<p><img src="https://simg.open-open.com/show/5260173ddd50082fc9d727eb2ac5e48a.jpg" alt="iOS 知识-常用小技巧大杂烩" width="9232" height="3843"></p>    <p><br> <strong>1，打印View所有子视图</strong></p>    <pre>  <code class="language-objectivec">po [[self view]recursiveDescription]</code></pre>    <p><strong>2，layoutSubviews调用的调用时机</strong></p>    <pre>  <code class="language-objectivec">* 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</code></pre>    <p><strong>3，NSString过滤特殊字符</strong></p>    <pre>  <code class="language-objectivec">// 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];</code></pre>    <p><strong>4，TransForm属性</strong></p>    <pre>  <code class="language-objectivec">//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;</code></pre>    <p><strong>5，去掉分割线多余15像素</strong></p>    <pre>  <code class="language-objectivec">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];          }  }</code></pre>    <p><strong>6，计算方法耗时时间间隔</strong></p>    <pre>  <code class="language-objectivec">// 获取时间间隔  #define TICK   CFAbsoluteTime start = CFAbsoluteTimeGetCurrent();  #define TOCK   NSLog(@"Time: %f", CFAbsoluteTimeGetCurrent() - start)</code></pre>    <p><strong>7，Color颜色宏定义</strong></p>    <pre>  <code class="language-objectivec">// 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]  #define RGBACOLOR(r, g, b, a) [UIColor colorWithRed:(r)/255.0f green:(g)/255.0f blue:(b)/255.0f alpha:(a)]</code></pre>    <p><strong>8，Alert提示宏定义</strong></p>    <pre>  <code class="language-objectivec">#define Alert(_S_, ...) [[[UIAlertView alloc] initWithTitle:@"提示" message:[NSString stringWithFormat:(_S_), ##__VA_ARGS__] delegate:nil cancelButtonTitle:@"确定" otherButtonTitles:nil] show]</code></pre>    <p><strong>8，让 iOS 应用直接退出</strong></p>    <pre>  <code class="language-objectivec">- (void)exitApplication {      AppDelegate *app = [UIApplication sharedApplication].delegate;      UIWindow *window = app.window;        [UIView animateWithDuration:1.0f animations:^{          window.alpha = 0;      } completion:^(BOOL finished) {          exit(0);      }];  }</code></pre>    <p><strong>8，NSArray 快速求总和 最大值 最小值 和 平均值 </strong></p>    <pre>  <code class="language-objectivec">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);</code></pre>    <p><strong>9，修改Label中不同文字颜色</strong></p>    <pre>  <code class="language-objectivec">- (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;  }</code></pre>    <p><strong>10，播放声音</strong></p>    <pre>  <code class="language-objectivec">  #import<AVFoundation/AVFoundation.h>     //  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];</code></pre>    <p><strong>11，检测是否IPad Pro</strong></p>    <pre>  <code class="language-objectivec">- (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_EPSILON;        BOOL hasIPadProHeight = fabs(height - 1366.f) < DBL_EPSILON;      return isIpad && hasIPadProHeight && hasIPadProWidth;  }</code></pre>    <p><strong>11，修改Tabbar Item的属性</strong></p>    <pre>  <code class="language-objectivec">    // 修改标题位置      self.tabBarItem.titlePositionAdjustment = UIOffsetMake(0, -10);      // 修改图片位置      self.tabBarItem.imageInsets = UIEdgeInsetsMake(-3, 0, 3, 0);        // 批量修改属性      for (UIBarItem *item in self.tabBarController.tabBar.items) {          [item setTitleTextAttributes:[NSDictionary dictionaryWithObjectsAndKeys:                   [UIFont fontWithName:@"Helvetica" size:19.0], NSFontAttributeName, nil]                              forState:UIControlStateNormal];      }        // 设置选中和未选中字体颜色      [[UITabBar appearance] setShadowImage:[[UIImage alloc] init]];        //未选中字体颜色      [[UITabBarItem appearance] setTitleTextAttributes:@{NSForegroundColorAttributeName:[UIColor greenColor]} forState:UIControlStateNormal];        //选中字体颜色      [[UITabBarItem appearance] setTitleTextAttributes:@{NSForegroundColorAttributeName:[UIColor cyanColor]} forState:UIControlStateSelected];</code></pre>    <p><strong>12，NULL - nil - Nil - NSNULL的区别</strong></p>    <pre>  <code class="language-objectivec">* nil是OC的，空对象，地址指向空（0）的对象。