iOS小技巧总结(持续更新)

释放双眼,带上耳机,听听看~!

UITableView的Group样式下顶部空白处理


//分组列表头部空白处理
UIView *view = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 0, 0.1)];
self.tableView.tableHeaderView = view;

获取某个view所在的控制器


- (UIViewController *)viewController
{
UIViewController *viewController = nil;
UIResponder *next = self.nextResponder;
while (next)
{
if ([next isKindOfClass:[UIViewController class]])
{
viewController = (UIViewController *)next;
break;
}
next = next.nextResponder;
}
return viewController;
}

两种方法删除NSUserDefaults所有记录


  • 方法一
NSString *appDomain = [[NSBundle mainBundle] bundleIdentifier];
[[NSUserDefaults standardUserDefaults] removePersistentDomainForName:appDomain];
  • 方法二
- (void)resetDefaults
{
NSUserDefaults * defs = [NSUserDefaults standardUserDefaults];
NSDictionary * dict = [defs dictionaryRepresentation];
for (id key in dict)
{
[defs removeObjectForKey:key];
}
[defs synchronize];
}

打印系统所有已注册的字体名称


#pragma mark - 打印系统所有已注册的字体名称
void enumerateFonts()
{
for(NSString *familyName in [UIFont familyNames])
{
NSLog(@"%@",familyName);
NSArray *fontNames = [UIFont fontNamesForFamilyName:familyName];
for(NSString *fontName in fontNames)
{
NSLog(@"t|- %@",fontName);
}
}
}

获取图片某一点的颜色



- (UIColor*) getPixelColorAtLocation:(CGPoint)point inImage:(UIImage *)image
{
UIColor* color = nil;
CGImageRef inImage = image.CGImage;
CGContextRef cgctx = [self createARGBBitmapContextFromImage:inImage];
if (cgctx == NULL) {
return nil; /* error */
}
size_t w = CGImageGetWidth(inImage);
size_t h = CGImageGetHeight(inImage);
CGRect rect = {{0,0},{w,h}};
CGContextDrawImage(cgctx, rect, inImage);
unsigned char* data = CGBitmapContextGetData (cgctx);
if (data != NULL) {
int offset = 4*((w*round(point.y))+round(point.x));
int alpha =  data[offset];
int red = data[offset+1];
int green = data[offset+2];
int blue = data[offset+3];
color = [UIColor colorWithRed:(red/255.0f) green:(green/255.0f) blue:
(blue/255.0f) alpha:(alpha/255.0f)];
}
CGContextRelease(cgctx);
if (data) {
free(data);
}
return color;
}

字符串反转


  • 第一种:
- (NSString *)reverseWordsInString:(NSString *)str
{
NSMutableString *newString = [[NSMutableString alloc] initWithCapacity:str.length];
for (NSInteger i = str.length - 1; i >= 0 ; i --)
{
unichar ch = [str characterAtIndex:i];
[newString appendFormat:@"%c", ch];
}
return newString;
}
  • 第二种:
- (NSString*)reverseWordsInString:(NSString*)str
{
NSMutableString *reverString = [NSMutableString stringWithCapacity:str.length];
[str enumerateSubstringsInRange:NSMakeRange(0, str.length) options:NSStringEnumerationReverse | NSStringEnumerationByComposedCharacterSequences  usingBlock:^(NSString *substring, NSRange substringRange, NSRange enclosingRange, BOOL *stop) {
[reverString appendString:substring];
}];
return reverString;
}

禁止锁屏


默认情况下,当设备一段时间没有触控动作时,iOS会锁住屏幕。但有一些应用是不需要锁屏的,比如视频播放器。

[UIApplication sharedApplication].idleTimerDisabled = YES;

[[UIApplication sharedApplication] setIdleTimerDisabled:YES];

模态推出透明界面



UIViewController *vc = [[UIViewController alloc] init];
UINavigationController *na = [[UINavigationController alloc] initWithRootViewController:vc];
if ([[[UIDevice currentDevice] systemVersion] floatValue] >= 8.0)
{
na.modalPresentationStyle = UIModalPresentationOverCurrentContext;
}
else
{
self.modalPresentationStyle=UIModalPresentationCurrentContext;
}
[self presentViewController:na animated:YES completion:nil];

