異步處理1

在新線程中執行處理:

問題:應用需要執行非常耗時的任務,但是又希望用戶界面保持響應,不會受到新操作的影響.

• 不開辟一個新線程的做法

#import "ViewController.h"
@interface ViewController ()
@property(nonatomic,strong)UIActivityIndicatorView*myActivityIndicator;
@property(nonatomic,strong)UIButton*myButton;
@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
   
//    創建button
    self.myButton=[UIButton buttonWithType:UIButtonTypeRoundedRect];
    self.myButton.frame=CGRectMake(20, 403, 280, 37);
    
    [self.myButton addTarget:self action:@selector(bigTaskAction) forControlEvents:UIControlEventTouchUpInside];
    
    [self.myButton setTitle:@"do long task" forState:UIControlStateNormal];

    [self.view addSubview:_myButton];
    
    //創建indicator
    self.myActivityIndicator=[[UIActivityIndicatorView alloc]init];
    self.myActivityIndicator.frame=CGRectMake(142, 211, 37, 37);
    
    self.myActivityIndicator.activityIndicatorViewStyle=UIActivityIndicatorViewStyleWhiteLarge ;
    
    self.myActivityIndicator.hidesWhenStopped=NO;
    
    [self.view addSubview:self.myActivityIndicator];
    
}
-(void)bigTask{
    @autoreleasepool {
        for (int i=0; i<10000; i++) {
            NSString*newString=[NSString stringWithFormat:@"i=%d",i];
            NSLog(@"%@ ",newString);
        }
        [self.myActivityIndicator stopAnimating];
    }
}

//沒有開辟新線程
-(void)bigTaskAction{
    [self.myActivityIndicator startAnimating];
    [self bigTask];
   
    
}

@end

• 開辟一個新線程

-(void)bigTaskAction{
    [self.myActivityIndicator startAnimating];
//開辟新的線程
   [NSThread detachNewThreadSelector:@selector(bigTask) toTarget:self withObject:nil];
}

總結:

一般情況下執行代碼的時候,是一行一行的執行,上一行沒有執行完成會等待,現在進行開辟線程,可同時執行 這里就是: 一邊for循環在處理 ,一邊指示器在界面上響應