IndexOfView
int32 IndexOfView(BView* child) const;
int32 index = layout->IndexOfView(view);
fButtonLayout->AddView(fButtonLayout->IndexOfView(beforeButton), button);
int32 index = layout->IndexOfView(view);
int32 index = layout->IndexOfView(view);
return AreaFor(ItemAt(IndexOfView(const_cast<BView*>(control))));
fContentLayout->SetVisibleItem(fContentLayout->IndexOfView(fAudioView));
fContentLayout->SetVisibleItem(fContentLayout->IndexOfView(fVideoView));
fContentLayout->SetVisibleItem(fContentLayout->IndexOfView(fMidiView));