多线程开发之二 NSOperation

效果如下：

ViewController.h

1 #import <UIKit/UIKit.h>
2
3 @interface ViewController : UITableViewController
4 @property (strong, nonatomic) NSArray *arrSampleName;
5
6 - (instancetype)initWithSampleNameArray:(NSArray *)arrSampleName;
7
8 @end 

ViewController.m

 1 #import "ViewController.h"
 2 #import "FirstSampleViewController.h"
 3 #import "SecondSampleViewController.h"
 4
 5 @interface ViewController ()
 6 - (void)layoutUI;
 7 @end
 8
 9 @implementation ViewController
10 - (void)viewDidLoad {
11     [super viewDidLoad];
12
13     [self layoutUI];
14 }
15
16 - (void)didReceiveMemoryWarning {
17     [super didReceiveMemoryWarning];
18     // Dispose of any resources that can be recreated.
19 }
20
21 - (instancetype)initWithSampleNameArray:(NSArray *)arrSampleName {
22     if (self = [super initWithStyle:UITableViewStyleGrouped]) {
23         self.navigationItem.title = @"多线程开发之二 NSOperation";
24         self.navigationItem.backBarButtonItem = [[UIBarButtonItem alloc] initWithTitle:@"返回首页" style:UIBarButtonItemStylePlain target:nil action:nil];
25
26         _arrSampleName = arrSampleName;
27     }
28     return self;
29 }
30
31 - (void)layoutUI {
32 }
33
34 #pragma mark - UITableViewController相关方法重写
35 - (CGFloat)tableView:(UITableView *)tableView heightForHeaderInSection:(NSInteger)section {
36     return 0.1;
37 }
38
39 - (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
40     return 1;
41 }
42
43 - (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
44     return [_arrSampleName count];
45 }
46
47 - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
48     static NSString *cellIdentifier = @"cell";
49     UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:cellIdentifier];
50     if (!cell) {
51         cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:cellIdentifier];
52     }
53     cell.textLabel.text = _arrSampleName[indexPath.row];
54     return cell;
55 }
56
57 - (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
58     switch (indexPath.row) {
59         case 0: {
60             FirstSampleViewController *firstSampleVC = [FirstSampleViewController new];
61             [self.navigationController pushViewController:firstSampleVC animated:YES];
62             break;
63         }
64         case 1: {
65             SecondSampleViewController *secondSampleVC = [SecondSampleViewController new];
66             [self.navigationController pushViewController:secondSampleVC animated:YES];
67             break;
68         }
69         default:
70             break;
71     }
72 }
73
74 @end 

UIImage+RescaleImage.h

 1 #import <UIKit/UIKit.h>
 2
 3 @interface UIImage (RescaleImage)
 4 /**
 5  *  根据宽高大小，获取对应的缩放图片
 6  *
 7  *  @param size 宽高大小
 8  *
 9  *  @return 对应的缩放图片
10  */
11 - (UIImage *)rescaleImageToSize:(CGSize)size;
12
13 @end 

UIImage+RescaleImage.m

 1 #import "UIImage+RescaleImage.h"
 2
 3 @implementation UIImage (RescaleImage)
 4
 5 - (UIImage *)rescaleImageToSize:(CGSize)size {
 6     CGRect rect = CGRectMake(0.0, 0.0, size.width, size.height);
 7
 8     UIGraphicsBeginImageContext(rect.size);
 9     [self drawInRect:rect];
10     UIImage *imgScale = UIGraphicsGetImageFromCurrentImageContext();
11     UIGraphicsEndImageContext();
12
13     return imgScale;
14 }
15
16 @end 

Common.h

1 #import <Foundation/Foundation.h>
2
3 @interface Common : NSObject
4 + (NSURL *)randomImageURL;
5
6 @end 

Common.m

 1 #import "Common.h"
 2
 3 @implementation Common
 4
 5 + (NSURL *)randomImageURL {
 6     NSUInteger randomVal = (arc4random() % 20) + 1; //1-20的随机数
 7     NSString *randomValStr = [NSString stringWithFormat:@"%lu", (unsigned long)randomVal];
 8     if (randomVal < 10) {
 9         randomValStr = [@"0" stringByAppendingString:randomValStr];
10     }
11
12     NSString *imageURLStr = [NSString stringWithFormat:@"http://images.apple.com/v/watch/e/apple-watch/images/collection_%@_large.jpg", randomValStr];
13     return [NSURL URLWithString:imageURLStr];
14 }
15
16 @end 

