看網(wǎng)上有人整理 iOS 開發(fā)中常用的易忘知識(shí)點(diǎn)的畴，iOS 開發(fā)小冷易忘知識(shí)點(diǎn)總結(jié)塘砸，覺得不錯(cuò)末融，于是自己也想著整理一些易忘的知識(shí)點(diǎn)。會(huì)持續(xù)更新......

• iOS 控制器的基類暇韧，搭建框架之初一般都會(huì)設(shè)計(jì)一個(gè) ViewController 基類勾习，這里設(shè)置的基類是 NNBaseViewController，繼承自 UIViewController懈玻。

#import "NNBaseViewController.h"

@interface NNBaseViewController ()

@end

@implementation NNBaseViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    [self setupViews];
    // 判斷是否有上級(jí)頁(yè)面巧婶，有的話再設(shè)置返回按鈕
    if ([self.navigationController.viewControllers indexOfObject:self] != 0) {
        [self setupLeftBarButton];
    }
}

- (void)setupViews {
    // 設(shè)置應(yīng)用的背景色
    self.view.backgroundColor = [UIColor lightGrayColor];
    // 不允許 viewController 自動(dòng)調(diào)整，我們自己布局酪刀；如果設(shè)置為YES粹舵，視圖會(huì)自動(dòng)下移 64 像素
    self.automaticallyAdjustsScrollViewInsets = NO;
}

#pragma mark - 自定義返回按鈕
- (void)setupLeftBarButton {
    // 自定義 leftBarButtonItem ，UIImageRenderingModeAlwaysOriginal 防止圖片被渲染
    self.navigationItem.leftBarButtonItem = [[UIBarButtonItem alloc]
                                             initWithImage:[[UIImage imageNamed:@"Back-藍(lán)"] imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal]
                                             style:UIBarButtonItemStylePlain
                                             target:self
                                             action:@selector(leftBarButtonClick)];
    // 防止返回手勢(shì)失效
    self.navigationController.interactivePopGestureRecognizer.delegate = (id<UIGestureRecognizerDelegate>)self;
}

- (void)leftBarButtonClick {
    [self.navigationController popViewControllerAnimated:YES];
}

@end

• 隱藏 navigationControll 左側(cè)的返回按鈕

因?yàn)轫?xiàng)目需要骂倘，有時(shí)需要隱藏 navigationControll 左側(cè)或右側(cè)的按鈕眼滤。

    // 這兩句貌似不太管用
    self.navigationItem.leftBarButtonItems = nil;
    self.navigationItem.rightBarButtonItem = nil;
    // 可以試試這兩句代碼
    self.navigationItem.hidesBackButton = YES;
    self.navigationItem.rightBarButtonItem.customView.hidden = YES;

• 改變 button 內(nèi)部的圖片以及文字的偏移量

有時(shí)候需要在 button 的右部添加指示箭頭，但 button 默認(rèn)的是圖片在左历涝，文字在右诅需，因此想要實(shí)現(xiàn)項(xiàng)目需求，我們需要改變 button 內(nèi)部的偏移量荧库。在 storyboard 或 xib 中也可以改變 button 內(nèi)部的圖片以及文字的偏移量堰塌，但貌似沒有做適配的地方，那么在不同機(jī)型上的顯示就會(huì)有問題（如果哪位道友發(fā)現(xiàn)可以在 storyboard 或 xib 中可以做適配分衫，還請(qǐng)告知）场刑，下面是改變 button 內(nèi)部圖片以及文字偏移量的代碼。

    // 已經(jīng)做了適配蚪战，各位可以根據(jù)需要做屏幕適配
    self.changeSpecialistBtn.titleEdgeInsets = UIEdgeInsetsMake(0, -lengthFit(16), 0, 0);
    self.changeSpecialistBtn.imageEdgeInsets = UIEdgeInsetsMake(0, lengthFit(76), 0, 0);

• tableView 滾動(dòng)時(shí)自動(dòng)收起鍵盤

項(xiàng)目中某個(gè) tableView 頁(yè)面有文字搜索功能牵现，輸入文本完畢之后滾動(dòng) tableView，要求鍵盤自動(dòng)收起邀桑。

    self.tableView.keyboardDismissMode = UIScrollViewKeyboardDismissModeOnDrag;

• 判斷上級(jí)頁(yè)面是哪個(gè)頁(yè)面

    // 我這里的項(xiàng)目需求是瞎疼，如果上一個(gè)頁(yè)面是 KXOrderCenterViewController，就隱藏稍后支付按鈕壁畸，否則不隱藏
    NSArray *array = self.navigationController.viewControllers;
    if ([array[0] isKindOfClass:[KXOrderCenterViewController class]]) {
        self.payLaterBtn.hidden = YES;
    } else {
        self.payLaterBtn.hidden = NO;
    }
      

