iOS学习笔记之开发实用小技巧(持续更新)

解决同时按两个按钮进入两个View的问题

[button setExclusiveTouch:YES];

在6p模拟器上输出宽度是414，在6p真机上输出是375。是测试机本身设置的问题，到 设置->显示与亮度->显示模式，改为“标准”


修改tableViewCell选中状态的颜色

cell.selectedBackgroundView = [[UIView alloc] initWithFrame: cell.frame];
cell.selectedBackgroundView.backgroundColor = [UIColor whiteColor];

默认选中第一个cell

NSInteger selectedIndex = 0;
NSIndexPath *selectedIndexPath = [NSIndexPath indexPathForRow:selectedIndex inSection:0];
[self.tableView selectRowAtIndexPath:selectedIndexPath animated:NO scrollPosition:UITableViewScrollPositionNone];

修改textFieldplaceholder字体颜色和大小

textField.placeholder = @"iOS";
[textField setValue:[UIColor redColor] forKeyPath:@"_placeholderLabel.textColor"];
[textField setValue:[UIFont boldSystemFontOfSize:16] forKeyPath:@"_placeholderLabel.font"];

关于右滑返回上一级
自定义leftBarButtonItem后无法启用系统自带的右滑返回，可以设置一下代码：

self.navigationController.interactivePopGestureRecognizer.delegate
= self;

取掉导航栏下边的黑线

[self.navigationController.navigationBar setBackgroundImage: [UIImage alloc]init]];
self.navigationController.navigationBar.shadowImage = [[UIImage alloc]init];

点击cell单元格的时候取消选中cell

func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {
self.tableView.deselectRowAtIndexPath(indexPath, animated: true)
}

UITextField默认显示键盘

textField.becomeFirstResponder()

UIImage设置圆角
说到设置圆角，你是否首先想到的是：

self.iconImage.layer.cornerRadius = 20;
self.iconImage.layer.masksToBounds = YES;

建议大家尽量不要这么设置, 因为使用图层过量会有卡顿现象, 特别是弄圆角或者阴影会很卡, 如果设置图片圆角我们一般用绘图来做:

/** 设置圆形图片(放到分类中使用) */
-(UIImage *)cutCircleImage {
UIGraphicsBeginImageContextWithOptions(self.size, NO, 0.0);
// 获取上下文
CGContextRef ctr = UIGraphicsGetCurrentContext();
// 设置圆形
CGRect rect = CGRectMake(0, 0, self.size.width, self.size.height);
CGContextAddEllipseInRect(ctr, rect);
// 裁剪
CGContextClip(ctr);
// 将图片画上去
[self drawInRect:rect];
UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return image;
}

这个方法就是设置圆角图片, 效率很高, 不会造成卡顿现象, 大家要把这个方法单独放到分类中使用


磁盘总空间大小
1.获取磁盘总空间大小

//磁盘总空间
+(CGFloat)diskOfAllSizeMBytes{
CGFloat size = 0.0;
NSError *error;
NSDictionary *dic = [[NSFileManager defaultManager]attributesOfFileSystemForPath:NSHomeDirectory() error:&error];
if (error) {
#ifdef DEBUG
NSLog(@"error: %@", error.localizedDescription);
#endif
}else{
NSNumber *number = [dic objectForKey:NSFileSystemSize];
size = [number floatValue]/1024/1024;
}
return size;
}

2.获取磁盘可用空间大小

//磁盘可用空间
+(CGFloat)diskOfFreeSizeMBytes{
CGFloat size = 0.0;
NSError *error;
NSDictionary *dic = [[NSFileManager defaultManager] attributesOfFileSystemForPath:NSHomeDirectory() error:&error];
if (error) {
#ifdef DEBUG
NSLog(@"error: %@", error.localizedDescription);
#endif
}else{
NSNumber *number = [dic objectForKey:NSFileSystemFreeSize];
size = [number floatValue]/1024/1024;
}
return size;
}

3.获取指定路径下某个文件的大小

//获取文件大小
+(long long)fileSizeAtPath:(NSString *)filePath{
NSFileManager *fileManager = [NSFileManager defaultManager];
if (![fileManager fileExistsAtPath:filePath]) return 0;
return [[fileManager attributesOfItemAtPath:filePath error:nil] fileSize];
}