FirstSampleViewController.h

1 #import <UIKit/UIKit.h>
2
3 @interface FirstSampleViewController : UIViewController
4 @property (assign, nonatomic) CGSize rescaleImageSize;
5
6 @property (strong, nonatomic) IBOutlet UIImageView *imgV;
7 @property (strong, nonatomic) IBOutlet UIButton *btnLoadImage;
8
9 @end 

FirstSampleViewController.m

 1 #import "FirstSampleViewController.h"
 2 #import "UIImage+RescaleImage.h"
 3 #import "Common.h"
 4
 5 @interface FirstSampleViewController ()
 6 - (void)layoutUI;
 7 - (void)updateImage:(NSData *)imageData;
 8 - (void)loadImageFromNetwork;
 9 @end
10
11 @implementation FirstSampleViewController
12
13 - (void)viewDidLoad {
14     [super viewDidLoad];
15
16     [self layoutUI];
17 }
18
19 - (void)didReceiveMemoryWarning {
20     [super didReceiveMemoryWarning];
21     // Dispose of any resources that can be recreated.
22 }
23
24 - (void)dealloc {
25     _imgV.image = nil;
26 }
27
28 - (void)layoutUI {
29     CGFloat width = [[UIScreen mainScreen] bounds].size.width; //bounds 返回整个屏幕大小；applicationFrame 返回去除状态栏后的屏幕大小
30     CGFloat height = width * 438.0 / 366.0;
31     const CGFloat percentVal = 3.0 / 4.0; //以屏幕宽度的3/4比例显示
32     _rescaleImageSize = CGSizeMake(width * percentVal, height * percentVal);
33
34     //NSString *path = [[NSBundle mainBundle] pathForResource:@"[email protected]" ofType:@"png"];
35     //_imgV.image = [UIImage imageWithContentsOfFile:path];
36
37     _btnLoadImage.tintColor = [UIColor darkGrayColor];
38     _btnLoadImage.layer.masksToBounds = YES;
39     _btnLoadImage.layer.cornerRadius = 10.0;
40     _btnLoadImage.layer.borderColor = [UIColor grayColor].CGColor;
41     _btnLoadImage.layer.borderWidth = 1.0;
42 }
43
44 - (void)updateImage:(NSData *)imageData {
45     UIImage *img = [UIImage imageWithData:imageData];
46     _imgV.image = [img rescaleImageToSize:_rescaleImageSize];
47 }
48
49 - (void)loadImageFromNetwork {
50     NSURL *url = [Common randomImageURL];
51     NSData *data = [NSData dataWithContentsOfURL:url];
52
53     //mainQueue 是 UI 主线程，调用主线程队列的方法进行操作
54     [[NSOperationQueue mainQueue] addOperationWithBlock:^{
55         [self updateImage:data];
56     }];
57 }
58
59 - (IBAction)loadImage:(id)sender {
60     //方法一：使用 NSInvocationOperation
61 //    NSInvocationOperation *invocationOperation = [[NSInvocationOperation alloc]
62 //                                                  initWithTarget:self
63 //                                                  selector:@selector(loadImageFromNetwork)
64 //                                                  object:nil];
65 //    NSOperationQueue *operationQueue = [NSOperationQueue new]; //操作队列
66 //    [operationQueue addOperation:invocationOperation];
67
68
69     //方法二：使用 NSBlockOperation
70     NSBlockOperation *blockOperation = [NSBlockOperation blockOperationWithBlock:^{
71         [self loadImageFromNetwork];
72     }];
73     [blockOperation addExecutionBlock:^{ //还可以为 blockOperation 添加代码块；多个代码块会被分到多个线程去执行，存在两个代码块被分配到同一个线程执行的情况
74         NSLog(@"代码块");
75     }];
76     [blockOperation addExecutionBlock:[blockOperation executionBlocks][1]]; //这里可以调用他的 executionBlocks 获取到添加的代码块数组；上面打印的内容「代码块」会被执行两次
77
78     [blockOperation setCompletionBlock:^{
79         NSLog(@"所有代码块操作执行完毕后（无论已取消还是已完成），做一些事情，只执行一次");
80     }];
81
82     //[blockOperation start]; //使用 start 方法，则此操作在主线程中执行；一般不这样操作，而是添加到操作队列中
83     NSOperationQueue *operationQueue = [NSOperationQueue new]; //操作队列
84     [operationQueue addOperation:blockOperation]; //添加到操作队列，这时队列会开启一个线程去执行此操作；一个线程可以执行多个操作
85
86     //方法三：直接使用 NSOperationQueue
87 //    NSOperationQueue *operationQueue = [NSOperationQueue new]; //操作队列
88 //    [operationQueue addOperationWithBlock:^{
89 //        [self loadImageFromNetwork];
90 //    }];
91 }
92
93 @end 

