How to Highlight Searched Text in RecyclerView with ListAdapter: Why Does It Sometimes Fail and How Can You Fix It?

Highlighting Searched Text in RecyclerView with ListAdapter

When using a SearchView within a Toolbar above a RecyclerView list of CardViews, highlighting the search text within the CardViews using ListAdapter may encounter issues. The initial CardView and subsequent ones may not highlight the search text correctly, or the highlighting may not appear until scrolling the list.

To address this, it's important to consider the nature of ListAdapter. ListAdapter updates views on a background thread, so the dataset may not be immediately ready to process.

In the provided code, the issue stems from the filter method in MainActivity, specifically the line:

submitList(tempList);

This line removes and replaces the existing items in the list. For existing items on the RecyclerView, it doesn't trigger onBindViewHolder because the data of the item doesn't change. Therefore, to correct this, the searchString property should be defined as part of the Card model.

When filtering, instead of modifying the existing Card model, create a new Card model with the updated search string:

public void setFilter(List<Card> newSearchList, String adapSearchText) {

    if (newSearchList != null && !newSearchList.isEmpty()) {
        this.searchString = adapSearchText.toLowerCase(Locale.US);
        ArrayList<Card> tempList = new ArrayList<>();
        for (Card card : newSearchList) {
            tempList.add(new Card(card.getTodo(), searchString));
        }
        submitList(tempList);
    }
}

By creating new Card models with the updated searchString, the onBindViewHolder method is triggered for all items on the RecyclerView, ensuring correct highlighting of the search text.

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