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iOS面试题知识小集分析

iOS面试题知识小集分析

作者: 冬天里寒风起 | 来源:发表于2018-05-31 15:06 被阅读85次

    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

    (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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