微博项目地址https://github.com/shidayangli/SinaWeiBo.git

微博项目上传github好久了，由于项目太多东西，竟不知从何说起，最近要开始找工作了，回顾一下，想到哪里说哪里吧。今天先说说自定义一个textV

iew，带有placeholder的。大家都用过微博，在发微博的那个界面，很明显是一个textView，但是textView又没有placeholder属性，所以选择自定义来解决问题。看效果。

未命名.gif

在写这个自定义控件之前，我先提一点，就是我们在开发中经常遇见会定义控件的frame情况，可是这个frame赋值起来有些费劲，如果你只想改变x值的话，还得定义一个新的rect然后传值，所以我给UIView写了一个category，会很大程度上方便你的开发，先给大家看这段代码那，相信我，磨刀不误砍柴工！

UIView+Extension.h

#import <UIKit/UIKit.h>
@interface UIView (Extension)

@property(nonatomic, assign)CGFloat x;
@property(nonatomic, assign)CGFloat y;
@property(nonatomic, assign)CGFloat width;
@property(nonatomic, assign)CGFloat height;
@property(nonatomic, assign)CGSize size;
@property(nonatomic, assign)CGPoint origin;
@property(nonatomic, assign)CGFloat centerX;
@property(nonatomic, assign)CGFloat centerY;

@end

UIView+Extension.m

#import "UIView+Extension.h"

@implementation UIView (Extension)

-(void)setX:(CGFloat)x
{
   CGRect frame = self.frame;
    frame.origin.x = x;
    self.frame = frame;
}

-(void)setY:(CGFloat)y
{
    CGRect frame = self.frame;
    frame.origin.y = y;
    self.frame = frame;
}

-(CGFloat)x
{
    return self.frame.origin.x;
}

-(CGFloat)y
{
    return self.frame.origin.y;
}

-(void)setWidth:(CGFloat)width{
    CGRect frame = self.frame;
    frame.size.width = width;
    self.frame = frame;
}
-(void)setHeight:(CGFloat)height
{
    CGRect frame = self.frame;
    frame.size.height = height;
    self.frame = frame;
}

-(CGFloat)width
{
    return self.frame.size.width;
}

-(CGFloat)height
{
    return self.frame.size.height;
}

-(void)setSize:(CGSize)size
{
    CGRect frame = self.frame;
    frame.size = size;
    self.frame = frame;
}
-(CGSize)size
{
    return self.frame.size;
}

-(void)setOrigin:(CGPoint)origin{
    CGRect frame = self.frame;
    frame.origin = origin;
    self.frame = frame;
}
-(CGPoint)origin
{
    return self.frame.origin;
}

-(void)setCenterX:(CGFloat)centerX
{
    CGPoint point = self.center;
    point.x = centerX;
    self.center = point;
}

-(CGFloat)centerX
{
    return self.center.x;
}

-(void)setCenterY:(CGFloat)centerY
{    
    CGPoint point = self.center;
    point.y = centerY;
    self.center = point;
}

-(CGFloat)centerY
{
    return self.center.y;
}

@end

代码很简单易懂，就是有点长，下面进入正题，一般添加placeholder有好几种方法，有添加一个UILabel在textView上，然后监听文字变化，或者是使用NSString的方法直接将文字画上去，这里并无好坏之分，只有适合不适合，我选用的是采用NSString的方法，就是在textView的 drawRect:方法中用NSString的drawInRect:placeholderRect withAttributes:方法画出，代码如下：

-(void)drawRect:(CGRect)rect
{
    if (self.hasText) {
        [super drawRect:rect];
    }else{
        //采用画的方式得到placeholder文字
        NSMutableDictionary *attr = [NSMutableDictionary dictionary];
        attr[NSFontAttributeName] = self.font;
        attr[NSForegroundColorAttributeName] = [UIColor grayColor];
    
        CGRect placeholderRect = CGRectMake(5, 8, rect.size.width - 10, rect.size.height - 16);
        [self.placeholder drawInRect:placeholderRect withAttributes:attr];
    }
}

if语句是判断现在输入框里是否有文字，如果有就不再画placeholder了。再设置通知，监听自己发出的通知就好。

-(instancetype)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self) {
        [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(textChanged) name:UITextViewTextDidChangeNotification object:self];
    }
    return self;
}

当然别忘了注销通知，这里就不写了，好了，就这么简单，直接就可以拿着用啦。