objective-c - 根据 UILabel 动态调整 uitableViewCell 的大小(带段落间距)

Question

我有一个 UITableView，它由来自 JSON 文件的文本和图像填充。 TableView Cell 当前正在为文本中不包含许多换行符的“帖子”正确调整大小，但是我无法让它计算具有 4 或 5 个换行符的“帖子”的正确高度。

获取高度的代码:

-(float)height :(NSMutableAttributedString*)string
{
  NSString *stringToSize = [NSString stringWithFormat:@"%@", string];

  CGSize constraint = CGSizeMake(LABEL_WIDTH - (LABEL_MARGIN *2), 2000.f);

  CGSize size = [stringToSize sizeWithFont:[UIFont systemFontOfSize:FONT_SIZE] constrainedToSize:contraint lineBreakMode:NSLineBreakByWordWrapping];

  return size.height;
}

如何在允许换行符和空格的情况下计算正确的大小？

编辑

方法的其余部分，

TableView CellForRow 内部:

-(UITableViewCell*)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
NSString *row = [NSString stringWithFormat:@"%i", indexPath.row];

float postTextHeight = [self height:postText];

NSString *height = [NSString stringWithFormat:@"%f", heightOfPostText + 70];

[_cellSizes setObject:height forKey:row];
}

以及Table Cell的高度:

-(CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
{
NSString *imageHeightString = [NSString stringWithFormat:@"%@", [_cellSizes objectForKey:indexPath.row]];

float heightOfCell = [imageHeightString floatValue];

 if (heightOfCell == 0) {
    
    return 217;
};

return heightOfCell + 5;
}

Answer 1

最好先计算高度，不要在方法中包含高度计算部分:

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath

最好用方法计算:

- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath 

因为你是从 json 中获取数据，所以你很容易计算 在“heightForRowAtIndexPath”方法中。

以下代码将给出计算文本高度的示例，根据您的要求进行更改。希望这对你有帮助:)

// i am using an array 
- (void)viewDidLoad
{
   [super viewDidLoad]; 
   // Do any additional setup after loading the view, typically from a nib.

   UIFont *labelFont = [UIFont fontWithName:@"Noteworthy-Bold" size:20];
   NSDictionary *arialdict = [NSDictionary dictionaryWithObject:labelFont forKey:NSFontAttributeName];

   NSMutableAttributedString *message = [[NSMutableAttributedString alloc] initWithString:@"this is just the sample example of how to calculate the dynamic height for tableview cell which is of around 7 to 8 lines. you will need to set the height of this string first, not seems to be calculated in cellForRowAtIndexPath method." attributes:arialdict];

   array = [NSMutableArray arrayWithObjects:message, nil];
   NSMutableAttributedString *message_1 = [[NSMutableAttributedString alloc] initWithString:@"you will need to set the height of this string first, not seems to be calculated in cellForRowAtIndexPath method." attributes:arialdict];
  [array addObject:message_1];   
}

 - (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
 {
     return 2;
 }

 - (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
 {
     return 2;
 }


 - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
   UITableViewCell *Cell = [self.aTableView dequeueReusableCellWithIdentifier:@"cell"];
   if(Cell == nil)
    {
       Cell = [[UITableViewCell alloc]initWithStyle:UITableViewCellStyleDefault reuseIdentifier:@"cell"];
     }

     //dont include the height calculation part hear, becz heights are already set for all the cell 
    [Cell.textLabel sizeToFit];
    Cell.textLabel.attributedText = [array objectAtIndex:indexPath.row]; // dont calculate height hear it will be called after "heightForRowAtIndexPath" method
    Cell.textLabel.numberOfLines = 8;
    return Cell;
 }

  // put ur height calculation method i took some hardcoded values change it :)
  -(float)height :(NSMutableAttributedString*)string
 {
    /*
      NSString *stringToSize = [NSString stringWithFormat:@"%@", string]; 
  // CGSize constraint = CGSizeMake(LABEL_WIDTH - (LABEL_MARGIN *2), 2000.f);
     CGSize maxSize = CGSizeMake(280, MAXFLOAT);//set max height //set the constant width, hear MAXFLOAT gives the maximum height

     CGSize size = [stringToSize sizeWithFont:[UIFont systemFontOfSize:20.0f] constrainedToSize:maxSize lineBreakMode:NSLineBreakByWordWrapping];
return size.height; //finally u get the correct height
    */
     //commenting the above code because "sizeWithFont: constrainedToSize:maxSize: lineBreakMode: " has been deprecated to avoid above code use below

    NSAttributedString *attributedText = string;
    CGRect rect = [attributedText boundingRectWithSize:(CGSize){225, MAXFLOAT}
                           options:NSStringDrawingUsesLineFragmentOrigin
                              context:nil];//you need to specify the some width, height will be calculated
    CGSize requiredSize = rect.size;
    return requiredSize.height; //finally u return your height
}


- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
 {
     //whatever the height u need to calculate calculate hear only    
     CGFloat heightOfcell = [self height:[array objectAtIndex:indexPath.row]];
     NSLog(@"%f",heightOfcell);
     return heightOfcell;
 }

希望这对你有帮助:)

对于 SWIFT 版本

class ViewController: UIViewController,UITableViewDataSource,UITableViewDelegate 
{

var messageArray:[String] = [] //array to holde the response form son for example 
override func viewDidLoad()
{
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.
    messageArray = ["One of the most interesting features of Newsstand is that once an asset downloading has started it will continue even if the application is suspended (that is: not running but still in memory) or it is terminated. Of course during while your app is suspended it will not receive any status update but it will be woken up in the background",
                    "In case that app has been terminated while downloading was in progress, the situation is different. Infact in the event of a finished downloading the app can not be simply woken up and the connection delegate finish download method called, as when an app is terminated its App delegate object doesn’t exist anymore. In such case the system will relaunch the app in the background.", 
                    " If defined, this key will contain the array of all asset identifiers that caused the launch. From my tests it doesn’t seem this check is really required if you reconnect the pending downloading as explained in the next paragraph.",
                    ]
}

func numberOfSectionsInTableView(tableView: UITableView) -> Int
{
    return 1;
}

func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int
{
    return messageArray.count;
}

func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell
{
    var cell:UITableViewCell? = tableView.dequeueReusableCellWithIdentifier("CELL") as? UITableViewCell;
    if(cell == nil)
    {
        cell = UITableViewCell(style:UITableViewCellStyle.Default, reuseIdentifier: "CELL")
        cell?.selectionStyle = UITableViewCellSelectionStyle.None
    }
    cell?.textLabel.font = UIFont.systemFontOfSize(15.0)
    cell?.textLabel.sizeToFit()
    cell?.textLabel.text = messageArray[indexPath.row]
    cell?.textLabel.numberOfLines = 0
    return cell!;
}

func tableView(tableView: UITableView, heightForRowAtIndexPath indexPath: NSIndexPath) -> CGFloat
{
    var height:CGFloat = self.calculateHeightForString(messageArray[indexPath.row])
    return height + 70.0
}

func calculateHeightForString(inString:String) -> CGFloat
{
    var messageString = inString
    var attributes = [UIFont(): UIFont.systemFontOfSize(15.0)]
    var attrString:NSAttributedString? = NSAttributedString(string: messageString, attributes: attributes)
    var rect:CGRect = attrString!.boundingRectWithSize(CGSizeMake(300.0,CGFloat.max), options: NSStringDrawingOptions.UsesLineFragmentOrigin, context:nil )
    var requredSize:CGRect = rect
    return requredSize.height  //to include button's in your tableview

 }
}