Xcode调试不显示内存占用


editSCheme 里面有个选项叫叫做 enable zoombie Objects取消选中

显示隐藏文件

  • 显示
defaults write com.apple.finder AppleShowAllFiles -bool true
killall Finder
  • 隐藏
defaults write com.apple.finder AppleShowAllFiles -bool false
killall Finder

iOS跳转到App Store下载应用评分


[[UIApplication sharedApplication] openURL:[NSURL URLWithString:@"itms-apps://itunes.apple.com/WebObjects/MZStore.woa/wa/viewContentsUserReviews?type=Purple+Software&id=APPID"]];

iOS 获取汉字的拼音


+ (NSString *)transform:(NSString *)chinese
{
//将NSString装换成NSMutableString
NSMutableString *pinyin = [chinese mutableCopy];
//将汉字转换为拼音(带音标)
CFStringTransform((__bridge CFMutableStringRef)pinyin, NULL, kCFStringTransformMandarinLatin, NO);
NSLog(@"%@", pinyin);
//去掉拼音的音标
CFStringTransform((__bridge CFMutableStringRef)pinyin, NULL, kCFStringTransformStripCombiningMarks, NO);
NSLog(@"%@", pinyin);
//返回最近结果
return pinyin;
}

手动更改iOS状态栏的颜色


- (void)setStatusBarBackgroundColor:(UIColor *)color
{
UIView *statusBar = [[[UIApplication sharedApplication] valueForKey:@"statusBarWindow"] valueForKey:@"statusBar"];
if ([statusBar respondsToSelector:@selector(setBackgroundColor:)])
{
statusBar.backgroundColor = color;
}
}

判断当前ViewController是push还是present的方式显示的


NSArray *viewcontrollers=self.navigationController.viewControllers;
if (viewcontrollers.count > 1)
{
if ([viewcontrollers objectAtIndex:viewcontrollers.count - 1] == self)
{
//push方式
[self.navigationController popViewControllerAnimated:YES];
}
}
else
{
//present方式
[self dismissViewControllerAnimated:YES completion:nil];
}

获取实际使用的LaunchImage图片


- (NSString *)getLaunchImageName
{
CGSize viewSize = self.window.bounds.size;
// 竖屏
NSString *viewOrientation = @"Portrait";
NSString *launchImageName = nil;
NSArray* imagesDict = [[[NSBundle mainBundle] infoDictionary] valueForKey:@"UILaunchImages"];
for (NSDictionary* dict in imagesDict)
{
CGSize imageSize = CGSizeFromString(dict[@"UILaunchImageSize"]);
if (CGSizeEqualToSize(imageSize, viewSize) && [viewOrientation isEqualToString:dict[@"UILaunchImageOrientation"]])
{
launchImageName = dict[@"UILaunchImageName"];
}
}
return launchImageName;
}

iOS在当前屏幕获取第一响应


UIWindow * keyWindow = [[UIApplication sharedApplication] keyWindow];
UIView * firstResponder = [keyWindow performSelector:@selector(firstResponder)];

判断对象是否遵循了某协议



if ([self.selectedController conformsToProtocol:@protocol(RefreshPtotocol)])
{
[self.selectedController performSelector:@selector(onTriggerRefresh)];
}

判断view是不是指定视图的子视图


BOOL isView = [textView isDescendantOfView:self.view];

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(@"%fn%fn%fn%f",sum,avg,max,min);

修改UITextField中Placeholder的文字颜色


[textField setValue:[UIColor redColor] forKeyPath:@"_placeholderLabel.textColor"];

关于NSDateFormatter的格式


  • G: 公元时代,例如AD公元
  • yy: 年的后2位
  • yyyy: 完整年
  • MM: 月,显示为1-12
  • MMM: 月,显示为英文月份简写,如 Jan
  • MMMM: 月,显示为英文月份全称,如 Janualy
  • dd: 日,2位数表示,如02
  • d: 日,1-2位显示,如 2
  • EEE: 简写星期几,如Sun
  • EEEE: 全写星期几,如Sunday
  • aa: 上下午,AM/PM
  • H: 时,24小时制,0-23
  • K:时,12小时制,0-11
  • m: 分,1-2位
  • mm: 分,2位
  • s: 秒,1-2位
  • ss: 秒,2位
  • S: 毫秒

获取一个类的所有子类


+ (NSArray *) allSubclasses
{
Class myClass = [self class];
NSMutableArray *mySubclasses = [NSMutableArray array];
unsigned int numOfClasses;
Class *classes = objc_copyClassList(&numOfClasses;);
for (unsigned int ci = 0; ci < numOfClasses; ci++)
{
Class superClass = classes[ci];
do{
superClass = class_getSuperclass(superClass);
} while (superClass && superClass != myClass);
if (superClass)
{
[mySubclasses addObject: classes[ci]];
}
}
free(classes);
return mySubclasses;
}

