Unbalanced calls to begin/end appearance transitions for QLRemotePreviewContentController

Question

I'm using Objective-C. I want to open a local file with quick look. And I have this code in my mainViewController:

- (IBAction)open:(id)sender {
    QLPreviewController *myQlPreViewController = [[QLPreviewController alloc]init];
    myQlPreViewController.delegate = self;
    myQlPreViewController.dataSource = self;
    [myQlPreViewController setCurrentPreviewItemIndex:0];
    [self presentViewController:myQlPreViewController animated:YES completion:nil];
}

- (NSInteger)numberOfPreviewItemsInPreviewController:(QLPreviewController *)controller
{
    return 1;
}

- (id<QLPreviewItem>)previewController:(QLPreviewController *)controller previewItemAtIndex:(NSInteger)index
{
    return [NSURL URLWithString:self.filePath];
}

But it shows a gray background and file name on it. How can I fix it to show the file content?

Thanks in advance!

Answer 1

In fact, it's because quick look can't open that file. So, it can only show a file name on the screen.