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()
}

我对bcd的解决方案做了一些小修改，以允许从Xib文件初始化、文本包装和保持背景颜色。希望它能为其他人省去麻烦。

UIPlaceHolderTextView.h:

#import <Foundation/Foundation.h>
IB_DESIGNABLE
@interface UIPlaceHolderTextView : UITextView

@property (nonatomic, retain) IBInspectable NSString *placeholder;
@property (nonatomic, retain) IBInspectable UIColor *placeholderColor;

-(void)textChanged:(NSNotification*)notification;

@end

UIPlaceHolderTextView.m:

#import "UIPlaceHolderTextView.h"

@interface UIPlaceHolderTextView ()

@property (nonatomic, retain) UILabel *placeHolderLabel;

@end

@implementation UIPlaceHolderTextView

CGFloat const UI_PLACEHOLDER_TEXT_CHANGED_ANIMATION_DURATION = 0.25;

- (void)dealloc
{
    [[NSNotificationCenter defaultCenter] removeObserver:self];
#if __has_feature(objc_arc)
#else
    [_placeHolderLabel release]; _placeHolderLabel = nil;
    [_placeholderColor release]; _placeholderColor = nil;
    [_placeholder release]; _placeholder = nil;
    [super dealloc];
#endif
}

- (void)awakeFromNib
{
    [super awakeFromNib];

    // Use Interface Builder User Defined Runtime Attributes to set
    // placeholder and placeholderColor in Interface Builder.
    if (!self.placeholder) {
        [self setPlaceholder:@""];
    }

    if (!self.placeholderColor) {
        [self setPlaceholderColor:[UIColor lightGrayColor]];
    }

    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(textChanged:) name:UITextViewTextDidChangeNotification object:nil];
}

- (id)initWithFrame:(CGRect)frame
{
    if( (self = [super initWithFrame:frame]) )
    {
        [self setPlaceholder:@""];
        [self setPlaceholderColor:[UIColor lightGrayColor]];
        [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(textChanged:) name:UITextViewTextDidChangeNotification object:nil];
    }
    return self;
}

- (void)textChanged:(NSNotification *)notification
{
    if([[self placeholder] length] == 0)
    {
        return;
    }

    [UIView animateWithDuration:UI_PLACEHOLDER_TEXT_CHANGED_ANIMATION_DURATION animations:^{
    if([[self text] length] == 0)
    {
        [[self viewWithTag:999] setAlpha:1];
    }
    else
    {
        [[self viewWithTag:999] setAlpha:0];
    }
    }];
}

- (void)setText:(NSString *)text {
    [super setText:text];
    [self textChanged:nil];
}

- (void)drawRect:(CGRect)rect
{
    if( [[self placeholder] length] > 0 )
    {
        if (_placeHolderLabel == nil )
        {
            _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];
}

@end

简单的Swift 3解决方案

添加UITextViewDelegate到类中

设置你的textview .delegate = self

创建placeholderLabel和位置它在你的textview

现在动画placeholderLabel。alpha在textViewDidChange:

  func textViewDidChange(_ textView: UITextView) {
    let newAlpha: CGFloat = textView.text.isEmpty ? 1 : 0
    if placeholderLabel.alpha != newAlpha {
      UIView.animate(withDuration: 0.3) {
        self.placeholderLabel.alpha = newAlpha
      }
    }
  }

你可能不得不使用placeholderLabel位置来设置它，但这应该不会太难

你可以在UITextView上设置标签

[UITextView addSubView:lblPlaceHoldaer];

并隐藏在TextViewdidChange方法上。

这是一个简单易行的方法。

我扩展了KmKndy的答案，这样在用户开始编辑UITextView之前，占位符仍然是可见的，而不仅仅是点击它。这反映了Twitter和Facebook应用程序的功能。我的解决方案不需要你子类和工作，如果用户类型直接或粘贴文本!

