example.java

public class CustomView extends FrameLayout {

    public CustomView(Context context) {
        super(context, null);
    }

    public CustomView(Context context, AttributeSet attrs) {
        super(context, attrs, 0);
    }

    public CustomView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        
        inflate(getContext(), R.layout.ac_main, this);
        //findviews by id
    }
}