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iOS 知识-常用小技巧(转)

iOS 知识-常用小技巧(转)

作者: b82e0191c0fe | 来源:发表于2016-07-29 09:44 被阅读62次

    目录(原文http://blog.cocoachina.com/article/28221)

    1. 打印View所有子视图
    
    po [[self view]recursiveDescription]
    
    2. layoutSubviews调用的调用时机
    
    * 当视图第一次显示的时候会被调用
    * 当这个视图显示到屏幕上了,点击按钮
    * 添加子视图也会调用这个方法
    * 当本视图的大小发生改变的时候是会调用的
    * 当子视图的frame发生改变的时候是会调用的
    * 当删除子视图的时候是会调用的
    
    3. NSString过滤特殊字符
    
    // 定义一个特殊字符的集合
    NSCharacterSet *set = [NSCharacterSet characterSetWithCharactersInString:
    @"@/:;()¥「」"、[]{}#%-*+=_\\|~<>$€^•'@#$%^&*()_+'\""];
    // 过滤字符串的特殊字符
    NSString *newString = [trimString stringByTrimmingCharactersInSet:set];
    
    4. TransForm属性
    
    //平移按钮
    CGAffineTransform transForm = self.buttonView.transform;
    self.buttonView.transform = CGAffineTransformTranslate(transForm, 10, 0);
    
    //旋转按钮
    CGAffineTransform transForm = self.buttonView.transform;
    self.buttonView.transform = CGAffineTransformRotate(transForm, M_PI_4);
    
    //缩放按钮
    self.buttonView.transform = CGAffineTransformScale(transForm, 1.2, 1.2);
    
    //初始化复位
    self.buttonView.transform = CGAffineTransformIdentity;
    
    5. 去掉分割线多余15像素
    
    首先在viewDidLoad方法加入以下代码:
     if ([self.tableView respondsToSelector:@selector(setSeparatorInset:)]) {
            [self.tableView setSeparatorInset:UIEdgeInsetsZero];    
    }   
     if ([self.tableView respondsToSelector:@selector(setLayoutMargins:)]) {        
            [self.tableView setLayoutMargins:UIEdgeInsetsZero];
    }
    然后在重写willDisplayCell方法
    - (void)tableView:(UITableView *)tableView willDisplayCell:(UITableViewCell *)cell 
    forRowAtIndexPath:(NSIndexPath *)indexPath{   
        if ([cell respondsToSelector:@selector(setSeparatorInset:)]) {       
                 [cell setSeparatorInset:UIEdgeInsetsZero];    
        }    
        if ([cell respondsToSelector:@selector(setLayoutMargins:)]) {        
                 [cell setLayoutMargins:UIEdgeInsetsZero];    
        }
    }
    
    6. 计算方法耗时时间间隔
    
    // 获取时间间隔
    #define TICK   CFAbsoluteTime start = CFAbsoluteTimeGetCurrent();
    #define TOCK   NSLog(@"Time: %f", CFAbsoluteTimeGetCurrent() - start)
    
    7. Color颜色宏定义
    
    // 随机颜色
    #define RANDOM_COLOR [UIColor colorWithRed:arc4random_uniform(256) / 255.0 green:arc4random_uniform(256) / 255.0 blue:arc4random_uniform(256) / 255.0 alpha:1]
    // 颜色(RGB)
    #define RGBCOLOR(r, g, b) [UIColor colorWithRed:(r)/255.0f green:(g)/255.0f blue:(b)/255.0f alpha:1]
    // 利用这种方法设置颜色和透明值,可不影响子视图背景色
    #define RGBACOLOR(r, g, b, a) [UIColor colorWithRed:(r)/255.0f green:(g)/255.0f blue:(b)/255.0f alpha:(a)]
    
    8. Alert提示宏定义
    
    #define Alert(_S_, ...) [[[UIAlertView alloc] initWithTitle:@"提示" message:[NSString stringWithFormat:(_S_), ##__VA_ARGS__] delegate:nil cancelButtonTitle:@"确定" otherButtonTitles:nil] show]
    
