Question

When creating it in xml, the params layout_width and layout_height are required.
What about items created in Java code? What’s their default layout?
How can I set their layout to fill_parent or wrap_content programmatically?

Answer 1

public void addView (View child)
Since: API Level 1

Adds a child view. If no layout parameters are already set on the child, the default parameters for this ViewGroup are set on the child.
Parameters
child the child view to add
See Also

generateDefaultLayoutParams()

---

Without additional parameters, addView(View) uses the default parameters (mostly WRAP_CONTENT). Looking at the source code,

protected LayoutParams  [More ...] generateDefaultLayoutParams() {
    if (mOrientation == HORIZONTAL) {
        return new LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT);
    } else if (mOrientation == VERTICAL) {
        return new LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.WRAP_CONTENT);
    }
    return null;
}