iOS textView添加占位符

其实需求很简单，想必你也会！但是万一有需要的同学呢！废话少说，看需求效果图：

WechatIMG2983.jpeg WechatIMG2986.jpeg WechatIMG2991.jpeg

textView正常情况下是没有占位符的，但是我们可以通过继承与textview 用他的drawRect方法绘制，代码如下：
.h文件中添加属性

@interface DXFeedBackTextView : UITextView
/** 占位文字 /
@property(nonatomic, copy) NSString placeholder;
/ 占位文字颜色 */
@property(nonatomic, strong) UIColor *placeholderColor;
@end
.m文件中实现代码如：
@implementation DXFeedBackTextView

  - (instancetype)init{


   if (self = [super init]) {
    // 设置默认字
    self.font = [UIFont systemFontOfSize:17];
    // 设置默认颜色
    self.placeholderColor = [UIColor grayColor];
    // 使用通知监听文字改变
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(textDidChange:) name:UITextViewTextDidChangeNotification object:self];

}
   return self;

}

- (void)textDidChange:(NSNotification *)note{

// 会重新调用drawRect:方法
  [self setNeedsDisplay];

}

- (void)dealloc{
[[NSNotificationCenter defaultCenter] removeObserver:self];
}
  /**
 * 每次调用drawRect:方法，都会将以前画的东西清除掉
 */
  - (void)drawRect:(CGRect)rect{
// 如果有文字，就直接返回，不需要画占位文字
if (self.hasText) return;
// 属性
NSMutableDictionary *attrs = [NSMutableDictionary dictionary];
attrs[NSFontAttributeName] = self.font;
attrs[NSForegroundColorAttributeName] = self.placeholderColor;
// 画文字
rect.origin.x = 5;
rect.origin.y = 8;
rect.size.width -= 2 * rect.origin.x;
[self.placeholder drawInRect:rect withAttributes:attrs];
}

- (void)layoutSubviews{
  [super layoutSubviews];
  [self setNeedsDisplay];
}

#pragma mark - setter
//重写setter方法调用setNeedsDisplay方法刷新
  - (void)setPlaceholder:(NSString *)placeholder{
    _placeholder = [placeholder copy];
    [self setNeedsDisplay];
  }

- (void)setPlaceholderColor:(UIColor *)placeholderColor{
    _placeholderColor = placeholderColor;
    [self setNeedsDisplay];
}

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

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

- (void)setAttributedText:(NSAttributedString *)attributedText{
    [super setAttributedText:attributedText];
    [self setNeedsDisplay];
}

@end

打完收工！