Android ViewGroup: what should I do in the onLayout() override?

Question

When extending an Android ViewGroup class, what is the purpose of the `onLayout()` override? I'm making a custom control in Android but for some reason the content (child `View` objects) isn't displaying. My approach was to extend the ViewGroup class, adding child-Views via the `addView()` method of ViewGroup. Then, in my main activity, I have the following code: ``` ChannelController myCC = new ChannelController(this); setContentView(myCC); ``` ChannelController is the name of my custom class that extends ViewGroup. I must be doing something wrong because nothing is shown on the screen. I understand that I must override and implement the onLayout() method, but with what? I know there's an entire page dedicated to this on the dev.android site, but it didn't help me much, mostly because I'm a newbie I guess. Any insight would be appreciated. For reference, my ViewGroup extension looks like below: ``` public class ChannelController extends ViewGroup { final String TAG = "JAL"; public Ch…

Accepted Answer

In `onLayout` you need to call `layout` method on each child of this `ViewGroup` and provide desired position (relatively to parent) for them. You can check source code of `FrameLayout` (one of the simpliest subclasses of `ViewGroup`) to find out how it works.

Although, if you don't need any "special" layouting, you have other options:

- Extend some another subclass of `ViewGroup` instead (`FrameLayout` for example)

- Use `LayoutInflater` if you just need your control to look exactly as in XML (which, I think, is exactly your case)

Android ViewGroup: what should I do in the onLayout() override?

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