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

//
//  ViewController.m
//  绘制TextView
//
//  Created by zjj on 15/7/1.
//  Copyright (c) 2015年 zjj. All rights reserved.
//

#import "ViewController.h"
#import "DJTextView.h"
#import "DJplaceHolderTextView.h"
@interface ViewController () <UITextViewDelegate>
@property (nonatomic,strong)DJplaceHolderTextView *placeHolderText;
@end

@implementation ViewController

- (void)viewDidLoad {
[super viewDidLoad];
UITextField *text1 = [[UITextField alloc]initWithFrame:CGRectMake(150, 150, 100, 30)];
text1.backgroundColor = [UIColor grayColor];
text1.placeholder = @"请输入账号";
text1.clearButtonMode = UITextFieldViewModeWhileEditing;
[self.view addSubview:text1];

// 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
DJTextView *text = [[DJTextView alloc]initWithFrame:CGRectMake(50, 50, 100, 100)];
text.backgroundColor = [UIColor grayColor];
text.placeholder = @"请输入账号";
text.placeholderColor = [UIColor whiteColor];
[self.view addSubview:text];

// 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
_placeHolderText = [[DJplaceHolderTextView alloc]initWithFrame:CGRectMake(250, 250, 100, 100)];
_placeHolderText.backgroundColor = [UIColor grayColor];
_placeHolderText.placeholder = @"请输入账号";
_placeHolderText.text = _placeHolderText.placeholder;
_placeHolderText.delegate = self;
[self.view addSubview:_placeHolderText];
}
/**
*  开始编辑事件
*/
- (void)textViewDidBeginEditing:(UITextView *)textView
{
//  NSLog(@"textViewDidBeginEditing%@ - %ld - %@",textView.text,textView.text.length,self.placeHolderText.placeholder);
if ([textView.text isEqualToString:self.placeHolderText.placeholder]) {
textView.text = @"";
}
}
/**
*  结束编辑事件
*/
- (void)textViewDidEndEditing:(UITextView *)textView
{
//    NSLog(@"textViewDidBeginEditing%@ - %ld - %@",textView.text,textView.text.length,self.placeHolderText.placeholder);
if (textView.text.length < 1) {
textView.text = self.placeHolderText.placeholder;
}
}

@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

//
//  DJplaceHolderTextView.h
//  绘制TextView
//
//  Created by zjj on 15/7/2.
//  Copyright (c) 2015年 zjj. All rights reserved.
//

#import <UIKit/UIKit.h>

@interface DJplaceHolderTextView : UITextView
/**
*  placehold 用户输入前文本提示
*/
@property (nonatomic,copy) NSString *placeholder;
@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

//
//  DJTextView.h
//  绘制TextView
//
//  Created by zjj on 15/7/1.
//  Copyright (c) 2015年 zjj. All rights reserved.
//

#import <UIKit/UIKit.h>
/**
*  UITextView 实现 placeholder 及隐藏键盘
*/
@interface DJTextView : UITextView
/**
*  placehold 用户输入前文本提示
*/
@property (nonatomic,copy) NSString *placeholder;
/**
*  placeholder 文字颜色
*/
@property (nonatomic,strong)UIColor *placeholderColor;
/**
*  placeholder 提示label
*/
@property (nonatomic,strong)UILabel *placeholderLabel;
/**
*  文本改变事件
*/
-(void)textChanged:(NSNotification*)notification;
@end

//
//  DJTextView.m
//  绘制TextView
//
//  Created by zjj on 15/7/1.
//  Copyright (c) 2015年 zjj. All rights reserved.
//

#import "DJTextView.h"

@implementation DJTextView

//-(void)setPlaceholder:(NSString *)placeholder
//{
//    _placeholder = placeholder;
//
//    [self setNeedsDisplay];
//}
//
//- (void)drawRect:(CGRect)rect
//{
//
//    [self.placeholder drawInRect:rect withAttributes:nil];
//}

- (void)dealloc

{

[[NSNotificationCenter defaultCenter] removeObserver:self];

//    placeHolderLabel = nil;
//
//    [placeholderColor release]; placeholderColor = nil;
//
//    [placeholder release]; placeholder = nil;

//    [super dealloc];

}

- (void)awakeFromNib

{

[super awakeFromNib];

[self setPlaceholder:@""];

[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;

}

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 ( self.placeholderLabel == nil )

{

self.placeholderLabel = [[UILabel alloc] initWithFrame:CGRectMake(8,8,self.bounds.size.width - 16,0)];
self.placeholderLabel.lineBreakMode = UILineBreakModeWordWrap;//过时的
self.placeholderLabel.numberOfLines = 0;

self.placeholderLabel.font = self.font;

self.placeholderLabel.backgroundColor = [UIColor clearColor];

self.placeholderLabel.textColor = self.placeholderColor;

self.placeholderLabel.alpha = 0;

self.placeholderLabel.tag = 999;

[self addSubview:self.placeholderLabel];

}

self.placeholderLabel.text = self.placeholder;

[self.placeholderLabel sizeToFit];

[self sendSubviewToBack:self.placeholderLabel];

}

if( [[self text] length] == 0 && [[self placeholder] length] > 0 )

{

[[self viewWithTag:999] setAlpha:1];

}

[super drawRect:rect];

}
////隐藏键盘，实现UITextViewDelegate
//
//-(BOOL)textView:(UITextView *)textView shouldChangeTextInRange:(NSRange)range replacementText:(NSString*)text
//
//{
//
//    if ([text isEqualToString:@"\n"]) {
//
//        [textView resignFirstResponder];
//
//        return NO;
//
//    }
//
//    return YES;
//
//}

@end

推荐使用第一种