每個 iOS 應用程序都有個專門用來更新顯示 UI 界面、處理用戶的觸摸事件的主線程，因此不能將其他太耗時的操作放在主線程中執行，不然會造成主線程堵塞（出現卡機現象），帶來不好的用戶體驗。
一般的解決方案就是：將那些耗時的操作放到另外一個線程中去執行，多線程編程就是防止主線程堵塞和增加運行效率的最佳方法。
iOS 支持多個層次的多線程編程，層次越高的抽象程度越高，使用也越方便，也是 Apple 最推薦使用的方法。
?下面根據抽象層次從低到高依次列出 iOS 所支持的多線程編程方法：
NSThread ：是三種方法里面相對輕量級的，但需要管理線程的生命周期、同步、加鎖問題，這會導致一定的性能開銷
NSOperation：是基于 OC 實現的，NSOperation 以面向對象的方式封裝了需要執行的操作，不必關心線程管理、同步等問題。
NSOperation 是一個抽象基類，iOS 提供了兩種默認實現：NSInvocationOperation 和 NSBlockOperation，當然也可以自定義 NSOperation
Grand Central Dispatch(簡稱 GCD ，iOS4 才開始支持)：提供了一些新特性、運行庫來支持多核并行編程，他的關注點更高：如何在多個 CPU 上提升效率
效果如下：
ViewController.h
1 #import <UIKit/UIKit.h>2 3 @interface ViewController : UITableViewController4 @PRoperty (copy, 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 #import "ThirdSampleViewController.h" 5 6 @interface ViewController () 7 - (void)layoutUI; 8 @end 9 10 @implementation ViewController11 - (void)viewDidLoad {12 [super viewDidLoad];13 14 [self layoutUI];15 }16 17 - (void)didReceiveMemoryWarning {18 [super didReceiveMemoryWarning];19 // Dispose of any resources that can be recreated.20 }21 22 - (instancetype)initWithSampleNameArray:(NSArray *)arrSampleName {23 if (self = [super initWithStyle:UITableViewStyleGrouped]) {24 self.navigationItem.title = @"多線程開發之一 NSThread";25 self.navigationItem.backBarButtonItem = [[UIBarButtonItem alloc] initWithTitle:@"返回首頁" style:UIBarButtonItemStylePlain target:nil action:nil];26 27 _arrSampleName = arrSampleName;28 }29 return self;30 }31 32 - (void)layoutUI {33 34 }35 36 #pragma mark - UITableViewController相關方法重寫37 - (CGFloat)tableView:(UITableView *)tableView heightForHeaderInSection:(NSInteger)section {38 return 0.1;39 }40 41 - (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {42 return 1;43 }44 45 - (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {46 return [_arrSampleName count];47 }48 49 - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {50 static NSString *cellIdentifier = @"cell";51 UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:cellIdentifier];52 if (!cell) {53 cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:cellIdentifier];54 }55 cell.textLabel.text = _arrSampleName[indexPath.row];56 return cell;57 }58 59 - (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {60 switch (indexPath.row) {61 case 0: {62 FirstSampleViewController *firstSampleVC = [FirstSampleViewController new];63 [self.navigationController pushViewController:firstSampleVC animated:YES];64 break;65 }66 case 1: {67 SecondSampleViewController *secondSampleVC = [SecondSampleViewController new];68 [self.navigationController pushViewController:secondSampleVC animated:YES];69 break;70 }71 case 2: {72 ThirdSampleViewController *thirdSampleVC = [ThirdSampleViewController new];73 [self.navigationController pushViewController:thirdSampleVC animated:YES];74 break;75 76 /*77 類似堆棧的先進后出的原理：78 返回到（上一級）、（任意級）、（根級）導航79 [self.navigationController popViewControllerAnimated:YES];80 [self.navigationController popToViewController:thirdSampleVC animated:YES];81 [self.navigationController popToRootViewControllerAnimated:YES];82 */83 }84 default:85 break;86 }87 }88 89 @end
