我的应用程序使用UITextView。现在我想让UITextView有一个占位符,类似于你可以为UITextField设置的占位符。
如何做到这一点?
我的应用程序使用UITextView。现在我想让UITextView有一个占位符,类似于你可以为UITextField设置的占位符。
如何做到这一点?
当前回答
Jason的答案在iOS7中看起来有点不对劲,通过调整_placeHolderLabel的偏移量来修复它:
- (void)drawRect:(CGRect)rect
{
if( [[self placeholder] length] > 0 )
{
if (_placeHolderLabel == nil )
{
if ([[UIDevice currentDevice].systemVersion floatValue] >= 7)
_placeHolderLabel = [[UILabel alloc] initWithFrame:CGRectMake(4,8,self.bounds.size.width - 8,0)];
else
_placeHolderLabel = [[UILabel alloc] initWithFrame:CGRectMake(8,8,self.bounds.size.width - 16,0)];
_placeHolderLabel.lineBreakMode = NSLineBreakByWordWrapping;
_placeHolderLabel.numberOfLines = 0;
_placeHolderLabel.font = self.font;
_placeHolderLabel.backgroundColor = [UIColor clearColor];
_placeHolderLabel.textColor = self.placeholderColor;
_placeHolderLabel.alpha = 0;
_placeHolderLabel.tag = 999;
[self addSubview:_placeHolderLabel];
}
_placeHolderLabel.text = self.placeholder;
[_placeHolderLabel sizeToFit];
[self sendSubviewToBack:_placeHolderLabel];
}
if( [[self text] length] == 0 && [[self placeholder] length] > 0 )
{
[[self viewWithTag:999] setAlpha:1];
}
[super drawRect:rect];
}
其他回答
看一下UTPlaceholderTextView。
这是UITextView的一个方便的子类,它支持类似于UITextField的占位符。主要特点:
不使用子视图 不重写drawRect: 占位符的长度可以是任意的,并以与通常文本相同的方式呈现
抱歉添加了另一个答案,但我只是拉出了这样的东西,这创建了最接近uitextfield的占位符。
希望这能帮助到一些人。
-(void)textViewDidChange:(UITextView *)textView{
if(textView.textColor == [UIColor lightGrayColor]){
textView.textColor = [UIColor blackColor]; // look at the comment section in this answer
textView.text = [textView.text substringToIndex: 0];// look at the comment section in this answer
}else if(textView.text.length == 0){
textView.text = @"This is some placeholder text.";
textView.textColor = [UIColor lightGrayColor];
textView.selectedRange = NSMakeRange(0, 0);
}
}
-(void)textViewDidChangeSelection:(UITextView *)textView{
if(textView.textColor == [UIColor lightGrayColor] && (textView.selectedRange.location != 0 || textView.selectedRange.length != 0)){
textView.selectedRange = NSMakeRange(0, 0);
}
}
我用swift写了一个类。您可以在需要时导入这个类。
import UIKit
public class CustomTextView: UITextView {
private struct Constants {
static let defaultiOSPlaceholderColor = UIColor(red: 0.0, green: 0.0, blue: 0.0980392, alpha: 0.22)
}
private let placeholderLabel: UILabel = UILabel()
private var placeholderLabelConstraints = [NSLayoutConstraint]()
@IBInspectable public var placeholder: String = "" {
didSet {
placeholderLabel.text = placeholder
}
}
@IBInspectable public var placeholderColor: UIColor = CustomTextView.Constants.defaultiOSPlaceholderColor {
didSet {
placeholderLabel.textColor = placeholderColor
}
}
override public var font: UIFont! {
didSet {
placeholderLabel.font = font
}
}
override public var textAlignment: NSTextAlignment {
didSet {
placeholderLabel.textAlignment = textAlignment
}
}
override public var text: String! {
didSet {
textDidChange()
}
}
override public var attributedText: NSAttributedString! {
didSet {
textDidChange()
}
}
override public var textContainerInset: UIEdgeInsets {
didSet {
updateConstraintsForPlaceholderLabel()
}
}
override public init(frame: CGRect, textContainer: NSTextContainer?) {
