iOS 开发技巧

一、判断当前iOS设备的类型和型号。

-(NSString*)deviceVersion{

    // 需要#import "sys/utsname.h"

   structutsname systemInfo;

   uname(&systemInfo);

    NSString *deviceString = [NSStringstringWithCString:systemInfo.machineencoding:NSUTF8StringEncoding];

   if ([deviceStringisEqualToString:@"iPhone1,1"])return @"iPhone 2G";

   if ([deviceStringisEqualToString:@"iPhone1,2"])return @"iPhone 3G";

   if ([deviceStringisEqualToString:@"iPhone2,1"])return @"iPhone 3GS";

   if ([deviceStringisEqualToString:@"iPhone3,1"])return @"iPhone 4";

   if ([deviceStringisEqualToString:@"iPhone3,2"])return @"iPhone 4";

   if ([deviceStringisEqualToString:@"iPhone3,3"])return @"iPhone 4";

   if ([deviceStringisEqualToString:@"iPhone4,1"])return @"iPhone 4S";

   if ([deviceStringisEqualToString:@"iPhone5,1"])return @"iPhone 5";

   if ([deviceStringisEqualToString:@"iPhone5,2"])return @"iPhone 5";

   if ([deviceStringisEqualToString:@"iPhone5,3"])return @"iPhone 5c";

   if ([deviceStringisEqualToString:@"iPhone5,4"])return @"iPhone 5c";

   if ([deviceStringisEqualToString:@"iPhone6,1"])return @"iPhone 5s";

   if ([deviceStringisEqualToString:@"iPhone6,2"])return @"iPhone 5s";

   if ([deviceStringisEqualToString:@"iPhone7,1"])return@"iPhone 6 Plus";

   if ([deviceStringisEqualToString:@"iPhone7,2"])return @"iPhone 6";

   if ([deviceStringisEqualToString:@"iPhone8,1"])return @"iPhone 6s";

   if ([deviceStringisEqualToString:@"iPhone8,2"])return@"iPhone 6s Plus";

      

   if ([deviceStringisEqualToString:@"iPod1,1"])  return @"iPod Touch 1G";

   if ([deviceStringisEqualToString:@"iPod2,1"])  return @"iPod Touch 2G";

   if ([deviceStringisEqualToString:@"iPod3,1"])  return @"iPod Touch 3G";

   if ([deviceStringisEqualToString:@"iPod4,1"])  return @"iPod Touch 4G";

   if ([deviceStringisEqualToString:@"iPod5,1"])  return @"iPod Touch 5G";

   if ([deviceStringisEqualToString:@"iPod6,1"])  return @"iPod Touch 6G";

   if ([deviceStringisEqualToString:@"iPod7,1"])  return @"iPod Touch 7G";

    

   if ([deviceStringisEqualToString:@"iPad1,1"])  return @"iPad 1G";

   if ([deviceStringisEqualToString:@"iPad2,1"])  return @"iPad 2";

   if ([deviceStringisEqualToString:@"iPad2,2"])  return @"iPad 2";

   if ([deviceStringisEqualToString:@"iPad2,3"])  return @"iPad 2";

   if ([deviceStringisEqualToString:@"iPad2,4"])  return @"iPad 2";

   if ([deviceStringisEqualToString:@"iPad2,5"])  return @"iPad Mini 1G";

   if ([deviceStringisEqualToString:@"iPad2,6"])  return @"iPad Mini 1G";

   if ([deviceStringisEqualToString:@"iPad2,7"])  return @"iPad Mini 1G";

    

   if ([deviceStringisEqualToString:@"iPad3,1"])  return @"iPad 3";

   if ([deviceStringisEqualToString:@"iPad3,2"])  return @"iPad 3";

   if ([deviceStringisEqualToString:@"iPad3,3"])  return @"iPad 3";

   if ([deviceStringisEqualToString:@"iPad3,4"])  return @"iPad 4";

   if ([deviceStringisEqualToString:@"iPad3,5"])  return @"iPad 4";

   if ([deviceStringisEqualToString:@"iPad3,6"])  return @"iPad 4";