FirstSampleViewController.xib

 1 <?xml version="1.0" encoding="UTF-8" standalone="no"?>
 2 <document type="com.apple.InterfaceBuilder3.CocoaTouch.XIB" version="3.0" toolsVersion="7706" systemVersion="14E46" targetRuntime="iOS.CocoaTouch" propertyAccessControl="none" useAutolayout="YES" useTraitCollections="YES">
 3     <dependencies>
 4         <deployment identifier="iOS"/>
 5         <plugIn identifier="com.apple.InterfaceBuilder.IBCocoaTouchPlugin" version="7703"/>
 6     </dependencies>
 7     <objects>
 8         <placeholder placeholderIdentifier="IBFilesOwner" id="-1" userLabel="File‘s Owner" customClass="FirstSampleViewController">
 9             <connections>
10                 <outlet property="btnLoadImage" destination="sLs-f1-Gzc" id="kX8-J0-v0V"/>
11                 <outlet property="imgV" destination="4Qp-uk-KAb" id="RM3-Ha-glh"/>
12                 <outlet property="view" destination="i5M-Pr-FkT" id="sfx-zR-JGt"/>
13             </connections>
14         </placeholder>
15         <placeholder placeholderIdentifier="IBFirstResponder" id="-2" customClass="UIResponder"/>
16         <view clearsContextBeforeDrawing="NO" contentMode="scaleToFill" id="i5M-Pr-FkT">
17             <rect key="frame" x="0.0" y="0.0" width="600" height="600"/>
18             <autoresizingMask key="autoresizingMask" widthSizable="YES" heightSizable="YES"/>
19             <subviews>
20                 <imageView userInteractionEnabled="NO" contentMode="scaleToFill" horizontalHuggingPriority="251" verticalHuggingPriority="251" image="PictureNo.png" translatesAutoresizingMaskIntoConstraints="NO" id="4Qp-uk-KAb">
21                     <rect key="frame" x="205" y="225" width="190" height="150"/>
22                     <constraints>
23                         <constraint firstAttribute="height" constant="150" id="SIp-Wd-idU"/>
24                         <constraint firstAttribute="height" constant="150" id="VwM-i1-atB"/>
25                         <constraint firstAttribute="width" constant="190" id="mUh-Bu-tUd"/>
26                         <constraint firstAttribute="width" constant="190" id="mdJ-1c-QFa"/>
27                         <constraint firstAttribute="width" constant="190" id="sVS-bU-Ty9"/>
28                         <constraint firstAttribute="height" constant="150" id="uMG-oN-J56"/>
29                         <constraint firstAttribute="height" constant="150" id="vws-Qw-UrB"/>
30                     </constraints>
31                     <variation key="default">
32                         <mask key="constraints">
33                             <exclude reference="SIp-Wd-idU"/>
34                             <exclude reference="VwM-i1-atB"/>
35                             <exclude reference="mUh-Bu-tUd"/>
36                             <exclude reference="mdJ-1c-QFa"/>
37                             <exclude reference="sVS-bU-Ty9"/>
38                             <exclude reference="uMG-oN-J56"/>
39                             <exclude reference="vws-Qw-UrB"/>
40                         </mask>
41                     </variation>
42                 </imageView>
43                 <button opaque="NO" contentMode="scaleToFill" contentHorizontalAlignment="center" contentVerticalAlignment="center" buttonType="roundedRect" lineBreakMode="middleTruncation" translatesAutoresizingMaskIntoConstraints="NO" id="sLs-f1-Gzc">
44                     <rect key="frame" x="230" y="500" width="140" height="50"/>
45                     <constraints>
46                         <constraint firstAttribute="width" constant="140" id="1jv-9K-mdH"/>
47                         <constraint firstAttribute="height" constant="50" id="Q2w-vR-9ac"/>
48                     </constraints>
49                     <state key="normal" title="加载网络图片">
50                         <color key="titleShadowColor" white="0.5" alpha="1" colorSpace="calibratedWhite"/>
51                     </state>
52                     <connections>
53                         <action selector="loadImage:" destination="-1" eventType="touchUpInside" id="fdy-Ln-5oS"/>
54                     </connections>
55                 </button>
56             </subviews>
57             <color key="backgroundColor" white="1" alpha="1" colorSpace="custom" customColorSpace="calibratedWhite"/>
58             <constraints>
59                 <constraint firstItem="4Qp-uk-KAb" firstAttribute="leading" secondItem="i5M-Pr-FkT" secondAttribute="leading" constant="205" id="2a2-mS-WFa"/>
60                 <constraint firstItem="sLs-f1-Gzc" firstAttribute="top" secondItem="i5M-Pr-FkT" secondAttribute="top" id="ES4-wl-RBz"/>
61                 <constraint firstItem="4Qp-uk-KAb" firstAttribute="centerY" secondItem="i5M-Pr-FkT" secondAttribute="centerY" id="MUJ-WA-sUf"/>
62                 <constraint firstItem="4Qp-uk-KAb" firstAttribute="centerX" secondItem="sLs-f1-Gzc" secondAttribute="centerX" id="Q8a-1k-DzJ"/>
63                 <constraint firstAttribute="bottom" secondItem="4Qp-uk-KAb" secondAttribute="bottom" constant="71" id="V0a-9y-Dwa"/>
64                 <constraint firstAttribute="bottom" secondItem="sLs-f1-Gzc" secondAttribute="bottom" constant="50" id="VMG-CV-eeq"/>
65                 <constraint firstItem="4Qp-uk-KAb" firstAttribute="top" secondItem="i5M-Pr-FkT" secondAttribute="top" constant="-71" id="gqW-Wq-4Zv"/>
66                 <constraint firstItem="sLs-f1-Gzc" firstAttribute="centerX" secondItem="i5M-Pr-FkT" secondAttribute="centerX" id="kNf-6d-EJ8"/>
67             </constraints>
68             <variation key="default">
69                 <mask key="constraints">
70                     <exclude reference="2a2-mS-WFa"/>
71                     <exclude reference="V0a-9y-Dwa"/>
72                     <exclude reference="gqW-Wq-4Zv"/>
73                     <exclude reference="ES4-wl-RBz"/>
74                 </mask>
75             </variation>
76         </view>
77     </objects>
78     <resources>
79         <image name="PictureNo.png" width="190" height="150"/>
80     </resources>
81 </document> 