super.init(frame: frame, textContainer: textContainer)
commonInit()
}
required public init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
commonInit()
}
private func commonInit() {
NSNotificationCenter.defaultCenter().addObserver(self,
selector: #selector(textDidChange),
name: UITextViewTextDidChangeNotification,
object: nil)
placeholderLabel.font = font
placeholderLabel.textColor = placeholderColor
placeholderLabel.textAlignment = textAlignment
placeholderLabel.text = placeholder
placeholderLabel.numberOfLines = 0
placeholderLabel.backgroundColor = UIColor.clearColor()
placeholderLabel.translatesAutoresizingMaskIntoConstraints = false
addSubview(placeholderLabel)
updateConstraintsForPlaceholderLabel()
}
private func updateConstraintsForPlaceholderLabel() {
var newConstraints = NSLayoutConstraint.constraintsWithVisualFormat("H:|-(\(textContainerInset.left + textContainer.lineFragmentPadding))-[placeholder]",
options: [],
metrics: nil,
views: ["placeholder": placeholderLabel])
newConstraints += NSLayoutConstraint.constraintsWithVisualFormat("V:|-(\(textContainerInset.top))-[placeholder]",
options: [],
metrics: nil,
views: ["placeholder": placeholderLabel])
newConstraints.append(NSLayoutConstraint(
item: placeholderLabel,
attribute: .Width,
relatedBy: .Equal,
toItem: self,
attribute: .Width,
multiplier: 1.0,
constant: -(textContainerInset.left + textContainerInset.right + textContainer.lineFragmentPadding * 2.0)
))
removeConstraints(placeholderLabelConstraints)
addConstraints(newConstraints)
placeholderLabelConstraints = newConstraints
}
@objc private func textDidChange() {
placeholderLabel.hidden = !text.isEmpty
}
public override func layoutSubviews() {
super.layoutSubviews()
placeholderLabel.preferredMaxLayoutWidth = textContainer.size.width - textContainer.lineFragmentPadding * 2.0
}
deinit {
NSNotificationCenter.defaultCenter().removeObserver(self,
name: UITextViewTextDidChangeNotification,
object: nil)
}
}
首先在.h文件中取一个标签。
这里我取
UILabel * lbl;
然后在。m中viewDidLoad下声明它
lbl = [[UILabel alloc] initWithFrame:CGRectMake(8.0, 0.0,250, 34.0)];
lbl.font=[UIFont systemFontOfSize:14.0];
[lbl setText:@"Write a message..."];
[lbl setBackgroundColor:[UIColor clearColor]];
[lbl setTextColor:[UIColor lightGrayColor]];
[textview addSubview:lbl];
textview是我的textview。
现在声明
-(void)textViewDidChange:(UITextView *)textView {
if (![textView hasText]){
lbl.hidden = NO;
}
else{
lbl.hidden = YES;
}
}
和你的Textview占位符准备好了!
斯威夫特3.1
在尝试了所有快速的答案之后,这个答案将为我节省3个小时的研究时间。希望这能有所帮助。
确保你的textField(不管你有什么自定义名称)指向它在Storyboard中的委托,并且有一个@IBOutlet和你的customtextfield 将以下内容添加到viewDidLoad()中,加载视图时会出现:
告诉我什么看起来是占位符:
yourCustomTextField = "Start typing..."
yourCustomTextField.textColor = .lightGray
在viewDidLoad外部但在同一个类内部添加以下声明:UIViewController, UITextViewDelegate, UINavigationControllerDelegate
这段代码将使yourCustomTextField在输入textField时消失:
func textViewDidBeginEditing (_ textView: UITextView) {
if (textView.text == "Start typing...") {
textView.text = ""
textView.textColor = .black
}
textView.becomeFirstResponder()
}
func textViewDidEndEditing(_ textView: UITextView) {
if (textView.text == "") {
textView.text = "Start typing..."
textView.textColor = .lightGray
}
textView.resignFirstResponder()
}