viewDidLoad中的iOS订购行为

Question

In the viewDidLoad , I have an initial setup like this -

// Output all the appropriate text to UITextLabel depending on the state of the app
[self presentData];

// Button sizing 
UIelement.frame=CGRectMake(blah blah blah);

Why is it that when I do it in the previous order, I get the text outputted without the size adjusting until present data is called again by another function while when I type the code in the order of

UIelement.frame=CGRectMake(blah blah blah);
[self presentData];

it will size it appropriately to start. I understand that the order is important but what I want to know is why? How would I go about finding out why something like this happens the next time I have a problem like this? my guess is that presenting the data, changing the uilabel, updates the view but for some reason cgrectmake does not update the view but just changes the value of the uilabel's frame in the model. Am I correct? How would I go about finding the answer to a question like this without having to ask the online community next time?

Answer 1

A couple of possibilities:

1. You are apparently using auto layout . With auto layout, the process of setting the text property of a label will result in the constraints being reapplied for the view. When you manually set a frame , that only stays in effect until the auto layout constraints are reapplied (eg you update a UILabel again or you call layoutIfNeeded ), at which point the frame is recalculated/adjusted. Generally in auto layout, one wouldn't adjust a frame manually.

2. Perhaps presentData is calling sizeToFit , or something like that? This will obviously change the frame , too.