    9. 让iOS应用直接退出
    
    - (void)exitApplication {
        AppDelegate *app = [UIApplication sharedApplication].delegate;
        UIWindow *window = app.window;
    
        [UIView animateWithDuration:1.0f animations:^{
            window.alpha = 0;
        } completion:^(BOOL finished) {
            exit(0);
        }];
    }
    
    10. NSArray 快速求总和 最大值 最小值 和 平均值
    
    NSArray *array = [NSArray arrayWithObjects:@"2.0", @"2.3", @"3.0", @"4.0", @"10", nil];
    CGFloat sum = [[array valueForKeyPath:@"@sum.floatValue"] floatValue];
    CGFloat avg = [[array valueForKeyPath:@"@avg.floatValue"] floatValue];
    CGFloat max =[[array valueForKeyPath:@"@max.floatValue"] floatValue];
    CGFloat min =[[array valueForKeyPath:@"@min.floatValue"] floatValue];
    NSLog(@"%f\n%f\n%f\n%f",sum,avg,max,min);
    10. 修改Label中不同文字颜色
    
    - (void)touchesEnded:(NSSet<UITouch> *)touches withEvent:(UIEvent *)event
    {
        [self editStringColor:self.label.text editStr:@"好" color:[UIColor blueColor]];
    }
    
    - (void)editStringColor:(NSString *)string editStr:(NSString *)editStr color:(UIColor *)color {
        // string为整体字符串, editStr为需要修改的字符串
        NSRange range = [string rangeOfString:editStr];
    
        NSMutableAttributedString *attribute = [[NSMutableAttributedString alloc] initWithString:string];
    
        // 设置属性修改字体颜色UIColor与大小UIFont
        [attribute addAttributes:@{NSForegroundColorAttributeName:color} range:range];
    
        self.label.attributedText = attribute;
    }
    
    11. 播放声音
    
      #import<AVFoundation>
       //  1.获取音效资源的路径
       NSString *path = [[NSBundle mainBundle]pathForResource:@"pour_milk" ofType:@"wav"];
       //  2.将路劲转化为url
       NSURL *tempUrl = [NSURL fileURLWithPath:path];
       //  3.用转化成的url创建一个播放器
       NSError *error = nil;
       AVAudioPlayer *play = [[AVAudioPlayer alloc]initWithContentsOfURL:tempUrl error:&error];
       self.player = play;
       //  4.播放
       [play play];
    
    12. 检测是否IPad Pro
    
    - (BOOL)isIpadPro
    {   
      UIScreen *Screen = [UIScreen mainScreen];   
      CGFloat width = Screen.nativeBounds.size.width/Screen.nativeScale;  
      CGFloat height = Screen.nativeBounds.size.height/Screen.nativeScale;         
      BOOL isIpad =[[UIDevice currentDevice] userInterfaceIdiom] == UIUserInterfaceIdiomPad;   
      BOOL hasIPadProWidth = fabs(width - 1024.f) < DBL xss=removed xss=removed xss=removed xss=removed xss=removed xss=removed xss=removed xss=removed xss=removed>> ~/.lldbinit
        echo target stop-hook add -o \"target stop-hook disable\" >> ~/.lldbinit
    下次重新运行项目,然后就不报错了。
    
    25. Label行间距
    
    -(void)test{
        NSMutableAttributedString *attributedString =    
       [[NSMutableAttributedString alloc] initWithString:self.contentLabel.text];
        NSMutableParagraphStyle *paragraphStyle =  [[NSMutableParagraphStyle alloc] init];  
       [paragraphStyle setLineSpacing:3];
    
        //调整行间距       
       [attributedString addAttribute:NSParagraphStyleAttributeName 
                             value:paragraphStyle 
                             range:NSMakeRange(0, [self.contentLabel.text length])];
         self.contentLabel.attributedText = attributedString;
    }
    
