主线程和后台线程的通信

本篇要达到的效果就是:一边执行for循环 ,一边界面能实时查看进度条

代码是在异步处理1的基础上增加的看不清代码可先去看1

 -(void)viewDidLoad添加代码段
    //新建label
    self.myProcessView=[[UIProgressView alloc]init];
    
    self.myProcessView.frame=CGRectMake(20, 20, 280, 10);
    
    [self.view addSubview:self.myProcessView];

//进度条
-(void)updateProgressViewWithPercentage:(NSNumber*)percentageDone{
    
 
    [self.myProcessView setProgress:[percentageDone floatValue] animated:YES];
    
    
}

-(void)bigTask{
    @autoreleasepool {

        int updateUIWhen = 1000;
        for (int i=0; i<10000; i++) {
            
            NSString*newString=[NSString stringWithFormat:@"i=%d",i];
            NSLog(@"%@ ",newString);
            
            if (i==updateUIWhen) {
              
                float f=(float)i/10000;
               
                NSNumber*percentDone=[NSNumber numberWithFloat:f];
               
                [self performSelectorOnMainThread:@selector(updateProgressViewWithPercentage:)withObject:percentDone waitUntilDone:YES];
                
                updateUIWhen=updateUIWhen+1000;

            }
            
            
        }
        
        [self performSelectorOnMainThread:@selector(updateProgressViewWithPercentage:)withObject:[NSNumber numberWithFloat:1.0] waitUntilDone:YES];
        
        [self.myActivityIndicator stopAnimating];
    }
}

更新界面根据updateUIWhen 这个整数 通过判断所占总共进度的多少 达到实时10% 就会更新界面

performSelectorOnMainThread: WithObject: waitUntilDone: 是主线程和后台线程通信的根本

主线程于后台线程之间通讯.png