UITextView 添加placeholder

1、首先定义一个类UIPlaceHolderTextView继承UITextView.

头文件如下：

#import <UIKit/UIKit.h>@interface UIPlaceHolderTextView : UITextView@property (nonatomic,retain) NSString *placeHolder;@property(nonatomic,retain) UIColor *placeHolderColor;-(void)textChanged:(NSNotification *)notification;@end

实现内容代码如下：

#import "UIPlaceHolderTextView.h"@interface UIPlaceHolderTextView()@property(nonatomic,retain) UILabel *placeHolderLabel;@end@implementation UIPlaceHolderTextView-(void)dealloc{    [[NSNotificationCenter defaultCenter] removeObserver:self];    [_placeHolder release];    _placeHolder=nil;    [_placeHolderColor release];    _placeHolderColor=nil;    [_placeHolder release];    _placeHolder=nil;    [super dealloc];}-(void)awakeFromNib{    [super awakeFromNib];    if(!self.placeHolder){        [self setPlaceHolder:@""];    }    if(!self.placeHolderColor){        [self setPlaceHolderColor:[UIColor lightGrayColor]];    }    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(textChanged:) name:UITextViewTextDidBeginEditingNotification object:nil];}-(void)textChanged:(NSNotification *)notification{    if([[self placeHolder] length]==0){        return;    }    if([[self text] length]==0){        [[self viewWithTag:1000] setAlpha:1];    }else{        [[self viewWithTag:1000] setAlpha:0];    }}-(void)setText:(NSString *)text{    [super setText:text];    [self textChanged:nil];} // Only override drawRect: if you perform custom drawing. // An empty implementation adversely affects performance during animation. -(void)drawRect:(CGRect)rect {     // Drawing code     if([[self placeHolder] length]>0){         if(_placeHolderLabel==nil){             _placeHolderLabel=[[UILabel alloc] initWithFrame:CGRectMake(8,8,self.bounds.size.width-16,0)];             _placeHolderLabel.lineBreakMode=NSLineBreakByCharWrapping;             _placeHolderLabel.numberOfLines=0;             _placeHolderLabel.font=self.font;             _placeHolderLabel.backgroundColor=[UIColor clearColor];             _placeHolderLabel.textColor=self.placeHolderColor;             _placeHolderLabel.alpha=0;             _placeHolderLabel.tag=1000;             [self addSubview:_placeHolderLabel];         }         _placeHolderLabel.text=self.placeHolder;         [_placeHolderLabel sizeToFit];         [self sendSubviewToBack:_placeHolderLabel];     }     if([[self text] length]==0&&[[self placeHolder] length]>0){         [[self viewWithTag:1000] setAlpha:1];     }     [super drawRect:rect]; } - (id)initWithFrame:(CGRect)frame{    self = [super initWithFrame:frame];    if (self) {        // Initialization code        [self setPlaceHolderColor:[UIColor lightGrayColor]];        [self setPlaceHolder:@""];        [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(textChanged:) name:UITextViewTextDidBeginEditingNotification object:nil];    }    return self;}@end

2.UIPlaceHolderTextView的调用

调用方法如下，首先在xib上面拖放一个UITextView，让它继承UIPlaceHolderTextView或者直接创建一个UIPlaceHolderTextView添加到xib上面，这里我们拖放一个UITextView让它继承UIPlaceHolderTextView,代码如下：

#import <UIKit/UIKit.h>#import "UIPlaceHolderTextView.h"@interface LTViewController : UIViewController@property(nonatomic,retain) IBOutlet UIPlaceHolderTextView *textview;//定义一个UIPlaceHolderTextView@end

实现代码如下：

#import "LTViewController.h"#import <QuartzCore/QuartzCore.h>@interface LTViewController ()<UITextViewDelegate>@end@implementation LTViewController@synthesize textview;-(void)dealloc{        [textview release];    [super dealloc];}- (void)viewDidLoad{    [super viewDidLoad];

    //设置一下UITextView的样式，需用用的<QuartzCore/QuartzCore.h>    [textview.layer setBorderColor:[[[UIColor grayColor] colorWithAlphaComponent:0.5] CGColor]];    [textview.layer setBorderWidth:2.0];    textview.layer.cornerRadius=10;    textview.clipsToBounds=YES;    textview.delegate=self;        textview.placeHolder=@"请输入详细信息";//设置textview的placeHolder的显示内容// Do any additional setup after loading the view, typically from a nib.}- (void)didReceiveMemoryWarning{    [super didReceiveMemoryWarning];    // Dispose of any resources that can be recreated.}@end