SecondSampleViewController.h

1 #import <UIKit/UIKit.h>
2
3 @interface SecondSampleViewController : UIViewController
4 @property (assign, nonatomic) CGSize rescaleImageSize;
5 @property (strong, nonatomic) NSMutableArray *mArrImageView;
6
7 @property (strong, nonatomic) IBOutlet UIButton *btnLoadImage;
8
9 @end 

SecondSampleViewController.m

  1 #import "SecondSampleViewController.h"
  2 #import "UIImage+RescaleImage.h"
  3 #import "Common.h"
  4
  5 #define kRowCount 4
  6 #define kColumnCount 3
  7 #define kCellSpacing 10.0
  8
  9 @interface SecondSampleViewController ()
 10 - (void)layoutUI;
 11 - (void)updateImage:(NSData *)imageData withImageIndex:(NSInteger)imageIndex;
 12 -(NSData *)requestData:(NSInteger)imageIndex;
 13 - (void)loadImageFromNetwork:(NSInteger)imageIndex;
 14 @end
 15
 16 @implementation SecondSampleViewController
 17
 18 - (void)viewDidLoad {
 19     [super viewDidLoad];
 20
 21     [self layoutUI];
 22 }
 23
 24 - (void)didReceiveMemoryWarning {
 25     [super didReceiveMemoryWarning];
 26     // Dispose of any resources that can be recreated.
 27 }
 28
 29 - (void)dealloc {
 30     _mArrImageView = nil;
 31 }
 32
 33 - (void)layoutUI {
 34     CGFloat width = ([[UIScreen mainScreen] bounds].size.width - ((kColumnCount + 1) * kCellSpacing)) / kColumnCount;
 35     _rescaleImageSize = CGSizeMake(width, width);
 36
 37     CGFloat heightOfStatusAndNav = 20.0 + 44.0;
 38     NSString *path = [[NSBundle mainBundle] pathForResource:@"[email protected]" ofType:@"png"];
 39     UIImage *img = [UIImage imageWithContentsOfFile:path];
 40     _mArrImageView = [NSMutableArray arrayWithCapacity:kRowCount * kColumnCount];
 41     //初始化多个图片视图
 42     for (NSUInteger i=0; i<kRowCount; i++) {
 43         for (NSUInteger j=0; j<kColumnCount; j++) {
 44             UIImageView *imgV = [[UIImageView alloc] initWithFrame:
 45                                  CGRectMake(_rescaleImageSize.width * j + kCellSpacing * (j+1),
 46                                             _rescaleImageSize.height * i + kCellSpacing * (i+1) + heightOfStatusAndNav,
 47                                             _rescaleImageSize.width,
 48                                             _rescaleImageSize.height)];
 49             imgV.image = img;
 50             [self.view addSubview:imgV];
 51             [_mArrImageView addObject:imgV];
 52         }
 53     }
 54
 55     _btnLoadImage.tintColor = [UIColor darkGrayColor];
 56     _btnLoadImage.layer.masksToBounds = YES;
 57     _btnLoadImage.layer.cornerRadius = 10.0;
 58     _btnLoadImage.layer.borderColor = [UIColor grayColor].CGColor;
 59     _btnLoadImage.layer.borderWidth = 1.0;
 60 }
 61
 62 - (void)updateImage:(NSData *)imageData withImageIndex:(NSInteger)imageIndex {
