如何指定行的高度？ [英] how to specify height of row?

问题描述

我想实现一个tableview，它显示特定行的可扩展单元格，因此我创建了自定义表格单元格，如果将其expandContent设置如下，将会展开：

I want to implement a tableview which shows an expandable cell for a specific row, so I create my custom table cell which will be expanded if setting its expandContent as following:

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *CellIdentifier = @"Cell";
    CustomCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
    NSString *shouldExpand = [self.datasource objectAtIndex:indexPath.row];
    if([shouldExpand isEqualToString:@"expand"]){
        [cell setExpandContent:@"Expand"];
    }
    else{
        [cell setTitle:@"a line"];
    }
    return cell;
}

但是，为了告诉tableview行高，我需要实现以下代码：

however, in order to tell tableview the row height, I need to implement the following code:

- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
{
    CustomCell *cell = [self tableView:tableView cellForRowAtIndexPath:indexPath];
    return [cell cellHeight];
}

问题是heightForRowAtIndexPath方法会调用1000次tableView：cellForRowAtIndexPath：if my datasource包含1000个数据，花费的时间太长。

The problem is heightForRowAtIndexPath method will call 1000 times of tableView:cellForRowAtIndexPath: if my datasource contains 1000 data, and it cost too much time.

如何解决问题？

推荐答案

没有你应该首先找到单元格的大小然后发送高度计算，不要调用tableView：cellForRowAtIndexPath：它将导致递归，首先计算并发送高度。例如

no u should find the size of cell first then send the hight calculated, dont call tableView:cellForRowAtIndexPath: it will results in recursion instead, first calculate and send the height . for example

         //say suppose you are placing the string inside tableview cell then u need to   calculate cell for example

    NSString *string = @"hello world happy coding";
    CGSize maxSize = CGSizeMake(280, MAXFLOAT);//set max height
     CGSize cellSize = [self.str sizeWithFont:[UIFont systemFontOfSize:17]
                   constrainedToSize:maxSize
                   lineBreakMode:NSLineBreakByWordWrapping];//this will return correct height for text
    return cellSize.height +10; //finally u return your height

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