提问人:ximmyxiao 提问时间:12/2/2014 最后编辑:ximmyxiao 更新时间:7/17/2015 访问量:9275
uitablviewcell 动态高度与 systemLayoutSizeFittingSize 不一致
uitablviewcell dynamic height is not correct from systemLayoutSizeFittingSize
问:
我正在使用 xib 和自动布局来构建我的自定义单元格,在我的单元格中,有一个多行标签。在表视图的 heightForRowAtIndexPath 中,我将使用
1 dequeueReusableCellWithIdentifier 获取单元格
2 然后调用 [cell.contentView systemLayoutSizeFittingSize:UILayoutFittingCompressedSize] 获取正确的高度。
但是在调试中,我发现当调用heightForRowAtIndexPath时,我的单元格的宽度不是tableview的宽度,单元格的宽度与xib文件的宽度相同(因为在xcode6中,你可以将xib大小设置为any)。所以从 systemLayoutSizeFittingSize 得到的高度不正确。如何解决此问题以获得正确的单元格高度
从systemLayoutSizeFittingSize获取的尺寸不正确,此尺寸的宽度可能为340+(而设备是iPhone5,其宽度为320),而340+是单元格的xib文件的宽度
最后,我得到了解决方案,感谢 Ashish Gabani 的帮助,事实上,解决方案包括 2 个步骤: 1 将单元格框架重置为tableView大小 2 在调用 systemLayoutSizeFittingSize 之前调用单元格的 layoutSubViews,在自定义单元格中,需要重写 layoutSubViews 方法。 这是解决这个问题的代码,我用红色方块来标记它们,享受它
答:
您可以通过传递单元格高度来解决此问题,例如
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
// Determine which reuse identifier should be used for the cell at this index path,
// depending on the particular layout required (you may have just one, or may have many).
NSString *reuseIdentifier = ...;
// Dequeue a cell for the reuse identifier.
// Note that this method will init and return a new cell if there isn't one available in the reuse pool,
// so either way after this line of code you will have a cell with the correct constraints ready to go.
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:reuseIdentifier];
// Configure the cell with content for the given indexPath, for example:
// cell.textLabel.text = someTextForThisCell;
// ...
// Make sure the constraints have been set up for this cell, since it may have just been created from scratch.
// Use the following lines, assuming you are setting up constraints from within the cell's updateConstraints method:
[cell setNeedsUpdateConstraints];
[cell updateConstraintsIfNeeded];
// If you are using multi-line UILabels, don't forget that the preferredMaxLayoutWidth needs to be set correctly.
// Do it at this point if you are NOT doing it within the UITableViewCell subclass -[layoutSubviews] method.
// For example:
// cell.multiLineLabel.preferredMaxLayoutWidth = CGRectGetWidth(tableView.bounds);
return cell;
}
- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
{
// Determine which reuse identifier should be used for the cell at this index path.
NSString *reuseIdentifier = ...;
// Use a dictionary of offscreen cells to get a cell for the reuse identifier, creating a cell and storing
// it in the dictionary if one hasn't already been added for the reuse identifier.
// WARNING: Don't call the table view's dequeueReusableCellWithIdentifier: method here because this will result
// in a memory leak as the cell is created but never returned from the tableView:cellForRowAtIndexPath: method!
UITableViewCell *cell = [self.offscreenCells objectForKey:reuseIdentifier];
if (!cell) {
cell = [[YourTableViewCellClass alloc] init];
[self.offscreenCells setObject:cell forKey:reuseIdentifier];
}
// Configure the cell with content for the given indexPath, for example:
// cell.textLabel.text = someTextForThisCell;
// ...
// Make sure the constraints have been set up for this cell, since it may have just been created from scratch.
// Use the following lines, assuming you are setting up constraints from within the cell's updateConstraints method:
[cell setNeedsUpdateConstraints];
[cell updateConstraintsIfNeeded];
// Set the width of the cell to match the width of the table view. This is important so that we'll get the
// correct cell height for different table view widths if the cell's height depends on its width (due to
// multi-line UILabels word wrapping, etc). We don't need to do this above in -[tableView:cellForRowAtIndexPath]
// because it happens automatically when the cell is used in the table view.
// Also note, the final width of the cell may not be the width of the table view in some cases, for example when a
// section index is displayed along the right side of the table view. You must account for the reduced cell width.
cell.bounds = CGRectMake(0.0f, 0.0f, CGRectGetWidth(tableView.bounds), CGRectGetHeight(cell.bounds));
// Do the layout pass on the cell, which will calculate the frames for all the views based on the constraints.
// (Note that you must set the preferredMaxLayoutWidth on multi-line UILabels inside the -[layoutSubviews] method
// of the UITableViewCell subclass, or do it manually at this point before the below 2 lines!)
[cell setNeedsLayout];
[cell layoutIfNeeded];
// Get the actual height required for the cell's contentView
CGFloat height = [cell.contentView systemLayoutSizeFittingSize:UILayoutFittingCompressedSize].height;
// Add an extra point to the height to account for the cell separator, which is added between the bottom
// of the cell's contentView and the bottom of the table view cell.
height += 1.0f;
return height;
}
// NOTE: Set the table view's estimatedRowHeight property instead of implementing the below method, UNLESS
// you have extreme variability in your row heights and you notice the scroll indicator "jumping" as you scroll.
- (CGFloat)tableView:(UITableView *)tableView estimatedHeightForRowAtIndexPath:(NSIndexPath *)indexPath
{
// Do the minimal calculations required to be able to return an estimated row height that's
// within an order of magnitude of the actual height.
// For example:
if ([self isTallCellAtIndexPath:indexPath])
{
return 350.0f;
} else {
return 40.0f;
}
}
您也可以从这里找到解决方案 链接
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