iOS開發-UITextView實現PlaceHolder的方式

標籤：

之前開發遇到過UITextField中加入一個PlaceHolder的問題，直接設定一下即可，不過這次是需要在UITextView中實現一個PlaceHolder，跟之前有點不同。在網上參考了各位前輩的解決方案，大概有兩種方式，第一種方式很猥瑣，就是直接給UITextView的text賦值，比如說預設提示是"部落格園FlyElephant"，在textViewDidChange中判斷是不是“部落格園FlyElephant”，如果是就清空，如果不是就繼續提示，弊端就是使用者輸入的內容不能和你的預設提示一樣，第二種方式需要加入一個UILabel，同樣在textViewDidChange中進行判斷，一般都是這麼實現，不過有的都是建立textView中的時候建立UILabel，這樣做無可厚非，不過最好還是抽象出來。繼承UITextView擴充一下，建立一個FEPlaceHolderTextView：

標頭檔:

////  FEPlaceHolderTextView.h//  MyTextViewDemo//http://www.cnblogs.com/xiaofeixiang//  Created by keso on 15/5/17.//  Copyright (c) 2015年 keso. All rights reserved.//#import <UIKit/UIKit.h>@interface FEPlaceHolderTextView : UITextView@property (nonatomic, retain) NSString *placeholder;@property (nonatomic, retain) UIColor *placeholderColor;-(void)textChanged:(NSNotification*)notification;@end

　實現檔案:

////  FEPlaceHolderTextView.m//  MyTextViewDemo//http://www.cnblogs.com/xiaofeixiang//  Created by keso on 15/5/17.//  Copyright (c) 2015年 keso. All rights reserved.//#import "FEPlaceHolderTextView.h"@interface FEPlaceHolderTextView ()@property (nonatomic, retain) UILabel *placeHolderLabel;@end@implementation FEPlaceHolderTextViewCGFloat const UI_PLACEHOLDER_TEXT_CHANGED_ANIMATION_DURATION = 0.25;- (void)dealloc{    [[NSNotificationCenter defaultCenter] removeObserver:self];}- (void)awakeFromNib{    [super awakeFromNib];    if (!self.placeholder) {        [self setPlaceholder:@""];    }        if (!self.placeholderColor) {        [self setPlaceholderColor:[UIColor lightGrayColor]];    }        [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(textChanged:) name:UITextViewTextDidChangeNotification object:nil];}- (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];    }    return self;}- (void)textChanged:(NSNotification *)notification{    if([[self placeholder] length] == 0)    {        return;    }        [UIView animateWithDuration:UI_PLACEHOLDER_TEXT_CHANGED_ANIMATION_DURATION animations:^{        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( [[self placeholder] length] > 0 )    {        if (_placeHolderLabel == nil )        {            _placeHolderLabel = [[UILabel alloc] initWithFrame:CGRectMake(8,8,self.bounds.size.width,10)];            _placeHolderLabel.lineBreakMode = NSLineBreakByWordWrapping;            _placeHolderLabel.numberOfLines =0;            _placeHolderLabel.font = self.font;            _placeHolderLabel.backgroundColor = [UIColor clearColor];            _placeHolderLabel.textColor = self.placeholderColor;            _placeHolderLabel.alpha = 0;            _placeHolderLabel.tag = 999;            [self addSubview:_placeHolderLabel];        }                _placeHolderLabel.text = self.placeholder;        [_placeHolderLabel sizeToFit];        [self sendSubviewToBack:_placeHolderLabel];    }        if( [[self text] length] == 0 && [[self placeholder] length] > 0 )    {        [[self viewWithTag:999] setAlpha:1];    }        [super drawRect:rect];}@end

　調用:

    self.textView=[[FEPlaceHolderTextView alloc]initWithFrame:CGRectMake(10, 30, CGRectGetWidth(self.view.frame)-20, 200)];    [email protected]"部落格園FlyElephant\n部落格地址:http://www.cnblogs.com/xiaofeixiang";    self.textView.layer.borderColor=[UIColor lightGrayColor].CGColor;    self.textView.layer.borderWidth=1.0;    self.textView.scrollEnabled = YES;    self.textView.autoresizingMask =    UIViewAutoresizingFlexibleHeight; //自適應高度    self.textView.returnKeyType = UIReturnKeyDefault; //返回鍵的類型        self.textView.keyboardType = UIKeyboardTypeDefault; //鍵盤類型    [self.view addSubview:self.textView];

效果:

iOS開發-UITextView實現PlaceHolder的方式