    26. UIImageView填充模式
    
    @"UIViewContentModeScaleToFill",      // 拉伸自适应填满整个视图  
    @"UIViewContentModeScaleAspectFit",   // 自适应比例大小显示  
    @"UIViewContentModeScaleAspectFill",  // 原始大小显示  
    @"UIViewContentModeRedraw",           // 尺寸改变时重绘  
    @"UIViewContentModeCenter",           // 中间  
    @"UIViewContentModeTop",              // 顶部  
    @"UIViewContentModeBottom",           // 底部  
    @"UIViewContentModeLeft",             // 中间贴左  
    @"UIViewContentModeRight",            // 中间贴右  
    @"UIViewContentModeTopLeft",          // 贴左上  
    @"UIViewContentModeTopRight",         // 贴右上  
    @"UIViewContentModeBottomLeft",       // 贴左下  
    @"UIViewContentModeBottomRight",      // 贴右下
    
    27. 宏定义检测block是否可用
    
    #define BLOCK_EXEC(block, ...) if (block) { block(__VA_ARGS__); };   
    // 宏定义之前的用法
     if (completionBlock)   {   
        completionBlock(arg1, arg2); 
      }    
    // 宏定义之后的用法
     BLOCK_EXEC(completionBlock, arg1, arg2);
    
    28. Debug栏打印时自动把Unicode编码转化成汉字
    
    // 有时候我们在xcode中打印中文,会打印出Unicode编码,还需要自己去一些在线网站转换,有了插件就方便多了。
     DXXcodeConsoleUnicodePlugin 插件
    
    29. 设置状态栏文字样式颜色
    
    [[UIApplication sharedApplication] setStatusBarHidden:NO];
    [[UIApplication sharedApplication] setStatusBarStyle:UIStatusBarStyleLightContent];
    
    30. 自动生成模型代码的插件
    
    // 可自动生成模型的代码,省去写模型代码的时间
    ESJsonFormat-for-Xcode
    
    31. iOS中的一些手势
    
    轻击手势(TapGestureRecognizer)
    轻扫手势(SwipeGestureRecognizer)
    长按手势(LongPressGestureRecognizer)
    拖动手势(PanGestureRecognizer)
    捏合手势(PinchGestureRecognizer)
    旋转手势(RotationGestureRecognizer)
    
    32. iOS 开发中一些相关的路径
    
    模拟器的位置:
    /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs 
    
    文档安装位置:
    /Applications/Xcode.app/Contents/Developer/Documentation/DocSets
    
    插件保存路径:
    ~/Library/ApplicationSupport/Developer/Shared/Xcode/Plug-ins
    
    自定义代码段的保存路径:
    ~/Library/Developer/Xcode/UserData/CodeSnippets/ 
    如果找不到CodeSnippets文件夹,可以自己新建一个CodeSnippets文件夹。
    
    证书路径
    ~/Library/MobileDevice/Provisioning Profiles
    
    33. 获取 iOS 路径的方法
    
    获取家目录路径的函数
    NSString *homeDir = NSHomeDirectory();
    
    获取Documents目录路径的方法
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *docDir = [paths objectAtIndex:0];
    
    获取Documents目录路径的方法
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES);
    NSString *cachesDir = [paths objectAtIndex:0];
    
    获取tmp目录路径的方法:
    NSString *tmpDir = NSTemporaryDirectory();
    34. 字符串相关操作
    
    去除所有的空格
    [str stringByReplacingOccurrencesOfString:@" " withString:@""]
    
    去除首尾的空格
    [str stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceCharacterSet]];
    
    - (NSString *)uppercaseString; 全部字符转为大写字母
    - (NSString *)lowercaseString 全部字符转为小写字母
    
    35. CocoaPods pod install/pod update更新慢的问题
    
    pod install --verbose --no-repo-update 
    pod update --verbose --no-repo-update
    如果不加后面的参数,默认会升级CocoaPods的spec仓库,加一个参数可以省略这一步,然后速度就会提升不少。
    
