NSThread那些事兒
阿新 • • 發佈：2017-08-30
sage com strong prop block cti 線程優先級 初始化 tar
NSThread
哎呀，它面向對象，再去看看蘋果提供的API，對比一下Pthreads，簡單明了，人生仿佛又充滿了陽光和希望，我們先來一看一下系統提供給我們的API自然就知道怎麽用了，來來來，我給你註釋一下啊：
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@interface NSThread : NSObject//當前線程
@property (class, readonly, strong) NSThread *currentThread;
//使用類方法創建線程執行任務
+ (void)detachNewThreadWithBlock:(void (^)(void))block API_AVAILABLE(macosx(10.12), ios(10.0), watchos(3.0), tvos(10.0));
+ (void)detachNewThreadSelector:(SEL)selector toTarget:(id)target withObject:(nullable id)argument;
//判斷當前是否為多線程+ (BOOL)isMultiThreaded;
//指定線程的線程參數，例如設置當前線程的斷言處理器。
@property (readonly, retain) NSMutableDictionary *threadDictionary;
//當前線程暫停到某個時間
+ (void)sleepUntilDate:(NSDate *)date;
//當前線程暫停一段時間
+ (void)sleepForTimeInterval:(NSTimeInterval)ti;
//退出當前線程
+ (void)exit;
//當前線程優先級
+ (double)threadPriority;
//設置當前線程優先級
+ (BOOL)setThreadPriority:(double)p;//指定線程對象優先級 0.0～1.0，默認值為0.5
@property double threadPriority NS_AVAILABLE(10_6, 4_0);
//服務質量
@property NSQualityOfService qualityOfService NS_AVAILABLE(10_10, 8_0);
//線程名稱
@property (nullable, copy) NSString *name NS_AVAILABLE(10_5, 2_0);
//棧區大小
@property NSUInteger stackSize NS_AVAILABLE(10_5, 2_0);
//是否為主線程
@property (class, readonly) BOOL isMainThread NS_AVAILABLE(10_5, 2_0);
//獲取主線程
@property (class, readonly, strong) NSThread *mainThread NS_AVAILABLE(10_5, 2_0);
//初始化
- (instancetype)init NS_AVAILABLE(10_5, 2_0) NS_DESIGNATED_INITIALIZER;
//實例方法初始化，需要再調用start方法
- (instancetype)initWithTarget:(id)target selector:(SEL)selector object:(nullable id)argument NS_AVAILABLE(10_5, 2_0);
- (instancetype)initWithBlock:(void (^)(void))block API_AVAILABLE(macosx(10.12), ios(10.0), watchos(3.0), tvos(10.0));
//線程狀態，正在執行
@property (readonly, getter=isExecuting) BOOL executing NS_AVAILABLE(10_5, 2_0);
//線程狀態，正在完成
@property (readonly, getter=isFinished) BOOL finished NS_AVAILABLE(10_5, 2_0);
//線程狀態，已經取消
@property (readonly, getter=isCancelled) BOOL cancelled NS_AVAILABLE(10_5, 2_0);
//取消，僅僅改變線程狀態，並不能像exist一樣真正的終止線程
- (void)cancel NS_AVAILABLE(10_5, 2_0);
//開始
- (void)start NS_AVAILABLE(10_5, 2_0);
//線程需要執行的代碼，一般寫子類的時候會用到
- (void)main NS_AVAILABLE(10_5, 2_0);
@end
另外，還有一個NSObject的分類，瞅一眼：
@interface NSObject (NSThreadPerformAdditions)
//隱式的創建並啟動線程，並在指定的線程（主線程或子線程）上執行方法。
- (void)performSelectorOnMainThread:(SEL)aSelector withObject:(nullable id)arg waitUntilDone:(BOOL)wait modes:(nullable NSArray<nsstring *> *)array;
- (void)performSelectorOnMainThread:(SEL)aSelector withObject:(nullable id)arg waitUntilDone:(BOOL)wait;
- (void)performSelector:(SEL)aSelector onThread:(NSThread *)thr withObject:(nullable id)arg waitUntilDone:(BOOL)wait modes:(nullable NSArray<nsstring *> *)array NS_AVAILABLE(10_5, 2_0);
- (void)performSelector:(SEL)aSelector onThread:(NSThread *)thr withObject:(nullable id)arg waitUntilDone:(BOOL)wait NS_AVAILABLE(10_5, 2_0);
- (void)performSelectorInBackground:(SEL)aSelector withObject:(nullable id)arg NS_AVAILABLE(10_5, 2_0);
@end</nsstring *></nsstring *>
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上面的介紹您還滿意嗎？小的幫您下載一張圖片，您瞧好：
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-(void)creatBigImageView{
self.bigImageView = [[UIImageView alloc] initWithFrame:self.view.bounds];
[self.view addSubview:_bigImageView];
UIButton *startButton = [UIButton buttonWithType:UIButtonTypeSystem];
startButton.frame = CGRectMake(0, 0, self.view.frame.size.width / 2, 50);
startButton.backgroundColor = [UIColor grayColor];
[startButton setTitle:@"開始加載" forState:UIControlStateNormal];
