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iOS开发小技巧

一、调用代码使APP进入后台,达到点击Home键的效果。(私有API)

[[UIApplication sharedApplication] performSelector:@selector(suspend)]; 

suspend的英文意思:悬、挂、暂停

二、获取UIWebView的高度 个人

(void)webViewDidFinishLoad:(UIWebView *)webView  {      CGFloat height = [[webView stringByEvaluatingJavaScriptFromString:@``"document.body.offsetHeight"``] floatValue];      CGRect frame = webView.frame;      webView.frame = CGRectMake(frame.origin.x, frame.origin.y, frame.size.width, height);  } 

三、UITableView收起键盘何必这么麻烦 一个属性搞定,效果好(UIScrollView同样可以使用) 以前是不是觉得[self.view endEditing:YES];很屌,这个下面的更屌。

yourTableView.keyboardDismissMode = UIScrollViewKeyboardDismissModeOnDrag; 

四、设置UILable 的行间距 和 计算带行间距的高度

/* UILabel* 展示的控件 (NSString*)str  内容 withFont:(float)font 字体大小 WithSpace:(float)space 行间距 */ //给UILabel设置行间距和字间距 -(void)setLabelSpace:(UILabel*)label withValue:(NSString*)str withFont:(float)font WithSpace:(float)space{ NSMutableParagraphStyle *paraStyle = [[NSMutableParagraphStyle alloc] init]; paraStyle.lineBreakMode = NSLineBreakByCharWrapping; paraStyle.alignment = NSTextAlignmentLeft; paraStyle.lineSpacing = space; //设置行间距 paraStyle.hyphenationFactor = 1.0; paraStyle.firstLineHeadIndent = 0.0; paraStyle.paragraphSpacingBefore = 0.0; paraStyle.headIndent = 0; paraStyle.tailIndent = 0; //设置字间距 NSKernAttributeName:@1.5f UIFont *tfont = [UIFont systemFontOfSize:font]; NSDictionary *dic = @{NSFontAttributeName:tfont, NSParagraphStyleAttributeName:paraStyle, NSKernAttributeName:@1.5f }; NSAttributedString *attributeStr = [[NSAttributedString alloc] initWithString:str attributes:dic]; label.attributedText = attributeStr; } /* 计算UILabel的高度(带有行间距的情况) (NSString*)str  内容 withFont:(float)font 字体大小 WithSpace:(float)space 行间距 (CGFloat)width  UILable的宽度 */ //计算UILabel的高度(带有行间距的情况) -(CGFloat)getSpaceLabelHeight:(NSString*)str withFont:(float)font withWidth:(CGFloat)width WithSpace:(float)space{ NSMutableParagraphStyle *paraStyle = [[NSMutableParagraphStyle alloc] init]; paraStyle.lineBreakMode = NSLineBreakByCharWrapping; paraStyle.alignment = NSTextAlignmentLeft; paraStyle.lineSpacing = space; paraStyle.hyphenationFactor = 1.0; paraStyle.firstLineHeadIndent = 0.0; paraStyle.paragraphSpacingBefore = 0.0; paraStyle.headIndent = 0; paraStyle.tailIndent = 0; UIFont *tfont = [UIFont systemFontOfSize:font]; NSDictionary *dic = @{NSFontAttributeName:tfont, NSParagraphStyleAttributeName:paraStyle, NSKernAttributeName:@1.5f }; CGSize size = [str boundingRectWithSize:CGSizeMake(width, CGFLOAT_MAX) options:NSStringDrawingUsesLineFragmentOrigin attributes:dic context:nil].size; return size.height; } 

五、 禁止程序运行时自动锁屏

[[UIApplication sharedApplication] setIdleTimerDisabled:YES]; 

六、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。 

七、修改textFieldplaceholder字体颜色和大小

textField.placeholder = @``"请输入用户名"``;  [textField setValue:[UIColor redColor] forKeyPath:@``"_placeholderLabel.textColor"``];  [textField setValue:[UIFont boldSystemFontOfSize:16] forKeyPath:@``"_placeholderLabel.font"``]; 

八、禁止textField和textView的复制粘贴菜单

-(BOOL)canPerformAction:(SEL)action withSender:(id)sender{    ``if` `([UIMenuController sharedMenuController]) {      [UIMenuController sharedMenuController].menuVisible = NO;    }    ``return` `NO;} 

九、级三级页面隐藏系统tabbar 1、单个处理

YourViewController *yourVC = [YourViewController ``new``];yourVC.hidesBottomBarWhenPushed = YES;[self.navigationController pushViewController:yourVC animated:YES]; 

十、取消系统的返回手势

self.navigationController.interactivePopGestureRecognizer.enabled = NO; 

十一、百度坐标跟火星坐标相互转换

//百度转火星坐标 + (CLLocationCoordinate2D )bdToGGEncrypt:(CLLocationCoordinate2D)coord { double x = coord.longitude - 0.0065, y = coord.latitude - 0.006; double z = sqrt(x * x + y * y) - 0.00002 * sin(y * M_PI); double theta = atan2(y, x) - 0.000003 * cos(x * M_PI); CLLocationCoordinate2D transformLocation ; transformLocation.longitude = z * cos(theta); transformLocation.latitude = z * sin(theta); return transformLocation; } //火星坐标转百度坐标 + (CLLocationCoordinate2D )ggToBDEncrypt:(CLLocationCoordinate2D)coord { double x = coord.longitude, y = coord.latitude; double z = sqrt(x * x + y * y) + 0.00002 * sin(y * M_PI); double theta = atan2(y, x) + 0.000003 * cos(x * M_PI); CLLocationCoordinate2D transformLocation ; transformLocation.longitude = z * cos(theta) + 0.0065; transformLocation.latitude = z * sin(theta) + 0.006; return transformLocation; } 

