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#import "YGTextView.h" #define kPlaceholderDefaultTopMargin 4     // Placeholder上下间距 #define kPlaceholderDefaultLeftMargin 5    // Placeholder左右间距 @implementation YGTextView #pragma mark - 初始化PlaceholderTextView - (instancetype)initWithFrame:(CGRect)frame {     self = [super initWithFrame:frame];          if (self)     {         self.opaque = YES;                  // 设置通知, 当TextView文字发生改变时, 向自己发送通知         [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(textDidChanged) name:UITextViewTextDidChangeNotification object:self];     }          return self; } #pragma mark - 通知事件 - (void)textDidChanged {     // 重新绘制     [self setNeedsDisplay]; } #pragma mark - 重写属性方法, 实时绘制 - (void)setPlaceholder:(NSString *)placeholder {     _placeholder = [placeholder copy];          [self setNeedsDisplay]; } - (void)setPlaceholderColor:(UIColor *)placeholderColor {     _placeholderColor = placeholderColor;          [self setNeedsDisplay]; } - (void)setText:(NSString *)text {     [super setText:text]; // 系统自带属性          [self setNeedsDisplay]; } - (void)setAttributedText:(NSAttributedString *)attributedText {     [super setAttributedText:attributedText];          [self setNeedsDisplay]; } - (void)setFont:(UIFont *)font {     [super setFont:font];          // 会在下一个消息循环调用drawRect     [self setNeedsDisplay]; } #pragma mark - 绘制子控件 - (void)drawRect:(CGRect)rect {     // 若TextView有文字     if (self.hasText)     {         return;     }          // 文字属性     NSMutableDictionary *attrs = [NSMutableDictionary dictionary];     attrs[NSFontAttributeName] = self.font; // 获取当前PlaceholderTextView的文字属性     attrs[NSForegroundColorAttributeName] = self.placeholderColor ? self.placeholderColor : [UIColor lightGrayColor];          // 绘制范围     CGFloat placeholderTopMargin = self.placeholderTopMargin ? self.placeholderTopMargin : kPlaceholderDefaultTopMargin;     CGFloat placeholderLeftMargin = self.placeholderLeftMargin ? self.placeholderLeftMargin : kPlaceholderDefaultTopMargin;          CGFloat placeholderX = placeholderTopMargin;     CGFloat placeholderY = placeholderLeftMargin;     CGFloat placeholderW = rect.size.width - 2 * placeholderLeftMargin;     CGFloat placeholderH = rect.size.height - 2 * placeholderTopMargin;     CGRect placeholderRect = CGRectMake(placeholderX, placeholderY, placeholderW, placeholderH);          [self.placeholder drawInRect:placeholderRect withAttributes:attrs]; } #pragma mark - 移除通知 - (void)dealloc {     [[NSNotificationCenter defaultCenter] removeObserver:self]; } @end

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