Android自定义Adapter无法过滤MySQL数据源数据求助

Hey there! Let's fix your SearchView filtering issue step by step. I’ve gone through your code and spotted a few key gaps and tweaks needed to get the filtering working properly.

First, the Core Issue: Missing Filter Logic in Your Adapter #

Your CustomStockList has a skeleton getFilter() method, but there’s no actual logic to check if an item matches the search query. Plus, there’s a bug in how you initialize your original and filtered lists (they’re pointing to the same reference, which will cause unexpected behavior).

Step 1: Fix the Adapter Initialization & Filter Logic #

Update your CustomStockList with these changes:

private Activity activity;
private LayoutInflater inflater;
private List<StockData> originalItems; // Store original unfiltered data
private List<StockData> filteredItems;
private static class ViewHolder { // Add ViewHolder to optimize ListView performance
    TextView model;
    TextView stock;
}

public CustomStockList(Activity activity, List<StockData> items) {
    this.activity = activity;
    this.inflater = (LayoutInflater) activity.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    // Create copies of the original list to avoid reference issues
    this.originalItems = new ArrayList<>(items);
    this.filteredItems = new ArrayList<>(items);
}

@Override
public int getCount() {
    return filteredItems.size();
}

@Override
public Object getItem(int location) {
    return filteredItems.get(location);
}

@Override
public long getItemId(int position) {
    return position;
}

@Override
public View getView(int position, View convertView, ViewGroup parent) {
    ViewHolder holder;
    if (convertView == null) {
        convertView = inflater.inflate(R.layout.activity_custom_stock_list, parent, false);
        holder = new ViewHolder();
        holder.model = convertView.findViewById(R.id.model);
        holder.stock = convertView.findViewById(R.id.stock);
        convertView.setTag(holder);
    } else {
        holder = (ViewHolder) convertView.getTag();
    }

    StockData item = filteredItems.get(position);
    holder.model.setText(item.getModelno());
    holder.stock.setText(item.getStock());
    return convertView;
}

@Override
public Filter getFilter() {
    return new Filter() {
        @Override
        protected void publishResults(CharSequence constraint, FilterResults results) {
            filteredItems = (List<StockData>) results.values;
            notifyDataSetChanged(); // This updates the ListView with filtered data
        }

        @Override
        protected FilterResults performFiltering(CharSequence constraint) {
            FilterResults results = new FilterResults();
            List<StockData> tempFilteredList = new ArrayList<>();

            if (constraint == null || constraint.length() == 0) {
                // No filter applied: use original full list
                tempFilteredList.addAll(originalItems);
            } else {
                // Lowercase the query to make filtering case-insensitive
                String filterQuery = constraint.toString().toLowerCase().trim();
                // Check each item against the query
                for (StockData item : originalItems) {
                    if (item.getModelno().toLowerCase().contains(filterQuery)) {
                        tempFilteredList.add(item);
                    }
                }
            }

            results.values = tempFilteredList;
            results.count = tempFilteredList.size();
            return results;
        }
    };
}

Key changes here:

• Created separate originalItems and filteredItems lists (no more shared references)
• Added actual filtering logic to match the search query against modelno (case-insensitive)
• Implemented ViewHolder pattern to optimize ListView scrolling performance
• Fixed the filter’s performFiltering method to return the correct filtered results

Step 2: Fix Null Pointer & Adapter Initialization in ListActivity #

Your current code tries to call customStockList.getFilter() in onCreate() before the adapter is actually initialized (it’s created later in onPostExecute). Let’s fix that:

First, declare your adapter as a global variable in StockList:

public class StockList extends AppCompatActivity {
    private ListView lv3;
    private SearchView sv;
    private CustomStockList customStockList;
    private List<StockData> stockList = new ArrayList<>(); // Initialize empty list upfront

    // ... rest of your code
}

Then update the onPostExecute method to properly initialize the adapter:

@Override
protected void onPostExecute(Void aVoid) {
    try {
        JSONObject object = new JSONObject(result);
        JSONArray jsonArray = object.getJSONArray("itemstock");
        for (int i = 0; i < jsonArray.length(); i++) {
            JSONObject obj = jsonArray.getJSONObject(i);
            StockData stockData = new StockData();
            stockData.setModelno(obj.getString("modelno"));
            stockData.setStock(obj.getString("stock"));
            stockList.add(stockData);
        }
    } catch (JSONException e) {
        Log.e("log_tag", "Error parsing data " + e.toString());
    }
    // Initialize adapter and assign to global variable
    customStockList = new CustomStockList(StockList.this, stockList);
    lv3.setAdapter(customStockList);
}

Finally, tweak the SearchView listener to avoid null pointers and remove redundant code:

sv.setOnQueryTextListener(new SearchView.OnQueryTextListener() {
    @Override
    public boolean onQueryTextSubmit(String s) {
        return false;
    }

    @Override
    public boolean onQueryTextChange(String s) {
        if (customStockList != null) {
            customStockList.getFilter().filter(s);
            // No need for notifyDataSetChanged here - the filter handles it
        }
        return true; // Indicate we've handled the text change event
    }
});

Why This Works #

• The adapter now keeps a copy of the original full dataset, so filtering can always reset to the complete list
• The filter logic checks if the item’s modelno contains the search query (case-insensitive for better user experience)
• We fixed the timing issue where you tried to use the adapter before it was initialized
• The ViewHolder pattern reduces unnecessary view inflation, making your ListView smoother

Give these changes a try, and your SearchView should start filtering the ListView items as expected!

内容的提问来源于stack exchange，提问作者Arpan Sarkar