   50            } else {  
 
   51                break;  
 
   52            }  
 
   53        }   
 
   54           
 
   55        // Look forward to load visible cells  
 
   56        for (int  j = basicVisibleRow + 1; j < [singleRectArray count]; ++j) {  
 
   57            cellRect = [(NSValue *)[singleRectArray objectAtIndex:j] CGRectValue];  
 
   58            if (![self canRemoveCellForRect:cellRect]) {  
 
   59                WFIndexPath *indexPath = [WFIndexPath indexPathForRow:j inColumn:i];  
 
   60                if ([self containVisibleCellForIndexPath:indexPath]) {  
 
   61                    continue ;  
 
   62                }  
 
   63                   
 
   64                cell = [self.waterFlowDataSource waterFlowView:self cellForRowAtIndexPath:indexPath]; // nil ?  
 
   65                cell.indexPath = indexPath;  
 
   66                cell.frame = cellRect;  
 
   67                if (!cell.superview) [self addSubview:cell];  
 
   68                NSLog(@"Cell Info : %@\n", cell);  
 
   69                   
 
   70                [singleVisibleArray insertObject:cell atIndex:0];  
 
   71            } else {  
 
   72                break;  
 
   73            }  
 
   74        }   
 
   75           
 
   76        // Recycle invisible cells  
 
   77        for (int  j = 0; j < [singleVisibleArray count]; ++j) {  
 
   78            cell = [singleVisibleArray objectAtIndex:j];  
 
   79            if ([self canRemoveCellForRect:cell.frame]) {  
 
   80                [cell removeFromSuperview];  
 
   81                [self addReusableCell:cell];  
 
   82                [singleVisibleArray removeObject:cell];  
 
   83                --j;  
 
   84                NSLog(@"Removable Cell Info : %@\n", cell);  
 
   85            }  
 
   86        }   
 
   87    }   
 
   88}