十二、添加pch文件的步聚

1:创建新文件 ios->other->PCH file,创建一个pch文件:“工程名-Prefix.pch”:

2:将building setting中的precompile header选项的路径添加“$(SRCROOT)/项目名称/pch文件名”(例如:$(SRCROOT)/LotteryFive/LotteryFive-Prefix.pch)

3:将Precompile Prefix Header为YES,预编译后的pch文件会被缓存起来,可以提高编译速度

十三、关于Masonry
a:

make.equalTo 或 make.greaterThanOrEqualTo (至多) 或 make.lessThanOrEqualTo(至少) make.left.greaterThanOrEqualTo(label); make.left.greaterThanOrEqualTo(label.mas_left); //width >= 200 && width <= 400 make.width.greaterThanOrEqualTo(@200); make.width.lessThanOrEqualTo(@400) 

b:masequalTo 和 equalTo 区别:masequalTo 比equalTo多了类型转换操作,一般来说,大多数时候两个方法都是 通用的,但是对于数值元素使用mas_equalTo。对于对象或是多个属性的处理,使用equalTo。特别是多个属性时,必须使用equalTo

c:一些简便赋值

// make top = superview.top + 5, left = superview.left + 10, // bottom = superview.bottom - 15, right = superview.right - 20 make.edges.equalTo(superview).insets(UIEdgeInsetsMake(5, 10, 15, 20)) // make width and height greater than or equal to titleLabel make.size.greaterThanOrEqualTo(titleLabel) // make width = superview.width + 100, height = superview.height - 50 make.size.equalTo(superview).sizeOffset(CGSizeMake(100, -50)) // make centerX = superview.centerX - 5, centerY = superview.centerY + 10 make.center.equalTo(superview).centerOffset(CGPointMake(-5, 10)) d:and关键字运用 make.left.right.and.bottom.equalTo(superview); make.top.equalTo(otherView); e:优先;优先权(.priority,.priorityHigh,.priorityMedium,.priorityLow) .priority允许您指定一个确切的优先级 .priorityHigh 等价于UILayoutPriorityDefaultHigh .priorityMedium 介于高跟低之间 .priorityLow 等价于UILayoutPriorityDefaultLow 

实例:

make.left.greaterThanOrEqualTo(label.mas_left).with.priorityLow(); make.top.equalTo(label.mas_top).with.priority(600); g:使用mas_makeConstraints创建constraint后,你可以使用局部变量或属性来保存以便下次引用它;如果创建多个constraints,你可以采用数组来保存它们 // 局部或者全局 @property (nonatomic, strong) MASConstraint *topConstraint; // 创建约束并赋值 [view1 mas_makeConstraints:^(MASConstraintMaker *make) { self.topConstraint = make.top.equalTo(superview.mas_top).with.offset(padding.top); make.left.equalTo(superview.mas_left).with.offset(padding.left); }]; // 过后可以直接访问self.topConstraint [self.topConstraint uninstall]; h:mas_updateConstraints更新约束,有时你需要更新constraint(例如,动画和调试)而不是创建固定constraint,可以使用mas_updateConstraints方法 - (void)updateConstraints { [self.growingButton mas_updateConstraints:^(MASConstraintMaker *make) { make.center.equalTo(self); make.width.equalTo(@(self.buttonSize.width)).priorityLow(); make.height.equalTo(@(self.buttonSize.height)).priorityLow(); make.width.lessThanOrEqualTo(self); make.height.lessThanOrEqualTo(self); }]; //调用父updateConstraints [super updateConstraints]; } i:mas_remakeConstraints更新约束,mas_remakeConstraints与mas_updateConstraints比较相似,都是更新constraint。不过,mas_remakeConstraints是删除之前constraint,然后再添加新的constraint(适用于移动动画);而mas_updateConstraints只是更新constraint的值。 - (void)changeButtonPosition { [self.button mas_remakeConstraints:^(MASConstraintMaker *make) { make.size.equalTo(self.buttonSize); if (topLeft) { make.top.and.left.offset(10); } else { make.bottom.and.right.offset(-10); } }]; } 

十四、UIWebView在IOS9下底部出现黑边解决方式

UIWebView底部的黑条很难看(在IOS8下不会,在IOS9会出现),特别是在底部还有透明控件的时候,隐藏的做法其实很简单,只需要将opaque设为NO,背景色设为clearColor即可

十五、数组逆序遍历

1、枚举法

NSArray *array = @[@"1",@"2",@"3",@"5",@"6"]; [array enumerateObjectsWithOptions:NSEnumerationReverse usingBlock:^(id  _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) { NSLog(@"%@",obj); }]; 

2、for循环

NSArray*array=@[@"1",@"2",@"3",@"5",@"6"]; for (NSInteger index = array.count-1; index>=0; index--) { NSLog(@"%@",array[index]); } 

十六、把时间字符串2015-04-10格式化日期转为NSDate类型

参考答案:

NSString *timeStr = @"2015-04-10"; NSDateFormatter *formatter = [[NSDateFormatter alloc] init]; formatter.dateFormat = @"yyyy-MM-dd"; formatter.timeZone = [NSTimeZone defaultTimeZone]; NSDate *date = [formatter dateFromString:timeStr]; // 2015-04-09 16:00:00 +0000 NSLog(@"%@", date); 

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