iphone自定义UITextView的placeholder

#import <UIKit/UIKit.h>   
  
@interface UIPlaceholderTextView : UITextView  
@property(nonatomic, strong) NSString *placeholder;     //占位符   
  
-(void)addObserver;//添加通知   
-(void)removeobserver;//移除通知   
@end  

#import <UIKit/UIKit.h>

@interface UIPlaceholderTextView : UITextView
@property(nonatomic, strong) NSString *placeholder;     //占位符

-(void)addObserver;//添加通知
-(void)removeobserver;//移除通知
@end
UIPlaceholderTextView.m

#import "UIPlaceholderTextView.h"   
  
@interface UIPlaceholderTextView ()  
  
@property (nonatomic, strong) UIColor* textColor;  
  
- (void) beginEditing:(NSNotification*) notification;  
- (void) endEditing:(NSNotification*) notification;  
  
@end  
  
@implementation UIPlaceholderTextView  
@synthesize placeholder;  
@synthesize textColor;  
- (id) initWithFrame:(CGRect)frame {  
    if ((self = [super initWithFrame:frame])) {  
        [self awakeFromNib];  
    }  
    return self;  
}  
//当用nib创建时会调用此方法   
- (void)awakeFromNib {  
    textColor = [UIColor redColor];  
    [self addObserver];  
}  
-(void)addObserver  
{  
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(beginEditing:) name:UITextViewTextDidBeginEditingNotification object:self];  
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(endEditing:) name:UITextViewTextDidEndEditingNotification object:self];  
}  
-(void)removeobserver  
{  
    [[NSNotificationCenter defaultCenter] removeObserver:self];  
}  
  
#pragma mark -   
#pragma mark Setter/Getters   
- (void) setPlaceholder:(NSString *)aPlaceholder {  
    placeholder = aPlaceholder;  
    [self endEditing:nil];  
}  
  
- (NSString *) text {  
    NSString* text = [super text];  
    if ([text isEqualToString:placeholder]) return @"";  
    return text;  
}  
  
- (void) beginEditing:(NSNotification*) notification {  
    if ([super.text isEqualToString:placeholder]) {  
        super.text = nil;  
        //字体颜色   
        [super setTextColor:textColor];  
    }  
      
}  
  
- (void) endEditing:(NSNotification*) notification {  
    if ([super.text isEqualToString:@""] || self.text == nil) {  
        super.text = placeholder;  
        //注释颜色   
        [super setTextColor:[UIColor lightGrayColor]];  
    }  
}  

#import "UIPlaceholderTextView.h"

@interface UIPlaceholderTextView ()

@property (nonatomic, strong) UIColor* textColor;

- (void) beginEditing:(NSNotification*) notification;
- (void) endEditing:(NSNotification*) notification;

@end

@implementation UIPlaceholderTextView
@synthesize placeholder;
@synthesize textColor;
- (id) initWithFrame:(CGRect)frame {
    if ((self = [super initWithFrame:frame])) {
        [self awakeFromNib];
    }
    return self;
}
//当用nib创建时会调用此方法
- (void)awakeFromNib {
    textColor = [UIColor redColor];
    [self addObserver];
}
-(void)addObserver
{
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(beginEditing:) name:UITextViewTextDidBeginEditingNotification object:self];
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(endEditing:) name:UITextViewTextDidEndEditingNotification object:self];
}
-(void)removeobserver
{
    [[NSNotificationCenter defaultCenter] removeObserver:self];
}

#pragma mark -
#pragma mark Setter/Getters
- (void) setPlaceholder:(NSString *)aPlaceholder {
    placeholder = aPlaceholder;
    [self endEditing:nil];
}

- (NSString *) text {
    NSString* text = [super text];
    if ([text isEqualToString:placeholder]) return @"";
    return text;
}

- (void) beginEditing:(NSNotification*) notification {
    if ([super.text isEqualToString:placeholder]) {
        super.text = nil;
        //字体颜色
        [super setTextColor:textColor];
    }
    
}

- (void) endEditing:(NSNotification*) notification {
    if ([super.text isEqualToString:@""] || self.text == nil) {
        super.text = placeholder;
        //注释颜色
        [super setTextColor:[UIColor lightGrayColor]];
    }
}