一、创建多线程的五种方式 |
1.开启线程的方法一
NSThread * thread=[[NSThread alloc] initWithTarget:self selector:@selector(_update) object:nil];
2.开启线程的方法二
[NSThread detachNewThreadSelector:@selector(_update) toTarget:self withObject:nil];
3.开启线程的方法三
[self performSelectorInBackground:@selector(_update) withObject:nil];
4.开启线程的方法四
NSOperationQueue *queue=[[NSOperationQueue alloc] init];
[queue addOperationWithBlock:^{
for(int i=0;i<50;i++){
printf("子线程\n");
}
}];
5.开启线程的方法五
//第一步开启线程池
NSOperationQueue * queue=[[NSOperationQueue alloc] init];
//设置并发数目
[queue setMaxConcurrentOperationCount:2]; //第二部创建多线程添加到线程池
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、多线程应用实例,加载图片。 |
1.核心思想
考虑到如果加载网络图片会延迟,在一个主线程加载会影响控件的渲染,此时可以采取多线程,异步加载完成后刷新UI。
2.实现思路
通过为UIImageView 增加类目来实现多线程下载。
主要代码:
#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]; }
}