    36. MRC和ARC混编设置方式
    
    在XCode中targets的build phases选项下Compile Sources下选择 不需要arc编译的文件
    双击输入 -fno-objc-arc 即可
    
    MRC工程中也可以使用ARC的类,方法如下:
    在XCode中targets的build phases选项下Compile Sources下选择要使用arc编译的文件
    双击输入 -fobjc-arc 即可
    
    37. 把tableview里cell的小对勾的颜色改成别的颜色
    
    _mTableView.tintColor = [UIColor redColor];
    
    38. 调整tableview的separaLine线的位置
    
    tableView.separatorInset = UIEdgeInsetsMake(0, 100, 0, 0);
    
    39. 设置滑动的时候隐藏navigationbar
    
    navigationController.hidesBarsOnSwipe = Yes
    
    40. 自动处理键盘事件,实现输入框防遮挡的插件
    
    IQKeyboardManager
    https://github.com/hackiftekhar/IQKeyboardManager
    
    41. Quartz2D相关
    
    图形上下是一个CGContextRef类型的数据。
    图形上下文包含:
    1,绘图路径(各种各样图形)
    2,绘图状态(颜色,线宽,样式,旋转,缩放,平移)
    3,输出目标(绘制到什么地方去?UIView、图片)
    
    1,获取当前图形上下文
    CGContextRef ctx = UIGraphicsGetCurrentContext();
    2,添加线条
    CGContextMoveToPoint(ctx, 20, 20);
    3,渲染
    CGContextStrokePath(ctx);
    CGContextFillPath(ctx);
    4,关闭路径
    CGContextClosePath(ctx);
    5,画矩形
    CGContextAddRect(ctx, CGRectMake(20, 20, 100, 120));
    6,设置线条颜色
    [[UIColor redColor] setStroke];
    7, 设置线条宽度
    CGContextSetLineWidth(ctx, 20);
    8,设置头尾样式
    CGContextSetLineCap(ctx, kCGLineCapSquare);
    9,设置转折点样式
    CGContextSetLineJoin(ctx, kCGLineJoinBevel);
    10,画圆
    CGContextAddEllipseInRect(ctx, CGRectMake(30, 50, 100, 100));
    11,指定圆心
    CGContextAddArc(ctx, 100, 100, 50, 0, M_PI * 2, 1);
    12,获取图片上下文
    UIGraphicsGetImageFromCurrentImageContext();
    13,保存图形上下文
    CGContextSaveGState(ctx)
    14,恢复图形上下文
    CGContextRestoreGState(cox)
    
    42. 屏幕截图
    
        // 1. 开启一个与图片相关的图形上下文
        UIGraphicsBeginImageContextWithOptions(self.view.bounds.size,NO,0.0);
    
        // 2. 获取当前图形上下文
        CGContextRef ctx = UIGraphicsGetCurrentContext();
    
        // 3. 获取需要截取的view的layer
        [self.view.layer renderInContext:ctx];
    
        // 4. 从当前上下文中获取图片
        UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    
        // 5. 关闭图形上下文
        UIGraphicsEndImageContext();
    
        // 6. 把图片保存到相册
        UIImageWriteToSavedPhotosAlbum(image, nil, nil, nil);
    
    43. 隐藏导航栏上的返回字体
    
    //Swift
    UIBarButtonItem.appearance().setBackButtonTitlePositionAdjustment(UIOffsetMake(0, -60), forBarMetrics: .Default)
    //OC
    [[UIBarButtonItem appearance] setBackButtonTitlePositionAdjustment:UIOffsetMake(0, -60) forBarMetrics:UIBarMetricsDefault];
    
