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iOS开发-UITextView实现PlaceHolder的方式

之前开发遇到过UITextField中加入一个PlaceHolder的问题，直接设置一下即可，不过这次是需要在UITextView中实现一个PlaceHolder，跟之前有点不同。在网上参考了各位前辈的解决方案，大概有两种方式，第一种方式很猥琐，就是直接给UITextView的text赋值，比如说默认提示是"博客园FlyElephant"，在textViewDidChange中判断是不是“博客园FlyElephant”，如果是就清空，如果不是就继续提示，弊端就是用户输入的内容不能和你的默认提示一样，第二种方式需要加入一个UILabel，同样在textViewDidChange中进行判断，一般都是这么实现，不过有的都是创建textView中的时候创建UILabel，这样做无可厚非，不过最好还是抽象出来。继承UITextView扩展一下，新建一个 FEPlaceHolderTextView：

头文件:

// //  FEPlaceHolderTextView.h //  MyTextViewDemo //http://www.cnblogs.com/xiaofeixiang //  Created by keso on 15/5/17. //  Copyright (c) 2015年 keso. All rights reserved. //  #import <UIKit/UIKit.h>  @interface FEPlaceHolderTextView : UITextView  @property (nonatomic, retain) NSString *placeholder; @property (nonatomic, retain) UIColor *placeholderColor;  -(void)textChanged:(NSNotification*)notification;   @end

实现文件:

// //  FEPlaceHolderTextView.m //  MyTextViewDemo //http://www.cnblogs.com/xiaofeixiang //  Created by keso on 15/5/17. //  Copyright (c) 2015年 keso. All rights reserved. // #import "FEPlaceHolderTextView.h" @interface FEPlaceHolderTextView () @property (nonatomic, retain) UILabel *placeHolderLabel; @end @implementation FEPlaceHolderTextView CGFloat const UI_PLACEHOLDER_TEXT_CHANGED_ANIMATION_DURATION = 0.25; - (void)dealloc {  [[NSNotificationCenter defaultCenter] removeObserver:self]; } - (void)awakeFromNib {  [super awakeFromNib];  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,10)];    _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

调用:

self.textView=[[FEPlaceHolderTextView alloc]initWithFrame:CGRectMake(10, 30, CGRectGetWidth(self.view.frame)-20, 200)];     self.textView.placeholder=@"博客园FlyElephant/n博客地址:http://www.cnblogs.com/xiaofeixiang";     self.textView.layer.borderColor=[UIColor lightGrayColor].CGColor;     self.textView.layer.borderWidth=1.0;     self.textView.scrollEnabled = YES;     self.textView.autoresizingMask =     UIViewAutoresizingFlexibleHeight; //自适应高度     self.textView.returnKeyType = UIReturnKeyDefault; //返回键的类型          self.textView.keyboardType = UIKeyboardTypeDefault; //键盘类型     [self.view addSubview:self.textView];

效果:

iOS开发-UITextView实现PlaceHolder的方式