百思不得其姐學習筆記

appearance 的使用注意點

+(void)load
{
    //appearance 通常在load中加載使用,若要操做控件,必須在UI沒有顯示的狀況下去操做
    NSArray *array =@[self];
    UITabBarItem *tabBarItem =  [UITabBarItem appearanceWhenContainedInInstancesOfClasses:array];
    NSMutableDictionary *dict =[NSMutableDictionary dictionary];
    dict[NSForegroundColorAttributeName] = [UIColor whiteColor];
    [tabBarItem setTitleTextAttributes:dict forState:UIControlStateSelected];
    
    //設置字體大小  必須是在UIControlStateNormal 設置纔有效果
    NSMutableDictionary *dict1 =[NSMutableDictionary dictionary];
    dict1[NSFontAttributeName] = [UIFont systemFontOfSize:13];
    [tabBarItem setTitleTextAttributes:dict1 forState:UIControlStateNormal];
}

若是直接用UIButton包裝成UIBarButtonItem,會擴大點擊區域

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包裝成UIBarButtonItem,會擴大點擊區域
// UIBarButtonItem *barbtn =[[UIBarButtonItem alloc]initWithCustomView:btn];
    
//阻止擴大點擊區域的解決辦法只有在外面再次包裝一層UIview
UIView *uiview = [[UIView alloc]initWithFrame:btn.bounds];
[uiview addSubview:btn];
[[UIBarButtonItem alloc]initWithCustomView:uiview]

UIBarButtonItem:描述按鈕具體的內容.<br>UINavigationItem:設置導航條上內容(左邊,右邊,中間). <br>TabBarItem: 設置tabBar上按鈕內容(tabBarButton)

導航控制器滑動的失效分析以及解決,經打印發現代理作了別的事情,就先清除的了代理,

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

//清除以後,發現會出現假死狀態,再次判斷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;
}

導航控制器實現全屏滑動返回

- (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];
    //控制手勢何時觸發,只有在非根控制器的時候才觸發
    pan.delegate = self;
    //禁止以前手勢
    self.interactivePopGestureRecognizer.enabled = NO;

}


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

UITableView 的複用(由Xib 加載 Cell)

//首先進行註冊
 [self.tableView registerNib:[UINib nibWithNibName:NSStringFromClass([TLYSubTagViewCell class]) bundle:nil] forCellReuseIdentifier:ID];
 //拿出來能夠直接使用
 TLYSubTagViewCell *cell = [tableView dequeueReusableCellWithIdentifier:ID];

設置圖片爲圓角

self.imaView.layer.cornerRadius = 30;//30爲圖片的一半  設置爲圓角
self.imaView.layer.masksToBounds = YES;//把多餘的進行裁剪

設置UITableView 分割先全屏

//清空tabview的的間隙
 self.tableView.separatorInset = UIEdgeInsetsZero;
//清空cell自身的間隙
 cell.separatorInset = UIEdgeInsetsZero;

設置UITableView分割線的第二種方法思路:<br>前提要理解的是tableview的frame是先計算出來後,而後才調用了cellForRowAtIndexPath,作法是:首先將系統默認的分割線設置爲none,將整個tableview的背景顏色設置爲分割線顏色,而後重寫cell的setframe方法.

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

修改UITextField的光標顏色,和佔位字顏色

-(void)awakeFromNib
{
    [super awakeFromNib];
    //設置光標的顏色
    self.tintColor = [UIColor whiteColor];
    
    
    //監聽編輯開始和結束
    [self addTarget:self action:@selector(touchBegin) forControlEvents:UIControlEventEditingDidBegin];
     [self addTarget:self action:@selector(touchEnd) forControlEvents:UIControlEventEditingDidEnd];
    
    //第一種方法
    NSMutableDictionary *dict =[NSMutableDictionary dictionary];
    dict[NSForegroundColorAttributeName] = [UIColor lightGrayColor];
    self.attributedPlaceholder = [[NSAttributedString alloc]initWithString:self.placeholder attributes:dict];
    
    //第二種方法,也能夠直接利用kvc的方式拿到placeholder的lable
   UILabel *placeHolder = [self valueForKey:@"_placeholderLabel"];
  [placeHolder setTextColor:[UIColor lightGrayColor]];
}