    44. 解决tableview的分割线短一截
    
    -(void)viewDidLayoutSubviews{
    if ([self.tableView respondsToSelector:@selector(setSeparatorInset:)])
    { 
    [self.tableView setSeparatorInset:UIEdgeInsetsMake(0,0,0,0)];
    }
    if ([self.tableView respondsToSelector:@selector(setLayoutMargins:)]) 
    {
    [self.tableView setLayoutMargins:UIEdgeInsetsMake(0,0,0,0)]; 
    }
    }
    -(void)tableView:(UITableView *)tableView willDisplayCell:(UITableViewCell *)cell forRowAtIndexPath:(NSIndexPath *)indexPath{
    if ([cell respondsToSelector:@selector(setSeparatorInset:)]) 
    {
    [cell setSeparatorInset:UIEdgeInsetsZero]; 
    } 
    if ([cell respondsToSelector:@selector(setLayoutMargins:)]) 
    {
    [cell setLayoutMargins:UIEdgeInsetsZero]; 
    }
    }
    
    45. 动态隐藏NavigationBar
    
    //1.当我们的手离开屏幕时候隐藏
    - (void)scrollViewWillEndDragging:(UIScrollView *)scrollView withVelocity:(CGPoint)velocity targetContentOffset:(inout CGPoint *)targetContentOffset
    { 
    if(velocity.y > 0) 
    {
    [self.navigationController setNavigationBarHidden:YES animated:YES];
    } else {
    [self.navigationController setNavigationBarHidden:NO animated:YES]; 
    }
    }
    velocity.y这个量,在上滑和下滑时,变化极小(小数),但是因为方向不同,有正负之分,这就很好处理了。
    //2.在滑动过程中隐藏
    //像safari
    (1) 
    self.navigationController.hidesBarsOnSwipe = YES;
    (2)
    - (void)scrollViewDidScroll:(UIScrollView *)scrollView
    {
     CGFloat offsetY = scrollView.contentOffset.y + __tableView.contentInset.top;
     CGFloat panTranslationY = [scrollView.panGestureRecognizer translationInView:self.tableView].y;
     if (offsetY > 64) {
     if (panTranslationY > 0) 
    { 
    //下滑趋势,显示 
    [self.navigationController setNavigationBarHidden:NO animated:YES];
    } else { 
    //上滑趋势,隐藏 
    [self.navigationController setNavigationBarHidden:YES animated:YES]; 
    }
    } else {
    [self.navigationController setNavigationBarHidden:NO animated:YES]; 
    }
    }
    这里的offsetY > 64只是为了在视图滑过navigationBar的高度之后才开始处理,防止影响展示效果。panTranslationY是scrollView的pan手势的手指位置的y值,可能不是太好,因为panTranslationY这个值在较小幅度上下滑动时,可能都为正或都为负,这就使得这一方式不太灵敏.
    效果图
    
    
    
    46. 设置导航栏透明
    
    //方法一:设置透明度
    [[[self.navigationController.navigationBar subviews]objectAtIndex:0] setAlpha:0.1];
    //方法二:设置背景图片
    /**
     * 设置导航栏,使其透明
     *
    */
    - (void)setNavigationBarColor:(UIColor *)color targetController:(UIViewController *)targetViewController{
    //导航条的颜色 以及隐藏导航条的颜色targetViewController.navigationController.navigationBar.shadowImage = [[UIImage alloc]init]; 
    CGRect rect=CGRectMake(0.0f, 0.0f, 1.0f, 1.0f); UIGraphicsBeginImageContext(rect.size);
    CGContextRef context = UIGraphicsGetCurrentContext(); CGContextSetFillColorWithColor(context, [color CGColor]); CGContextFillRect(context, rect); 
    UIImage *theImage = UIGraphicsGetImageFromCurrentImageContext(); UIGraphicsEndImageContext(); [targetViewController.navigationController.navigationBar setBackgroundImage:theImage forBarMetrics:UIBarMetricsDefault];
    }
    