监测IOS设备是否设置了代理,需要CFNetwork.framework


NSDictionary *proxySettings = (__bridge NSDictionary *)(CFNetworkCopySystemProxySettings());
NSArray *proxies = (__bridge NSArray *)(CFNetworkCopyProxiesForURL((__bridge CFURLRef _Nonnull)([NSURL URLWithString:@"http://www.baidu.com"]), (__bridge CFDictionaryRef _Nonnull)(proxySettings)));
NSLog(@"n%@",proxies);
NSDictionary *settings = proxies[0];
NSLog(@"%@",[settings objectForKey:(NSString *)kCFProxyHostNameKey]);
NSLog(@"%@",[settings objectForKey:(NSString *)kCFProxyPortNumberKey]);
NSLog(@"%@",[settings objectForKey:(NSString *)kCFProxyTypeKey]);
if ([[settings objectForKey:(NSString *)kCFProxyTypeKey] isEqualToString:@"kCFProxyTypeNone"])
{
NSLog(@"没代理");
}
else
{
NSLog(@"设置了代理");
}

取消UICollectionView的隐式动画


UICollectionView在reloadItems的时候,默认会附加一个隐式的fade动画,有时候很讨厌,尤其是当你的cell是复合cell的情况下(比如cell使用到了UIStackView)。

  • 下面几种方法都可以帮你去除这些动画
    • 方法一
      [UIView performWithoutAnimation:^{
      [collectionView reloadItemsAtIndexPaths:@[[NSIndexPath    indexPathForItem:index inSection:0]]];
      }];
    • 方法二
      [UIView animateWithDuration:0 animations:^{
      [collectionView performBatchUpdates:^{
      [collectionView reloadItemsAtIndexPaths:@[[NSIndexPath indexPathForItem:index inSection:0]]];
      } completion:nil];
      }];
    • 方法三
      [UIView setAnimationsEnabled:NO];
      [self.trackPanel performBatchUpdates:^{
      [collectionView reloadItemsAtIndexPaths:@[[NSIndexPath indexPathForItem:index inSection:0]]];
      } completion:^(BOOL finished) {
      [UIView setAnimationsEnabled:YES];
      }];

让Xcode的控制台支持LLDB类型的打印


  • 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

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

UIImage 占用内存大小



UIImage *image = [UIImage imageNamed:@"aa"];
NSUInteger size  = CGImageGetHeight(image.CGImage) * CGImageGetBytesPerRow(image.CGImage);

GCD timer定时器


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, ^{
//@"倒计时结束,关闭"
dispatch_source_cancel(timer);
dispatch_async(dispatch_get_main_queue(), ^{
});
});
dispatch_resume(timer);

图片上绘制文字 写一个UIImage的category

- (UIImage *)imageWithTitle:(NSString *)title fontSize:(CGFloat)fontSize
{
//画布大小
CGSize size=CGSizeMake(self.size.width,self.size.height);
//创建一个基于位图的上下文
UIGraphicsBeginImageContextWithOptions(size,NO,0.0);//opaque:NO  scale:0.0
[self drawAtPoint:CGPointMake(0.0,0.0)];
//文字居中显示在画布上
NSMutableParagraphStyle* paragraphStyle = [[NSParagraphStyle defaultParagraphStyle] mutableCopy];
paragraphStyle.lineBreakMode = NSLineBreakByCharWrapping;
paragraphStyle.alignment=NSTextAlignmentCenter;//文字居中
//计算文字所占的size,文字居中显示在画布上
CGSize sizeText=[title boundingRectWithSize:self.size options:NSStringDrawingUsesLineFragmentOrigin
attributes:@{NSFontAttributeName:[UIFont systemFontOfSize:fontSize]}context:nil].size;
CGFloat width = self.size.width;
CGFloat height = self.size.height;
CGRect rect = CGRectMake((width-sizeText.width)/2, (height-sizeText.height)/2, sizeText.width, sizeText.height);
//绘制文字
[title drawInRect:rect withAttributes:@{ NSFontAttributeName:[UIFont systemFontOfSize:fontSize],NSForegroundColorAttributeName:[ UIColor whiteColor],NSParagraphStyleAttributeName:paragraphStyle}];
//返回绘制的新图形
UIImage *newImage= UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return newImage;
}

查找一个视图的所有子视图


- (NSMutableArray *)allSubViewsForView:(UIView *)view
{
NSMutableArray *array = [NSMutableArray arrayWithCapacity:0];
for (UIView *subView in view.subviews)
{
[array addObject:subView];
if (subView.subviews.count > 0)
{
[array addObjectsFromArray:[self allSubViewsForView:subView]];
}
}
return array;
}

 

更新

iOS cell添加点击时改变字体的颜色及背景

  cell.selectedBackgroundView.backgroundColor = [UIColor whiteColor];//选中后变换,色彩的变换
cell.textLabel.highlightedTextColor = [UIColor whiteColor];//选中字体颜色
cell.textLabel.textColor = [UIColor whiteColor];
cell.backgroundView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"cc"]];        cell.selectedBackgroundView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"cc_no"]];//选中后变换,图片的变换

 

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