- (void)textViewDidChangeSelection:(UITextView *)textView{
    if ([textView.text isEqualToString:@"What's happening?"] && [textView.textColor isEqual:[UIColor lightGrayColor]])[textView setSelectedRange:NSMakeRange(0, 0)];

}

- (void)textViewDidBeginEditing:(UITextView *)textView{

    [textView setSelectedRange:NSMakeRange(0, 0)];
}

- (void)textViewDidChange:(UITextView *)textView
{
    if (textView.text.length != 0 && [[textView.text substringFromIndex:1] isEqualToString:@"What's happening?"] && [textView.textColor isEqual:[UIColor lightGrayColor]]){
        textView.text = [textView.text substringToIndex:1];
        textView.textColor = [UIColor blackColor]; //optional

    }
    else if(textView.text.length == 0){
        textView.text = @"What's happening?";
        textView.textColor = [UIColor lightGrayColor];
        [textView setSelectedRange:NSMakeRange(0, 0)];
    }
}

- (void)textViewDidEndEditing:(UITextView *)textView
{
    if ([textView.text isEqualToString:@""]) {
        textView.text = @"What's happening?";
        textView.textColor = [UIColor lightGrayColor]; //optional
    }
    [textView resignFirstResponder];
}

- (BOOL)textView:(UITextView *)textView shouldChangeTextInRange:(NSRange)range replacementText:(NSString *)text{
    if (textView.text.length > 1 && [textView.text isEqualToString:@"What's happening?"]) {
         textView.text = @"";
         textView.textColor = [UIColor blackColor];
    }

    return YES;
}

只需要记住在创建时使用准确的文本设置myUITextView即可。

UITextView *myUITextView = [[UITextView alloc] init];
myUITextView.delegate = self;
myUITextView.text = @"What's happening?";
myUITextView.textColor = [UIColor lightGrayColor]; //optional

在包含这些方法之前，让父类成为一个UITextView委托。

@interface MyClass () <UITextViewDelegate>
@end

下面是swift 3.1的代码

原始代码由杰森乔治在第一个答案。

不要忘记设置你的自定义类的TextView在接口生成器UIPlaceHolderTextView，然后设置占位符和占位符属性。

import UIKit

@IBDesignable
class UIPlaceHolderTextView: UITextView {

@IBInspectable var placeholder: String = ""
@IBInspectable var placeholderColor: UIColor = UIColor.lightGray

private let uiPlaceholderTextChangedAnimationDuration: Double = 0.05
private let defaultTagValue = 999

private var placeHolderLabel: UILabel?

override func awakeFromNib() {
    super.awakeFromNib()
    NotificationCenter.default.addObserver(
        self,
        selector: #selector(textChanged),
        name: NSNotification.Name.UITextViewTextDidChange,
        object: nil
    )
}

override init(frame: CGRect, textContainer: NSTextContainer?) {
    super.init(frame: frame, textContainer: textContainer)
    NotificationCenter.default.addObserver(
        self,
        selector: #selector(textChanged),
        name: NSNotification.Name.UITextViewTextDidChange,
        object: nil
    )
}

required init?(coder aDecoder: NSCoder) {
    super.init(coder: aDecoder)
    NotificationCenter.default.addObserver(
        self,
        selector: #selector(textChanged),
        name: NSNotification.Name.UITextViewTextDidChange,
        object: nil
    )
}

deinit {
    NotificationCenter.default.removeObserver(
        self,
        name: NSNotification.Name.UITextViewTextDidChange,
        object: nil
    )
}

@objc private func textChanged() {
    guard !placeholder.isEmpty else {
        return
    }
    UIView.animate(withDuration: uiPlaceholderTextChangedAnimationDuration) {
        if self.text.isEmpty {
            self.viewWithTag(self.defaultTagValue)?.alpha = CGFloat(1.0)
        }
        else {
            self.viewWithTag(self.defaultTagValue)?.alpha = CGFloat(0.0)
        }
    }
}

override var text: String! {
    didSet{
        super.text = text
        textChanged()
    }
}

override func draw(_ rect: CGRect) {
    if !placeholder.isEmpty {
        if placeHolderLabel == nil {
            placeHolderLabel = UILabel.init(frame: CGRect(x: 0, y: 8, width: bounds.size.width - 16, height: 0))
            placeHolderLabel!.lineBreakMode = .byWordWrapping
            placeHolderLabel!.numberOfLines = 0
            placeHolderLabel!.font = font
            placeHolderLabel!.backgroundColor = UIColor.clear
            placeHolderLabel!.textColor = placeholderColor
            placeHolderLabel!.alpha = 0
            placeHolderLabel!.tag = defaultTagValue
            self.addSubview(placeHolderLabel!)
        }

        placeHolderLabel!.text = placeholder
        placeHolderLabel!.sizeToFit()
        self.sendSubview(toBack: placeHolderLabel!)

        if text.isEmpty && !placeholder.isEmpty {
            viewWithTag(defaultTagValue)?.alpha = 1.0
        }
    }

    super.draw(rect)
}
}