优秀是一种习惯
前言:大家项目中肯定经常用到UITextView,但是对于这个控件有一个很大的缺点,那就是没有placeHolerLabel,搞不懂苹果为什么不给一个这种属性,明明应用的很广泛
网上关于UITextView实现placeHolerLabel的方法大概有四五种,在文章后面会一一列举
因为网上很多了,就复制来了,本来打算跳转一下,但是不是很喜欢,便复制了一下
原文:http://www.jianshu.com/p/426a3fc8b067
终极篇效果.png
怕各位看官,看烦了,先上终极篇
终极篇采取了runtime方法+类别
直接上代码
终极方法
1. 新建一个UITextView的分类（Category）
2. 声明一个属性placeholder
3. 实现get,set方法
代码如下
.h
#import <UIKit/UIKit.h>
@interface UITextView (Category)
@property (nonatomic,copy)NSString * hc_placeHolerLabel;
@end
//-----------------------------------------//
.m
#import "UITextView+Category.h"
@implementation UITextView (Category)
-(void)setHc_placeHolerLabel:(NSString *)hc_placeHolerLabel{
// _placeholderLabel
UILabel *Label = [[UILabel alloc] init];
Label.text = @"请输入内容";
Label.numberOfLines = 0;
Label.textColor = [UIColor lightGrayColor];
[Label sizeToFit];
[self addSubview:Label];
//很重要的一句话,如果字体大小跟textView大小不一样会出问题
Label.font = [UIFont systemFontOfSize:self.font.pointSize];
[self setValue:Label forKey:@"_placeholderLabel"];
}
-(NSString *)hc_placeHolerLabel{
UILabel * label = [self valueForKey:@"_placeholderLabel"];
return label.text;
}
@end
第一种
1.把UITextView的text属性当成“placeholder”使用。
2.在开始编辑的代理方法里清除“placeholder”。
3.在结束编辑的代理方法里根据条件设置“placeholder”。
缺点很明显:当textView的文字跟placeHolerLabel相同时就有问题了
// 创建textView
UITextView *textView = [[UITextViewalloc]initWithFrame:CGRectMake(20,70,SCREEN.width-40,100)];
textView.backgroundColor= [UIColor whiteColor];
textView.text = @"我是placeholder";
textView.textColor = [UIColor grayColor];
textView.delegate = self;
[self.view addSubview:textView];
#pragma mark - UITextViewDelegate
- (void)textViewDidEndEditing:(UITextView *)textView
{
if(textView.text.length < 1){
textView.text = @"我是placeholder";
textView.textColor = [UIColor grayColor];
}
}
- (void)textViewDidBeginEditing:(UITextView *)textView
{
if([textView.text isEqualToString:@"我是placeholder"]){
textView.text=@"";
textView.textColor=[UIColor blackColor];
}
}
第二种
1.创建textView
2.给textView添加一个UILabel子控件，作为placeholder
3.在文本改变的代理方法里面显示/隐藏UILabel
太麻烦了.....大哥
#import "WSViewController.h"
@interface WSViewController () <UITextViewDelegate>
@property(nonatomic, weak)UITextView *textView;
@property(nonatomic, weak)UILabel *placeHolder;
@end
@implementation WSViewController
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view.
[self setupTextView];
}
// 添加textView
- (void)setupTextView
{
UITextView *textView = [[UITextView alloc] initWithFrame:CGRectMake(10, 74, SCREEN_WIDTH - 2 * 10, 200)];
textView.frame = CGRectMake(10, 74, SCREEN_WIDTH - 2 * 10, 200);
[self.view addSubview:textView];
self.textView = textView;
textView.contentInset = UIEdgeInsetsMake(-64, 0, 0, 0);
textView.delegate = self;
[self setupPlaceHolder];
//在弹出的键盘上面加一个view来放置退出键盘的Done按钮
UIToolbar * topView = [[UIToolbar alloc] initWithFrame:CGRectMake(0, 0, 320, 30)];
[topView setBarStyle:UIBarStyleDefault];
UIBarButtonItem * btnSpace = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemFlexibleSpace target:self action:nil];
UIBarButtonItem * doneButton = [[UIBarButtonItem alloc] initWithTitle:@"完成" style:UIBarButtonItemStyleDone target:self action:@selector(dismissKeyBoard)];
NSArray * buttonsArray = [NSArray arrayWithObjects:btnSpace, doneButton, nil];
[topView setItems:buttonsArray];
[textView setInputAccessoryView:topView];
}
// 给textView添加一个UILabel子控件
- (void)setupPlaceHolder
{
UILabel *placeHolder = [[UILabel alloc] initWithFrame:CGRectMake(15, -2, SCREEN_WIDTH - 2 * 15, 200)];
self.placeHolder = placeHolder;
placeHolder.text = @"我是placeholder";
placeHolder.textColor = [UIColor lightGrayColor];
placeHolder.numberOfLines = 0;
placeHolder.contentMode = UIViewContentModeTop;
[self.textView addSubview:placeHolder];
}
#pragma mark - UITextViewDelegate
- (void)textViewDidChange:(UITextView *)textView
{
if (!textView.text.length) {
self.placeHolder.alpha = 1;
} else {
self.placeHolder.alpha = 0;
}
}
//关闭键盘
-(void) dismissKeyBoard{
[self.textView resignFirstResponder];
}
@end
第三种
1.自定义UITextView
2.给UITextView添加placeholder和placeholderColor属性
3.重写initWithFrame方法
4.重写drawRect：方法
5.重写相关属性的set方法
不麻烦吗?