UIImage+RescaleImage.h
1 #import <UIKit/UIKit.h> 2 3 @interface UIImage (RescaleImage) 4 /** 5 * 根據寬高大小，獲取對應的縮放圖片 6 * 7 * @param size 寬高大小 8 * 9 * @return 對應的縮放圖片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
KMImageData.h
1 #import <Foundation/Foundation.h>2 3 @interface KMImageData : NSObject4 @property (assign, nonatomic) NSInteger index;5 @property (strong, nonatomic) NSData *data;6 7 - (instancetype)initWithData:(NSData *)data withIndex:(NSInteger)index;8 9 @end
KMImageData.m
1 #import "KMImageData.h" 2 3 @implementation KMImageData 4 5 - (instancetype)initWithData:(NSData *)data withIndex:(NSInteger)index { 6 if (self = [super init]) { 7 _data = data; 8 _index = index; 9 }10 return self;11 }12 13 @end
FirstSampleViewController.h
1 #import <UIKit/UIKit.h>2 3 @interface FirstSampleViewController : UIViewController4 @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 4 @interface FirstSampleViewController () 5 - (void)layoutUI; 6 - (void)updateImage:(NSData *)imageData; 7 - (void)loadImageFromNetwork; 8 @end 9 10 @implementation FirstSampleViewController11 12 - (void)viewDidLoad {13 [super viewDidLoad];14 15 [self layoutUI];16 }17 18 - (void)didReceiveMemoryWarning {19 [super didReceiveMemoryWarning];20 // Dispose of any resources that can be recreated.21 }22 23 - (void)dealloc {24 _imgV.image = nil;25 }26 27 - (void)layoutUI {28 CGFloat width = [[UIScreen mainScreen] bounds].size.width; //bounds 返回整個屏幕大小；applicationFrame 返回去除狀態欄后的屏幕大小29 CGFloat height = width * 150.0 / 190.0;30 _rescaleImageSize = CGSizeMake(width, height);31 32 //NSString *path = [[NSBundle mainBundle] pathForResource:@"PictureNo@2x" ofType:@"png"];33 //_imgV.image = [UIImage imageWithContentsOfFile:path];34 35 _btnLoadImage.tintColor = [UIColor darkGrayColor];36 _btnLoadImage.layer.masksToBounds = YES;37 _btnLoadImage.layer.cornerRadius = 10.0;38 _btnLoadImage.layer.borderColor = [UIColor grayColor].CGColor;39 _btnLoadImage.layer.borderWidth = 1.0;40 }41 42 - (void)updateImage:(NSData *)imageData {43 UIImage *img = [UIImage imageWithData:imageData];44 _imgV.image = [img rescaleImageToSize:_rescaleImageSize];45 }46 47 - (void)loadImageFromNetwork {48 NSURL *url = [NSURL URLWithString:@"http://images.apple.com/v/macbook/c/overview/images/hero_static_large.jpg"];49 NSData *data = [NSData dataWithContentsOfURL:url];50 51 /*將數據顯示到UI控件，注意只能在主線程中更新UI；52 另外 performSelectorOnMainThread 方法是 NSObject 的分類方法，每個 NSObject 對象都有此方法；53 它調用的 selector 方法是當前調用控件的方法，例如使用 UIImageView 調用的時候 selector 就是 UIImageView 的方法54 withObject：代表調用方法的參數，不過只能傳遞一個參數（如果有多個參數請使用對象進行封裝）55 waitUntilDone：是否線程任務完成執行56 */57 [self performSelectorOnMainThread:@selector(updateImage:)58 withObject:data59 waitUntilDone:YES];60 }61 62 - (IBAction)loadImage:(id)sender {63 //方法一：使用線程對象實例方法創建一個線程64 //NSThread *thread = [[NSThread alloc] initWithTarget:self65 // selector:@selector(loadImageFromNetwork)66 // object:nil];67 //[thread start]; //啟動一個線程；注意啟動一個線程并非就一定立即執行，而是處于就緒狀態，當系統調度時才真正執行68 69 //方法二：使用線程類方法創建一個線程70 [NSThread detachNewThreadSelector:@selector(loadImageFromNetwork)71 toTarget:self72 withObject:nil];73 }74 75 @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="S/>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="加載網絡圖片">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 : UIViewController4 @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 "KMImageData.h" 3 #import "UIImage+RescaleImage.