performSelector：withObject：afterDelay：不进行调用 [英] performSelector:withObject:afterDelay: not making call

问题描述

在一个方法中，我想在n秒后调用一个方法：

in a method, i want to call a method after n seconds:

    self.toolBarState = [NSNumber numberWithInt:1];
    [self changeButtonNames];
    [self drawMap];
    [self performSelector:@selector(showActionSheet) withObject:nil afterDelay:2];

我想在drawMap完成后2秒显示操作表。当我使用这个performSelector时，它永远不会进行调用。

i want to show the action sheet 2 seconds after drawMap is complete. when i use this performSelector, it never makes the call.

如果我只是放[self showActionSheet];它就可以了。是否有理由为什么performSelector没有进行调用？

if i just put [self showActionSheet];, it works just fine. is there reason why the performSelector is not making the call?

编辑：在我的代码的另一部分，我进行相同的调用并且它有效：

in another part of my code, i make the same call and it works:

HUD = [[MBProgressHUD alloc] initWithView:self.view];
[self.view addSubview:HUD];
HUD.delegate = (id) self;
[HUD showWhileExecuting:@selector(drawMap) onTarget:self withObject:nil animated:YES];

[self performSelector:@selector(showActionSheet) withObject:nil afterDelay:6];

这里，showActionSheet在drawMap完成后6秒被调用。我猜这个线程还有什么东西我还不明白...

here, the showActionSheet gets called 6 seconds after drawMap has completed. i'm guessing there is something going on with the threads that i don't understand yet...

EDIT2：

-(void)showActionSheet
{
    InspectAppDelegate *dataCenter = (InspectAppDelegate *) [[UIApplication sharedApplication] delegate];

    if (dataCenter.fieldIDToPass == nil)
    {
        UIActionSheet *actionSheet = [[UIActionSheet alloc] initWithTitle:@"Selected Boundary Options" delegate:(id) self cancelButtonTitle:@"Cancel" destructiveButtonTitle:nil otherButtonTitles:@"Analyze a Field",@"Retrieve Saved Analysi", @"Geotag Photos", @"Refresh the map",nil];
        actionSheet.tag = 0;
        [actionSheet showInView:self.view];
    }
    else
    {
        UIActionSheet *actionSheet = [[UIActionSheet alloc] initWithTitle:@"Selected Boundary Options" delegate:(id) self cancelButtonTitle:@"Cancel" destructiveButtonTitle:nil otherButtonTitles:@"Analyze a Field",@"Retrieve Saved Analysi", @"Geotag Photos", @"Attribute the Field", @"Refresh the map",nil];
        actionSheet.tag = 0;
        [actionSheet showInView:self.view];

    }
}

EDIT3：

好，所以方法调用的进度是：

ok, so the progress of method calls is:

-(void) foundDoubleTap:(UITapGestureRecognizer *) recognizer
{        
    [HUD showWhileExecuting:@selector(select) onTarget:self withObject:nil animated:YES];
}

-(void) select
{   
        [self changeButtonNames];
        [self drawMap];
        [self performSelector:@selector(showActionSheet) withObject:nil afterDelay:2];
}

showActionSheet永远不会被调用。就像我说的，我很确定它是一个线程问题。如果用[self showActionSheet]调用它，它将运行。 = /

showActionSheet never gets called. like i said, i'm pretty sure its a threading issue. if call it with [self showActionSheet], it will run. =/

推荐答案

尝试使用 -

  -(void) select {   
    [self changeButtonNames];
    [self drawMap];
    [self performSelectorOnMainThread:@selector(showActionSheet) withObject:nil waitUntilDone:YES];
}

-performSelector：withObject：afterDelay：在同一个线程上调度一个计时器来调用传递延迟后的选择器。

-performSelector:withObject:afterDelay: schedules a timer on the same thread to call the selector after the passed delay.

可能是你的工作 -

Might be this work for you -

-(void) select {   
    [self changeButtonNames];
    [self drawMap];
    [self performSelectorOnMainThread:@selector(someA) withObject:nil waitUntilDone:YES];
}

-(void)someA {
    [self performSelector:@selector(showActionSheet) withObject:nil afterDelay:2];
}

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