• 從任意界面返回 NavigationController 中的任意一個(gè)

這個(gè)方法還是挺實(shí)用的贼急，從某個(gè)界面跳轉(zhuǎn)到任意一個(gè)界面。

    // 得到當(dāng)前的 NavigationController
    [[APPDELEGATE getCurrentViewController].navigationController popToRootViewControllerAnimated:NO];
    
    // 跳轉(zhuǎn)到哪個(gè) NavigationController捏萍，這里下標(biāo)為1太抓，表示第二個(gè)
    [APPDELEGATE.tabBarController setSelectedIndex:1];
    
    // 退出當(dāng)前界面并執(zhí)行 block 中的內(nèi)容
    [self.navigationController dismissViewControllerAnimated:YES completion:^{
            
        UINavigationController *navi = APPDELEGATE.tabBarController.viewControllers[1];
        
        // 保險(xiǎn)起見，再判斷下是否是將要跳轉(zhuǎn)到的頁(yè)面
        if ([navi.viewControllers[0] isKindOfClass:[KXOrderCenterViewController class]]) {
        
            // 我這里需要刷新
            KXOrderCenterViewController *orderCenter = navi.viewControllers[0];
            [orderCenter beginRefreshing];
            }
    }];
        

• 設(shè)置導(dǎo)航欄右部點(diǎn)擊按鈕令杈，并添加點(diǎn)擊事件

// 添加文字按鈕
    UIBarButtonItem *rightBarButton = [[UIBarButtonItem alloc] initWithTitle:@"編輯" style:UIBarButtonItemStylePlain target:self action:@selector(editor)];
        
    self.navigationItem.rightBarButtonItem = rightBarButton;
        
// 添加圖片按鈕
    UIBarButtonItem *rightBarBtn = [[UIBarButtonItem alloc] initWithImage:[[UIImage imageNamed:@"圖片名"] imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal] style:UIBarButtonItemStylePlain target:self action:@selector(rightBarButtonEvent)];
    
    [self.navigationItem setRightBarButtonItem:rightBarBtn];

• 給 view 添加手勢(shì)腻异，并加入點(diǎn)擊事件

    UITapGestureRecognizer *operationTap = [[UITapGestureRecognizer alloc]initWithTarget:self action:@selector(gotoCapture:)];

    [self.operationView addGestureRecognizer:operationTap];
    

• textview 輸入文本，服務(wù)器那邊要求返回文本個(gè)數(shù)不超過32

服務(wù)器那邊有限制这揣，要求返回文本個(gè)數(shù)不超過32個(gè)悔常。影斑。。于是這里做了判斷机打，如果超過32個(gè)就不再允許輸入矫户，允許刪除。

- (void)textViewDidChange:(UITextView *)textView {
    
    [self updateViewHeight];
    // 該判斷用于聯(lián)想輸入
    if (textView == self.secondDiagnosisTextView) {
        if (textView.text.length > 32) {
            // 截取字符串
            textView.text = [textView.text substringToIndex:32];
            // HUD 提示
            [CommunityPublicClass showHUDwithLabelText:@"最多輸入32個(gè)字" andDetailsLabelText:nil];
        }
    }
}

// 代理方法規(guī)定只能輸入32個(gè)字
- (BOOL)textView:(UITextView *)textView shouldChangeTextInRange:(NSRange)range replacementText:(NSString *)text {

    // 輸入32字之后残邀，允許刪除
    if ([text isEqualToString:@""]) {
        return YES;
    }
    
    if (textView == self.secondDiagnosisTextView) {
        if (textView.text.length == 0)
            return YES;
        NSInteger existedLength = textView.text.length;
        NSInteger selectedLength = range.length;
        NSInteger replaceLength = text.length;
        if (existedLength - selectedLength + replaceLength > 32) {
            // HUD 提示
            [CommunityPublicClass showHUDwithLabelText:@"最多輸入32個(gè)字" andDetailsLabelText:nil];
            return NO;
        }
    }
    return YES;
}

• textfield 中輸入手機(jī)號(hào)皆辽，只允許輸入數(shù)字

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string{
    
    if (textField == self.secondAgeTextField) {
        
        if ([self isPureInt:string] || [string isEqualToString:@""]) {
            return YES;
        }else{
            return NO;
        }
    }
    return YES;
}

// 判斷輸入的是否是純數(shù)字
- (BOOL)isPureInt:(NSString*)string{
    NSScanner *scan = [NSScanner scannerWithString:string];
    int val;
    return [scan scanInt:&val] && [scan isAtEnd];
}