    

   if ([deviceStringisEqualToString:@"iPad4,1"])  return @"iPad Air";

   if ([deviceStringisEqualToString:@"iPad4,2"])  return @"iPad Air ";

   if ([deviceStringisEqualToString:@"iPad4,3"])  return @"iPad Air ";

   if ([deviceStringisEqualToString:@"iPad4,4"])  return @"iPad Mini 2G";

   if ([deviceStringisEqualToString:@"iPad4,5"])  return @"iPad Mini 2G";

   if ([deviceStringisEqualToString:@"iPad4,6"])  return @"iPad Mini 2G";

   if ([deviceStringisEqualToString:@"iPad4,7"]

        ||[deviceStringisEqualToString:@"iPad4,8"]

        ||[deviceStringisEqualToString:@"iPad4,9"])return@"iPad mini 3";

    

   if ([deviceStringisEqualToString:@"i386"])     return @"iPhone Simulator";

   if ([deviceStringisEqualToString:@"x86_64"])   return @"iPhone Simulator";

    elsereturn@"";

   return deviceString;

}

二、获取当前设备系统版本

[[[[UIDevicecurrentDevice]systemVersion]componentsSeparatedByString:@"."][0]intValue] >=7;

三、计算日期时间间隔(可用于根据用户的生日来计算年龄)

//创建日期格式化对象

NSDateFormatter *dateFormatter=[[NSDateFormatteralloc]init];

[dateFormatter setDateFormat:@"yyyy-MM-dd HH:mm"];

//创建了两个日期对象

NSDate *date1=[dateFormatterdateFromString:@"2010-3-3 11:00"];

NSDate *date2=[dateFormatterdateFromString:@"2010-3-4 12:00"];

//NSDate *date=[NSDate date];

//NSString *curdate=[dateFormatter stringFromDate:date];

//取两个日期对象的时间间隔：

//这里的NSTimeInterval并不是对象，是基本型，其实是double类型，是由c定义的:typedef double NSTimeInterval;

NSTimeInterval time=[date2 timeIntervalSinceDate:date1];

int days=((int)time)/(3600*24);

int hours=((int)time)%(3600*24)/3600;

NSString *dateContent=[[NSStringalloc]initWithFormat:@"%i天%i小时",days,hours];

先将标准时间(格式如：1990-12-12)转时间戳，再计算出年龄

NSString *timeStr = [NSStringstringWithFormat:@"%@",self.medicalRecord.birthday];

        NSDateFormatter *formatter =[[NSDateFormatteralloc]init];

        [formattersetDateFormat:@"yyyy-MM-dd"];

       NSDate *date = [formatterdateFromString:timeStr];

        NSString *timeSp = [NSStringstringWithFormat:@"%ld",(long)[datetimeIntervalSince1970]];

        NSDate *confromTimesp = [NSDatedateWithTimeIntervalSince1970:[timeSpintegerValue]];

       NSString *age = [NSStringstringWithFormat:@"%@",[NSDategetAgeByBirthDay:confromTimesp]];//计算患者年龄

计算年龄的方法：

//年龄计算

+(NSString*)getAgeByBirthDay:(NSDate*)birthDay{

   NSDate *birthday = birthDay;

   NSDate *today = [NSDatedate];

    NSCalendar *gregorian = [[NSCalendaralloc]initWithCalendarIdentifier:NSGregorianCalendar];

    

   NSDateComponents *components = [gregoriancomponents:NSYearCalendarUnitfromDate:birthdaytoDate:todayoptions:0];

   return [NSStringstringWithFormat:@"%zi",components.year];

}

四、解决xib加载时，内部空间位置(跑偏)问题(适用于将xib文件装到另外一个父视图里面的情况，比如此处为将topView装入到header中，作为tableView的头视图)；

UIView *header = [[UIViewalloc]initWithFrame:CGRectMake(0,0,WIDTH,200)];

   self.tableView.tableHeaderView = header;

PHomeTopMenuView *topView = [[[NSBundlemainBundle]loadNibNamed:@"PHomeTopMenuView"owner:selfoptions:nil]firstObject];

topView.frame = header.bounds;

