textView实现placehodle

.H文件里面需要实现：

#import <UIKit/UIKit.h>

@interface UIPHTextView : UITextView

{

    NSString *placeholder;

    UIColor *placeholderColor;

    @private

    UILabel *placeHolderLabel;

}

@property(nonatomic,retain) UILabel *placeHolderLabel;

@property(nonatomic,retain) NSString *placeholder;

@property(nonatomic,retain) UIColor *placeholderColor;

-(void)textChanged:(NSNotification*)notification;

@end

.M需要实现：

#import "UIPHTextView.h"

@implementation UIPHTextView

- (instancetype)init{

    self = [super init];

    if (self) {

        [super awakeFromNib];

        [self setPlaceholder:@""];

        [self setPlaceholderColor:[UIColor lightGrayColor]];

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

    }

    returnself;

}

- (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];

    }

    returnself;

}

- (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( [[selfplaceholder] length] >0 )

    {

        if (placeHolderLabel == nil )

        {

            placeHolderLabel = [[UILabelalloc] initWithFrame:CGRectMake(8,8,self.bounds.size.width - 16,0)];

            placeHolderLabel.lineBreakMode =UILineBreakModeWordWrap;

            placeHolderLabel.numberOfLines =0;

            placeHolderLabel.font = [UIFontsystemFontOfSize:14];

            placeHolderLabel.backgroundColor = [UIColorclearColor];

            placeHolderLabel.textColor =self.placeholderColor;

            placeHolderLabel.alpha =0;

            placeHolderLabel.tag =999;

            [selfaddSubview:placeHolderLabel];

        }

        placeHolderLabel.text =self.placeholder;

        [placeHolderLabelsizeToFit];

        [selfsendSubviewToBack:placeHolderLabel];

    }

    if( [[selftext] length] ==0 && [[selfplaceholder] length] >0 )

    {

        [[selfviewWithTag:999]setAlpha:1];

    }    

    [superdrawRect:rect];

}

@end

ViewController.m里面需要实现：

#import "ViewController.h"

#import "UIPHTextView.h"

@interface ViewController ()<UITextViewDelegate>

{

    UIView *_bgView;

    UIPHTextView *_textView;

}

@end

@implementation ViewController

- (void)viewDidLoad {

    [superviewDidLoad];

    [self_createView];

}

- (void)_createView{

    if (_bgView ==nil) {

        _bgView = [[UIViewalloc]initWithFrame:CGRectMake(0,10, self.view.frame.size.width,200)];

        _bgView.backgroundColor = [UIColorgreenColor];

        [self.viewaddSubview:_bgView];

    }

    _textView = [[UIPHTextViewalloc] initWithFrame:CGRectMake(5,5, self.view.frame.size.width - 10, 200 -85)];

    _textView.placeholder =@"说点什么...";

    _textView.font = [UIFontsystemFontOfSize:15];

    _textView.delegate =self;

    _textView.showsVerticalScrollIndicator =NO;

    _textView.placeholderColor = [UIColorgrayColor];

    [_bgViewaddSubview:_textView];

}

- (void)didReceiveMemoryWarning {

    [superdidReceiveMemoryWarning];

    // Dispose of any resources that can be recreated.

}

@end