UIPlaceHolderTextView

項目開發中有時候需要給UITextView增加PlaceHolder，在以前的開發中封裝過這樣的一個類，繼承於UITextView，可直接設置PlaceHolder和顏色。

實現的思路是直接在UITextView中增加一個透明的不可響應事件的子UITextView，子UITextView的文字即爲PlachHolder。使用NSNotificationCenter監聽UITextView的輸入事件，根據是否存在文字來調整子UITextView的顯示和隱藏。

什麼都不說了，還是上代碼吧。。。因爲我平時是用純代碼寫界面的，所以該代碼只適合於純代碼寫界面的情況，其它情況請無視。。。

頭文件

//
//  UIPlaceHolderTextView.h
//  LoveLive
//
//  Created by chaoye on 15/10/22.
//  Copyright © 2015年 chaoye. All rights reserved.
//

#import <UIKit/UIKit.h>

@interface UIPlaceHolderTextView : UITextView

@property (nonatomic, strong) NSString *placeHolder;
@property (nonatomic, strong) UIColor *placeHolderColor;

@end

實現文件

//
//  UIPlaceHolderTextView.m
//  LoveLive
//
//  Created by chaoye on 15/10/22.
//  Copyright © 2015年 chaoye. All rights reserved.
//

#import "UIPlaceHolderTextView.h"

@interface UIPlaceHolderTextView ()

@property (nonatomic, strong) UITextView *placeHolderTextView;

@end

@implementation UIPlaceHolderTextView

- (instancetype)initWithFrame:(CGRect)frame {
    
    self = [super initWithFrame:frame];
    if (self) {
    
        [self addSubview:self.placeHolderTextView];
        
        [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(textDidChanged:) name:UITextViewTextDidChangeNotification object:nil];
    }
    
    return self;
}

- (UITextView *)placeHolderTextView {
    
    if (!_placeHolderTextView) {
        
        _placeHolderTextView = ({
            
            UITextView *textView = [[UITextView alloc] initWithFrame:self.bounds];
            textView.font = self.font;
            textView.backgroundColor = [UIColor clearColor];
            textView.textColor = [UIColor lightGrayColor];
            textView.userInteractionEnabled = NO;
            textView.autoresizingMask = UIViewAutoresizingFlexibleHeight | UIViewAutoresizingFlexibleWidth;
            textView;
        });
    }
    
    return _placeHolderTextView;
}

- (void)textDidChanged:(NSNotification *)notification {
    
    if (self.text.length > 0) {
        [_placeHolderTextView setHidden:YES];
    } else {
        [_placeHolderTextView setHidden:NO];
    }
}

- (void)setPlaceHolder:(NSString *)placeHolder {
    
    _placeHolderTextView.text = placeHolder;
}

- (void)setPlaceHolderColor:(UIColor *)placeHolderColor {
    
    _placeHolderTextView.textColor = placeHolderColor;
}

- (void)setText:(NSString *)text {
    
    [super setText:text];
    [self textDidChanged:nil];
}

- (void)setFont:(UIFont *)font {
    
    [super setFont:font];
    [_placeHolderTextView setFont:font];
}

- (void)dealloc {
    
    [[NSNotificationCenter defaultCenter] removeObserver:self];
}

@end