1、很多需求中有需要多行输入，需要站位文字的输入框，这时候最好使用UITextView，下面就新建一个类，继承自UITextView
#import <UIKit/UIKit.h>
@interface PlaceholderTextView : UITextView
/** 占位符*/
@property (copy ,nonatomic) NSString *placeholder;
/** 占位符颜色*/
@property (strong ,nonatomic) UIColor *placeholderColor;
/** 占位符字号*/
@property (strong ,nonatomic) UIFont *placeholderFont;
/** 占位符尺寸*/
@property (assign ,nonatomic) CGRect placeholderRect;
@end
#import "PlaceholderTextView.h"
@interface PlaceholderTextView()<UITextViewDelegate>
@end
@implementation PlaceholderTextView
- (instancetype)initWithFrame:(CGRect)frame{
if (self = [super initWithFrame:frame]) {
// self.font = [UIFont systemFontOfSize:15];
self.placeholderColor = [UIColor grayColor];
// 监听文字改变
[QFMNotiCenter addObserver:self selector:@selector(textDidChange:) name:UITextViewTextDidChangeNotification object:nil];
}
return self;
}
/**
*绘制站位文字 (每次调用此方法之前，会自动清除掉之前的内容)
*/
- (void)drawRect:(CGRect)rect {
// 如果有文字，直接返回，不绘制站位文字
// if (self.text.length || self.attributedText.length) return;
if (self.hasText) return;
// 处理rect
rect.origin.x = 3;
rect.origin.y = 7;
rect.size.width -= 2*rect.origin.x;
// 文字属性
NSMutableDictionary *attrs = [NSMutableDictionary dictionary];
attrs[NSFontAttributeName] = self.placeholderFont;
attrs[NSForegroundColorAttributeName] = self.placeholderColor;
// [self.placeholder drawInRect:CGRectMake(3, 7, self.width, self.height) withAttributes:attrs];
[self.placeholder drawInRect:rect withAttributes:attrs];
}
- (void)textDidChange:(UITextView *)textView{
QFMLOGFUNC;
[self setNeedsDisplay];
}
- (void)dealloc{
[QFMNotiCenter removeObserver:self];
}
#pragma mark - **************** 重写setter 防止外部改写属性
- (void)setPlaceholder:(NSString *)placeholder{
_placeholder = [placeholder copy];
[self setNeedsDisplay];
}
- (void)setPlaceholderColor:(UIColor *)placeholderColor{
_placeholderColor = placeholderColor;
[self setNeedsDisplay];
}
- (void)setPlaceholderFont:(UIFont *)placeholderFont{
_placeholderFont = placeholderFont;
[self setNeedsDisplay];
}
- (void)setText:(NSString *)text{
[super setText:text];
[self setNeedsDisplay];
}
- (void)setAttributedText:(NSAttributedString *)attributedText{
[super setAttributedText:attributedText];
[self setNeedsDisplay];
}
@end
2、第二种方法
.m文件
#import "PlaceholderTextView.h"
@interface PlaceholderTextView()<UITextViewDelegate>
/** 站位文字label*/
@property(weak ,nonatomic)UILabel *placeholderLabel;
@end
@implementation PlaceholderTextView
#pragma mark - **************** 第二种方法
-(UILabel *)placeholderLabel{
if (!_placeholderLabel) {
// 添加一个用来显示站位文字的label
UILabel *placeholderLabel = [[UILabel alloc] init];
// placeholderLabel.hidden = YES;
placeholderLabel.x = 4;
placeholderLabel.y = 7;
placeholderLabel.numberOfLines = 0;
[self addSubview:placeholderLabel];
self.placeholderLabel = placeholderLabel;
}
return _placeholderLabel;
}
-(instancetype)initWithFrame:(CGRect)frame{
if (self = [super initWithFrame:frame]) {
// 竖直方向永远可以拖动
self.alwaysBounceVertical = YES;
self.font = [UIFont systemFontOfSize:15];
// 默认的站位文字颜色
self.placeholderColor = [UIColor grayColor];
[QFMNotiCenter addObserver:self selector:@selector(textDidChange) name:UITextViewTextDidChangeNotification object:nil];