• 給 button 設(shè)置邊框、圓角芥挣、邊框設(shè)置顏色

    [self.completeBtn.layer setBorderWidth:1.0];
    self.completeBtn.layer.cornerRadius = 1;
    [self.completeBtn.layer setBorderColor:KXColorTextBlack.CGColor];
    

• 設(shè)置圖片拉伸

有時(shí) UI 設(shè)計(jì)師給出的圖片并不合適驱闷，比如我們這的 UI 設(shè)計(jì)師一邊忙 web 端，一邊忙我們移動(dòng)端空免，有時(shí)候都不忍心讓他重新作圖空另，于是只好自己想辦法

  // 設(shè)置圖片拉伸
  UIImage *bgImage = [UIImage imageNamed:@""];
  _bgImageView.image = [bgImage stretchableImageWithLeftCapWidth:15 topCapHeight:15];
  

• 點(diǎn)擊單元格時(shí)，默認(rèn)的點(diǎn)擊效果比較丑蹋砚，大多時(shí)候不顯示點(diǎn)擊效果

  - (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
  {
      [tableView deselectRowAtIndexPath:indexPath animated:YES] ;
  }

• 改變導(dǎo)航欄標(biāo)題的顏色

    UIColor *color = [UIColor cyanColor];
    NSDictionary *dictionary = [NSDictionary dictionaryWithObject: color forKey:NSForegroundColorAttributeName];
    self.navigationController.navigationBar.titleTextAttributes = dictionary;
    

• 延遲調(diào)用

 // 延遲兩秒鐘調(diào)用 beginAction 方法
[self performSelector:@selector(beginAction) withObject:nil afterDelay:0.2] ;

• 項(xiàng)目中用到了 UISwitch 控件扼菠，需要更改它的大小

// 改變 UISwitch  的大小，CGAffineTransformMakeScale(CGFloat x, CGFloat y) 對(duì) view 的長(zhǎng)和寬進(jìn)行縮放坝咐，不改變 view 的中心點(diǎn)
self.orderSwitch.transform = CGAffineTransformMakeScale(0.7, 0.7); 

// 改變 UISwitch 開啟時(shí)的顏色
self.orderSwitch.onTintColor = KXColorBlue;

• 在做明暗文切換(密碼輸入框)的時(shí)候遇見一個(gè)坑——就是切換 secureTextEntry 的時(shí)候循榆，輸入框的光標(biāo)會(huì)偏移，下面是解決辦法及明暗文切換的方法：

- (IBAction)btnClick:(UIButton *)sender {
    
    sender.selected = !sender.selected;
    NSString *passwordString = self.passwordText.text;
    // 這句代碼可以防止切換的時(shí)候光標(biāo)偏移
    self.passwordText.text = @"";

    if (sender.selected) { // 明文
        self.passwordText.secureTextEntry = NO;
    } else { // 暗文
        self.passwordText.secureTextEntry = YES;
    }
    
    self.passwordText.text = passwordString;
}

• 判斷屏幕橫屏/豎屏(在ViewController里面)

// 屏幕發(fā)生翻轉(zhuǎn)的時(shí)候會(huì)調(diào)用
- (void)viewWillLayoutSubviews {
    [self shouldRotateToOrientation:(UIDeviceOrientation)[UIApplication sharedApplication].statusBarOrientation];
}

- (void)shouldRotateToOrientation:(UIDeviceOrientation)orientation {
    if (orientation == UIDeviceOrientationPortrait ||orientation == UIDeviceOrientationPortraitUpsideDown) {
        NSLog(@"這是豎屏");
    } else {
        NSLog(@"這是橫屏");
    }
}

• 加載本地的 HTML 文件墨坚，比如文件名字是serviceDescription.html

NSString *resourcePath = [[NSBundle mainBundle] resourcePath];
    NSString *filePath = [resourcePath stringByAppendingPathComponent:@"serviceDescription.html"];
    NSString *htmlString = [[NSString alloc] initWithContentsOfFile:filePath encoding:NSUTF8StringEncoding error:nil];
    [self.webView loadHTMLString: htmlString baseURL: [NSURL fileURLWithPath:[[NSBundle mainBundle] bundlePath]]];

• iOS 項(xiàng)目開發(fā)中用的一部分宏定義

/** self的弱引用 */
#define NNWeakSelf __weak typeof(self) weakSelf = self;
/** self的強(qiáng)引用 */
#define NNStrongSelf __strong __typeof(weakSelf)strongSelf = weakSelf;

#define NNColorBlue [UIColor colorWithRed:0.0/255.0f green:135.0/255.0f blue:209.0/255.0f alpha:1]
#define NNFontBoldText [UIFont boldSystemFontOfSize:fontFit(16)]
#define NNFontText [UIFont systemFontOfSize:fontFit(16)]

