Creating Custom Views that accept other layouts in xml attributes

Question

I have an open question on here that I am trying to solve, and I might have found a possible solution that is less error-prone; however, I don't know how to code up the solution.

The solution would be very similar to how android.support.design.widget.NavigationView handles the header view in XML!! The only problem is that I have tried to search for the source code for NavigationView, but I cannot seem to find it. I can find other Android Source code easily - except for the newer Design Library.

If I can find the Source code from Google, then I can implement something similar.

Code

<android.support.design.widget.NavigationView
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:layout_gravity="start"
        app:menu="@menu/drawer"
        app:headerLayout="@layout/drawer_header"  />

See that last line? I want to be able to do something like that for my own customView to insert another view inside it.

So my question is:

• Where is the source code for the Design Library's NavigationView?

  OR

• Is there another custom view that allows you to insert layouts inside of it that has code posted online?

  OR

• If there is nothing online, then how would a person go about doing that? It is possible. The NavigationView does it.

Answer 1

Here is an exmaple how you might do it:
In your resources.xml:

<declare-styleable name="MyCustomView">
   <attr name="child_view" format="reference" />
</declare-styleable>

In your MyCustomView.java:

public class MyCustomView extends ViewGroup {

    public MyCustomView(Context context, AttributeSet attrs) {
        super(context, attrs);

        TypedArray a = context.getTheme().obtainStyledAttributes(attrs, R.styleable.MyCustomView, 0, 0);

        int childView = a.getResourceId(R.styleable.MyCustomView_child_view, R.layout.default_child_view);
        a.recycle();

        LayoutInflater.from(context).inflate(childView, this, true);
    }
}

In your layout file:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
              xmlns:custom_view="http://schemas.android.com/apk/res-auto"
              android:layout_width="match_parent"
              android:layout_height="match_parent">

<your.package.MyCustomView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        custom_view:child_view="@layout/some_layout" />

</LinearLayout>