    47. 设置字体和行间距
    
    //设置字体和行间距 
    UILabel * lable = [[UILabel alloc]initWithFrame:CGRectMake(50, 100, 300, 200)]; 
    lable.text = @"大家好,我是Frank_chun,在这里我们一起学习新的知识,总结我们遇到的那些坑,共同的学习,共同的进步,共同的努力,只为美好的明天!!!有问题一起相互的探讨--438637472!!!"; 
    lable.numberOfLines = 0;
    lable.font = [UIFont systemFontOfSize:12];
    lable.backgroundColor = [UIColor grayColor]; 
    [self.view addSubview:lable]; 
    //设置每个字体之间的间距 
    //NSKernAttributeName 这个对象所对应的值是一个NSNumber对象(包含小数),作用是修改默认字体之间的距离调整,值为0的话表示字距调整是禁用的; NSMutableAttributedString * str = [[NSMutableAttributedString alloc]initWithString:lable.text attributes:@{NSKernAttributeName:@(5.0)}];
    //设置某写字体的颜色
    //NSForegroundColorAttributeName 设置字体颜色
    NSRange blueRange = NSMakeRange([[str string] rangeOfString:@"Frank_chun"].location, [[str string] rangeOfString:@"Frank_chun"].length); 
    [str addAttribute:NSForegroundColorAttributeName value:[UIColor redColor] range:blueRange]; 
    NSRange blueRange1 = NSMakeRange([[str string] rangeOfString:@"438637472"].location, [[str string] rangeOfString:@"438637472"].length);
    [str addAttribute:NSForegroundColorAttributeName value:[UIColor redColor] range:blueRange1];
    //设置每行之间的间距 
    //NSParagraphStyleAttributeName 设置段落的样式
    NSMutableParagraphStyle * par = [[NSMutableParagraphStyle alloc]init];
    [par setLineSpacing:20];
    //为某一范围内文字添加某个属性
    //NSMakeRange表示所要的范围,从0到整个文本的长度
    [str addAttribute:NSParagraphStyleAttributeName value:par range:NSMakeRange(0, lable.text.length)]; [lable setAttributedText:str];
    效果图
    
