我有一个UILabel,它有两行文字的空间。有时,当文本太短时,此文本会显示在标签的垂直中心。
如何垂直对齐文本,使其始终位于UILabel的顶部?
我有一个UILabel,它有两行文字的空间。有时,当文本太短时,此文本会显示在标签的垂直中心。
如何垂直对齐文本,使其始终位于UILabel的顶部?
当前回答
对于Swift 3。。。
@IBDesignable class TopAlignedLabel: UILabel {
override func drawText(in rect: CGRect) {
if let stringText = text {
let stringTextAsNSString = stringText as NSString
let labelStringSize = stringTextAsNSString.boundingRect(with: CGSize(width: self.frame.width,height: CGFloat.greatestFiniteMagnitude),
options: NSStringDrawingOptions.usesLineFragmentOrigin,
attributes: [NSFontAttributeName: font],
context: nil).size
super.drawText(in: CGRect(x:0,y: 0,width: self.frame.width, height:ceil(labelStringSize.height)))
} else {
super.drawText(in: rect)
}
}
override func prepareForInterfaceBuilder() {
super.prepareForInterfaceBuilder()
layer.borderWidth = 1
layer.borderColor = UIColor.black.cgColor
}
}
其他回答
Swift 4.0中有一个解决方案:
func viewDidLoad() {
super.viewDidLoad()
// 20 point top and left margin. Sized to leave 20 pt at right.
let labelFrame = CGRect(x: 20, y: 20, width: 280, height: 150)
let myLabel = UILabel(frame: labelFrame)
myLabel.backgroundColor = UIColor.orange
let labelText = "I am the very model of a modern Major-General,
I've information vegetable, animal, and mineral"
myLabel.text = labelText
// Tell the label to use an unlimited number of lines
myLabel.numberOfLines = 0
myLabel.sizeToFit()
view.addSubview(myLabel) // add label
}
就像上面的答案一样,但它不太正确,或者很容易插入代码,所以我稍微清理了一下。将此扩展名添加到它自己的.h和.m文件中,或者直接粘贴到您打算使用的实现上方:
#pragma mark VerticalAlign
@interface UILabel (VerticalAlign)
- (void)alignTop;
- (void)alignBottom;
@end
@implementation UILabel (VerticalAlign)
- (void)alignTop
{
CGSize fontSize = [self.text sizeWithFont:self.font];
double finalHeight = fontSize.height * self.numberOfLines;
double finalWidth = self.frame.size.width; //expected width of label
CGSize theStringSize = [self.text sizeWithFont:self.font constrainedToSize:CGSizeMake(finalWidth, finalHeight) lineBreakMode:self.lineBreakMode];
int newLinesToPad = (finalHeight - theStringSize.height) / fontSize.height;
for(int i=0; i<= newLinesToPad; i++)
{
self.text = [self.text stringByAppendingString:@" \n"];
}
}
- (void)alignBottom
{
CGSize fontSize = [self.text sizeWithFont:self.font];
double finalHeight = fontSize.height * self.numberOfLines;
double finalWidth = self.frame.size.width; //expected width of label
CGSize theStringSize = [self.text sizeWithFont:self.font constrainedToSize:CGSizeMake(finalWidth, finalHeight) lineBreakMode:self.lineBreakMode];
int newLinesToPad = (finalHeight - theStringSize.height) / fontSize.height;
for(int i=0; i< newLinesToPad; i++)
{
self.text = [NSString stringWithFormat:@" \n%@",self.text];
}
}
@end
然后要使用,请将文本放入标签中,然后调用适当的方法将其对齐:
[myLabel alignTop];
or
[myLabel alignBottom];
对于Adaptive UI(iOS8或更高版本),要通过更改财产从StoryBoard设置UILabel的垂直对齐noOfLines=0`和
限制条件调整UILabel LefMargin、RightMargin和Top Margin约束。更改垂直=1000的内容压缩阻力优先级,使垂直>水平。
编辑日期:
noOfLines=0
并且以下约束足以实现期望的结果。
对于Swift 3。。。
@IBDesignable class TopAlignedLabel: UILabel {
override func drawText(in rect: CGRect) {
if let stringText = text {
let stringTextAsNSString = stringText as NSString
let labelStringSize = stringTextAsNSString.boundingRect(with: CGSize(width: self.frame.width,height: CGFloat.greatestFiniteMagnitude),
options: NSStringDrawingOptions.usesLineFragmentOrigin,
attributes: [NSFontAttributeName: font],
context: nil).size
super.drawText(in: CGRect(x:0,y: 0,width: self.frame.width, height:ceil(labelStringSize.height)))
} else {
super.drawText(in: rect)
}
}
override func prepareForInterfaceBuilder() {
super.prepareForInterfaceBuilder()
layer.borderWidth = 1
layer.borderColor = UIColor.black.cgColor
}
}
一种更快(更脏)的方法是将UILabel的换行模式设置为“Clip”并添加固定数量的换行符。
myLabel.lineBreakMode = UILineBreakModeClip;
myLabel.text = [displayString stringByAppendingString:"\n\n\n\n"];
这种解决方案不适用于所有人——特别是,如果您仍然希望在字符串末尾显示“…”,如果它超过了您要显示的行数,则需要使用较长的代码段之一——但在很多情况下,这将满足您的需要。