@interface BTPlaceholderTextView : UITextView
/**
* 占位文字
*/
@property (nonatomic,strong) NSString *placeholder;
/**<#属性名#> */
@property(nonatomic,assign) CGFloat placeholderX;
/**<#属性名#> */
@property(nonatomic,assign) CGFloat placeholderY;
@end
#import "BTPlaceholderTextView.h"
@implementation BTPlaceholderTextView
- (instancetype)initWithFrame:(CGRect)frame
{
if (self = [super initWithFrame:frame]) {
// 添加监听器，监听自己的文字改变通知
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(textDidChange) name:UITextViewTextDidChangeNotification object:nil];
}
return self;
}
// 时刻监听文字键盘文字的变化，文字一旦改变便调用setNeedsDisplay方法
- (void)textDidChange
{
// 该方法会调用drawRect:方法，立即重新绘制占位文字
[self setNeedsDisplay];
}
// 占位文字的setter方法
- (void)setPlaceholder:(NSString *)placeholder
{
_placeholder = placeholder;
// 文字一旦改变，立马重写绘制（内部会调drawRect:方法）
[self setNeedsDisplay];
}
// 字体属性setter方法
- (void)setFont:(UIFont *)font
{
[super setFont:font];
[self setNeedsDisplay];
}
/**
* 绘制占位文字
*/
- (void)drawRect:(CGRect)rect {
// 如果一旦有输入文字，直接返回，不再绘制占位文字
if (self.hasText) return;
NSMutableDictionary *attrs = [NSMutableDictionary dictionary];
attrs[NSFontAttributeName] = self.font;
attrs[NSForegroundColorAttributeName] = [UIColor lightGrayColor];
// 在textView的矩形框中绘制文字
[self.placeholder drawInRect:CGRectMake(self.placeholderX + 5.0, self.placeholderY, self.frame.size.width, self.frame.size.height) withAttributes:attrs];
}
- (void)dealloc
{
[[NSNotificationCenter defaultCenter] removeObserver:self];
}
@end
