ios多线程编程nsthread的使用方法
nsthread是多线程的一种，有两种方法创建子线程
（1）优点：nsthread 比gcd、nsoperation都轻量级
（2）缺点：需要自己管理线程的生命周期，线程同步。线程同步对数据的加锁会有一定的系统开销
第一种是隐藏创建，有以下几种方式：
（1）多用于串行：- (id)performselector:(sel)aselector withobject:(id)object;
（2）后台执行，多用于并行：- (void)performselectorinbackground:(sel)aselector withobject:(nullable id)arg;
（3）延迟执行：- (void)performselector:(sel)aselector withobject:(nullable id)anargument afterdelay:(nstimeinterval)delay;
（4）回到主线程执行：- (void)performselectoronmainthread:(sel)aselector withobject:(nullable id)arg waituntildone:(bool)wait;
注意：
（1）通过方法" + (void)cancelpreviousperformrequestswithtarget:(id)atarget selector:(sel)aselector object:(nullable id)anargument;"，或"+ (void)cancelpreviousperformrequestswithtarget:(id)atarget"停止执行；
示例：
//创建子线程-隐式方法
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// 子线程-串行
[self performselector:@selector(showcount:) withobject:@(11)];
[self performselector:@selector(showcount:) withobject:@(12)];
[self performselector:@selector(showcount:) withobject:@(23)];
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// 子线程-并行（后台）
[self performselectorinbackground:@selector(showcount:) withobject:@(41)];
[self performselectorinbackground:@selector(showcount:) withobject:@(42)];
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// 回到主线程
[self performselectoronmainthread:@selector(showcount:) withobject:@(51) waituntildone:yes];
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// 子线程延迟执行
[self performselector:@selector(showcount:) withobject:@(61) afterdelay:5.0];
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// 停止
[nsobject cancelpreviousperformrequestswithtarget:self];
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第二种是显示创建，方式如下：
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- (instancetype)initwithtarget:(id)target selector:(sel)selector object:(nullable id)argument;
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注意：
（1）通过方法" – (void)start; "开始执行；
（2）通过方法" – (void)cancel; "停止执行；
示例：
//创建子线程-显示方法
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self.thread = [[nsthread alloc] initwithtarget:self selector:@selector(showcount:) object:@(61)];
self.thread.name = @"计数";
[self.thread start];
[self.thread cancel];
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代码示例
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- (void)showcount:(nsnumber *)number
{
nsinteger count = arc4random() % 1000;
count = 1000;
for (int i = 0; i < count; i++)
{
nslog(@"第 %@ 个 i = %@", number, @(i));
// 休眠n秒再执行
[nsthread sleepfortimeinterval:0.2];
// 停止
// bool isstop = [self.thread iscancelled];
// if (isstop)
// {
// nslog(@"2 停止");
// break;
// }
if (iscancelthread)
{
nslog(@"2 停止");
break;
}
}
}
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bool iscancelthread = no;
- (void)stopclick
{
[nsobject cancelpreviousperformrequestswithtarget:self];
if (self.thread)
{
bool isexecuting = [self.thread isexecuting];
if (isexecuting)
{
nslog(@"1 停止");
// [self.thread cancel];
iscancelthread = yes;
}
}
}
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- (void)downloadimage:(nsstring *)imageurl
{
nsurl *url = [nsurl urlwithstring:imageurl];
nsdata *data = [[nsdata alloc] initwithcontentsofurl:url];
uiimage *image = [[uiimage alloc] initwithdata:data];
if (image == nil)
{
}
else
{
// [self performselectoronmainthread:@selector(updateimage:) withobject:image waituntildone:yes];
[self performselectorinbackground:@selector(updateimage:) withobject:image];
}
// nsurl *url = [nsurl urlwithstring:imageurl];
// nsurlrequest *request = [nsurlrequest requestwithurl:url];
// nsurlsession *session = [nsurlsession sharedsession];
// nsurlsessiondatatask *datatask = [session datataskwithrequest:request completionhandler: ^(nsdata *data, nsurlresponse *response, nserror *error) {
//
// // 输出返回的状态码，请求成功的话为200
// nshttpurlresponse *httpresponse = (nshttpurlresponse *)response;
// nsinteger responsestatuscode = [httpresponse statuscode];
// nslog(@"%ld", responsestatuscode);
//
// uiimage *image = [uiimage imagewithdata:data];
//// [self performselectoronmainthread:@selector(updateimage:) withobject:image waituntildone:yes];
// [self performselectorinbackground:@selector(updateimage:) withobject:image];
// }];
//
// // 使用resume方法启动任务
// [datatask resume];
}
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- (void)updateimage:(uiimage *)image
{
self.imageview.image = image;
// self.imageview = [[uiimageview alloc] initwithframe:cgrectmake(10.0, 10.0, (cgrectgetwidth(self.view.bounds) - 10.0 * 2), (cgrectgetwidth(self.view.bounds) - 10.0 * 2))];
// [self.view addsubview:self.imageview];
// self.imageview.backgroundcolor = [uicolor colorwithwhite:0.5 alpha:0.2];
//
// self.imageview.image = image;
}
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nsstring *imageurl = @"http://ww1.sinaimg.cn/crop.0.0.1242.1242.1024/763fb12bjw8empveq3eq8j20yi0yiwhw.jpg";
// 隐藏创建
// [self performselectorinbackground:@selector(downloadimage:) withobject:imageurl];
[self performselectoronmainthread:@selector(downloadimage:) withobject:imageurl waituntildone:yes];
// 创建子线程-显示方法
self.thread = [[nsthread alloc] initwithtarget:self selector:@selector(downloadimage:) object:imageurl];
self.thread.name = @"imagedownload";
[self.thread start];
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