如何用两个uitestview加placehoder
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参考技术A 方案定位:采用扩展的方式,以极简的风格作为参考依据。Tip:所谓极简,即对外接口最简,对内部可以很复杂
扩展头文件
#import <UIKit/UIKit.h>
/**
* @author huangyibiao
*
* 给UITextView添加placeholder
*
* @note 注意,此扩展有点小问题,如果在添加placeholder后,又直接赋值Text属性,则不会自动消失
* 解决办法是:如果有初始值,先给text,再设置holder
*/
@interface UITextView (HDFTextView)
/**
* 占位提示语
*/
@property (nonatomic, copy) NSString *hdf_placeholder;
/**
* 占位提示语的字体颜色
*/
@property (nonatomic, strong) UIColor *hdf_placeholderColor;
/**
* 占位提示语的字体
*/
@property (nonatomic, strong) UIFont *hdf_placeholderFont;
/**
* 占位提示语标签
*/
@property (nonatomic, strong, readonly) UILabel *hdf_placeholderLabel;
@end
##
说明:头文件中其实只需要公开hdf_placeholderLabel属性就可以实现了,但是依然公开了对hdf_placeholderLabel直
接属性,可以根据个人习惯使用。扩展是不能扩展属性的,但是这里写成了属性的形式,其实只是利用了getter/setter方式,重写其API。内部会
使用动态运行时机制来完成扩展伪属性的功能(称为伪属性是因为本质上是扩展不了属性的)
实现文件
#import "UITextView+HDFTextView.h"
static const void *s_hdfTextViewPlaceholderLabelKey = "s_hdfTextViewPlaceholderLabelKey";
static const void *s_hdfTextViewPlaceholderTextKey = "s_hdfTextViewPlaceholderTextKey";
@interface UIApplication (HDFTextViewHolder)
@end
@implementation UIApplication (HDFTextViewHolder)
- (void)hdf_placehoderTextChange:(NSNotification *)nofitication
if (kIsios7OrLater)
return;
UITextView *textView = nofitication.object;
if ([textView isKindOfClass:[UITextView class]])
if (!kIsEmptyString(textView.text))
textView.hdf_placeholderLabel.text = @"";
else
textView.hdf_placeholderLabel.text = textView.hdf_placeholder;
@end
@interface UITextView (HDFPlaceholderTextView)
@property (nonatomic, strong) UILabel *placeholderLabel;
@end
@implementation UITextView (HDFPlaceholderTextView)
- (void)setPlaceholderLabel:(UILabel *)placeholderLabel
objc_setAssociatedObject(self,
s_hdfTextViewPlaceholderLabelKey,
placeholderLabel,
OBJC_ASSOCIATION_RETAIN_NONATOMIC);
- (UILabel *)placeholderLabel
UILabel *label = objc_getAssociatedObject(self, s_hdfTextViewPlaceholderLabelKey);
if (label == nil || ![label isKindOfClass:[UILabel class]])
label = [[UILabel alloc] init];
label.textAlignment = NSTextAlignmentLeft;
label.font = self.font;
label.backgroundColor = [UIColor clearColor];
label.textColor = kHolderTipColor;
[self addSubview:label];
kWeakObject(self);
self.placeholderLabel = label;
CGFloat left = kIsIOS7OrLater ? 5 : 7;
[label mas_makeConstraints:^(MASConstraintMaker *make)
make.edges.mas_equalTo(weakObject).insets(UIEdgeInsetsMake(7.5, left, 0, 0));
];
label.enabled = NO;
[kNotificationCenter addObserver:kIsIOS7OrLater ? self : [UIApplication sharedApplication]
selector:@selector(hdf_placehoderTextChange:)
name:UITextViewTextDidChangeNotification
object:nil];
return label;
@end
@implementation UITextView (HDFTextView)
- (void)hdf_placehoderTextChange:(NSNotification *)notification
if (kIsIOS7OrLater)
if (!kIsEmptyString(self.text))
self.placeholderLabel.text = @"";
else
self.placeholderLabel.text = self.hdf_placeholder;
- (UILabel *)hdf_placeholderLabel
return self.placeholderLabel;
- (void)setHdf_placeholder:(NSString *)hdf_placeholder
if (kIsEmptyString(hdf_placeholder))
objc_setAssociatedObject(self, s_hdfTextViewPlaceholderLabelKey, nil, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
[self.placeholderLabel removeFromSuperview];
return;
objc_setAssociatedObject(self,
s_hdfTextViewPlaceholderTextKey,
hdf_placeholder,
OBJC_ASSOCIATION_COPY_NONATOMIC);
if (!kIsEmptyString(self.text))
self.placeholderLabel.text = @"";
else
self.placeholderLabel.text = hdf_placeholder;
- (NSString *)hdf_placeholder
return objc_getAssociatedObject(self, s_hdfTextViewPlaceholderTextKey);
- (void)setHdf_placeholderColor:(UIColor *)hdf_placeholderColor
self.placeholderLabel.textColor = hdf_placeholderColor;
- (UIColor *)hdf_placeholderColor
return self.placeholderLabel.textColor;
- (void)setHdf_placeholderFont:(UIFont *)hdf_placeholderFont
self.placeholderLabel.font = hdf_placeholderFont;
- (UIFont *)hdf_placeholderFont
return self.placeholderLabel.font;
@end
说明:这里的实现文件中使用了运行时机制(runtime)来实现,这里对文本改变的监听,交给了自己和UIApplication,是为了兼容到IOS6.0,在6.0下,交给自己是不可行的,会崩溃,因此移交给UIApplication单例对象来管理。
############提示:这里使用了Masonary这个自动布局的三方库,让这个placeholderlabel自动根据uitextview的大小变化而变化。代码中使用了判断IOS系统,判断是否为空串的代码,这里不写出来了,自己替掉即可。
下面就是使用了,使用起来就很简单了
self.remarkView.text = @"哈哈,很简单吧";
self.remarkView.hdf_placeholder = @"写点什么...";12
备注:当需求中需要给textview添加placeholder时,网上的都是继承的方式,还需要修改很多地方,这是不可行的,所以我才提出这个问题来,然后做出了自己的解决方案。如果对大家有用,请放心地拿去用吧。
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