Iphone - Drawing into a view : philosophy and interactions

I've understood that I need to subclass a UIView t be able to draw inside it.

The thing I don't understand yet, is the philosophy of the way i must be done...

Let's say I have a view controller, and depending on context, I may want to draw a line into one of the subviews it manages, or a circle,开发者_Go百科 or a rect, or a processed graphic. Or lets say two points that are moving inside a view into a defined rect and that display a bigger point when they are close.

How may I subclass and define the subview to make it able to do this only into its drawRect method ?

How does the controller, that manages more than this simple UIView (let's imagine you have a view controller that manages a view inside which there are many other view, and you want to make some drawings in two of them), and that knows what is needed to be drawn into the correct view (it's a controller, isn't it ?), may interact with the views ? And when the drawing is done, how may the views interact with the controller ?

I've read many doc about drawings (apple, web, forums, tutorials, ...), but I still can't touch the philosophy of the way this must be done.

it's very simple. Make a new class, OliverView, which is a UIView. (ie, it is a subclass of UIView.) In that view, make it draw stuff in a fancy way, inside drawRect.

Now make a UIViewController, called OliverVC. In storyboard put an OliverView inside OliverVC. (beginner explanation of how to do that).

In the OliverView, have properties "hours", "minutes", "seconds".

Now, in OliverView - in the drawRect - have a fancy way to display those values. (Pie chart, glowing letters, animation - whatever you want.)

Now, up in OliverVC, do some calculations to determine the time in Zimbabwe, for example.

Once you want a time displayed, simply set those properties in OliverView - - and you are done.

Your colleague could be programming the OliverView. You need know nothing about how she is going to display the time. Conversely, your colleague need know nothing about your calculations in OliverVC..

So, it's simpleL One part has the job of displaying the data. One part has the job of coming up with the data (doing whatever sort of calculation is relevant in the app).

It's the only architecture possible in a "real time" screen device where the views can and do change at any time.

In answer to your question below: you've forgotten that quite simply, if you have a button that would be a whole separate element. (Perhaps sitting "on top of" the OliverView.) So, it's easy!

The -drawRect method in your UIView subclass defines the onscreen appearance of the view. All drawing is done in -drawRect. Your UIViewController calls methods on its UIView to tell it to draw something differently or to perform some other action.

The UIViewController manages everything to do with the view that is not inherently associated with the drawing of the content. Data associated with the view is often stored in the controller.