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:(KMImageData *)imageData; 12 -(KMImageData *)requestData:(NSInteger)imageIndex; 13 - (void)loadImageFromNetwork:(NSNumber *)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:@"PictureNo@2x" ofType:@"png"]; 39 UIImage *img = [UIImage imageWithContentsOfFile:path]; 40 _mArrImageView = [NSMutableArray arrayWithCapacity:kRowCount * kColumnCount]; 41 //初始化多個圖片視圖 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:(KMImageData *)imageData { 63 UIImage *img = [UIImage imageWithData:imageData.data]; 64 UIImageView *imgVCurrent = _mArrImageView[imageData.index]; 65 imgVCurrent.image = [img rescaleImageToSize:_rescaleImageSize]; 66 } 67 68 -(KMImageData *)requestData:(NSInteger)imageIndex { 69 //對于多線程操作，建議把線程操作放到 @autoreleasepool 中 70 @autoreleasepool { 71 if (imageIndex != kRowCount * kColumnCount - 1) { //雖然設置了最后一個線程的優先級為1.0，但無法保證他是第一個加載的。所以我們這里讓其他線程掛起0.5秒，這樣基本能保證最后一個線程第一個加載，除非網絡非常差的情況 72 [NSThread sleepForTimeInterval:0.5]; 73 } 74 75 NSURL *url = [NSURL URLWithString:@"http://images.apple.com/v/macbook/c/overview/images/hero_static_large.jpg"]; 76 NSData *data = [NSData dataWithContentsOfURL:url]; 77 KMImageData *imageData = [[KMImageData alloc] initWithData:data 78 withIndex:imageIndex]; 79 return imageData; 80 } 81 } 82 83 - (void)loadImageFromNetwork:(NSNumber *)imageIndex { 84 NSLog(@"Current thread:%@",[NSThread currentThread]); 85 86 /*將數據顯示到UI控件，注意只能在主線程中更新UI； 87 另外 performSelectorOnMainThread 方法是 NSObject 的分類方法，每個 NSObject 對象都有此方法； 88 它調用的 selector 方法是當前調用控件的方法，例如使用 UIImageView 調用的時候 selector 就是 UIImageView 的方法 89 withObject：代表調用方法的參數，不過只能傳遞一個參數（如果有多個參數請使用對象進行封裝） 90 waitUntilDone：是否線程任務完成執行 91 */ 92 [self performSelectorOnMainThread:@selector(updateImage:) 93 withObject:[self requestData:[imageIndex integerValue]] 94 waitUntilDone:YES]; 95 } 96 97 - (IBAction)loadImage:(id)sender { 98 for (NSUInteger i=0, len=kRowCount * kColumnCount; i<len; i++) { 99 NSThread *thread = [[NSThread alloc] initWithTarget:self100 selector:@selector(loadImageFromNetwork:)101 object:[NSNumber numberWithInteger:i]];102 thread.name = [NSString stringWithFormat:@"Thread %lu", (unsigned long)i];103 thread.threadPriority = i == len-1 ? 1.0 : 0.0; //設置線程優先級；0.0-1.0，值越高優先級越高，這樣可以提高他被優先加載的機率，但是他也未必就第一個加載。因為首先其他線程是先啟動的，其次網絡狀況我們沒辦法修改104 [thread start];105 }106 }107 108 @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="加載網絡圖片">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>
ThirdSampleViewController.h
1 #import <UIKit/UIKit.h> 2 3 @interface ThirdSampleViewController : UIViewController 4 @property (assign, nonatomic) CGSize rescaleImageSize; 5 @property (strong, nonatomic) NSMutableArray *mArrImageView; 6 @property (strong, nonatomic) NSMutableArray *mArrThread; 7 8 @property (strong, nonatomic) IBOutlet UIButton *btnLoadImage; 9 @property (strong, nonatomic) IBOutlet UIButton *btnStopLoadImage;10 11 @end
