Call Objective-C方法

Question

如何在延遲0.5秒後調用此方法- (void)displayView:(UIView *)view arg:(UILabel *)label { }？

我試過[self performSelector:@selector(displayView:) withObject:view afterDelay:.5];，但只通過查看作爲參數。

如何將兩個參數傳遞給延遲0.5秒的方法？

Answer 1

使用延遲的塊調用：

主線程：

dispatch_after(dispatch_time(DISPATCH_TIME_NOW, 0.5 * NSEC_PER_SEC), dispatch_get_main_queue(), ^{ 
    [self displayView:view arg:label]; 
}); 

後臺線程：

dispatch_after(dispatch_time(DISPATCH_TIME_NOW, 0.5 * NSEC_PER_SEC), dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{ 
    [self displayView:view arg:label]; 
}); 

Answer 2

- (id)performSelector:(SEL)aSelector 
      withObject:(id)anObject 
      withObject:(id)anotherObject 

從Apple Documentation：

[self performSelector:@selector(displayView:arg:) 
      withObject:myView 
      withObject:myLabel]; 

但我真的建議你GCD去：

另一種選擇是dispatch_after，這將需要一個塊，並在一定的時間排隊了。只要你需要，你可以否定這一計時器停止進程

myTimer = [NSTimer scheduledTimerWithTimeInterval:2.0 
    target:self 
    selector:@selector(displayViewWitharg:) 
    userInfo:dict 
    repeats:NO]; 

// where dict is NSDictioary with key-value pair, which contains your parameters which you want to pass. 

在這裏：

double delayInSeconds = 5.0; 
dispatch_time_t popTime = dispatch_time(DISPATCH_TIME_NOW, delayInSeconds * NSEC_PER_SEC); 

dispatch_after(popTime, dispatch_get_main_queue(), ^(void){ 

    [self displayView:myView arg:myLabel]; 

}); 

另一種方式是使用NSTimer。

希望這會幫助你