百思不得其姐学习笔记

appearance 的使用注意点

+(void)load
{
    //appearance 通常在load中加载使用,若要操做控件,必须在UI没有显示的状况下去操做
    NSArray *array =@[self];
    UITabBarItem *tabBarItem =  [UITabBarItem appearanceWhenContainedInInstancesOfClasses:array];
    NSMutableDictionary *dict =[NSMutableDictionary dictionary];
    dict[NSForegroundColorAttributeName] = [UIColor whiteColor];
    [tabBarItem setTitleTextAttributes:dict forState:UIControlStateSelected];
    
    //设置字体大小  必须是在UIControlStateNormal 设置才有效果
    NSMutableDictionary *dict1 =[NSMutableDictionary dictionary];
    dict1[NSFontAttributeName] = [UIFont systemFontOfSize:13];
    [tabBarItem setTitleTextAttributes:dict1 forState:UIControlStateNormal];
}

若是直接用UIButton包装成UIBarButtonItem,会扩大点击区域

UIButton *btn =[UIButton buttonWithType:UIButtonTypeCustom];
[btn setImage:image forState:UIControlStateNormal];
[btn setImage:heightImage forState:UIControlStateHighlighted];
[btn addTarget:target action:action forControlEvents:UIControlEventTouchUpInside];
[btn sizeToFit];
//若是直接用UIButton包装成UIBarButtonItem,会扩大点击区域
// UIBarButtonItem *barbtn =[[UIBarButtonItem alloc]initWithCustomView:btn];
    
//阻止扩大点击区域的解决办法只有在外面再次包装一层UIview
UIView *uiview = [[UIView alloc]initWithFrame:btn.bounds];
[uiview addSubview:btn];
[[UIBarButtonItem alloc]initWithCustomView:uiview]

UIBarButtonItem:描述按钮具体的内容.<br>UINavigationItem:设置导航条上内容(左边,右边,中间). <br>TabBarItem: 设置tabBar上按钮内容(tabBarButton)

导航控制器滑动的失效分析以及解决,经打印发现代理作了别的事情,就先清除的了代理,

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view.
    self.interactivePopGestureRecognizer.delegate =nil;
}

//清除以后,发现会出现假死状态,再次判断只有非根控制下才能有效
#pragma UIGestureRecognizerDelegate
-(BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldReceiveTouch:(UITouch *)touch
{

    return  self.childViewControllers.count>1;
}

导航控制器实现全屏滑动返回

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view.
    
    
    UIPanGestureRecognizer *pan = [[UIPanGestureRecognizer alloc]initWithTarget:self.interactivePopGestureRecognizer.delegate action:@selector(handleNavigationTransition:)];
    [self.view addGestureRecognizer:pan];
    //控制手势何时触发,只有在非根控制器的时候才触发
    pan.delegate = self;
    //禁止以前手势
    self.interactivePopGestureRecognizer.enabled = NO;

}


#pragma UIGestureRecognizerDelegate
-(BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldReceiveTouch:(UITouch *)touch
{
    return  self.childViewControllers.count>1;
}

UITableView 的复用(由Xib 加载 Cell)

//首先进行注册
 [self.tableView registerNib:[UINib nibWithNibName:NSStringFromClass([TLYSubTagViewCell class]) bundle:nil] forCellReuseIdentifier:ID];
 //拿出来能够直接使用
 TLYSubTagViewCell *cell = [tableView dequeueReusableCellWithIdentifier:ID];

设置图片为圆角

self.imaView.layer.cornerRadius = 30;//30为图片的一半  设置为圆角
self.imaView.layer.masksToBounds = YES;//把多余的进行裁剪

设置UITableView 分割先全屏

//清空tabview的的间隙
 self.tableView.separatorInset = UIEdgeInsetsZero;
//清空cell自身的间隙
 cell.separatorInset = UIEdgeInsetsZero;

设置UITableView分割线的第二种方法思路:<br>前提要理解的是tableview的frame是先计算出来后,而后才调用了cellForRowAtIndexPath,作法是:首先将系统默认的分割线设置为none,将整个tableview的背景颜色设置为分割线颜色,而后重写cell的setframe方法.

