Ios UITableViewCell动态高度与systemLayoutSizeFittingSize不符

我正在使用xib和auto layout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tableview的高度中，我将使用

1 dequeueReusableCellWithIdentifier以获取单元格

2然后调用[cell.contentView systemLayoutSizeFittingSize:UILayoutFittingCompressedSize]以获得正确的高度

但是在调试中，我发现当调用HeightForRowatineXpath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，可以将xib大小设置为任意大小）。因此，从systemLayoutSizeFittingSize获取的高度不正确。如何解决此问题以获得正确的单元格高度

从systemLayoutSizeFittingSize:获取的大小不正确，此大小的宽度可能为340+（而设备为宽度为320的iPhone5），340+准确地说是单元格的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，解决方案包括两个步骤： 1将单元格框重置为您的tableView大小 2在调用systemLayoutSizeFittingSize之前调用单元格的LayoutSubview，并且在自定义单元格中，需要重写LayoutSubview方法。 这是解决这个问题的代码，我用红色的方块标记它们，享受它

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您可以通过如下方式传递单元格高度来解决此问题

- (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;
}
}

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您也可以从这里找到解决方案

因为我的单元格高度是动态的，所以我是这样做的，使用systemLayoutSizeFittingSize获取单元格高度，并返回HeightForRowatineXpath中的高度。但正如我所说，在HeightForRowatineXpath中，单元格的宽度不正确，因此我得到的高度也不正确：（请你在你的项目中写下你的代码。好的，我已经发布了代码，请看一看，问题出在绿线上：尺寸的宽度可以比我的设备宽screen@ximmyxiao在tableView方法CellForRowatineXpath中，您写了什么？在CellForRowatineXpath中，我只创建了我的自定义单元格。我的自定义单元格与对于xib，单元格最重要的子视图是一个多行标签。我确信正是这个多行标签导致了systemLayoutSizeFittingSize问题。