//開始編輯 (第一種方法)
-(void)touchBegin{
    NSMutableDictionary *dict =[NSMutableDictionary dictionary];
    dict[NSForegroundColorAttributeName] = [UIColor whiteColor];
    self.attributedPlaceholder = [[NSAttributedString alloc]initWithString:self.placeholder attributes:dict];
}

///結束編輯(第一種方法)
-(void)touchEnd{
    NSMutableDictionary *dict =[NSMutableDictionary dictionary];
    dict[NSForegroundColorAttributeName] = [UIColor lightGrayColor];
    self.attributedPlaceholder = [[NSAttributedString alloc]initWithString:self.placeholder attributes:dict];
}

若是先設置顏色,placeHolderLable是nil的,爲了防止這種狀況,儘可能先保存顏色,利用runtime給系統增長一個屬性,在設置佔位文字的時候,同時把顏色設置上

+(void)load
{
    //方法進行交換   到時候直接調用setPlaceholder 便可直接設置顏色
    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];
    
    //若是先設置顏色,placeHolderLable是nil的,爲了防止這種狀況,儘可能先保存顏色,利用runtime給系統增長一個屬性,在設置佔位文字的時候,同時把顏色設置上
     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");
}

// 處理cell間距,默認tableView分組樣式,有額外頭部和尾部間距

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

獲取整個文件夾或者文件大小

-(void)getFileSize:(NSString *)directoryPath
{
    // NSFileManager
    // attributesOfItemAtPath:指定文件路徑,就能獲取文件屬性
    // 把全部文件尺寸加起來
    
    ///獲取文件管理者
    NSFileManager *manager =[NSFileManager defaultManager];
    //獲取文件夾下全部的子路徑
   NSArray *arrays = [manager subpathsAtPath:directoryPath];
    
    NSInteger totalSize =0;
    
    //進行遍歷
    for (NSString *path in arrays) {
            //拼接 獲取全路徑
       NSString *subPath = [directoryPath stringByAppendingPathComponent:path];
        if([subPath containsString:@".DS"])continue;//忽略隱藏文件
        
        //是不是文件夾
        BOOL isDirectory ;
        //判斷文件是否存在
       BOOL isExists = [manager fileExistsAtPath:subPath isDirectory:&isDirectory];
        if(!isExists || isDirectory)continue;
        //獲取文件的大小
        NSDictionary *attr =  [manager attributesOfItemAtPath:subPath error:nil];
        NSInteger filesize = [attr fileSize];
        totalSize+=filesize;
        
    }
    
    NSString *sizeStr = @"當前大小";
    // 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 在導航控制器中,ScrollView內部的全部自控制器會自動向下移動64(ScrollView的內邊距會自動向下64)

//不容許自動修改UIScrollView的內邊距
    self.automaticallyAdjustsScrollViewInsets=NO;
    scrollView.contentSize=CGSizeMake(80, 0);//表示能夠左右滑動,0表示上下不能夠滑動,通常狀況裏面嵌套UItabview這樣設置,只保證裏面的UITabview滑動就能夠了

若是設置背景色爲透明的,儘可能不要設置alpha,防止全部子控件透明,儘可能設置backgroundColor.

NS_DESIGNATED_INITIALIZER 表示OC中特定方法,若要覆蓋此方法,必須添加調用父類方法.否則會報以下警告

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

計算文字的高度

//ScreenW 表示屏幕的寬度 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的調用頻率<br>

1. 每次刷新表格的時候會調用<br>
2. 每當cell進入屏幕範圍內的時候,會再次調用

總結說明:若是在heightForRowAtIndexPath中計算高度,會很是的消耗性能,能夠嘗試設置一個估算的高度或者計算完高度進行保存.<br>

self.tableView.estimatedRowHeight =200;

使用估算高度(estimatedRowHeight)的優缺點<br> 優勢: 1 能夠下降heightForRowAtIndexPath方法的調用頻率 2 將計算cell高度的操做延遲執行了(至關於cell高度的計算是懶加載的,只有用到了才執行)<br> 缺點: 1.因爲是估算的,因此滾動條可能不許確,會形成跳動(若是不設置估算高度會好不少)