ThirdSampleViewController.m
1 #import "ThirdSampleViewController.h" 2 #import "KMImageData.h" 3 #import "UIImage+RescaleImage.h" 4 5 #define kRowCount 4 6 #define kColumnCount 3 7 #define kCellSpacing 10.0 8 9 @interface ThirdSampleViewController () 10 - (void)layoutUI; 11 - (void)updateImage:(KMImageData *)imageData; 12 -(KMImageData *)requestData:(NSInteger)imageIndex; 13 - (void)loadImageFromNetwork:(NSNumber *)imageIndex; 14 @end 15 16 @implementation ThirdSampleViewController 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 _mArrThread = nil; 32 } 33 34 - (void)layoutUI { 35 CGFloat width = ([[UIScreen mainScreen] bounds].size.width - ((kColumnCount + 1) * kCellSpacing)) / kColumnCount; 36 _rescaleImageSize = CGSizeMake(width, width); 37 38 CGFloat heightOfStatusAndNav = 20.0 + 44.0; 39 NSString *path = [[NSBundle mainBundle] pathForResource:@"PictureNo@2x" ofType:@"png"]; 40 UIImage *img = [UIImage imageWithContentsOfFile:path]; 41 _mArrImageView = [NSMutableArray arrayWithCapacity:kRowCount * kColumnCount]; 42 //初始化多個圖片視圖 43 for (NSUInteger i=0; i<kRowCount; i++) { 44 for (NSUInteger j=0; j<kColumnCount; j++) { 45 UIImageView *imgV = [[UIImageView alloc] initWithFrame: 46 CGRectMake(_rescaleImageSize.width * j + kCellSpacing * (j+1), 47 _rescaleImageSize.height * i + kCellSpacing * (i+1) + heightOfStatusAndNav, 48 _rescaleImageSize.width, 49 _rescaleImageSize.height)]; 50 imgV.image = img; 51 [self.view addSubview:imgV]; 52 [_mArrImageView addObject:imgV]; 53 } 54 } 55 56 void (^beautifulButton)(UIButton *, UIColor *) = ^(UIButton *btn, UIColor *tintColor) { 57 btn.tintColor = tintColor; 58 btn.layer.masksToBounds = YES; 59 btn.layer.cornerRadius = 10.0; 60 btn.layer.borderColor = [UIColor grayColor].CGColor; 61 btn.layer.borderWidth = 1.0; 62 }; 63 64 beautifulButton(_btnLoadImage, [UIColor darkGrayColor]); 65 beautifulButton(_btnStopLoadImage, [UIColor redColor]); 66 } 67 68 - (void)updateImage:(KMImageData *)imageData { 69 UIImage *img = [UIImage imageWithData:imageData.data]; 70 UIImageView *imgVCurrent = _mArrImageView[imageData.index]; 71 imgVCurrent.image = [img rescaleImageToSize:_rescaleImageSize]; 72 } 73 74 -(KMImageData *)requestData:(NSInteger)imageIndex { 75 //對于多線程操作，建議把線程操作放到 @autoreleasepool 中 76 @autoreleasepool { 77 if (imageIndex != kRowCount * kColumnCount - 1) { //雖然設置了最后一個線程的優先級為1.0，但無法保證他是第一個加載的。所以我們這里讓其他線程掛起0.5秒，這樣基本能保證最后一個線程第一個加載，除非網絡非常差的情況 78 [NSThread sleepForTimeInterval:0.5]; 79 } 80 81 NSURL *url = [NSURL URLWithString:@"http://images.apple.com/v/macbook/c/overview/images/hero_static_large.jpg"]; 82 NSData *data = [NSData dataWithContentsOfURL:url]; 83 KMImageData *imageData = [[KMImageData alloc] initWithData:data 84 withIndex:imageIndex]; 85 return imageData; 86 } 87 } 88 89 - (void)loadImageFromNetwork:(NSNumber *)imageIndex { //子線程中執行 90 //線程狀態：thread.isExecuting（是否執行中）、thread.isFinished（是否已完成）、thread.isCancelled（是否已取消） 91 //thread.isMainThread（是否主線程）、[NSThread