#define SCREENWIDTH [UIScreen mainScreen].bounds.size.width
#define SCREENHEIGHT [UIScreen mainScreen].bounds.size.height

#define iPhone5 (([[UIScreen mainScreen] bounds].size.height*[[UIScreen mainScreen] bounds].size.width <= 320*568)?YES:NO)

#define iPhone6 (([[UIScreen mainScreen] bounds].size.height*[[UIScreen mainScreen] bounds].size.width <= 375*667)?YES:NO)

#define iPhone6p (([[UIScreen mainScreen] bounds].size.height*[[UIScreen mainScreen] bounds].size.width <= 414*736)?YES:NO)

#define iOS7 ([[[UIDevice currentDevice] systemVersion] floatValue] >= 7.0 ? YES : NO) // 是否IOS7

static inline float lengthFit(float iphone6PlusLength)
{
    if (iPhone5) {
        return iphone6PlusLength *320.0f/414.0f;
    }
    if (iPhone6) {
        return iphone6PlusLength *375.0f/414.0f;
    }
    return iphone6PlusLength;
}

static inline float fontFit(float iphone6PlusFont)
{
    if (iPhone5) {
        return iphone6PlusFont - 2;
    }
    if (iPhone6) {
        return iphone6PlusFont - 1;
    }
    return iphone6PlusFont;
}

#define PlaceholderAvatarImage [UIImage imageNamed:@"默認(rèn)頭像"]

• 一句代碼隱藏 UITableView 中空的 cell

self.tableView.tableFooterView = [[UIView alloc] init];

• 自定義 leftBarButtonItem 返回按鈕時(shí)秧饮，防止返回手勢(shì)失效的辦法

- (void)setupLeftBarButton {
self.navigationItem.leftBarButtonItem = [[UIBarButtonItem alloc]
                                             initWithImage:[[UIImage imageNamed:@"Back-藍(lán)"] imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal]
                                                style:UIBarButtonItemStylePlain
                                                target:self
                                                action:@selector(leftBarButtonClick)];
    self.navigationController.interactivePopGestureRecognizer.delegate = (id<UIGestureRecognizerDelegate>)self;
}

- (void)leftBarButtonClick {
    [self.navigationController popViewControllerAnimated:YES];
}

• 不允許 viewController 自動(dòng)調(diào)整，我們自己布局泽篮；如果設(shè)置為YES盗尸，視圖會(huì)自動(dòng)下移 64 像素

    self.automaticallyAdjustsScrollViewInsets = NO;

• 去空格，開發(fā)中有些地方不需要空格咪辱，這里記錄一下

        // 去掉兩端的空格
        [trimString stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];
        
        // 去掉所有空格
        [trimString stringByReplacingOccurrencesOfString:@" " withString:@""];

• 判斷字符串中是否包含非法字符

if ([self.searchText.text rangeOfString:@"'"].location != NSNotFound) {
        // 用封裝好的提示框提示
        [CommunityPublicClass showHUDwithLabelText:@"您輸入的字符不合法" andDetailsLabelText:nil];
        return;
    }

• iOS 導(dǎo)航欄的正確隱藏方法

第一種方法

- (void)viewWillAppear:(BOOL)animated {
    [super viewWillAppear:animated];

    [self.navigationController setNavigationBarHidden:YES animated:YES];
}

- (void)viewWillDisappear:(BOOL)animated {
    [super viewWillDisappear:animated];

    [self.navigationController setNavigationBarHidden:NO animated:YES];
}

第二種方法

@interface NNViewController () <UINavigationControllerDelegate>

@end

@implementation NNViewController 

- (void)viewDidLoad {
    [super viewDidLoad];

    // 設(shè)置導(dǎo)航控制器的代理為self
    self.navigationController.delegate = self;
}

#pragma mark - UINavigationControllerDelegate
- (void)navigationController:(UINavigationController *)navigationController willShowViewController:(UIViewController *)viewController animated:(BOOL)animated {

    [self.navigationController setNavigationBarHidden: [viewController isKindOfClass:[self class]] animated:YES];
}

• 判斷字符串是否為空

// 判斷字符串是否為空
+ (BOOL)isBlankString:(NSString *)string {
    if (string == nil || string == NULL) {
        return YES;
    }
    if ([string isKindOfClass:[NSNull class]]) {
        return YES;
    }
    if ([[string stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceCharacterSet]] length]==0) {
        return YES;
    }
    return NO;
}

• 把一個(gè) view 的所有subview清空

[view.subviews makeObjectsPerformSelector:@selector(removeFromSuperview)];