iOS开发过程遇到的问题及解决方法

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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;

UITableView的plain样式下，取消区头停滞效果

- (void)scrollViewDidScroll:(UIScrollView *)scrollView {    CGFloat sectionHeaderHeight = sectionHead.height;    if (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);    }}

那个，其实，还是用Group样式吧哈哈。

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

//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

Mac显示隐藏文件

//显示defaults write com.apple.finder AppleShowAllFiles -bool truekillall Finder//隐藏defaults write com.apple.finder AppleShowAllFiles -bool falsekillall 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++){    }} 

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");}

阿拉伯数字转中文格式

+(NSString *)translation:(NSString *)arebic{      NSString *str = arebic;    NSArray *arabic_numerals = @[@"1",@"2",@"3",@"4",@"5",@"6",@"7",@"8",@"9",@"0"];    NSArray *chinese_numerals = @[@"一",@"二",@"三",@"四",@"五",@"六",@"七",@"八",@"九",@"零"];    NSArray *digits = @[@"个",@"十",@"百",@"千",@"万",@"十",@"百",@"千",@"亿",@"十",@"百",@"千",@"兆"];    NSDictionary *dictionary = [NSDictionary dictionaryWithObjects:chinese_numerals forKeys:arabic_numerals];

Base64编码与NSString对象或NSData对象的转换

// C

reate NSData objectNSData *nsdata = [@"iOS Developer Tips encoded in Base64"  dataUsingEncoding:NSUTF8StringEncoding];// Get NSString from NSData object in Base64NSString *base64Encoded = [nsdata base64EncodedStringWithOptions:0];// Print the Base64 encoded stringNSLog(@"Encoded: %@", base64Encoded);// Let's go the other way...// NSData from the Base64 encoded strNSData *nsdataFromBase64String = [[NSData alloc]  initWithBase64EncodedString:base64Encoded options:0];// Decoded NSString from the NSDataNSString *base64Decoded = [[NSString alloc]  initWithData:nsdataFromBase64String encoding:NSUTF8StringEncoding];NSLog(@"Decoded: %@", base64Decoded);

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 ~/.lldbinitecho display @import UIKit >> ~/.lldbinitecho 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;}