//在tableview中写的
self.tableView.separatorStyle = UITableViewCellSeparatorStyleNone;
self.tableView.backgroundColor = [UIColor colorWithRed:220/256.0 green:220/256.0 blue:221/256.0 alpha:1];
//重写cell的setframe方法  1表示分割线的高度
-(void)setFrame:(CGRect)frame
{
    frame.size.height-=1;
    [super setFrame:frame];
}

修改UITextField的光标颜色,和占位字颜色

-(void)awakeFromNib
{
    [super awakeFromNib];
    //设置光标的颜色
    self.tintColor = [UIColor whiteColor];
    
    
    //监听编辑开始和结束
    [self addTarget:self action:@selector(touchBegin) forControlEvents:UIControlEventEditingDidBegin];
     [self addTarget:self action:@selector(touchEnd) forControlEvents:UIControlEventEditingDidEnd];
    
    //第一种方法
    NSMutableDictionary *dict =[NSMutableDictionary dictionary];
    dict[NSForegroundColorAttributeName] = [UIColor lightGrayColor];
    self.attributedPlaceholder = [[NSAttributedString alloc]initWithString:self.placeholder attributes:dict];
    
    //第二种方法,也能够直接利用kvc的方式拿到placeholder的lable
   UILabel *placeHolder = [self valueForKey:@"_placeholderLabel"];
  [placeHolder setTextColor:[UIColor lightGrayColor]];
}

//开始编辑 (第一种方法)
-(void)touchBegin{
    NSMutableDictionary *dict =[NSMutableDictionary dictionary];
    dict[NSForegroundColorAttributeName] = [UIColor whiteColor];
    self.attributedPlaceholder = [[NSAttributedString alloc]initWithString:self.placeholder attributes:dict];
}

///结束编辑(第一种方法)
-(void)touchEnd{
    NSMutableDictionary *dict =[NSMutableDictionary dictionary];
    dict[NSForegroundColorAttributeName] = [UIColor lightGrayColor];
    self.attributedPlaceholder = [[NSAttributedString alloc]initWithString:self.placeholder attributes:dict];
}

若是先设置颜色,placeHolderLable是nil的,为了防止这种状况,尽可能先保存颜色,利用runtime给系统增长一个属性,在设置占位文字的时候,同时把颜色设置上

+(void)load
{
    //方法进行交换   到时候直接调用setPlaceholder 便可直接设置颜色
    Method m1 = class_getInstanceMethod(self, @selector(setPlaceholder:));
     Method m2 = class_getInstanceMethod(self, @selector(setTly_PlaceHolder:));
    
    method_exchangeImplementations(m1, m2);

}

-(void)setPlaceHolderColor:(UIColor *)placeHolderColor
{
    UILabel *placeHolder = [self valueForKey:@"_placeholderLabel"];
    [placeHolder setTextColor:placeHolderColor];
    
    //若是先设置颜色,placeHolderLable是nil的,为了防止这种状况,尽可能先保存颜色,利用runtime给系统增长一个属性,在设置占位文字的时候,同时把颜色设置上
     objc_setAssociatedObject(self, @"placeHolderColor", placeHolderColor, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
 
}


-(void)setTly_PlaceHolder:(NSString *)placeHolder
{
    [self setTly_PlaceHolder:placeHolder];
    self.placeHolderColor=self.placeHolderColor;
    
}


-(UIColor *)placeHolderColor
{
    return objc_getAssociatedObject(self.placeholder, @"placeHolderColor");
}

// 处理cell间距,默认tableView分组样式,有额外头部和尾部间距

self.tableView.sectionHeaderHeight = 0;
self.tableView.sectionFooterHeight = 10;
self.tableView.contentInset = UIEdgeInsetsMake(-25, 0, 0, 0);

