textview

光标定位

    _textField.textContainerInset = UIEdgeInsetsMake(10*kRating, 11*kRating, 15*kRating, 15*kRating);

#import "ZYTextView.h"

@implementation ZYTextView

- (instancetype)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self) {
        
        self.placeholderColor = [UIColor lightGrayColor];
        
        self.placeholder = @"请输入内容";
        // 设置默认字体
        self.font = [UIFont systemFontOfSize:15];
        
    }
    return self;
}

// Only override drawRect: if you perform custom drawing.
// An empty implementation adversely affects performance during animation.
- (void)drawRect:(CGRect)rect {
    // Drawing code
    NSMutableDictionary *attrs = [NSMutableDictionary dictionary];
    attrs[NSFontAttributeName] = self.font;
    attrs[NSForegroundColorAttributeName] = self.placeholderColor;
    
    [self.placeholder drawInRect:CGRectMake(15*kRating, 10*kRating, self.frame.size.width, self.frame.size.height) withAttributes:attrs];
}

// 布局子控件的时候需要重绘
- (void)layoutSubviews
{
    [super layoutSubviews];
    [self setNeedsDisplay];
    
}
// 设置属性的时候需要重绘，所以需要重写相关属性的set方法
- (void)setPlaceholder:(NSString *)placeholder
{
    _placeholder = placeholder;
    [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];
    if (text.length) { // 因为是在文本改变的代理方法中判断是否显示placeholder，而通过代码设置text的方式又不会调用文本改变的代理方法，所以再此根据text是否不为空判断是否显示placeholder。
        self.placeholder = @"";
    }
    [self setNeedsDisplay];
}

- (void)setAttributedText:(NSAttributedString *)attributedText
{
    [super setAttributedText:attributedText];
    if (attributedText.length) {
        self.placeholder = @"";
    }
    [self setNeedsDisplay];
}