TextView设置默认文本

//PlaceholderTextView.m

//Copyright (c)  All rights reserved.

#import"PlaceholderTextView.h"

@interface PlaceholderTextView()

/**占位文字label */

/**占位文字*/

@property(nonatomic,copy)NSString*placeholder;

/**占位文字的颜色*/

@property(nonatomic,strong)UIColor*placeholderColor;

@property(nonatomic,weak)UILabel*placeholderLabel;

@end

@implementation PlaceholderTextView

- (UILabel*)placeholderLabel

{

if(!_placeholderLabel) {

//添加一个用来显示占位文字的label

UILabel*placeholderLabel = [[UILabel alloc] init];

placeholderLabel.numberOfLines=0;

placeholderLabel.x=4;

placeholderLabel.y=7;

[self addSubview:placeholderLabel];

_placeholderLabel= placeholderLabel;

}

return_placeholderLabel;

}

- (instancetype)initWithFrame:(CGRect)frame

{

if(self= [super initWithFrame:frame]) {

//垂直方向上永远有弹簧效果

self.alwaysBounceVertical=YES;

//默认字体

self.font= [UIFont systemFontOfSize:15];

//默认的占位文字颜色

self.placeholderColor= [UIColor grayColor];

//监听文字改变

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(textDidChange) name:UITextViewTextDidChangeNotification object:nil];

}

returnself;

}

- (void)dealloc

{

[XMGNoteCenterremoveObserver:self];

}

/**

*监听文字改变

*/

- (void)textDidChange

{

//只要有文字,就隐藏占位文字label

self.placeholderLabel.hidden=self.hasText;

}

/**

*更新占位文字的尺寸

*/

- (void)layoutSubviews

{

[super layoutSubviews];

self.placeholderLabel.width=self.width-2*self.placeholderLabel.x;

[self.placeholderLabel sizeToFit];

}

#pragma mark -重写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];

}

/**

* 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