UITextView添加一个placeholder功能

控件UITextField有个placeholder属性，UITextField和UITextView使用方法基本类似，有两个小区别：1.UITextField单行输入，而UITextView可以多行输入。2.UITextField有placeholder属性，而UITextView没有。至于两者的代理方法，原理基本差不多，只是方法名略有差异。

实现该功能有两种方式一种是 ①使用通知显示隐藏遮盖物

②使用代理给文本框重新赋值

1.在创建textView的时候，赋值其文本属性

即textView.text = @"想说的话"；

2.在开始编辑和结束编辑的代理方法中进行判断

 1 //
 2 //  ViewController.m
 3 //  绘制TextView
 4 //
 5 //  Created by zjj on 15/7/1.
 6 //  Copyright (c) 2015年 zjj. All rights reserved.
 7 //
 8 
 9 #import "ViewController.h"
10 #import "DJTextView.h"
11 #import "DJplaceHolderTextView.h"
12 @interface ViewController () <UITextViewDelegate>
13 @property (nonatomic,strong)DJplaceHolderTextView *placeHolderText;
14 @end
15 
16 @implementation ViewController
17 
18 - (void)viewDidLoad {
19     [super viewDidLoad];
20     UITextField *text1 = [[UITextField alloc]initWithFrame:CGRectMake(150, 150, 100, 30)];
21     text1.backgroundColor = [UIColor grayColor];
22     text1.placeholder = @"请输入账号";
23     text1.clearButtonMode = UITextFieldViewModeWhileEditing;
24     [self.view addSubview:text1];
25     
26     // 做法① 使用通知 用一个UIlabel遮盖再UItextView上面 根据输入文字是否为0来隐藏显示遮盖物 文字提示
27     DJTextView *text = [[DJTextView alloc]initWithFrame:CGRectMake(50, 50, 100, 100)];
28     text.backgroundColor = [UIColor grayColor];
29     text.placeholder = @"请输入账号";
30     text.placeholderColor = [UIColor whiteColor];
31     [self.view addSubview:text];
32     
33     // 做法② 使用UITextViewDelegate代理 开始编辑和结束编辑事件重新赋值文本属性
34     _placeHolderText = [[DJplaceHolderTextView alloc]initWithFrame:CGRectMake(250, 250, 100, 100)];
35     _placeHolderText.backgroundColor = [UIColor grayColor];
36     _placeHolderText.placeholder = @"请输入账号";
37     _placeHolderText.text = _placeHolderText.placeholder;
38     _placeHolderText.delegate = self;
39     [self.view addSubview:_placeHolderText];
40 }
41 /**
42  *  开始编辑事件
43  */
44 - (void)textViewDidBeginEditing:(UITextView *)textView
45 {
46 //  NSLog(@"textViewDidBeginEditing%@ - %ld - %@",textView.text,textView.text.length,self.placeHolderText.placeholder);
47     if ([textView.text isEqualToString:self.placeHolderText.placeholder]) {
48         textView.text = @"";
49     }
50 }
51 /**
52  *  结束编辑事件
53  */
54 - (void)textViewDidEndEditing:(UITextView *)textView
55 {
56 //    NSLog(@"textViewDidBeginEditing%@ - %ld - %@",textView.text,textView.text.length,self.placeHolderText.placeholder);
57     if (textView.text.length < 1) {
58         textView.text = self.placeHolderText.placeholder;
59     }
60 }
61 
62 @end

 // 做法② 使用UITextViewDelegate代理 开始编辑和结束编辑事件重新赋值文本属性

 1 //
 2 //  DJplaceHolderTextView.h
 3 //  绘制TextView
 4 //
 5 //  Created by zjj on 15/7/2.
 6 //  Copyright (c) 2015年 zjj. All rights reserved.
 7 //
 8 
 9 #import <UIKit/UIKit.h>
10 
11 @interface DJplaceHolderTextView : UITextView
12 /**
13  *  placehold 用户输入前文本提示
14  */
15 @property (nonatomic,copy) NSString *placeholder;
16 @end

// 做法① 使用通知 用一个UIlabel遮盖再UItextView上面 根据输入文字是否为0来隐藏显示遮盖物 文字提示

 1 //
 2 //  DJTextView.h
 3 //  绘制TextView
 4 //
 5 //  Created by zjj on 15/7/1.
 6 //  Copyright (c) 2015年 zjj. All rights reserved.
 7 //
 8 
 9 #import <UIKit/UIKit.h>
10 /**
11  *  UITextView 实现 placeholder 及隐藏键盘
12  */
13 @interface DJTextView : UITextView
14 /**
15  *  placehold 用户输入前文本提示
16  */
17 @property (nonatomic,copy) NSString *placeholder;
18 /**
19  *  placeholder 文字颜色
20  */
21 @property (nonatomic,strong)UIColor *placeholderColor;
22 /**
23  *  placeholder 提示label
24  */
25 @property (nonatomic,strong)UILabel *placeholderLabel;
26 /**
27  *  文本改变事件
28  */
29 -(void)textChanged:(NSNotification*)notification;
30 @end

