UIWindow直到方法完成才显示

Question

我试图显示视图，因为该方法需要几秒钟才能完成。但是，在整个方法完成之前，加载UIWindow实际上并不是键和可见的。知道这里发生了什么吗？

// this line creates a uiwindow with view controller as root view controller, an activity indicator, and a label and makes the loading view key and visible
[XSELLoadingView presentLoadingViewWithTitle:@"Generating Report"]; // use loading view for long times

// these three lines process a lot of data and present the view on the main window
XSELCount *startCount = [[XSELCount counts] objectAtIndex:[self.startingPick selectedRowInComponent:0]];
XSELCount *endCount = [[XSELCount counts] objectAtIndex:[self.endingPick selectedRowInComponent:0
[self.navigationController pushViewController:[XSELReportView viewWithReportData:[XSELReportData compareStartCount:startCount toEndCount:endCount]] animated:false];   

// this line makes the main view key and visable 
[XSELLoadingView dismissLoadingView];

Answer 1

Apply your task inside this one.

 dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
    //Do background work
    dispatch_async(dispatch_get_main_queue(), ^{
        //Update UI
    });
});