 63     UIImage *img = [UIImage imageWithData:imageData];
 64     UIImageView *imgVCurrent = _mArrImageView[imageIndex];
 65     imgVCurrent.image = [img rescaleImageToSize:_rescaleImageSize];
 66 }
 67
 68 -(NSData *)requestData:(NSInteger)imageIndex {
 69     //对于多线程操作，建议把线程操作放到 @autoreleasepool 中
 70     @autoreleasepool {
 71         NSURL *url = [Common randomImageURL];
 72         NSData *data = [NSData dataWithContentsOfURL:url];
 73         return data;
 74     }
 75 }
 76
 77 - (void)loadImageFromNetwork:(NSInteger)imageIndex {
 78     /*
 79      对比之前 NSThread 加载图片，你会发现核心代码简化了不少，有两点值得提的：
 80      （1）使用 NSBlockOperation 方法，所有的操作不必单独定义方法，同时解决了只能传递一个参数的问题。类似的操作，例如：调用主线程队列的 addOperationWithBlock: 方法进行 UI 更新，不用再定义一个参数实体类来进行参数传递（之前必须定义一个 KMImageData 解决只能传递一个参数的问题）。
 81      （2）使用 NSOperation 进行多线程开发可以设置最大并发操作数，有效的对操作进行控制（如 Demo 的代码设置最大并发操作数为5，则图片最多是五个一次加载的）。
 82      */
 83     NSLog(@"Current thread:%@", [NSThread currentThread]);
 84
 85     //mainQueue 是 UI 主线程，调用主线程队列的方法进行操作
 86     [[NSOperationQueue mainQueue] addOperationWithBlock:^{
 87         [self updateImage:[self requestData:imageIndex] withImageIndex:imageIndex];
 88     }];
 89 }
 90
 91 - (IBAction)loadImage:(id)sender {
 92     NSOperationQueue *operationQueue = [NSOperationQueue new];
 93     operationQueue.maxConcurrentOperationCount = 5; //设置最大并发操作数
 94
 95     NSUInteger len = kRowCount * kColumnCount;
 96     NSBlockOperation *lastBlockOperation = [NSBlockOperation blockOperationWithBlock:^{
 97         [self loadImageFromNetwork:len - 1];
 98     }];
 99
100     for (NSUInteger i=0; i<len - 1; i++) {
101         NSBlockOperation *blockOperation = [NSBlockOperation blockOperationWithBlock:^{
102             [self loadImageFromNetwork:i];
103         }];
104
105         //实现控制「操作执行顺序」，例如：控制最后一个操作第一个执行，这里设置操作的依赖关系为：最后一张图片加载操作完成后才执行
106         //PS：注意请勿进行循环依赖，否则循环依赖相关的操作是不会被执行的
107         //这里添加依赖关系；其相对应的移除方法：- (void)removeDependency:(NSOperation *)op;
108         [blockOperation addDependency:lastBlockOperation];
109
110         //另外添加操作对象实例数组的方法：- (void)addOperations:(NSArray *)ops waitUntilFinished:(BOOL)wait;
111         [operationQueue addOperation:blockOperation];
112     }
113
114     [operationQueue addOperation:lastBlockOperation];
115
116     /*
117     lastBlockOperation.queuePriority = NSOperationQueuePriorityVeryHigh; //在某个操作队列中的队列优先级；这样可以提高他被优先加载的机率，但是他也未必就第一个加载；所以要实现控制「操作执行顺序」，就得用设置操作的依赖关系的方式
118
119     typedef enum : NSInteger {
120         NSOperationQueuePriorityVeryLow = -8,
121         NSOperationQueuePriorityLow = -4,
122         NSOperationQueuePriorityNormal = 0,
123         NSOperationQueuePriorityHigh = 4,
124         NSOperationQueuePriorityVeryHigh = 8
125     } NSOperationQueuePriority;
126      */
127 }
128
129 @end 