//直接设置xib文件的frame=CGRectMake(0, 0, WIDTH, 200)的话，可能会使xib内部的约束显示跑偏，所以可以直接将其frame设置为父视图的bounds。

五、重新定义图片大小

-(UIImage *)reSizeImage:(UIImage *)image toSize:(CGSize)reSize

{

    UIGraphicsBeginImageContext(CGSizeMake(reSize.width, reSize.height)); 

    [imagedrawInRect:CGRectMake(0,0, reSize.width, reSize.height)];  

    UIImage *reSizeImage =UIGraphicsGetImageFromCurrentImageContext(); 

    UIGraphicsEndImageContext();

   return reSizeImage;

}

六、如何修改Xcode中Copyright 2009 __MyCompanyName__. All rights reserved.的名称。

defaults write com.apple.xcode PBXCustomTemplateMacroDefinitions ‘{ ORGANIZATIONNAME = “名字”; }’

七、设置IPhone程序的启动画面

在XCode的项目的resource文件夹中追加名为Default.png的图片就可以了。你可以使用Organizer工 具来抓取iPhone实机上图片。

Organizer是XCode中内含的一个工具，通过选择菜单XCode -> Window -> Organizer来启动。这样就会在程序加载前的呢一会黑屏中运行该画面。

八、有用的色彩搭配表

http://www.print100.com/hk/html/csi.aspx

九、改变状态栏颜色(白底黑字)

    UIView *statusBarView=[[UIViewalloc]initWithFrame:CGRectMake(0,0,WIDTH,20)];

    statusBarView.backgroundColor=[UIColorblackColor];

    [self.viewaddSubview:statusBarView];

    [[UIApplicationsharedApplication]setStatusBarStyle:UIStatusBarStyleDefaultanimated:NO];

十、UISearchDisplayController 无搜索结果下的文字定义

现在需要修改UISearchDisplayController 在搜索不到数据的情况下，显示为:

需要更改红框里面的内容，调用此方法以下方法：

- (BOOL)searchDisplayController:(UISearchDisplayController *)controller

shouldReloadTableForSearchString:(NSString *)searchString

{ for(UIView *subview in self.searchDisplay.searchResultsTableView.subviews) {

 if([subview isKindOfClass:[UILabel class]]) { [(UILabel*)subview setText:@"XXXXXXX"];}}return YES;

}

[(UILabel*)subview setText:@"XXXXXXX"];输入你想要定义的内容，就可以达到你想要的效果了

十一、lib库所支持的框架类型：i386表示支持iphone模拟器，armv6应用在iphone 3gs上，armv7应用在iphone4，armv7s应用在iphone4s以及iphone5，arm64应用在最新的iphone5s上。

十二、双击手势

    UITapGestureRecognizer *doubleTap = [[UITapGestureRecognizer alloc]initWithTarget:self action:@selector(doDoubleTap)];
    doubleTap.numberOfTapsRequired = 2;
    doubleTap.numberOfTouchesRequired = 1;
    [self.view addGestureRecognizer:doubleTap];

十三、解决输入文字不从顶部开始的bug(例如：可用于解决UITextView中文字不从顶部开始显示，而是在中间开始显示文字的问题)

    self.automaticallyAdjustsScrollViewInsets = NO;

十四、给tabbar添加badgeValue

int indexICareAbout = 2; 
NSString *badgeValue = @"10";  
[[[[[self tabBarController] viewControllers] objectAtIndex: indexICareAbout] tabBarItem] setBadgeValue:badgeValue];

十五、block弱引用释义：__weak__typeof(self) weakself = self;

此句代码，声明了一个self类型的 weak指针 weakSelf ，typeof(self) 是获取到self的类型,这样定义出的weakSelf就是和self一个类型的, 加上__weak是建立一个若引用,整句就是给self定义了一个若引用性质的替身;这个一般用在使用block时会用到,因为block会copy它内部的变量,可能会造成引用循环,使用__weak性质的self替代self,可以切断block对self的引用,避免循环引用 。