#import <UIKit/UIKit.h>
@interface WSTextView : UITextView
/** 占位文字 */
@property (nonatomic,copy) NSString *placeholder;
/** 占位文字颜色 */
@property (nonatomic,strong) UIColor *placeholderColor;
@end
#import "WSTextView.h"
@implementation WSTextView
- (instancetype)initWithFrame:(CGRect)frame
{
if (self = [super initWithFrame:frame]) {
self.font = [UIFont systemFontOfSize:15];
self.placeholderColor = [UIColor lightGrayColor];
self.placeholder = @"请输入内容";
}
return self;
}
// Only override drawRect: if you perform custom drawing.
// An empty implementation adversely affects performance during animation.
- (void)drawRect:(CGRect)rect {
// Drawing code
NSMutableDictionary *attrs = [NSMutableDictionary dictionary];
attrs[NSFontAttributeName] = self.font;
attrs[NSForegroundColorAttributeName] = self.placeholderColor;
[self.placeholder drawInRect:CGRectMake(0, 0, self.frame.size.width, self.frame.size.height) withAttributes:attrs];
}
// 布局子控件的时候需要重绘
- (void)layoutSubviews
{
[super layoutSubviews];
[self setNeedsDisplay];
}
// 设置属性的时候需要重绘，所以需要重写相关属性的set方法
- (void)setPlaceholder:(NSString *)placeholder
{
_placeholder = placeholder;
[self setNeedsDisplay];
}
- (void)setPlaceholderColor:(UIColor *)placeholderColor
{
_placeholderColor = placeholderColor;
[self setNeedsDisplay];
}
- (void)setFont:(UIFont *)font
{
[super setFont:font];
[self setNeedsDisplay];
}
- (void)setText:(NSString *)text
{
[super setText:text];
if (text.length) { // 因为是在文本改变的代理方法中判断是否显示placeholder，而通 过代码设置text的方式又不会调用文本改变的代理方法，所以再此根据text是否不为空判 断是否显示placeholder。
self.placeholder = @"";
}
[self setNeedsDisplay];
}
- (void)setAttributedText:(NSAttributedString *)attributedText
{
[super setAttributedText:attributedText];
if (attributedText.length) {
self.placeholder = @"";
}
[self setNeedsDisplay];
}
@end
// 应用的时候需要配合UITextView的文本改变的代理方法
#import "ViewController.h"
#import "WSTextView.h"
@interface ViewController ()<UITextViewDelegate>
// @property(nonatomic,weak) WSTextView *textView;
@end
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
}
- (void)didReceiveMemoryWarning {
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event
{
WSTextView *textView = [[WSTextView alloc] initWithFrame:CGRectMake(10, 20, self.view.frame.size.width, 30)];
textView.placeholder = @"ws";
textView.delegate = self;
[self.view addSubview:textView];
// textView.text = @"试试会不会调用文本改变的代理方法"; // 不会调用文本改变的代理方法
textView.attributedText = [[NSAttributedString alloc] initWithString:@"富文本"];
// self.textView = textView;
}
#pragma mark - UITextViewDelegate
- (void)textViewDidChange:(WSTextView *)textView // 此处取巧，把代理方法参数类型直接改成自定义的WSTextView类型，为了可以使用自定义的placeholder属性，省去了通过给控制器WSTextView类型属性这样一步。
{
if (textView.hasText) { // textView.text.length
textView.placeholder = @"";
} else {
textView.placeholder = @"ws";
}
}
@end
第四种
runtime私有变量,高大上
然而也有问题,在8.1的时候是没有这个私有变量的,所以要适配iOS8.0是有问题的
终极方法也是根据这个来的
#import "ViewController.h"
#import <objc/runtime.h>
#import <objc/message.h>
@interface ViewController ()
@end
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
// 通过运行时，发现UITextView有一个叫做“_placeHolderLabel”的私有变量
unsigned int count = 0;
Ivar *ivars = class_copyIvarList([UITextView class], &count);
for (int i = 0; i < count; i++) {
Ivar ivar = ivars[i];
const char *name = ivar_getName(ivar);
NSString *objcName = [NSString stringWithUTF8String:name];
NSLog(@"%d : %@",i,objcName);
}
//8.1
/*
0 : _private
1 : _textStorage
2 : _textContainer
3 : _layoutManager
4 : _containerView
5 : _inputDelegate
6 : _tokenizer
7 : _inputController
8 : _interactionAssistant
9 : _textInputTraits
10 : _autoscroll
11 : _tvFlags
12 : _linkInteractionItem
13 : _scrollTarget
14 : _scrollTargetOffset
15 : _dataDetectorTypes
16 : _preferredMaxLayoutWidth
17 : _inputAccessoryView
18 : _streamingManager
19 : _characterStreamingManager
20 : _siriAnimationStyle
21 : _siriParameters
22 : _firstBaselineOffsetFromTop
23 : _lastBaselineOffsetFromBottom
24 : _clearsOnInsertion
25 : _inputView
*/
[self setupTextView];
}
- (void)setupTextView
{
//注意这里的textView的Font跟_placeholderLabel的font一定要相同
UITextView *textView = [[UITextView alloc] initWithFrame:CGRectMake(0, 100, [UIScreen mainScreen].bounds.size.width, 100];
textView.font = [UIFont systemFontOfSize:14];
[textView setBackgroundColor:[UIColor greenColor]];
[self.view addSubview:textView];
// _placeholderLabel
UILabel *placeHolderLabel = [[UILabel alloc] init];
placeHolderLabel.text = @"请输入内容";
placeHolderLabel.numberOfLines = 0;
placeHolderLabel.textColor = [UIColor lightGrayColor];
[placeHolderLabel sizeToFit];
placeHolderLabel.font = textView.font;
[textView addSubview:placeHolderLabel];
[textView setValue:placeHolderLabel forKey:@"_placeholderLabel"];
}
@end