isMultiThreaded]（是否多線程） 92 93 KMImageData *imageData = [self requestData:[imageIndex integerValue]]; 94 95 NSThread *thread = _mArrThread[[imageIndex integerValue]]; 96 if (thread.isCancelled) { //判斷線程是否已經取消，如是就退出當前線程；這里注意需讓 exit 操作有足夠的時間進行占用資源的釋放，否則有可能出現異常；比如 Demo 中：當點擊「停止加載」按鈕后，再次快速點擊「加載網絡圖片」按鈕 97 NSLog(@"Current thread:%@ will be cancelled.", thread); 98 [NSThread exit]; 99 } else {100 // //在后臺執行一個方法，本質就是重新創建一個線程來執行方法101 // [self performSelectorInBackground:@selector(updateImage:) withObject:imageData];102 // 103 // /*將數據顯示到UI控件，注意只能在主線程中更新UI；104 // 另外 performSelectorOnMainThread 方法是 NSObject 的分類方法，每個 NSObject 對象都有此方法；它調用的 selector 方法是當前調用控件的方法，例如使用 UIImageView 調用的時候 selector 就是 UIImageView 的方法105 // withObject：代表調用方法的參數，不過只能傳遞一個參數（如果有多個參數請使用對象進行封裝）106 // waitUntilDone：是否線程任務完成后執行107 // */108 // [self performSelectorOnMainThread:@selector(updateImage:)109 // withObject:imageData110 // waitUntilDone:YES];111 112 @try {113 //在指定的線程上執行一個方法，需要用戶創建一個線程對象實例114 [self performSelector:@selector(updateImage:)115 onThread:thread116 withObject:imageData117 waitUntilDone:YES];118 }119 @catch (NSException *exception) {120 NSLog(@"Exception: %@", [exception description]);121 }122 }123 }124 125 - (IBAction)loadImage:(id)sender {126 NSUInteger len = kRowCount * kColumnCount;127 _mArrThread = [NSMutableArray arrayWithCapacity:len];128 129 //循環創建多個線程130 for (NSUInteger i=0; i<len; i++) {131 NSThread *thread = [[NSThread alloc] initWithTarget:self132 selector:@selector(loadImageFromNetwork:)133 object:[NSNumber numberWithInteger:i]];134 thread.name = [NSString stringWithFormat:@"Thread %lu", (unsigned long)i];135 thread.threadPriority = i == len-1 ? 1.0 : 0.0; //設置線程優先級；0.0-1.0，值越高優先級越高，這樣可以提高他被優先加載的機率，但是他也未必就第一個加載。因為首先其他線程是先啟動的，其次網絡狀況我們沒辦法修改136 [_mArrThread addObject:thread];137 }138 139 //循環啟動線程140 for (NSUInteger i=0; i<len; i++) {141 NSThread *thread = _mArrThread[i];142 [thread start];143 }144 }145 146 - (IBAction)stopLoadImage:(id)sender { //主線程中執行147 for (NSUInteger i=0, len=kRowCount * kColumnCount; i<len; i++) {148 NSThread *thread = _mArrThread[i];149 if (!thread.isFinished) { //判斷線程是否完成，如果沒有完成則設置為取消狀態；取消狀態僅僅是改變了線程狀態而言，并不能終止線程150 [thread cancel];151 }152 }153 }154 155 @end
ThirdSampleViewController.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="ThirdSampleViewController"> 9 <connections>10 <outlet property="btnLoadImage" destination="F5h-ZI-gGL" id="I40-e2-bAa"/>11 <outlet property="btnStopLoadImage" destination="gnu-KE-bGq" id="tOA-t9-OA9"/>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 <button opaque="NO" contentMode="scaleToFill" contentHorizontalAlignment="center" contentVerticalAlignment="center" buttonType="roundedRect" lineBreakMode="middleTruncation" translatesAutoresizingMaskIntoConstraints="NO" id="F5h-ZI-gGL">21 <rect key="frame" x="20" y="530" width="130" height="50"/>22 <constraints>23 <constraint firstAttribute="height" constant="50" id="HWd-Xc-Wk7"/>24 <constraint firstAttribute="width" constant="130" id="vrH-qE-PNK"/>25 </constraints>26 <state key="normal" title="加載網絡圖片">27 <color