iOS开发技巧

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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;

或

[[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(@"%f\n%f\n%f\n%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

iOS开发技巧

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原文地址：http://www.cnblogs.com/duzhaoquan/p/5865712.html