NSThread

• 特點(diǎn)：
  • 更加面向?qū)ο?/li>
  • 簡(jiǎn)單易用，可直接操作線程對(duì)象
  • 使用語言：OC語言
  • 使用頻率：偶爾使用
  • 線程生命周期：由程序員進(jìn)行管理，任務(wù)結(jié)束后自行銷毀

NSThread的幾種創(chuàng)建方式

• 方式一：
  • 優(yōu)點(diǎn)：能拿到線程對(duì)象
  • 缺點(diǎn)：需要手動(dòng)啟動(dòng)線程

 NSThread *threadA = [[NSThread alloc] initWithTarget:self selector:@selector(run:) object:@"threadA"];
[threadA start];

• 方式二：
  • 優(yōu)點(diǎn)：自動(dòng)啟動(dòng)線程
  • 缺點(diǎn)：不能拿到線程對(duì)象

    [NSThread detachNewThreadSelector:@selector(run:) toTarget:self withObject:@"threadB"];

• 方式三：（后臺(tái)線程）
• 優(yōu)點(diǎn)：自動(dòng)啟動(dòng)線程
• 缺點(diǎn)：不能拿到線程對(duì)象

    [self performSelectorInBackground:@selector(run:) withObject:@"threadC"];

• 方式四：（自定義線程）
  • 缺點(diǎn)：需要自定義 NSThread 類妓蛮，重寫自定義類的 main 方法
  • 需要手動(dòng)開啟子線程

BWThread *threadD = [[BWThread alloc] init];
[threadD start];

-(void)main {
    NSLog(@"%@", [NSThread currentThread]);
    NSLog(@"自定義線程需要重寫 main 方法");
}

NSThread常用屬性

• 設(shè)置線程的名字

threadA.name = @"threadA";
[threadB setName:@"threadB"];
threadC.name = @"threadC";

• 設(shè)置線程的優(yōu)先級(jí)

threadA.threadPriority = 1.0;
threadC.threadPriority = 0.1;

• 優(yōu)先級(jí)的取值范圍是 0~1.0，默認(rèn)情況下是 0.5
• 系統(tǒng)在執(zhí)行任務(wù)時(shí)，會(huì)根據(jù)優(yōu)先級(jí)的大小調(diào)整任務(wù)的執(zhí)行順序蒲肋，優(yōu)先級(jí)大的任務(wù)會(huì)先執(zhí)行。

NSThread線程間的通信

• 涉及到 UI 界面的操作都要放到主線程中執(zhí)行

@interface ViewController ()
@property (weak, nonatomic) IBOutlet UIImageView *imageView;
@end
@implementation ViewController
 - (void)viewDidLoad {
    [super viewDidLoad];
}
 - (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {
    //創(chuàng)建線程
    [NSThread detachNewThreadSelector:@selector(download) toTarget:self withObject:nil];
}
 - (void)download {    
    //獲取開始時(shí)間
//    NSDate *start = [NSDate date];
    CFTimeInterval start = CFAbsoluteTimeGetCurrent();    
    //1.設(shè)置URL
    NSURL *url = [NSURL URLWithString:@"http://g.hiphotos.baidu.com/image/pic/item/bd315c6034a85edf9ba34e244b540923dd54758d.jpg"];
    //2.下載圖片的二進(jìn)制數(shù)據(jù)到本地
    NSData *imageData = [NSData dataWithContentsOfURL:url];
    //3.把二進(jìn)制數(shù)據(jù)轉(zhuǎn)換成圖片
    UIImage *image = [UIImage imageWithData:imageData];
    //4.回到主線程設(shè)置展示圖片
    // 4.1.方式一   waitUntilDone 是否等調(diào)用的方法執(zhí)行完畢再繼續(xù)執(zhí)行后面的任務(wù)
//    [self performSelectorOnMainThread:@selector(showImage:) withObject:image waitUntilDone:YES];
    // 4.2.方式二
//    [self performSelector:@selector(showImage:) onThread:[NSThread mainThread] withObject:image waitUntilDone:YES];
    // 4.3.方式三
    [self.imageView performSelector:@selector(setImage:) onThread:[NSThread mainThread] withObject:image waitUntilDone:YES];   
    //獲取結(jié)束時(shí)間
//    NSDate *end = [NSDate date];
//    NSLog(@"用時(shí)：%f", [end timeIntervalSinceDate:start]);
    CFTimeInterval end = CFAbsoluteTimeGetCurrent();
    NSLog(@"用時(shí)：%f", end - start);   
   NSLog(@"--- END ---");
}
 - (void)showImage:(UIImage *)image {
    self.imageView.image = image;
    NSLog(@"%@", [NSThread currentThread]);
}
@end