iOS: Dynamically adding a multiline UILabel

问题

I am having trouble dynamically adding a multiline UILabel. Here is the result I'm getting:

I would like the label in the "Summary" box to wrap naturally. Here is the code I'm using to add the label:

-(void)setSummary{
    summaryContentLabel = [[UILabel alloc] init];
    summaryContentLabel.numberOfLines=0;
    summaryContentLabel.lineBreakMode=NSLineBreakByWordWrapping;
    summaryContentLabel.text=self.summary;
    summaryContentLabel.font=[UIFont fontWithName:@"Helvetica" size:13.0];

    [summaryView addSubview:summaryContentLabel];
    [summaryContentLabel  setTranslatesAutoresizingMaskIntoConstraints:NO];
    NSDictionary *views = NSDictionaryOfVariableBindings(summaryView,summaryContentLabel ,summaryLabel);
    [summaryView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:[summaryLabel]-5-[summaryContentLabel(==100)]-5-|" options:nil metrics:nil views:views]];

}

You'll notice the title of the book wraps the way I want with no problem. That was done in IB. Unfortunately, I have to add this label in code. Auto Layout is also a requirement.

回答1:

Figured it out. I needed to add an additional constraint for the width of the label, like this:

[summaryView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|-[summaryContentLabel]-|" options:nil metrics:nil views:views]];

回答2:

May be I am late but any way I've found solution. You need to explicitly set preferredMaxLayoutWidth for summaryContentLabel. For example:

summaryContentLabel.preferredMaxLayoutWidth = 200;

And I've noticed that if you do the same view layout via xib then interface builder will set preferredMaxLayoutWidth with correct value.

回答3:

Use this code for multiline label:-

-(void)setSummary {

summaryContentLabel = [[UILabel alloc] init];
summaryContentLabel.numberOfLines=0;
summaryContentLabel.textAlignment   = UITextAlignmentLeft;
summaryContentLabel.font=[UIFont fontWithName:@"Helvetica" size:13.0];
[summaryView addSubview:summaryContentLabel];

CGSize size = [self.summary sizeWithFont:[UIFont fontWithName:@"Helvetica" size:13.0] constrainedToSize:CGSizeMake(240, 99999) lineBreakMode:UILineBreakModeWordWrap];
summaryContentLabel.frame=CGRectMake(72, 22, 240, size.height);  //set the frame according to your need
summaryContentLabel.text=self.summary;

}