key="titleShadowColor" white="0.5" alpha="1" colorSpace="calibratedWhite"/>28 </state>29 <connections>30 <action selector="loadImage:" destination="-1" eventType="touchUpInside" id="Hgw-q8-lHy"/>31 </connections>32 </button>33 <button opaque="NO" contentMode="scaleToFill" contentHorizontalAlignment="center" contentVerticalAlignment="center" buttonType="roundedRect" lineBreakMode="middleTruncation" translatesAutoresizingMaskIntoConstraints="NO" id="gnu-KE-bGq">34 <rect key="frame" x="450" y="530" width="130" height="50"/>35 <constraints>36 <constraint firstAttribute="height" constant="50" id="1R7-22-hMk"/>37 <constraint firstAttribute="width" constant="130" id="64l-yF-IFO"/>38 </constraints>39 <state key="normal" title="停止加載">40 <color key="titleShadowColor" white="0.5" alpha="1" colorSpace="calibratedWhite"/>41 </state>42 <connections>43 <action selector="loadImage:" destination="-1" eventType="touchUpInside" id="PyX-RW-cbL"/>44 <action selector="stopLoadImage:" destination="-1" eventType="touchUpInside" id="1Xa-Ek-D4B"/>45 </connections>46 </button>47 </subviews>48 <color key="backgroundColor" white="1" alpha="1" colorSpace="custom" customColorSpace="calibratedWhite"/>49 <constraints>50 <constraint firstItem="F5h-ZI-gGL" firstAttribute="leading" secondItem="i5M-Pr-FkT" secondAttribute="leading" constant="20" id="Glo-vW-SXd"/>51 <constraint firstAttribute="trailing" secondItem="gnu-KE-bGq" secondAttribute="trailing" constant="20" id="IdF-1v-bg2"/>52 <constraint firstAttribute="bottom" secondItem="gnu-KE-bGq" secondAttribute="bottom" constant="20" id="cyx-dg-K8M"/>53 <constraint firstAttribute="bottom" secondItem="F5h-ZI-gGL" secondAttribute="bottom" constant="20" id="jPY-fY-9XJ"/>54 <constraint firstAttribute="centerX" secondItem="F5h-ZI-gGL" secondAttribute="centerX" id="rH1-sV-pST"/>55 </constraints>56 <variation key="default">57 <mask key="constraints">58 <exclude reference="rH1-sV-pST"/>59 </mask>60 </variation>61 </view>62 </objects>63 </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:@[@"請求單張網絡圖片（解決線程阻塞）", @"請求多張網絡圖片（多個線程并發）", @"請求多張網絡圖片（線程狀態）"]];14 _navigationController = [[UINavigationController alloc] initWithRootViewController:viewController];15 _window.rootViewController = _navigationController;16 //[_window addSubview:_navigationController.view]; //當_window.rootViewController關聯時，這一句可有可無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
輸出結果：
1 2015-08-24 22:18:38.945 NSThreadDemo[5361:204621] INFO: Reveal Server started (Protocol Version 18). 2 2015-08-24 22:18:57.863 NSThreadDemo[5361:204847] Current thread:<NSThread: 0x7f9f60cd1f80>{number = 5, name = Thread 0} 3 2015-08-24 22:18:57.863 NSThreadDemo[5361:204848] Current thread:<NSThread: 0x7f9f60c74800>{number = 6, name = Thread 1} 4 2015-08-24 22:18:57.863 NSThreadDemo[5361:204849] Current thread:<NSThread: 0x7f9f60cb8f30>{number = 7, name = Thread 2} 5 2015-08-24 22:18:57.863 NSThreadDemo[5361:204850] Current thread:<NSThread: 0x7f9f60cb8500>{number = 8, name = Thread 3} 6 2015-08-24 22:18:57.864 NSThreadDemo[5361:204851] Current thread:<NSThread: 0x7f9f60cd0c60>{number = 