    
    48. 点击button倒计时
    
    //第一种方法
    //点击button倒计时
    #import "ViewController.h"
    @interface ViewController ()
    @property (nonatomic, strong) UIButton * timeButton;
    @property (nonatomic, strong) NSTimer * timer;
    @property (nonatomic, strong)UIButton * btn;
    @end@implementation ViewController
    { 
    NSInteger _time;
    }
    - (void)viewDidLoad {
    [super viewDidLoad]; 
    _time = 5; 
    self.btn = [UIButton buttonWithType:UIButtonTypeCustom]; _btn.backgroundColor = [UIColor orangeColor];
    [_btn setTitle:@"获取验证码" forState:UIControlStateNormal]; _btn.titleLabel.font = [UIFont systemFontOfSize:15];
    [_timeButton setTitleColor:[UIColor blackColor] forState:UIControlStateNormal];
    [_btn addTarget:self action:@selector(btnAction:) forControlEvents:UIControlEventTouchUpInside];
    [self refreshButtonWidth]; 
    [self.view addSubview:self.btn];
    }
    - (void)refreshButtonWidth{ 
    CGFloat width = 0; 
    if (_btn.enabled){
     width = 100; 
    } else { 
    width = 200;
    } 
    _btn.center = CGPointMake(self.view.frame.size.width/2, 200);
    _btn.bounds = CGRectMake(0, 0, width, 40); 
    //每次刷新,保证区域正确
    [_btn setBackgroundImage:[self imageWithColor:[UIColor orangeColor] andSize:_btn.frame.size] forState:UIControlStateNormal];
    [_btn setBackgroundImage:[self imageWithColor:[UIColor lightGrayColor] andSize:_btn.frame.size] forState:UIControlStateDisabled];
    }
    - (UIImage *)imageWithColor:(UIColor *)color andSize:(CGSize)aSize{
     CGRect rect = CGRectMake(0.0f, 0.0f, aSize.width, aSize.height); UIGraphicsBeginImageContext(rect.size);
     CGContextRef context = UIGraphicsGetCurrentContext(); CGContextSetFillColorWithColor(context, [color CGColor]); CGContextFillRect(context, rect);
     UIImage *image = UIGraphicsGetImageFromCurrentImageContext(); UIGraphicsEndImageContext();
    return image;
    }
    - (void)btnAction:(UIButton *)sender{
    sender.enabled = NO;
    [self refreshButtonWidth];
    [sender setTitle:[NSString stringWithFormat:@"获取验证码(%zi)", _time] forState:UIControlStateNormal]; 
    _timer = [NSTimer scheduledTimerWithTimeInterval:0.1 target:self selector:@selector(timeDown) userInfo:nil repeats:YES];
    }
    - (void)timeDown{ 
    _time --;
     if (_time == 0) {
     [_btn setTitle:@"重新获取" forState:UIControlStateNormal]; _btn.enabled = YES; 
    [self refreshButtonWidth]; 
    [_timer invalidate]; 
    _timer = nil; 
    _time = 5 ; 
    return; 
    } 
    [_btn setTitle:[NSString stringWithFormat:@"获取验证码(%zi)", _time] forState:UIControlStateNormal];
    }
    //第二种方法
    #pragma mark -点击发送验证码
    - (void)sendMessage:(UIButton *)btn{
    if (self.phoneField.text.length == 0) { 
    [self remindMessage:@"请输入正确的手机号"];
    }else{ 
    __block int timeout=60; 
    //倒计时时间 
    dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0); dispatch_source_t _timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0,queue); dispatch_source_set_timer(_timer,dispatch_walltime(NULL, 0),1.0*NSEC_PER_SEC, 0);
     //每秒执行 
    dispatch_source_set_event_handler(_timer, ^{ 
    if(timeout<=0){ 
    //倒计时结束,关闭 
    dispatch_source_cancel(_timer); dispatch_async(dispatch_get_main_queue(), ^{ 
    // 设置界面的按钮显示 根据自己需求设置 
    [btn setTitle:@"发送验证码" forState:UIControlStateNormal]; btn.userInteractionEnabled = YES; 
    }); 
    }else{ 
    int seconds = timeout % 60;
    NSString *strTime = [NSString stringWithFormat:@"%d", seconds];
    if ([strTime isEqualToString:@"0"]) {
     strTime = [NSString stringWithFormat:@"%d",60];
     } 
    dispatch_async(dispatch_get_main_queue(), ^{ 
    //设置界面的按钮显示 根据自己需求设置 
    //NSLog(@"____%@",strTime);
    [UIView beginAnimations:nil context:nil];
    [UIView setAnimationDuration:1]; 
    [btn setTitle:[NSString stringWithFormat:@"%@秒后重新发送",strTime] forState:UIControlStateNormal];
    [UIView commitAnimations]; 
    btn.userInteractionEnabled = NO;
     });
     timeout--;
     } 
    }); 
    dispatch_resume(_timer);
    }
    效果图
    
    49. UITextField默认占位符是居中显示,让其居上显示
    
    textField.contentVerticalAlignment = UIControlContentVerticalAlignmentTop;
    
    50. 解决同时按两个按钮进两个view的问题
    
    [button setExclusiveTouch:YES];
    
    51. 图片拉伸
    
    UIImage* img=[UIImage imageNamed:@"2.png"];//原图
    UIEdgeInsets edge=UIEdgeInsetsMake(0, 10, 0,10);
    //UIImageResizingModeStretch:拉伸模式,通过拉伸UIEdgeInsets指定的矩形区域来填充图片
    //UIImageResizingModeTile:平铺模式,通过重复显示UIEdgeInsets指定的矩形区域来填充图
    img= [img resizableImageWithCapInsets:edge resizingMode:UIImageResizingModeStretch];
    self.imageView.image=img;
    
    52. 修改textFieldplaceholder字体颜色和大小
    
    textField.placeholder = @"username is in here!";  
    [textField setValue:[UIColor redColor] forKeyPath:@"_placeholderLabel.textColor"];  
    [textField setValue:[UIFont boldSystemFontOfSize:16] forKeyPath:@"_placeholderLabel.font"];
    
