方法一

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”。

特点：这种方法的特点是，当用户点击了textView，placeholder占位文字就会立马消失，官方的placeholder是当系统监听到用户输入了文字后placeholder才会消失。

// 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];

    }

}

方法二

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

特点：该方法同样也可以实现类似于placeholder的功能。相比较方法一，方法二可以实现动态监听文本的改变，并非弹出键盘就立即清除placeholder，只有当用户开始输入文本的时候。placeholder才会消失。同样，当用户清空文本的时候，placeholder又会重新显示出来。

#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

同样地思路，我们也可以把作为占位文字的UILabel用UITextField或者UITextView来替换，同样可以实现带placeholder的textView，在次就不在详述。

方法三

1.自定义UITextView
2.给UITextView添加placeholder和placeholderColor属性
3.重写initWithFrame方法
4.添加通知监听文字改变
5.重写drawRect：方法
6.重写相关属性的set方法

特点：相比计较上面两种方法，这种方法可移植性、拓展性更好，这种方法，不仅乐意随意通过我们添加的placeholder属性设置默认文字，还可以通过我们添加的placeholderColor设置默认文字的颜色。今后，我们只需要写好这么一个自定义UITextView，就可以一劳永逸。

#import <UIKit/UIKit.h>

@interface WSPlaceholderTextView : UITextView

/** 占位文字 */

@property (nonatomic, copy) NSString *placeholder;

/** 占位文字颜色 */

@property (nonatomic, strong) UIColor *placeholderColor;

@end

#import "WSPlaceholderTextView.h"

@implementation WSPlaceholderTextView

- (instancetype)initWithFrame:(CGRect)frame

{

    if (self = [super initWithFrame:frame]) {

        // 设置默认字体

        self.font = [UIFont systemFontOfSize:15];

        // 设置默认颜色

        self.placeholderColor = [UIColor grayColor];

        // 使用通知监听文字改变

        [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(textDidChange:) name:UITextViewTextDidChangeNotification object:self];

    }

    return self;

}

- (void)textDidChange:(NSNotification *)note

{

    // 会重新调用drawRect:方法

    [self setNeedsDisplay];

}

- (void)dealloc

{

    [[NSNotificationCenter defaultCenter] removeObserver:self];

}

/**

 * 每次调用drawRect:方法，都会将以前画的东西清除掉

 */

- (void)drawRect:(CGRect)rect

{

    // 如果有文字，就直接返回，不需要画占位文字

    if (self.hasText) return;

    // 属性

    NSMutableDictionary *attrs = [NSMutableDictionary dictionary];

    attrs[NSFontAttributeName] = self.font;

    attrs[NSForegroundColorAttributeName] = self.placeholderColor;

    // 画文字

    rect.origin.x = 5;

    rect.origin.y = 8;

    rect.size.width -= 2 * rect.origin.x;

    [self.placeholder drawInRect:rect withAttributes:attrs];

}

- (void)layoutSubviews

{

    [super layoutSubviews];

    [self setNeedsDisplay];

}

#pragma mark - setter

- (void)setPlaceholder:(NSString *)placeholder

{

    _placeholder = [placeholder copy];

    [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];

    [self setNeedsDisplay];

}

- (void)setAttributedText:(NSAttributedString *)attributedText

{

    [super setAttributedText:attributedText];

    [self setNeedsDisplay];

}

@end

方法四

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

特点：这个方法的和方法三很相似，只是没有利用通知来监听文本的改变，需要配合textViewDidChanged:这个文本改变的代理方法使用。

#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

方法五

通过runtime，我们发现，UITextView内部有一个名为“_placeHolderLabel”的私有成员变量。大家知道，Objective-C没有绝对的私有变量，因为我们可以通过KVC来访问私有变量。

特点：相对于上面的4种方法，这种方法更加取巧，虽然Apple官方没有给我们开发者提供类似于placeholder的属性，但是通过运行时，我们遍历出了一个placeHolderLabel的私有变量。这种方法简单易懂，代码量少，推荐大家使用这种方法。

#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);

    }

    [self setupTextView];

}

- (void)setupTextView

{

    UITextView *textView = [[UITextView alloc] initWithFrame:CGRectMake(0, 100, [UIScreen mainScreen].bounds.size.width, 100];

    [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];

    [textView addSubview:placeHolderLabel];

    // same font

    textView.font = [UIFont systemFontOfSize:13.f];

    placeHolderLabel.font = [UIFont systemFontOfSize:13.f];

    [textView setValue:placeHolderLabel forKey:@"_placeholderLabel"];

}

@end