另外需要注意的是：在block内部引用实例变量要用weakSelf->实例变量 的方式来访问，而不能用原来的形式self.XXX进行访问，否则会造成block对self的强引用，从而引起循环引用。

十六、键盘处理

#pragma mark---监听键盘活动
- (void)viewLoad
{
   //增加监听，当键盘出现或改变时收出消息
    [[NSNotificationCenter defaultCenter] addObserver:self
                                             selector:@selector(keyboardWillShow:)
                                                 name:UIKeyboardWillShowNotification
                                               object:nil];
    //增加监听，当键退出时收出消息
    [[NSNotificationCenter defaultCenter] addObserver:self
                                             selector:@selector(keyboardWillHide:)
                                                 name:UIKeyboardWillHideNotification
                                               object:nil];
    
    
}
//当键盘出现或改变时调用
- (void)keyboardWillShow:(NSNotification *)aNotification
{
    //获取键盘的高度
    NSDictionary *userInfo = [aNotification userInfo];
    NSValue *aValue = [userInfo objectForKey:UIKeyboardFrameEndUserInfoKey];
    CGRect keyboardRect = [aValue CGRectValue];
    CGFloat height=keyboardRect.size.height;
    _TableView.frame=CGRectMake(0, 115, SCREEN_WIDTH, SCREEN_HEIGHT-115-50-40-height);
    _DownView.frame=CGRectMake(0, SCREEN_HEIGHT-90-height, SCREEN_WIDTH, 90);
}


//当键退出时调用
- (void)keyboardWillHide:(NSNotification *)aNotification
{
        _TableView.frame=CGRectMake(0, 115, SCREEN_WIDTH, SCREEN_HEIGHT-115-50-40);
        _DownView.frame=CGRectMake(0, SCREEN_HEIGHT-90, SCREEN_WIDTH, 90);
}

十七、向上取整 (当数据不确定时，可用于返回UITableViewCell的高度)

  ceil(dataArray.count/4.0);如:结果是"1.65",则会自动向上取到"2".

十八、直接从SDWebImage的缓存中取图片

UIImage *cachedImage = [[SDImageCache sharedImageCache] imageFromDiskCacheForKey:imgUrl]; 

十九、伪横屏

 //隐藏系统状态栏，并添加“伪横屏”

    [[UIApplicationsharedApplication]setStatusBarHidden:YESwithAnimation:UIStatusBarAnimationFade];

    [UIViewanimateWithDuration:0.35delay:0options:UIViewAnimationOptionTransitionCrossDissolveanimations:^{

        CGAffineTransform transform =CGAffineTransformIdentity;

        transform =CGAffineTransformRotate(transform,M_PI/2);

       self.view.transform = transform;

    } completion:NULL];

二十  修改uitextfield的placeholder字体和位置

自定义一个textfield，继承于uitextfield，并重写下面这个方法：

- (void) drawPlaceholderInRect:(CGRect)rect {

    [[UIColor blueColor] setFill];

    [self.placeholder drawInRect:rect withFont:self.font lineBreakMode:UILineBreakModeTailTruncation alignment:self.textAlignment];

}

二十一、判断tableview上下滑动

    func scrollViewDidScroll(_ scrollView:UIScrollView) {

        if scrollView.contentOffset.y>oldOff_y{

            self.addBtn.isHidden=true

        }else{

            self.addBtn.isHidden=false

        }

         oldOff_y = scrollView.contentOffset.y//将当前位移变成缓存位移

    }

二十二、创建假的状态栏

-(void)setupNavBar{

   //创建一个高20的假状态栏

    UIView *statusBarView = [[UIViewalloc] initWithFrame:CGRectMake(0, -20, self.view.bounds.size.width,20)];

    //设置成蓝色

    statusBarView.backgroundColor=[UIColorcolorWithRed:49/255.0fgreen:171/255.0fblue:248/255.0falpha:1];

    //添加到 navigationBar上

    [self.viewaddSubview:statusBarView];

    [self.navigationController.navigationBarsetBarStyle:UIBarStyleBlack];

}