UIScrollView Setting contentoffset in viewwillappe

问题:

I was wondering if it is possible to set contentoffset for uiscrollview in viewwillappear method.

-(void) viewWillAppear:(BOOL)animated{

    [self.scrollView setContentOffset:CGPointMake(320, 0) animated:YES];
    NSLog(@"CALLED");    
}

I can see viewwillappear is running but unfortunately it is not setting offset.

Thank you

回答1:

you should call [super viewWillAppear:animated]; before attempting to set the offset.

However, it is possible you are trying to set the offset too early in the view lifecycle.

it might be good to override -(void)viewDidLayoutSubviews;, and set the offset there.

as your view's frames should all be set appropriately by that time. (remember to call super there too)

回答2:

I have an alternative option that should work better:

Instead of overriding viewDidLayoutSubviews, you can manually set the layout:

override func viewWillAppear(_ animated: Bool) {
    super.viewWillAppear(animated)
    view.layoutIfNeeded()
    // Do something here
}

This way you get a fresh layout that should match your expectation

回答3:

I have tested with your scrollView's contentSize & contentOffset in viewWillAppear. It is working fine to me. So, Please check weather your scrollView object is properly bound to your scrollView or not.