appearance 的使用注意点

+(void)load
{//appearance 一般在load中加载使用,若要操作控件,必须在UI没有显示的情况下去操作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];
}

如果直接用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];
//如果直接用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,经打印发现代理做了别的事情,就先清除的了代理,

- (void)viewDidLoad {[super viewDidLoad];// Do any additional setup after loading the view.self.interactivePopGestureRecognizer.delegate =nil;
}//清除之后,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];//控制手势什么时候触发,只有在非根控制器的时候才触发pan.delegate = self;//禁止之前手势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];//拿出来可以直接使用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,然后才调用了cellForRowAtIndexPath,做法是: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,然后重写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,也可以直接利用kvc的方式拿到placeholder的lableUILabel *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];
}

如果先设置颜色,placeHolderLable是nil的,为了防止这种情况,尽量先保存颜色,利用runtime给系统增加一个属性,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 即可直接设置颜色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];//如果先设置颜色,placeHolderLable是nil的,为了防止这种情况,尽量先保存颜色,利用runtime给系统增加一个属性,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// 把所有文件尺寸加起来///获取文件管理者NSFileManager *manager =[NSFileManager defaultManager];//获取文件夹下所有的子路径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//是否是文件夹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 Bif (totalSize > 1000 * 1000) {// MBCGFloat sizeF = totalSize / 1000.0 / 1000.0;sizeStr = [NSString stringWithFormat:@"%@(%.1fMB)",sizeStr,sizeF];} else if (totalSize > 1000) {// KBCGFloat sizeF = totalSize / 1000.0;sizeStr = [NSString stringWithFormat:@"%@(%.1fKB)",sizeStr,sizeF];} else if (totalSize > 0) {// BsizeStr = [NSString stringWithFormat:@"%@(%.ldB)",sizeStr,totalSize];}NSLog(@"%@",sizeStr);}

如果ScrollView 在导航控制器中,ScrollView内部的所有自控制器会自动向下移动64(ScrollView的内边距会自动向下64)

//不允许自动修改UIScrollView的内边距self.automaticallyAdjustsScrollViewInsets=NO;scrollView.contentSize=CGSizeMake(80, 0);//表示可以左右滑动,0表示上下不可以滑动,一般情况里面嵌套UItabview这样设置,只保证里面的UITabview滑动就可以了

如果设置背景色为透明的,尽量不要设置alpha,防止所有子控件透明,尽量设置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.不然会报如下警告

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:如果在heightForRowAtIndexPath中计算高度,会非常的消耗性能,可以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> 优点: 1 可以降低heightForRowAtIndexPath方法的调用频率 2 将计算cell高度的操作延迟执行了(相当于cell高度的计算是懒加载的,只有用到了才执行)<br> 缺点: 1.由于是估算的,所以滚动条可能不准确,会造成跳动(如果不设置估算高度会好很多)