4.获取文件夹下所有文件的大小

//获取文件夹下所有文件的大小
+(long long)folderSizeAtPath:(NSString *)folderPath{
NSFileManager *fileManager = [NSFileManager defaultManager];
if (![fileManager fileExistsAtPath:folderPath]) return 0;
NSEnumerator *filesEnumerator = [[fileManager subpathsAtPath:folderPath] objectEnumerator];
NSString *fileName;
long long folerSize = 0;
while ((fileName = [filesEnumerator nextObject]) != nil) {
NSString *filePath = [folderPath stringByAppendingPathComponent:fileName];
folerSize += [self fileSizeAtPath:filePath];
}
return folerSize;
}

NSString处理
--获取字符串(或汉字)首字母

//获取字符串(或汉字)首字母
+(NSString *)firstCharacterWithString:(NSString *)string{
NSMutableString *str = [NSMutableString stringWithString:string];
CFStringTransform((CFMutableStringRef)str, NULL, kCFStringTransformMandarinLatin, NO);
CFStringTransform((CFMutableStringRef)str, NULL, kCFStringTransformStripDiacritics, NO);
NSString *pingyin = [str capitalizedString];
return [pingyin substringToIndex:1];
}

--字符串反转

-(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;
}

--字符串按多个符号分割

NSString *str = @“abc,def.ghi”
NSCharacterSet *set = [NSCharacterSet characterSetWithCharactersInString:@“,.”];
NSLog(@“%@”,[str componentsSeparatedByCharactersInSet:set]);

--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;
}

--字符串中是否含有中文

+(BOOL)checkIsChinese:(NSString *)string
{
for (int i=0; i<string.length; i++)
{
unichar ch = [string characterAtIndex:i];
if (0x4E00 <= ch  && ch <= 0x9FA5)
{
return YES;
}
}
return NO;
}

UILabel修改行距,首行缩进

1.UILabel修改文字行距,首行缩进
lineSpacing: 行间距
firstLineHeadIndent：首行缩进
font: 字体
textColor: 字体颜色
－ (NSDictionary *)settingAttributesWithLineSpacing:(CGFloat)lineSpacing FirstLineHeadIndent:(CGFloat)firstLineHeadIndent Font:(UIFont *)font TextColor:(UIColor *)textColor{
//分段样式
NSMutableParagraphStyle *paragraphStyle = [[NSMutableParagraphStyle alloc] init];
//行间距
paragraphStyle.lineSpacing = lineSpacing;
//首行缩进
paragraphStyle.firstLineHeadIndent = firstLineHeadIndent;
//富文本样式
NSDictionary *attributeDic = @{
NSFontAttributeName : font,
NSParagraphStyleAttributeName : paragraphStyle,
NSForegroundColorAttributeName : textColor
};
return attributeDic;
}

删除NSUserDefaults所有记录
第一种：

NSString *appDomain = [[NSBundle mainBundle] bundleIdentifier];
[[NSUserDefaults standardUserDefaults] removePersistentDomainForName:appDomain];

第二种：

-(void)resetDefaults
{
NSUserDefaults * defs = [NSUserDefaults standardUserDefaults];
NSDictionary * dict = [defs dictionaryRepresentation];
for (id key in dict)
{
[defs removeObjectForKey:key];
}
[defs synchronize];
}

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];

隐藏/显示文件

//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在当前屏幕获取第一响应

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

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);

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

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];

NSMutableArray *sums = [NSMutableArray array];
for (int i = 0; i < str.length; i ++) {
NSString *substr = [str substringWithRange:NSMakeRange(i, 1)];
NSString *a = [dictionary objectForKey:substr];
NSString *b = digits[str.length -i-1];
NSString *sum = [a stringByAppendingString:b];
if ([a isEqualToString:chinese_numerals[9]])
{
if([b isEqualToString:digits[4]] || [b isEqualToString:digits[8]])
{
sum = b;
if ([[sums lastObject] isEqualToString:chinese_numerals[9]])
{
[sums removeLastObject];
}
}else
{
sum = chinese_numerals[9];
}

if ([[sums lastObject] isEqualToString:sum])
{
continue;
}
}

[sums addObject:sum];
}

NSString *sumStr = [sums componentsJoinedByString:@""];
NSString *chinese = [sumStr substringToIndex:sumStr.length-1];
NSLog(@"%@",str);
NSLog(@"%@",chinese);
return chinese;
}

