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Focus and selection

It's important to distinguish between a selection event and a focus event.

You can change the selection state of a DpadRecyclerView while focus is in a completely separate view.

However, when focus changes to different ViewHolders inside DpadRecyclerView (due to DPAD navigation for example), this will automatically fire a selection event.

So, in short:

  1. Selection changes can happen without focus requests
  2. Focusing another view triggers a selection event

Focus changes

To enable focus changes in your RecyclerView.ViewHolder, you need to set a child view as focusable. Otherwise, DpadRecyclerView won't find it when the user presses the DPAD.

Do this either in XML or after onCreateViewHolder:

view.isFocusable = true
view.isFocusableInTouchMode = true

To observe focus changes, simply use a OnFocusChangeListener:

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view.setOnFocusChangeListener { _, hasFocus ->
    if (hasFocus) {
        // React to focus gain
    } else {
        // React to focus loss
    }
}

You can also observe focus changes inside DpadRecyclerView with the following:

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recyclerView.addOnViewFocusedListener(object : OnViewFocusedListener {
    override fun onViewFocused(parent: RecyclerView.ViewHolder, child: View) {
        // Child has focus
    }
})

Selection changes

You can observe selection changes using the following:

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recyclerView.addOnViewHolderSelectedListener(object : OnViewHolderSelectedListener {
    override fun onViewHolderSelected(
        parent: RecyclerView,
        child: RecyclerView.ViewHolder?,
        position: Int,
        subPosition: Int
    ) {}

    override fun onViewHolderSelectedAndAligned(
        parent: RecyclerView,
        child: RecyclerView.ViewHolder?,
        position: Int,
        subPosition: Int
    ) {}
})

If your ViewHolder implements the interface DpadViewHolder you can also get these events automatically from these callbacks:

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class ExampleViewHolder(
    view: View
) : RecyclerView.ViewHolder(view), DpadViewHolder {

    override fun onViewHolderSelected() {}

    override fun onViewHolderDeselected() {}

}