TextView占位符

import UIKit

@IBDesignable
open class KMPlaceholderTextView: UITextView {

    private struct Constants {
        static let defaultiOSPlaceholderColor = UIColor(red: 0.0, green: 0.0, blue: 0.0980392, alpha: 0.22)
    }

    public let placeholderLabel: UILabel = UILabel()

    private var placeholderLabelConstraints = [NSLayoutConstraint]()

    @IBInspectable open var placeholder: String = "" {
        didSet {
            placeholderLabel.text = placeholder
        }
    }

    @IBInspectable open var placeholderColor: UIColor = KMPlaceholderTextView.Constants.defaultiOSPlaceholderColor {
        didSet {
            placeholderLabel.textColor = placeholderColor
        }
    }

    override open var font: UIFont! {
        didSet {
            if placeholderFont == nil {
                placeholderLabel.font = font
            }
        }
    }

    open var placeholderFont: UIFont? {
        didSet {
            let font = (placeholderFont != nil) ? placeholderFont : self.font
            placeholderLabel.font = font
        }
    }

    override open var textAlignment: NSTextAlignment {
        didSet {
            placeholderLabel.textAlignment = textAlignment
        }
    }

    override open var text: String! {
        didSet {
            textDidChange()
        }
    }

    override open var attributedText: NSAttributedString! {
        didSet {
            textDidChange()
        }
    }

    override open 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() {
        #if swift(>=4.2)
        let notificationName = UITextView.textDidChangeNotification
        #else
        let notificationName = NSNotification.Name.UITextView.textDidChangeNotification
        #endif

        NotificationCenter.default.addObserver(self,
                                               selector: #selector(textDidChange),
                                               name: notificationName,
                                               object: nil)

        placeholderLabel.font = font
        placeholderLabel.textColor = placeholderColor
        placeholderLabel.textAlignment = textAlignment
        placeholderLabel.text = placeholder
        placeholderLabel.numberOfLines = 0
        placeholderLabel.backgroundColor = UIColor.clear
        placeholderLabel.translatesAutoresizingMaskIntoConstraints = false
        addSubview(placeholderLabel)
        updateConstraintsForPlaceholderLabel()
    }

    private func updateConstraintsForPlaceholderLabel() {
        var newConstraints = NSLayoutConstraint.constraints(withVisualFormat: "H:|-(\(textContainerInset.left + textContainer.lineFragmentPadding))-[placeholder]",
            options: [],
            metrics: nil,
            views: ["placeholder": placeholderLabel])
        newConstraints += NSLayoutConstraint.constraints(withVisualFormat: "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.isHidden = !text.isEmpty
        self.layoutIfNeeded()
    }

    open override func layoutSubviews() {
        super.layoutSubviews()
        placeholderLabel.preferredMaxLayoutWidth = textContainer.size.width - textContainer.lineFragmentPadding * 2.0
    }

    deinit {
        #if swift(>=4.2)
        let notificationName = UITextView.textDidChangeNotification
        #else
        let notificationName = NSNotification.Name.UITextView.textDidChangeNotification
        #endif

        NotificationCenter.default.removeObserver(self,
                                                  name: notificationName,
                                                  object: nil)
    }

}

使用

在h课上

@interface RateCommentViewController : UIViewController<UITextViewDelegate>{IBoutlet UITextview *commentTxtView;}

在。m类

- (void)viewDidLoad{      
    commentTxtView.text = @"Comment";
    commentTxtView.textColor = [UIColor lightGrayColor];
    commentTxtView.delegate = self;
}

- (BOOL) textViewShouldBeginEditing:(UITextView *)textView
{
    commentTxtView.text = @"";
    commentTxtView.textColor = [UIColor blackColor];
    return YES;
}

-(void) textViewDidChange:(UITextView *)textView
{
    if(commentTxtView.text.length == 0){
        commentTxtView.textColor = [UIColor lightGrayColor];
        commentTxtView.text = @"Comment";
        [commentTxtView resignFirstResponder];
    }
}

让我们简单点

创建一个UILabel并把它放在你的文本视图上(给文本作为占位符-设置颜色为灰色-你可以在你的xib中做这一切) 现在在头文件中声明UILabel和textviewDelegate 现在你可以简单地隐藏标签，当你点击textview