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

UIView设置部分圆角
你是不是也遇到过这样的问题，一个button或者label，只要右边的两个角圆角，或者只要一个圆角。该怎么办呢。这就需要图层蒙版来帮助我们了

CGRect rect = view.bounds;
CGSize radio = CGSizeMake(30, 30);//圆角尺寸
UIRectCorner corner = UIRectCornerTopLeft|UIRectCornerTopRight;//这只圆角位置
UIBezierPath *path = [UIBezierPath bezierPathWithRoundedRect:rect byRoundingCorners:corner cornerRadii:radio];
CAShapeLayer *masklayer = [[CAShapeLayer alloc]init];//创建shapelayer
masklayer.frame = view.bounds;
masklayer.path = path.CGPath;//设置路径
view.layer.mask = masklayer;

取上整与取下整

floor(x),有时候也写做Floor(x)，其功能是“下取整”，即取不大于x的最大整数 例如：
x=3.14，floor(x)=3
y=9.99999，floor(y)=9
与floor函数对应的是ceil函数，即上取整函数。
ceil函数的作用是求不小于给定实数的最小整数。
ceil(2)=ceil(1.2)=cei(1.5)=2.00
floor函数与ceil函数的返回值均为double型

去掉导航栏返回的back标题

[[UIBarButtonItemappearance]setBackButtonTitlePositionAdjustment:UIOffsetMake(0, -60)forBarMetrics:UIBarMetricsDefault];

navigationBar变为纯透明

//第一种方法
//导航栏纯透明
[self.navigationBar setBackgroundImage:[UIImage new] forBarMetrics:UIBarMetricsDefault];
//去掉导航栏底部的黑线
self.navigationBar.shadowImage = [UIImage new];
//第二种方法
[[self.navigationBar subviews] objectAtIndex:0].alpha = 0;

tabBar同理

[self.tabBar setBackgroundImage:[UIImage new]];
self.tabBar.shadowImage = [UIImage new];

navigationBar根据滑动距离的渐变色实现

第一种：

-(void)scrollViewDidScroll:(UIScrollView *)scrollView
{
CGFloat offsetToShow = 200.0;//滑动多少就完全显示
CGFloat alpha = 1 - (offsetToShow - scrollView.contentOffset.y) / offsetToShow;
[[self.navigationController.navigationBar subviews] objectAtIndex:0].alpha = alpha;
}

第二种：

-(void)scrollViewDidScroll:(UIScrollView *)scrollView
{
CGFloat offsetToShow = 200.0;
CGFloat alpha = 1 - (offsetToShow - scrollView.contentOffset.y) / offsetToShow;
[self.navigationController.navigationBar setShadowImage:[UIImage new]];
[self.navigationController.navigationBar setBackgroundImage:[self imageWithColor:[[UIColor orangeColor]colorWithAlphaComponent:alpha]] forBarMetrics:UIBarMetricsDefault];
}
//生成一张纯色的图片
-(UIImage *)imageWithColor:(UIColor *)color
{
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();

return theImage;
}

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。
描述文件路径
~/Library/MobileDevice/Provisioning Profiles

dispatch_group的使用

dispatch_group_t dispatchGroup = dispatch_group_create();
dispatch_group_enter(dispatchGroup);
dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(1 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
NSLog(@"第一个请求完成");
dispatch_group_leave(dispatchGroup);
});

dispatch_group_enter(dispatchGroup);

dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(10 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
NSLog(@"第二个请求完成");
dispatch_group_leave(dispatchGroup);
});

dispatch_group_notify(dispatchGroup, dispatch_get_main_queue(), ^(){
NSLog(@"请求完成");
});