    53. 修改状态栏字体颜色
    
    只能设置两种颜色,黑色和白色,系统默认黑色
    设置为白色方法:
    (1)在plist里面添加Status bar style,值为UIStatusBarStyleLightContent(白色)或UIStatusBarStyleDefault(黑 色)
    (2)在Info.plist中设置UIViewControllerBasedStatusBarAppearance 为NO
    
    54. 去掉导航栏下边的黑线
    
    [self.navigationController.navigationBar setBackgroundImage:[[UIImage alloc] init] forBarMetrics:UIBarMetricsDefault];
    self.navigationController.navigationBar.shadowImage = [[UIImage alloc] init];
    55. 修改pagecontrol颜色
    
    _pageControl.currentPageIndicatorTintColor=SFQRedColor;
    _pageControl.pageIndicatorTintColor=SFQGrayColor;
    
    56. 去掉UITableView的section的粘性,使其不会悬停
    
    //有时候使用UITableView所实现的列表,会使用到section,但是又不希望它粘在最顶上而是跟随滚动而消失或者出现
    - (void)scrollViewDidScroll:(UIScrollView *)scrollView {  
        if (scrollView == _tableView) {  
            CGFloat sectionHeaderHeight = 36;
    
            if (scrollView.contentOffset.y <= sectionHeaderHeight && scrollView.contentOffset.y >= 0) {  
                scrollView.contentInset = UIEdgeInsetsMake(-scrollView.contentOffset.y, 0, 0, 0);  
            } else if (scrollView.contentOffset.y >= sectionHeaderHeight) {  
                scrollView.contentInset = UIEdgeInsetsMake(-sectionHeaderHeight, 0, 0, 0);  
            }  
        }  
    }
    
    57. 通过2D仿射函数实现小的动画效果(变大缩小) --可用于自定义pageControl中
    
    [UIView animateWithDuration:0.3 animations:^{
           imageView.transform = CGAffineTransformMakeScale(2, 2);
           } completion:^(BOOL finished) {
           imageView.transform = CGAffineTransformMakeScale(1.0, 1.0);
           }];
    
    58. UIImage与字符串互转
    
    //图片转字符串  
    -(NSString *)UIImageToBase64Str:(UIImage *) image  
    {  
        NSData *data = UIImageJPEGRepresentation(image, 1.0f);  
        NSString *encodedImageStr = [data base64EncodedStringWithOptions:NSDataBase64Encoding64CharacterLineLength];  
        return encodedImageStr;  
    }
    
    //字符串转图片  
    -(UIImage *)Base64StrToUIImage:(NSString *)_encodedImageStr  
    {  
        NSData *_decodedImageData   = [[NSData alloc] initWithBase64Encoding:_encodedImageStr];  
        UIImage *_decodedImage      = [UIImage imageWithData:_decodedImageData];  
        return _decodedImage;  
    }
    
    59. 判断NSString中是否包含中文
    
    -(BOOL)isChinese:(NSString *)str{
        NSString *match=@"(^[\u4e00-\u9fa5]+$)";
        NSPredicate *predicate = [NSPredicate predicateWithFormat:@"SELF matches %@", match];
        return [predicate evaluateWithObject:str];
    }
    
    60. NSDate与NSString的相互转化
    
    -(NSString *)dateToString:(NSDate *)date {
      // 初始化时间格式控制器
      NSDateFormatter *matter = [[NSDateFormatter alloc] init];
      // 设置设计格式
      [matter setDateFormat:@"yyyy-MM-dd hh:mm:ss zzz"];
      // 进行转换
      NSString *dateStr = [matter stringFromDate:date];
      return dateStr;
    }
    -(NSDate *)stringToDate:(NSString *)dateStr {
    
      // 初始化时间格式控制器
      NSDateFormatter *matter = [[NSDateFormatter alloc] init];
      // 设置设计格式
      [matter setDateFormat:@"yyyy-MM-dd hh:mm:ss zzz"];
      // 进行转换
      NSDate *date = [matter dateFromString:dateStr];
      return date;
    }
    

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          本文标题: iOS 知识-常用小技巧(转)

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