9, name = Thread 4} 7 2015-08-24 22:18:57.865 NSThreadDemo[5361:204857] Current thread:<NSThread: 0x7f9f60dee540>{number = 11, name = Thread 6} 8 2015-08-24 22:18:57.864 NSThreadDemo[5361:204856] Current thread:<NSThread: 0x7f9f60cd2150>{number = 10, name = Thread 5} 9 2015-08-24 22:18:57.866 NSThreadDemo[5361:204859] Current thread:<NSThread: 0x7f9f60daf730>{number = 13, name = Thread 8}10 2015-08-24 22:18:57.866 NSThreadDemo[5361:204860] Current thread:<NSThread: 0x7f9f60db8530>{number = 14, name = Thread 9}11 2015-08-24 22:18:57.866 NSThreadDemo[5361:204862] Current thread:<NSThread: 0x7f9f60f3f7e0>{number = 16, name = Thread 11}12 2015-08-24 22:18:57.866 NSThreadDemo[5361:204858] Current thread:<NSThread: 0x7f9f60db2390>{number = 12, name = Thread 7}13 2015-08-24 22:18:57.867 NSThreadDemo[5361:204861] Current thread:<NSThread: 0x7f9f60f231c0>{number = 15, name = Thread 10}14 15 2015-08-24 22:19:07.073 NSThreadDemo[5361:204952] Current thread:<NSThread: 0x7f9f63010930>{number = 39, name = Thread 10} will be cancelled.16 2015-08-24 22:19:07.691 NSThreadDemo[5361:204951] Current thread:<NSThread: 0x7f9f60df0210>{number = 38, name = Thread 9} will be cancelled.17 2015-08-24 22:19:07.697 NSThreadDemo[5361:204957] Current thread:<NSThread: 0x7f9f60db8ee0>{number = 29, name = Thread 0} will be cancelled.18 2015-08-24 22:19:07.729 NSThreadDemo[5361:204958] Current thread:<NSThread: 0x7f9f60db2390>{number = 30, name = Thread 1} will be cancelled.19 2015-08-24 22:19:07.857 NSThreadDemo[5361:204949] Current thread:<NSThread: 0x7f9f63011190>{number = 36, name = Thread 7} will be cancelled.20 2015-08-24 22:19:08.025 NSThreadDemo[5361:204960] Current thread:<NSThread: 0x7f9f6300c2d0>{number = 32, name = Thread 3} will be cancelled.21 2015-08-24 22:19:08.047 NSThreadDemo[5361:204959] Current thread:<NSThread: 0x7f9f60dd4200>{number = 31, name = Thread 2} will be cancelled.22 2015-08-24 22:19:08.191 NSThreadDemo[5361:204942] Current thread:<NSThread: 0x7f9f60db8ee0>{number = 29, name = Thread 0} will be cancelled.23 2015-08-24 22:19:08.250 NSThreadDemo[5361:204965] Current thread:<NSThread: 0x7f9f630110b0>{number = 37, name = Thread 8} will be cancelled.24 2015-08-24 22:19:08.416 NSThreadDemo[5361:204962] Current thread:<NSThread: 0x7f9f60df7bc0>{number = 34, name = Thread 5} will be cancelled.25 2015-08-24 22:19:08.464 NSThreadDemo[5361:204963] Current thread:<NSThread: 0x7f9f60dc5ca0>{number = 35, name = Thread 6} will be cancelled.26 2015-08-24 22:19:08.495 NSThreadDemo[5361:204964] Current thread:<NSThread: 0x7f9f63011190>{number = 36, name = Thread 7} will be cancelled.27 2015-08-24 22:19:08.661 NSThreadDemo[5361:204966] Current thread:<NSThread: 0x7f9f60df0210>{number = 38, name = Thread 9} will be cancelled.28 2015-08-24 22:19:10.033 NSThreadDemo[5361:204961] Current thread:<NSThread: 0x7f9f60da3330>{number = 33, name = Thread 4} will be cancelled.29 2015-08-24 22:19:10.056 NSThreadDemo[5361:204967] Current thread:<NSThread: 0x7f9f63010930>{number = 39, name = Thread 10} will be cancelled.
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