获取整个文件夹或者文件大小

-(void)getFileSize:(NSString *)directoryPath
{
    // NSFileManager
    // attributesOfItemAtPath:指定文件路径,就能获取文件属性
    // 把全部文件尺寸加起来
    
    ///获取文件管理者
    NSFileManager *manager =[NSFileManager defaultManager];
    //获取文件夹下全部的子路径
   NSArray *arrays = [manager subpathsAtPath:directoryPath];
    
    NSInteger totalSize =0;
    
    //进行遍历
    for (NSString *path in arrays) {
            //拼接 获取全路径
       NSString *subPath = [directoryPath stringByAppendingPathComponent:path];
        if([subPath containsString:@".DS"])continue;//忽略隐藏文件
        
        //是不是文件夹
        BOOL isDirectory ;
        //判断文件是否存在
       BOOL isExists = [manager fileExistsAtPath:subPath isDirectory:&isDirectory];
        if(!isExists || isDirectory)continue;
        //获取文件的大小
        NSDictionary *attr =  [manager attributesOfItemAtPath:subPath error:nil];
        NSInteger filesize = [attr fileSize];
        totalSize+=filesize;
        
    }
    
    NSString *sizeStr = @"当前大小";
    // MB KB B
    if (totalSize > 1000 * 1000) {
        // MB
        CGFloat sizeF = totalSize / 1000.0 / 1000.0;
        sizeStr = [NSString stringWithFormat:@"%@(%.1fMB)",sizeStr,sizeF];
    } else if (totalSize > 1000) {
        // KB
        CGFloat sizeF = totalSize / 1000.0;
        sizeStr = [NSString stringWithFormat:@"%@(%.1fKB)",sizeStr,sizeF];
    } else if (totalSize > 0) {
        // B
        sizeStr = [NSString stringWithFormat:@"%@(%.ldB)",sizeStr,totalSize];
    }
    
    NSLog(@"%@",sizeStr);

}

若是ScrollView 在导航控制器中,ScrollView内部的全部自控制器会自动向下移动64(ScrollView的内边距会自动向下64)

//不容许自动修改UIScrollView的内边距
    self.automaticallyAdjustsScrollViewInsets=NO;
    scrollView.contentSize=CGSizeMake(80, 0);//表示能够左右滑动,0表示上下不能够滑动,通常状况里面嵌套UItabview这样设置,只保证里面的UITabview滑动就能够了

若是设置背景色为透明的,尽可能不要设置alpha,防止全部子控件透明,尽可能设置backgroundColor.

NS_DESIGNATED_INITIALIZER 表示OC中特定方法,若要覆盖此方法,必须添加调用父类方法.否则会报以下警告

Designated initializer missing a 'super' call to a designated initializer of the super class
//举例
-(instancetype)initWithFrame:(CGRect)frame
{
    if(self == [super initWithFrame:frame]){
       
    }
    return self;
}

计算文字的高度

//ScreenW 表示屏幕的宽度 表示最大高度 
  CGFloat height = [topic.text boundingRectWithSize:CGSizeMake(ScreenW-20, MAXFLOAT) options:NSStringDrawingUsesLineFragmentOrigin attributes:@{NSFontAttributeName:[UIFont systemFontOfSize:17.0]} context:nil].size.height;

heightForRowAtIndexPath的调用频率<br>

1. 每次刷新表格的时候会调用<br>
2. 每当cell进入屏幕范围内的时候,会再次调用

总结说明:若是在heightForRowAtIndexPath中计算高度,会很是的消耗性能,能够尝试设置一个估算的高度或者计算完高度进行保存.<br>

self.tableView.estimatedRowHeight =200;

使用估算高度(estimatedRowHeight)的优缺点<br> 优势: 1 能够下降heightForRowAtIndexPath方法的调用频率 2 将计算cell高度的操做延迟执行了(至关于cell高度的计算是懒加载的,只有用到了才执行)<br> 缺点: 1.因为是估算的,因此滚动条可能不许确,会形成跳动(若是不设置估算高度会好不少)