对象的字面零值    * Nil是Objective-C类的字面零值    * NULL是C的，空地址，地址的数值是0，是个长整数    * NSNull用于解决向NSArray和NSDictionary等集合中添加空值的问题</code></pre>    <p><strong>11，去掉BackBarButtonItem的文字</strong></p>    <pre>  <code class="language-objectivec">[[UIBarButtonItem appearance] setBackButtonTitlePositionAdjustment:UIOffsetMake(0, -60)                                                           forBarMetrics:UIBarMetricsDefault];</code></pre>    <p><strong>12，控件不能交互的一些原因</strong></p>    <pre>  <code class="language-objectivec">1，控件的userInteractionEnabled = NO  2，透明度小于等于0.01，aplpha  3，控件被隐藏的时候，hidden = YES  4，子视图的位置超出了父视图的有效范围，子视图无法交互，设置了</code></pre>    <p><strong>12，修改UITextField中Placeholder的文字颜色</strong></p>    <pre>  <code class="language-objectivec">[text setValue:[UIColor redColor] forKeyPath:@"_placeholderLabel.textColor"];  }</code></pre>    <p><strong>13，视图的生命周期</strong></p>    <pre>  <code class="language-objectivec">1、 alloc 创建对象，分配空间  2、 init (initWithNibName) 初始化对象，初始化数据  3、 loadView 从nib载入视图 ，除非你没有使用xib文件创建视图  4、 viewDidLoad 载入完成，可以进行自定义数据以及动态创建其他控件  5、 viewWillAppear视图将出现在屏幕之前，马上这个视图就会被展现在屏幕上了  6、 viewDidAppear 视图已在屏幕上渲染完成    1、viewWillDisappear 视图将被从屏幕上移除之前执行  2、viewDidDisappear 视图已经被从屏幕上移除，用户看不到这个视图了  3、dealloc 视图被销毁，此处需要对你在init和viewDidLoad中创建的对象进行释放.    viewVillUnload－ 当内存过低，即将释放时调用；  viewDidUnload－当内存过低，释放一些不需要的视图时调用。</code></pre>    <p><strong>14，应用程序的生命周期</strong></p>    <pre>  <code class="language-objectivec">1，启动但还没进入状态保存 ：  - (BOOL)application:(UIApplication *)application willFinishLaunchingWithOptions:(NSDictionary *)launchOptions     2，基本完成程序准备开始运行：  - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions    3，当应用程序将要入非活动状态执行，应用程序不接收消息或事件，比如来电话了：  - (void)applicationWillResignActive:(UIApplication *)application     4，当应用程序入活动状态执行，这个刚好跟上面那个方法相反：  - (void)applicationDidBecomeActive:(UIApplication *)application       5，当程序被推送到后台的时候调用。所以要设置后台继续运行，则在这个函数里面设置即可：  - (void)applicationDidEnterBackground:(UIApplication *)application      6，当程序从后台将要重新回到前台时候调用，这个刚好跟上面的那个方法相反：  - (void)applicationWillEnterForeground:(UIApplication *)application      7，当程序将要退出是被调用，通常是用来保存数据和一些退出前的清理工作：  - (void)applicationWillTerminate:(UIApplication *)application</code></pre>    <p><strong>15，判断view是不是指定视图的子视图</strong></p>    <pre>  <code class="language-objectivec"> BOOL isView =  [textView isDescendantOfView:self.view];</code></pre>    <p><strong>16，判断对象是否遵循了某协议</strong></p>    <pre>  <code class="language-objectivec">if ([self.selectedController conformsToProtocol:@protocol(RefreshPtotocol)]) {      [self.selectedController performSelector:@selector(onTriggerRefresh)];  }</code></pre>    <p><strong>17，页面强制横屏</strong></p>    <pre>  <code class="language-objectivec">#pragma mark - 强制横屏代码  - (BOOL)shouldAutorotate{          //是否支持转屏             return NO;  }  - (UIInterfaceOrientationMask)supportedInterfaceOrientations{          //支持哪些转屏方向          return UIInterfaceOrientationMaskLandscape;  }  - (UIInterfaceOrientation)preferredInterfaceOrientationForPresentation{                     return UIInterfaceOrientationLandscapeRight;  }  - (BOOL)prefersStatusBarHidden{         return NO;  }</code></pre>    <p><strong>18，系统键盘通知消息</strong></p>    <pre>  <code class="language-objectivec">1、UIKeyboardWillShowNotification-将要弹出键盘  2、UIKeyboardDidShowNotification-显示键盘  3、UIKeyboardWillHideNotification-将要隐藏键盘  4、UIKeyboardDidHideNotification-键盘已经隐藏  5、UIKeyboardWillChangeFrameNotification-键盘将要改变frame  6、UIKeyboardDidChangeFrameNotification-键盘已经改变frame</code></pre>    <p><strong>19，关闭navigationController的滑动返回手势</strong></p>    <pre>  <code class="language-objectivec">self.navigationController.interactivePopGestureRecognizer.enabled = NO;</code></pre>    <p><strong>20，设置状态栏为任意的颜色</strong></p>    <pre>  <code class="language-objectivec">- (void)setStatusColor  {      UIView *statusBarView = [[UIView alloc] initWithFrame:CGRectMake(0, 0,[UIScreen mainScreen].bounds.size.width, 20)];      statusBarView.backgroundColor = [UIColor orangeColor];      [self.view addSubview:statusBarView];  }</code></pre>    <p><strong>21，让Xcode的控制台支持LLDB类型的打印</strong></p>    <pre>  <code class="language-objectivec">打开终端输入三条命令:      touch ~/.lldbinit      echo display @import UIKit >> ~/.lldbinit      echo target stop-hook add -o \"target stop-hook disable\" >> ~/.lldbinit</code></pre>    <p>下次重新运行项目，然后就不报错了。</p>    <p><img src="https://simg.open-open.com/show/b72454ef1e9da2e2d389e09a51812731.png" alt="iOS 知识-常用小技巧大杂烩" width="426" height="74"></p>    <p><br> <strong>22，Label行间距</strong></p>    <pre>  <code class="language-objectivec">-（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;  }</code></pre>    <p><strong>23，UIImageView填充模式</strong></p>    <pre>  <code class="language-objectivec">@"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</code></pre>    <p><strong>24，宏定义检测block是否可用</strong></p>    <pre>  <code class="language-objectivec">#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);</code></pre>    <p> </p>    <p>文／品味_生活（简书）<br> via：http://www.jianshu.com/p/7c3ee5e67d03<br>  </p>