uitablviewcell動態高度不正確from systemLayoutSizeFittingSize

Question

我使用xib &自動佈局來構建我的自定義單元格，在我的單元格中，有一個多行標籤。一個在tableview中的heightForRowAtIndexPath，我會用

1個dequeueReusableCellWithIdentifier獲得細胞

2然後調用[cell.contentView systemLayoutSizeFittingSize：UILayoutFittingCompressedSize]以獲得正確的高度。

但在調試，我發現，當heightForRowAtIndexPath被調用時，我的手機的寬度是不tableview中的寬度，單元格的寬度是一樣的廈門國際銀行文件的寬度（因爲在xcode6，您可以設置XIB大小去任何）。所以從systemLayoutSizeFittingSize得到的高度是不正確的。我怎樣才能解決這個問題，以獲得正確的單元格高度

從systemLayoutSizeFittingSize獲取的大小：不正確，此大小可能有寬度340+（而設備是寬度爲320的iPhone5），和340+是accually細胞的XIB文件的寬度

最後，我得到了解決，感謝阿希什Gabani的幫助，事實上，該解決方案包括2步： 1單元框重置爲您的tableView大小 2在調用systemLayoutSizeFittingSize之前調用單元格的layoutSubView，並在您的自定義單元格中，您需要重寫layoutSubViews方法。 下面是修復代碼這個問題，我用的是紅色正方形，以紀念他們，享受它

Answer 1

就可以解決這個問題通過傳遞您的單元格高度等作爲

- (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; 
} 
} 

您還可以從這裏找到解決方案Link