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:
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//
// 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:
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//
// 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
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调用:
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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];
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效果:
本文转自Fly_Elephant博客园博客，原文链接：http://www.cnblogs.com/xiaofeixiang/p/4509665.html，如需转载请自行联系原作者
