UITextView 和 UITextField 的提示信息placeholder

一、UITextFiled和UITextView很像，區別是前一個是只顯示一行文本（即使打了回車，可只是顯示一行），后一個可顯示多行文本。兩個的delegate方法也很像.

但是UITextFiled有一個屬性placeholder,即文本框的提示信息。而UITextView則沒有。一般當點擊文本框的時候都需要將默認的提示信息去掉，將光標移動到開始位置。

 

但是對於UITextView則沒有placeholder這個屬性，可以直接設置textView.text = @"請您輸入電話號碼". 清除默認的text有幾種方法

1.在UITextView上添加一個UILabel,再在-(void)textviewDidChanged:(UITextView*)textView方法中移除掉這個Label，[label  removeFromSuperView];

2.繼承UITextView，在drawRect中添加或者刪除placeholder:  參考http://stackoverflow.com/questions/1328638/placeholder-in-uitextview

SSTextView.h

//
//  SSTextView.h
//  SSToolkit
//
//  Created by Sam Soffes on 8/18/10.
//  Copyright 2010-2011 Sam Soffes. All rights reserved.
//

/**
 UITextView subclass that adds placeholder support like UITextField has.
 */
@interface SSTextView : UITextView

/**
 The string that is displayed when there is no other text in the text view.

 The default value is `nil`.
 */
@property (nonatomic, retain) NSString *placeholder;

/**
 The color of the placeholder.

 The default is `[UIColor lightGrayColor]`.
 */
@property (nonatomic, retain) UIColor *placeholderColor;

@end

SSTextView.m

//
//  SSTextView.m
//  SSToolkit
//
//  Created by Sam Soffes on 8/18/10.
//  Copyright 2010-2011 Sam Soffes. All rights reserved.
//

#import "SSTextView.h"

@interface SSTextView ()
- (void)_initialize;
- (void)_updateShouldDrawPlaceholder;
- (void)_textChanged:(NSNotification *)notification;
@end


@implementation SSTextView {
    BOOL _shouldDrawPlaceholder;
}


#pragma mark - Accessors

@synthesize placeholder = _placeholder;
@synthesize placeholderColor = _placeholderColor;

- (void)setText:(NSString *)string {
    [super setText:string];
    [self _updateShouldDrawPlaceholder];
}


- (void)setPlaceholder:(NSString *)string {
    if ([string isEqual:_placeholder]) {
        return;
    }

    [_placeholder release];
    _placeholder = [string retain];

    [self _updateShouldDrawPlaceholder];
}


#pragma mark - NSObject

- (void)dealloc {
    [[NSNotificationCenter defaultCenter] removeObserver:self name:UITextViewTextDidChangeNotification object:self];

    [_placeholder release];
    [_placeholderColor release];
    [super dealloc];
}


#pragma mark - UIView

- (id)initWithCoder:(NSCoder *)aDecoder {
    if ((self = [super initWithCoder:aDecoder])) {
        [self _initialize];
    }
    return self;
}


- (id)initWithFrame:(CGRect)frame {
    if ((self = [super initWithFrame:frame])) {
        [self _initialize];
    }
    return self;
}


- (void)drawRect:(CGRect)rect {
    [super drawRect:rect];

    if (_shouldDrawPlaceholder) {
        [_placeholderColor set];
        [_placeholder drawInRect:CGRectMake(8.0f, 8.0f, self.frame.size.width - 16.0f, self.frame.size.height - 16.0f) withFont:self.font];
    }
}


#pragma mark - Private

- (void)_initialize {
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(_textChanged:) name:UITextViewTextDidChangeNotification object:self];

    self.placeholderColor = [UIColor colorWithWhite:0.702f alpha:1.0f];
    _shouldDrawPlaceholder = NO;
}


- (void)_updateShouldDrawPlaceholder {
    BOOL prev = _shouldDrawPlaceholder;
    _shouldDrawPlaceholder = self.placeholder && self.placeholderColor && self.text.length == 0;

    if (prev != _shouldDrawPlaceholder) {
        [self setNeedsDisplay];
    }
}


- (void)_textChanged:(NSNotification *)notificaiton {
    [self _updateShouldDrawPlaceholder];    
}

@end

 3.還是使用UITextView的delegate方法

- (BOOL) textViewShouldBeginEditing:(UITextView *)textView
{
    if(textView.tag == 0) {
        textView.text = @"";
        textView.textColor = [UIColor blackColor];
        textView.tag = 1;
    }
    return YES;
}
- (void)textViewDidChange:(UITextView *)textView
{
   if([textView.text length] == 0)
   {
       textView.text = @"Foobar placeholder";
       textView.textColor = [UIColor lightGrayColor];
       textView.tag = 0;
   }
}

 

二、如果希望一進入Controller頁面,就顯示鍵盤，可以在viewWillAppear或者viewDidAppear中 添加[textFiled becomeFirstResponser]