}
return self;
}
/*
*更新站位文字尺寸
* */
- (void)updatePlaceholderLabelSize{
CGSize placeholderSize = CGSizeMake(self.width - 2*self.placeholderLabel.x, MAXFLOAT);
self.placeholderLabel.size = [self.placeholder boundingRectWithSize:placeholderSize options:NSStringDrawingUsesLineFragmentOrigin attributes:@{NSFontAttributeName:self.font} context:nil].size;
//self.placeholderLabel.width = SCREEN_WIDTH - 2*self.placeholderLabel.x;
// [self.placeholderLabel sizeToFit]; 此方法亦可以
}
#pragma mark - **************** 重新setter
-(void)setPlaceholderColor:(UIColor *)placeholderColor{
_placeholderColor = placeholderColor;
self.placeholderLabel.textColor = placeholderColor;
}
- (void)setPlaceholder:(NSString *)placeholder{
_placeholder = [placeholder copy];
self.placeholderLabel.text = placeholder;
[self updatePlaceholderLabelSize];
}
- (void)setFont:(UIFont *)font{
[super setFont:font];
self.placeholderLabel.font = font;
[self updatePlaceholderLabelSize];
}
- (void)setText:(NSString *)text{
[super setText:text];
[self textDidChange];
}
- (void)setAttributedText:(NSAttributedString *)attributedText{
[super setAttributedText:attributedText];
[self textDidChange];
}
- (void)textDidChange{
self.placeholderLabel.hidden = self.hasText;
}
- (void)dealloc{
[QFMNotiCenter removeObserver:self];
}
@end
3、第三种方法
#pragma mark - **************** 第三种方法
-(UILabel *)placeholderLabel{
if (!_placeholderLabel) {
// 添加一个用来显示站位文字的label
UILabel *placeholderLabel = [[UILabel alloc] init];
// placeholderLabel.hidden = YES;
placeholderLabel.x = 4;
placeholderLabel.y = 7;
placeholderLabel.numberOfLines = 0;
[self addSubview:placeholderLabel];
self.placeholderLabel = placeholderLabel;
}
return _placeholderLabel;
}
-(instancetype)initWithFrame:(CGRect)frame{
if (self = [super initWithFrame:frame]) {
// 竖直方向永远可以拖动
self.alwaysBounceVertical = YES;
self.font = [UIFont systemFontOfSize:15];
// 默认的站位文字颜色
self.placeholderColor = [UIColor grayColor];
[QFMNotiCenter addObserver:self selector:@selector(textDidChange) name:UITextViewTextDidChangeNotification object:nil];
}
return self;
}
- (void)layoutSubviews{
[super layoutSubviews];
// 根据textView的宽度计算placeholder的宽度
self.placeholderLabel.width = self.width - 2*self.placeholderLabel.x;
[self.placeholderLabel sizeToFit];
}
#pragma mark - **************** 重新setter
-(void)setPlaceholderColor:(UIColor *)placeholderColor{
_placeholderColor = placeholderColor;
self.placeholderLabel.textColor = placeholderColor;
}
- (void)setPlaceholder:(NSString *)placeholder{
_placeholder = [placeholder copy];
self.placeholderLabel.text = placeholder;
[self setNeedsLayout];
}
- (void)setFont:(UIFont *)font{
[super setFont:font];
self.placeholderLabel.font = font;
[self setNeedsLayout];
}
- (void)setText:(NSString *)text{
[super setText:text];
[self textDidChange];
}
- (void)setAttributedText:(NSAttributedString *)attributedText{
[super setAttributedText:attributedText];
[self textDidChange];
}
- (void)textDidChange{
self.placeholderLabel.hidden = self.hasText;
}
- (void)dealloc{
[QFMNotiCenter removeObserver:self];
}
/**
* setNeedsDisplay方法：会在恰当的时刻自动调用drawRect方法
* setNeedsLayout方法：会在恰当的时刻调用layoutSubViews方法
*/
@end
此方法更为严谨
用label设置的一个好处是，站位文字可以拖动