  1 //
  2 //  DJTextView.m
  3 //  绘制TextView
  4 //
  5 //  Created by zjj on 15/7/1.
  6 //  Copyright (c) 2015年 zjj. All rights reserved.
  7 //
  8 
  9 #import "DJTextView.h"
 10 
 11 @implementation DJTextView
 12 
 13 
 14 //-(void)setPlaceholder:(NSString *)placeholder
 15 //{
 16 //    _placeholder = placeholder;
 17 //
 18 //    [self setNeedsDisplay];
 19 //}
 20 //
 21 //- (void)drawRect:(CGRect)rect
 22 //{
 23 //
 24 //    [self.placeholder drawInRect:rect withAttributes:nil];
 25 //}
 26 
 27 - (void)dealloc
 28 
 29 {
 30     
 31     [[NSNotificationCenter defaultCenter] removeObserver:self];
 32     
 33 //    placeHolderLabel = nil;
 34 //    
 35 //    [placeholderColor release]; placeholderColor = nil;
 36 //    
 37 //    [placeholder release]; placeholder = nil;
 38     
 39 //    [super dealloc];
 40     
 41 }
 42 
 43 
 44 
 45 - (void)awakeFromNib
 46 
 47 {
 48     
 49     [super awakeFromNib];
 50     
 51     [self setPlaceholder:@""];
 52     
 53     [self setPlaceholderColor:[UIColor lightGrayColor]];
 54     
 55     [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(textChanged:) name:UITextViewTextDidChangeNotification object:nil];
 56     
 57 }
 58 
 59 
 60 
 61 - (id)initWithFrame:(CGRect)frame
 62 
 63 {
 64     
 65     if( (self = [super initWithFrame:frame]) )
 66         
 67     {
 68         
 69         [self setPlaceholder:@""];
 70         
 71         [self setPlaceholderColor:[UIColor lightGrayColor]];
 72         
 73         [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(textChanged:) name:UITextViewTextDidChangeNotification object:nil];
 74         
 75     }
 76     
 77     return self;
 78     
 79 }
 80 
 81 
 82 
 83 - (void)textChanged:(NSNotification *)notification
 84 
 85 {
 86     
 87     if([[self placeholder] length] == 0)
 88         
 89     {
 90         
 91         return;
 92         
 93     }
 94     
 95     
 96     
 97     if([[self text] length] == 0)
 98         
 99     {
100         
101         [[self viewWithTag:999] setAlpha:1];
102         
103     }
104     
105     else
106         
107     {
108         
109         [[self viewWithTag:999] setAlpha:0];
110         
111     }
112     
113 }
114 
115 
116 
117 - (void)setText:(NSString *)text {
118     
119     [super setText:text];
120     
121     [self textChanged:nil];
122     
123 }
124 
125 
126 
127 - (void)drawRect:(CGRect)rect
128 
129 {
130     
131     if( [[self placeholder] length] > 0 )
132         
133     {
134         
135         if ( self.placeholderLabel == nil )
136             
137         {
138             
139             self.placeholderLabel = [[UILabel alloc] initWithFrame:CGRectMake(8,8,self.bounds.size.width - 16,0)];
140             self.placeholderLabel.lineBreakMode = UILineBreakModeWordWrap;//过时的
141             self.placeholderLabel.numberOfLines = 0;
142             
143             self.placeholderLabel.font = self.font;
144             
145             self.placeholderLabel.backgroundColor = [UIColor clearColor];
146             
147             self.placeholderLabel.textColor = self.placeholderColor;
148             
149             self.placeholderLabel.alpha = 0;
150             
151             self.placeholderLabel.tag = 999;
152             
153             [self addSubview:self.placeholderLabel];
154             
155         }
156         
157         
158         
159         self.placeholderLabel.text = self.placeholder;
160         
161         [self.placeholderLabel sizeToFit];
162         
163         [self sendSubviewToBack:self.placeholderLabel];
164         
165     }
166     
167     
168     
169     if( [[self text] length] == 0 && [[self placeholder] length] > 0 )
170         
171     {
172         
173         [[self viewWithTag:999] setAlpha:1];
174         
175     }
176     
177     
178     
179     [super drawRect:rect];
180     
181 }
182 ////隐藏键盘，实现UITextViewDelegate
183 //
184 //-(BOOL)textView:(UITextView *)textView shouldChangeTextInRange:(NSRange)range replacementText:(NSString*)text
185 //
186 //{
187 //    
188 //    if ([text isEqualToString:@"
"]) {
189 //        
190 //        [textView resignFirstResponder];
191 //        
192 //        return NO;
193 //        
194 //    }
195 //    
196 //    return YES;  
197 //    
198 //}
199 
200 @end

推荐使用第一种

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原文地址：https://www.cnblogs.com/zhangdashao/p/4617489.html