完整代码如下

头

@interface ViewController :UIViewController<UITextViewDelegate>{
 }
   @property (nonatomic,strong) IBOutlet UILabel *PlceHolder_label;
   @property (nonatomic,strong) IBOutlet UITextView *TextView;

@end

实现

@implementation UploadFoodImageViewController
@synthesize PlceHolder_label,TextView;

  - (void)viewDidLoad
    {
       [super viewDidLoad];
    }


 - (BOOL)textViewShouldBeginEditing:(UITextView *)textView{

       if([textView isEqual:TextView]){
            [PlceHolder_label setHidden:YES];
            [self.tabScrlVw setContentOffset:CGPointMake(0,150) animated:YES];
          }
      return YES;
    }

@end

别忘了连接textView和UILabel文件所有者从xib

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

你可以在textview上设置一个标签。

MyUITextView.h

@interface MyUITextView : UITextView {
    UILabel* _placeholderLabel;
}

@property(nonatomic, assign)NSString *placeholder;

MyUITextView.m

@implementation MyUITextView

- (id)initWithFrame:(CGRect)frame {
    if (self = [super initWithFrame:frame]) {
        // Create placeholder
        viewFrame = CGRectMake(0, 0, frame.size.width, 15);
        _placeholderLabel = [[UILabel alloc] initWithFrame:viewFrame];
        _placeholderLabel.textColor = [UIColor lightGrayColor];
        [self addSubview:_placeholderLabel];

        // Add text changed notification 
        [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(textChanged:) name:UITextViewTextDidChangeNotification object:nil];
    }
    return self;
}

- (void)setPlaceholder:(NSString *)placeholder {
    _placeholderLabel.text = placeholder;
}

- (NSString*)placeholder {
    return _placeholderLabel.text;
}

#pragma mark UITextViewTextDidChangeNotification

- (void)textChanged:(NSNotification *)notification {
    _placeholderLabel.hidden = ([self.text lenght] == 0);
}

@end

在swift 5。工作很好。

class BaseTextView: UITextView {

    // MARK: - Views
    private var placeholderLabel: UIlabel!

    // MARK: - Init
    override init(frame: CGRect, textContainer: NSTextContainer?) {
        super.init(frame: frame, textContainer: textContainer)
        setupUI()
        startupSetup()
    }

    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        setupUI()
        startupSetup()
    }

    deinit {
        NotificationCenter.default.removeObserver(self)
    }    
}

// MARK: - Setup UI
private extension BaseTextView {
    func setupUI() {
        addPlaceholderLabel()

        textColor = .textColor
    }

    func addPlaceholderLabel() {
        placeholderLabel = BaseLabel(frame: .zero)
        placeholderLabel.translatesAutoresizingMaskIntoConstraints = false
        insertSubview(placeholderLabel, at: 0)

        placeholderLabel.alpha = 0
        placeholderLabel.numberOfLines = 0
        placeholderLabel.backgroundColor = .clear
        placeholderLabel.textColor = .lightTextColor
        placeholderLabel.lineBreakMode = .byWordWrapping
        placeholderLabel.isUserInteractionEnabled = false
        placeholderLabel.font = UIFont.openSansSemibold.withSize(12)

        placeholderLabel.topAnchor.constraint(equalTo: topAnchor, constant: 8).isActive = true
        placeholderLabel.leftAnchor.constraint(equalTo: leftAnchor, constant: 5).isActive = true
        placeholderLabel.rightAnchor.constraint(lessThanOrEqualTo: rightAnchor, constant: -8).isActive = true
        placeholderLabel.bottomAnchor.constraint(lessThanOrEqualTo: bottomAnchor, constant: -8).isActive = true
    }
}

// MARK: - Startup
private extension BaseTextView {
    func startupSetup() {
        addObservers()
        textChanged(nil)
        font = UIFont.openSansSemibold.withSize(12)
    }    

    func addObservers() {
        NotificationCenter.default.addObserver(self, selector: #selector(textChanged(_:)), name: UITextView.textDidChangeNotification, object: nil)
    }
}

// MARK: - Actions
private extension BaseTextView {
    @objc func textChanged(_ sender: Notification?) {
        UIView.animate(withDuration: 0.2) {
            self.placeholderLabel.alpha = self.text.count == 0 ? 1 : 0
        }    
    }
}

// MARK: - Public methods
extension BaseTextView {
    public func setPlaceholder(_ placeholder: String) {
        placeholderLabel.text = placeholder
    }
}