关于UILabel的多行显示 UILabel numberOfLines

早上做了会实验结果如下：

1.N行完全自适应：

UILabel *testLabel = [[UILabel alloc] initWithFrame:CGRectMake(10, 30, 100, 21)];

NSString *txt = @"dffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff";

testLabel.numberOfLines = 0; ///相当于不限制行数

testLabel.text = txt;

这样不行，还需要调用 [testLabel sizeToFit];

2.限制在N行内自适应：

UILabel *testLabel = [[UILabel alloc] initWithFrame:CGRectMake(10, 30, 100, 21)];

NSString *txt = @"dffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff";

testLabel.numberOfLines = 3; ////限制在3行内自适应

testLabel.text = txt;

[testLabel sizeToFit];

结果不起作用，全部在一行显示了。

3.为了实现2的需求，需要这么做：

CGSize maxSize = CGSizeMake(100, 21*3);

UILabel *testLabel = [[UILabel alloc] initWithFrame:CGRectMake(10, 30, 100, 21)];

NSString *txt = @"dffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff";

CGSize labelSize = [txt sizeWithFont:testLabel.font constrainedToSize:maxSize lineBreakMode: UILineBreakModeTailTruncation];

testLabel.frame = CGRectMake(testLabel.frame.origin.x, testLabel.frame.origin.y, labelSize.width, labelSize.height);

testLabel.text = txt;

UILable显示文字，大多数情况下文字是动态的，所以UILable的大小需要自适用,下面是实现的具体代码：

myLable=[[UILabel
alloc] initWithFrame:CGRectMake(0, 23, 175, 33)];

[myLable setFont:[UIFont fontWithName:@"Helvetica" size:10.0]];

[myLable setNumberOfLines:0];

[myLable setBackgroundColor:[UIColor clearColor]];

[myAdView addSubview:myLable];

UIFont *font = [UIFont fontWithName:@"Helvetica" size:10.0];

CGSize size = [text sizeWithFont:font constrainedToSize:CGSizeMake(175.0f, 2000.0f) lineBreakMode:UILineBreakModeWordWrap];

CGRect rect=myLable.frame;

rect.size=size;

[myLable setFrame:rect];

[myLable setText:text];