一、創(chuàng)建多線(xiàn)程的五種方式

1.開(kāi)啟線(xiàn)程的方法一

NSThread * thread=[[NSThread alloc] initWithTarget:self selector:@selector(_update) object:nil];

2.開(kāi)啟線(xiàn)程的方法二

[NSThread detachNewThreadSelector:@selector(_update) toTarget:self withObject:nil];

3.開(kāi)啟線(xiàn)程的方法三

[self performSelectorInBackground:@selector(_update) withObject:nil];

4.開(kāi)啟線(xiàn)程的方法四

NSOperationQueue *queue=[[NSOperationQueue alloc] init];

[queue addOperationWithBlock:^{

for(int i=0;i<50;i++){

printf("子線(xiàn)程 ");

}

}];

5.開(kāi)啟線(xiàn)程的方法五

//第一步開(kāi)啟線(xiàn)程池

NSOperationQueue * queue=[[NSOperationQueue alloc] init];

//設(shè)置并發(fā)數(shù)目

[queue setMaxConcurrentOperationCount:2];

//第二部創(chuàng)建多線(xiàn)程添加到線(xiàn)程池

NSInvocationOperation * thread1=[[NSInvocationOperation alloc] initWithTarget:self selector:@selector(_update1) object:nil];

NSInvocationOperation *thread2=[[NSInvocationOperation alloc] initWithTarget:self selector:@selector(_update2) object:nil];

[thread1 setQueuePriority:NSOperationQueuePriorityVeryLow];

[thread2 setQueuePriority:NSOperationQueuePriorityVeryHigh];

[queue addOperation:thread1];

[queue addOperation:thread2];

二、多線(xiàn)程應(yīng)用實(shí)例，加載圖片。

1.核心思想

考慮到如果加載網(wǎng)絡(luò)圖片會(huì)延遲，在一個(gè)主線(xiàn)程加載會(huì)影響控件的渲染，此時(shí)可以采取多線(xiàn)程，異步加載完成后刷新UI。

2.實(shí)現(xiàn)思路

通過(guò)為UIImageView 增加類(lèi)目來(lái)實(shí)現(xiàn)多線(xiàn)程下載。

主要代碼：

#import "UIImageView+thread.h"

@implementation UIImageView(load)

- (void) setImageWithUrl:(NSString *)url{

[self performSelectorInBackground:@selector(_loadImage:) withObject:url];

}

- (void) _loadImage:(NSString *)u{

@autoreleasepool {

NSURL *url=[NSURL URLWithString:u];

NSData *data=[NSData dataWithContentsOfURL:url];

UIImage *image=[UIImage imageWithData:data];

[self performSelectorOnMainThread:@selector(setImage:) withObject:image waitUntilDone:NO];

}

}

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