[startButton addTarget:self action:@selector(loadImage) forControlEvents:UIControlEventTouchUpInside];
[self.view addSubview:startButton];
UIButton *jamButton = [UIButton buttonWithType:UIButtonTypeSystem];
jamButton.frame = CGRectMake(self.view.frame.size.width / 2, 0, self.view.frame.size.width / 2, 50);
jamButton.backgroundColor = [UIColor grayColor];
[jamButton setTitle:@"阻塞測試" forState:UIControlStateNormal];
[jamButton addTarget:self action:@selector(jamTest) forControlEvents:UIControlEventTouchUpInside];
[self.view addSubview:jamButton];
}
-(void)jamTest{
UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:@"線程阻塞" message:@"" delegate:nil cancelButtonTitle:@"好" otherButtonTitles:nil, nil];
[alertView show];
}
-(void)loadImage{
NSURL *imageUrl = [NSURL URLWithString:@"http://img5.duitang.com/uploads/item/201206/06/20120606174422_LZSeE.thumb.700_0.jpeg"];
NSData *imageData = [NSData dataWithContentsOfURL:imageUrl];
[self updateImageData:imageData];
}
-(void)updateImageData:(NSData*)imageData{
UIImage *image = [UIImage imageWithData:imageData];
self.bigImageView.image = image;
}
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運行結果：
我們可以清楚的看到，主線程阻塞了，用戶不可以進行其他操作，你見過這樣的應用嗎？
所以我們這樣改一下：
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-(void)creatBigImageView{
self.bigImageView = [[UIImageView alloc] initWithFrame:self.view.bounds];
[self.view addSubview:_bigImageView];
UIButton *startButton = [UIButton buttonWithType:UIButtonTypeSystem];
startButton.frame = CGRectMake(0, 20, self.view.frame.size.width / 2, 50);
startButton.backgroundColor = [UIColor grayColor];
[startButton setTitle:@"開始加載" forState:UIControlStateNormal];
[startButton addTarget:self action:@selector(loadImageWithMultiThread) forControlEvents:UIControlEventTouchUpInside];
[self.view addSubview:startButton];
UIButton *jamButton = [UIButton buttonWithType:UIButtonTypeSystem];
jamButton.frame = CGRectMake(self.view.frame.size.width / 2, 20, self.view.frame.size.width / 2, 50);
jamButton.backgroundColor = [UIColor grayColor];
[jamButton setTitle:@"阻塞測試" forState:UIControlStateNormal];
[jamButton addTarget:self action:@selector(jamTest) forControlEvents:UIControlEventTouchUpInside];
[self.view addSubview:jamButton];
}
-(void)jamTest{
UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:@"阻塞測試" message:@"" delegate:nil cancelButtonTitle:@"好" otherButtonTitles:nil, nil];
[alertView show];
}
-(void)loadImageWithMultiThread{
//方法1：使用對象方法
//NSThread *thread=[[NSThread alloc]initWithTarget:self selector:@selector(loadImage) object:nil];
//??啟動一個線程並非就一定立即執行，而是處於就緒狀態，當CUP調度時才真正執行
//[thread start];
//方法2：使用類方法
[NSThread detachNewThreadSelector:@selector(loadImage) toTarget:self withObject:nil];
}
-(void)loadImage{
NSURL *imageUrl = [NSURL URLWithString:@"http://img5.duitang.com/uploads/item/201206/06/20120606174422_LZSeE.thumb.700_0.jpeg"];
NSData *imageData = [NSData dataWithContentsOfURL:imageUrl];
//必須在主線程更新UI，Object：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)，waitUntilDone:是否線程任務完成執行
[self performSelectorOnMainThread:@selector(updateImageData:) withObject:imageData waitUntilDone:YES];
//[self updateImageData:imageData];
}
-(void)updateImageData:(NSData*)imageData{
UIImage *image = [UIImage imageWithData:imageData];
self.bigImageView.image = image;
}
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運行結果：
哎呀，用多線程果然能解決線程阻塞的問題，並且NSThread也比Pthreads好用，仿佛你對精通熟練使用多線程又有了一絲絲曙光。假如我有很多不同類型的任務，每個任務之間還有聯系和依賴，你是不是又懵逼了，上面的你是不是覺得又白看了，其實開發中我覺得NSThread用到最多的就是[NSThread currentThread];了。（不要慌，往下看... ...）
轉自：http://www.cocoachina.com/ios/20170829/20404.html
NSThread那些事兒