SecondSampleViewController.xib

 1 <?xml version="1.0" encoding="UTF-8" standalone="no"?>
 2 <document type="com.apple.InterfaceBuilder3.CocoaTouch.XIB" version="3.0" toolsVersion="7706" systemVersion="14E46" targetRuntime="iOS.CocoaTouch" propertyAccessControl="none" useAutolayout="YES" useTraitCollections="YES">
 3     <dependencies>
 4         <deployment identifier="iOS"/>
 5         <plugIn identifier="com.apple.InterfaceBuilder.IBCocoaTouchPlugin" version="7703"/>
 6     </dependencies>
 7     <objects>
 8         <placeholder placeholderIdentifier="IBFilesOwner" id="-1" userLabel="File‘s Owner" customClass="SecondSampleViewController">
 9             <connections>
10                 <outlet property="btnLoadImage" destination="F5h-ZI-gGL" id="I40-e2-bAa"/>
11                 <outlet property="view" destination="i5M-Pr-FkT" id="sfx-zR-JGt"/>
12             </connections>
13         </placeholder>
14         <placeholder placeholderIdentifier="IBFirstResponder" id="-2" customClass="UIResponder"/>
15         <view clearsContextBeforeDrawing="NO" contentMode="scaleToFill" id="i5M-Pr-FkT">
16             <rect key="frame" x="0.0" y="0.0" width="600" height="600"/>
17             <autoresizingMask key="autoresizingMask" widthSizable="YES" heightSizable="YES"/>
18             <subviews>
19                 <button opaque="NO" contentMode="scaleToFill" contentHorizontalAlignment="center" contentVerticalAlignment="center" buttonType="roundedRect" lineBreakMode="middleTruncation" translatesAutoresizingMaskIntoConstraints="NO" id="F5h-ZI-gGL">
20                     <rect key="frame" x="230" y="530" width="140" height="50"/>
21                     <constraints>
22                         <constraint firstAttribute="height" constant="50" id="HWd-Xc-Wk7"/>
23                         <constraint firstAttribute="width" constant="140" id="vrH-qE-PNK"/>
24                     </constraints>
25                     <state key="normal" title="加载网络图片">
26                         <color key="titleShadowColor" white="0.5" alpha="1" colorSpace="calibratedWhite"/>
27                     </state>
28                     <connections>
29                         <action selector="loadImage:" destination="-1" eventType="touchUpInside" id="Hgw-q8-lHy"/>
30                     </connections>
31                 </button>
32             </subviews>
33             <color key="backgroundColor" white="1" alpha="1" colorSpace="custom" customColorSpace="calibratedWhite"/>
34             <constraints>
35                 <constraint firstAttribute="bottom" secondItem="F5h-ZI-gGL" secondAttribute="bottom" constant="20" id="jPY-fY-9XJ"/>
36                 <constraint firstAttribute="centerX" secondItem="F5h-ZI-gGL" secondAttribute="centerX" id="rH1-sV-pST"/>
37             </constraints>
38         </view>
39     </objects>
40 </document> 

