微博項目地址https://github.com/shidayangli/SinaWeiBo.git
微博項目上傳github好久了媳否，由于項目太多東西特恬，竟不知從何說起执俩，最近要開始找工作了，回顧一下癌刽，想到哪里說哪里吧役首。今天先說說自定義一個textV
iew，帶有placeholder的显拜。大家都用過微博衡奥，在發(fā)微博的那個界面，很明顯是一個textView远荠，但是textView又沒有placeholder屬性矮固，所以選擇自定義來解決問題∑┐荆看效果档址。
未命名.gif
在寫這個自定義控件之前盹兢，我先提一點，就是我們在開發(fā)中經(jīng)常遇見會定義控件的frame情況辰晕，可是這個frame賦值起來有些費勁，如果你只想改變x值的話确虱，還得定義一個新的rect然后傳值含友，所以我給UIView寫了一個category，會很大程度上方便你的開發(fā)校辩，先給大家看這段代碼那窘问，相信我，磨刀不誤砍柴工宜咒！
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
代碼很簡單易懂惠赫，就是有點長，下面進入正題故黑，一般添加placeholder有好幾種方法儿咱，有添加一個UILabel在textView上，然后監(jiān)聽文字變化场晶，或者是使用NSString的方法直接將文字畫上去混埠，這里并無好壞之分，只有適合不適合诗轻，我選用的是采用NSString的方法钳宪，就是在textView的 drawRect:方法中用NSString的drawInRect:placeholderRect withAttributes:方法畫出，代碼如下：
-(void)drawRect:(CGRect)rect
{
if (self.hasText) {
[super drawRect:rect];
}else{
//采用畫的方式得到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語句是判斷現(xiàn)在輸入框里是否有文字扳炬，如果有就不再畫placeholder了吏颖。再設(shè)置通知，監(jiān)聽自己發(fā)出的通知就好恨樟。
-(instancetype)initWithFrame:(CGRect)frame
{
self = [super initWithFrame:frame];
if (self) {
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(textChanged) name:UITextViewTextDidChangeNotification object:self];
}
return self;
}
