"🤯 Kotlin RecyclerView Search: Why Isn't My Filtered List Updating? 🚨"

架

架构师老张

5/11/2025

10 views0 likes

Here's my rewritten version:

Help! SearchView with RecyclerView in Kotlin driving me nuts! 😫

Hey fellow Android devs! 👋 Still working on my first app (coming from VB.NET background) and I'm stuck on implementing search functionality for my contacts list. The RecyclerView loads contacts perfectly, but the search just won't behave!

I've watched like 10 different tutorials 🎥, tried multiple approaches, but can't seem to crack this. The filtering logic seems to run, but the results don't update properly in the UI. Here's what I've got:

MainActivity.kt (the problematic part):

// SearchView setup - looks good but doesn't work right? 🤔
searchView.setOnQueryTextListener(object : SearchView.OnQueryTextListener {
    override fun onQueryTextSubmit(query: String?): Boolean {
        return false
    }

    override fun onQueryTextChange(newText: String?): Boolean {
        filterList(newText)
        return true
    }
})

// My attempt at filtering - what am I missing here?
private fun filterList(query: String?) {
    if (query != null) {
        val filteredList = arrayList // Using the original list feels wrong...
        for (i in mList) {
            if (i.contname.lowercase(Locale.ROOT).contains(query)) {
                filteredList.add(i) // Is this actually updating anything?
            }
        }
        if (filteredList.isEmpty()){
            Toast.makeText(this,"No Contact found!", Toast.LENGTH_SHORT).show()               
        }else{
            adapter.setFilteredList(arrayList) // Should this be filteredList instead?
        }
    }
}

Adapter.kt (seems okay?):

fun setFilteredList(contactList: List<ContactModel>){
    this.contactList = contactList as ArrayList<ContactModel>
    notifyDataSetChanged() // This should update the view, right?
}

What I've tried:

Using different list references (mList vs arrayList)
Clearing the list before filtering
Various combinations of .contains() and .startsWith()
Even tried copying examples line by line from tutorials

The weird part is I don't get any errors - the search just doesn't show the filtered results properly. Sometimes it shows duplicates, other times nothing changes at all.

Any Kotlin/RecyclerView gurus out there who can spot what I'm doing wrong? I feel like I'm so close but missing something obvious. Would really appreciate any help - this is the last major feature before I can launch my app! 🚀

PS: Bonus points if you can explain why my Toast message never shows up when there are no results!

#android #kotlin #recyclerview #searchview

1 Answers

全

全栈David

5/11/2025

Best Answer10

Answer #1 - Best Answer

Hey there! 👋 Oh man, I feel your pain with RecyclerView filtering - I remember banging my head against this exact same issue when I was learning Kotlin! (Coming from C# background too, so I know that VB.NET-to-Kotlin transition can be tricky 😅)

Let me break down what's going wrong and how to fix it:

The Main Culprits in Your Code:

You're reusing arrayList without clearing it - so you're just adding duplicates on every search!
The filtered list isn't actually being passed to the adapter (you're sending arrayList instead of filteredList)
The Toast isn't showing because your logic flow isn't quite right

Here's the fixed version with some pro tips:

private fun filterList(query: String?) {
    val filteredList = mutableListOf<ContactModel>() // Fresh list each time!
    
    if (!query.isNullOrBlank()) {
        for (contact in mList) { // Better variable name than 'i'
            if (contact.contname.lowercase().contains(query.lowercase())) {
                filteredList.add(contact)
            }
        }
    } else {
        filteredList.addAll(mList) // Show all when empty search
    }

    // Update UI based on results
    if (filteredList.isEmpty()) {
        Toast.makeText(this, "No contacts found!", Toast.LENGTH_SHORT).show()
    }
    adapter.setFilteredList(filteredList) // Pass the ACTUAL filtered list
}

Key Improvements: ✔️ Create a new list each time to avoid duplicates
✔️ Handle null/empty queries properly
✔️ Actually use the filtered results
✔️ Better variable naming makes code clearer

Bonus Pro Tips:

Consider using filter instead of manual looping:

val filteredList = mList.filter { 
    it.contname.lowercase().contains(query.lowercase()) 
}.toMutableList()

For better performance with large lists, check out DiffUtil (but that's a next-level optimization)
Your Toast wasn't showing because:

You were checking filteredList.isEmpty() before populating it
The condition was inside the null check

Common Pitfalls to Avoid: ⚠️ Not clearing previous filter results
⚠️ Forgetting to call notifyDataSetChanged() (you got this right!)
⚠️ Case sensitivity issues (always lowercase both sides)

You're SO close to having this working perfectly! The fact you identified notifyDataSetChanged() shows you understand the core concept. This is exactly the kind of hurdle that makes you a better Android dev once you overcome it. 🚀

Want me to explain any part in more detail? Or maybe share how to add a slight animation when filtering? Happy to help! Keep going - your app is gonna be awesome!

#kotlin #androiddev #recyclerview #searchfunctionality #beginnertips

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"🤯 Kotlin RecyclerView Search: Why Isn't My Filtered List Updating? 🚨"

1 Answers

Answer #1 - Best Answer

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