AppDelegate.h

1 #import <UIKit/UIKit.h>
2
3 @interface AppDelegate : UIResponder <UIApplicationDelegate>
4
5 @property (strong, nonatomic) UIWindow *window;
6 @property (strong, nonatomic) UINavigationController *navigationController;
7
8 @end 

AppDelegate.m

 1 #import "AppDelegate.h"
 2 #import "ViewController.h"
 3
 4 @interface AppDelegate ()
 5
 6 @end
 7
 8 @implementation AppDelegate
 9
10
11 - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
12     _window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
13     ViewController *viewController = [[ViewController alloc] initWithSampleNameArray:@[@"请求单张网络图片（解决线程阻塞）", @"请求多张网络图片（多个线程并发）"]];
14     _navigationController = [[UINavigationController alloc] initWithRootViewController:viewController];
15     _window.rootViewController = _navigationController;
16     //[_window addSubview:_navigationController.view]; //当_window.rootViewController关联时，这一句可有可无
17     [_window makeKeyAndVisible];
18     return YES;
19 }
20
21 - (void)applicationWillResignActive:(UIApplication *)application {
22 }
23
24 - (void)applicationDidEnterBackground:(UIApplication *)application {
25 }
26
27 - (void)applicationWillEnterForeground:(UIApplication *)application {
28 }
29
30 - (void)applicationDidBecomeActive:(UIApplication *)application {
31 }
32
33 - (void)applicationWillTerminate:(UIApplication *)application {
34 }
35
36 @end 

输出结果：

 1 2015-08-28 00:26:36.878 NSOperationDemo[4228:48976] 代码块
 2 2015-08-28 00:26:36.878 NSOperationDemo[4228:48977] 代码块
 3 2015-08-28 00:26:37.366 NSOperationDemo[4228:48976] 所有代码块操作执行完毕后（无论已取消还是已完成），做一些事情，只执行一次
 4
 5 2015-08-28 00:26:42.505 NSOperationDemo[4228:48860] Current thread:<NSThread: 0x7fbd1bd335b0>{number = 3, name = (null)}
 6 2015-08-28 00:26:42.506 NSOperationDemo[4228:48978] Current thread:<NSThread: 0x7fbd1be0ad90>{number = 4, name = (null)}
 7 2015-08-28 00:26:42.507 NSOperationDemo[4228:48990] Current thread:<NSThread: 0x7fbd1e047390>{number = 5, name = (null)}
 8 2015-08-28 00:26:42.507 NSOperationDemo[4228:48990] Current thread:<NSThread: 0x7fbd1e047390>{number = 5, name = (null)}
 9 2015-08-28 00:26:42.507 NSOperationDemo[4228:48978] Current thread:<NSThread: 0x7fbd1be0ad90>{number = 4, name = (null)}
10 2015-08-28 00:26:42.507 NSOperationDemo[4228:49025] Current thread:<NSThread: 0x7fbd1be07c70>{number = 6, name = (null)}
11 2015-08-28 00:26:42.508 NSOperationDemo[4228:48978] Current thread:<NSThread: 0x7fbd1be0ad90>{number = 4, name = (null)}
12 2015-08-28 00:26:42.508 NSOperationDemo[4228:49025] Current thread:<NSThread: 0x7fbd1be07c70>{number = 6, name = (null)}
13 2015-08-28 00:26:42.508 NSOperationDemo[4228:48978] Current thread:<NSThread: 0x7fbd1be0ad90>{number = 4, name = (null)}
14 2015-08-28 00:26:42.508 NSOperationDemo[4228:48990] Current thread:<NSThread: 0x7fbd1e047390>{number = 5, name = (null)}
15 2015-08-28 00:26:42.508 NSOperationDemo[4228:48976] Current thread:<NSThread: 0x7fbd1e0335f0>{number = 7, name = (null)}
16 2015-08-28 00:26:42.508 NSOperationDemo[4228:48978] Current thread:<NSThread: 0x7fbd1be0ad90>{number = 4, name = (null)}