所以我的问题出现在库片段中的上下文。我收到以下错误。
CardAdapter（Android.content.Context，位于
ArrayList<Card>中 CardAdapter无法应用于资源库ArrayList<Card>
我很幸运地从朋友那里得到了一些代码，但我们似乎无法弄清楚其中的差异/错误。
在Library.java：
public class Library extends Fragment {
// Private variables
private RecyclerView recyclerView;
private CardAdapter cardAdapter;
private ArrayList<Card> cardArrayList;
private ArrayList<Card> tempList;
public Library() {}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate view
View view = inflater.inflate(R.layout.library, container, false);
// Find recyclerView
recyclerView = (RecyclerView) view.findViewById(R.id.recycler_view);
// Initialize cardArrayList
cardArrayList = new ArrayList<>();
// Initialize cardAdapter
cardAdapter = new CardAdapter(this.getContext(), cardArrayList);
// Initialize recyclerView
RecyclerView.LayoutManager layoutManager = new GridLayoutManager(this.getContext(), 1);
recyclerView.setLayoutManager(layoutManager);
recyclerView.setItemAnimator(new DefaultItemAnimator());
recyclerView.setAdapter(cardAdapter);
// Populate cardArrayList with test Cards
testCards();
// Return inflated view
return view;
}
public URL createURL(String constraint) {
try {
StringBuilder urlString = new StringBuilder();
//System.out.print(constraint);
if (constraint.length() > 0) {
urlString.append("https://camerondewey.000webhostapp.com/android_podcast_connect.php");
urlString.append(constraint);
System.out.print(urlString.toString());
}
String muhURL = urlString.toString();
//System.out.print(muhURL);
URL myURL = new URL(muhURL);
System.out.print(myURL);
return myURL;
//return new URL(muhURL);
} catch (Exception e) {
System.out.print("Failed to return url");
}
return null;
}
public class GetCardTask extends AsyncTask<URL, Void, JSONArray> {
@Override
protected JSONArray doInBackground(URL... params) {
//System.out.print("Params: " + params[0]);
HttpURLConnection connection = null;
StringBuilder result = new StringBuilder();
try {
connection = (HttpURLConnection) params[0].openConnection();
//System.out.println(connection.getResponseCode());
if (connection.getResponseCode() == HttpURLConnection.HTTP_OK) {
BufferedReader reader = new BufferedReader(
new InputStreamReader(connection.getInputStream()));
String line;
while ((line = reader.readLine()) != null) {
result.append(line);
}
try {
//System.out.print("SUCCESS");
return new JSONArray(result.toString());
} catch (JSONException je) {
//System.out.print("FAILURE2");
JSONArray jArray = new JSONArray();
jArray.put(new JSONObject(result.toString()));
return jArray;
}
} else {
throw new Exception();
}
} catch (Exception e) {
System.out.print("FAILURE1");
e.printStackTrace();
} finally {
connection.disconnect();
}
return null;
}
@Override
protected void onPostExecute(JSONArray article) {
if (article != null) {
convertJSONtoArrayList(article);
Library.this.updateDisplay();
} else {
System.out.print("failure to execute json conversion");
}
}
}
private void convertJSONtoArrayList(JSONArray articles) {
cardArrayList = new ArrayList<Card>(); // clear old player data
tempList = new ArrayList<Card>();
try {
for (int i = 0; i < articles.length(); i++) {
JSONObject currentArticle = articles.getJSONObject(i);
cardArrayList.add(new Card(
currentArticle.has("name") ? currentArticle.getString("name") : "No Headline",
currentArticle.has("description") ? currentArticle.getString("description") : "No Name"
));
tempList.add(new Card(
currentArticle.has("name") ? currentArticle.getString("name") : "No Headline",
currentArticle.has("description") ? currentArticle.getString("description") : "No Name"
));
}
} catch (JSONException e) {
e.printStackTrace();
}
}
private void updateDisplay() {
if (cardArrayList == null) {
System.out.print("Display failed to update");
}
ArrayList<HashMap<String, String>> data = new ArrayList<HashMap<String, String>>();
for (Card item : cardArrayList) {
HashMap<String, String> map = new HashMap<String, String>();
map.put("name", item.getCardName());
map.put("description", item.getDescription());
data.add(map);
}
int resource = R.layout.card;
String[] from = {"name", "description"};
int[] to = {R.id.card_name, R.id.podcast_desc};
//The error happens here.
CardAdapter cardAdapter = new CardAdapter(this, cardArrayList);
recyclerView.setAdapter(cardAdapter);
cardAdapter.notifyDataSetChanged();
}
在CardAdapter.java
public class CardAdapter extends RecyclerView.Adapter<CardAdapter.CardViewHolder> implements Filterable {
// Private variables
private Context cardContext;
ArrayList<Card> cardList, filteredList;
public class CardViewHolder extends RecyclerView.ViewHolder{
public View view;
public TextView cardName;
public Card currentItem;
public CardViewHolder(View v) {
// Invoke super on view
super(v);
view = v;
this.cardName = (TextView) v.findViewById(R.id.card_name);
v.setOnClickListener(new View.OnClickListener(){
@Override
public void onClick(View v){
Intent i = new Intent(v.getContext(),PodcastPage.class);
//item clicked
v.getContext().startActivity(i);
}
});
// Find cardText
cardName = (TextView) view.findViewById(R.id.card_name);
}
}
public CardAdapter(Context c, ArrayList<Card> l) {
this.cardContext = c;
this.cardList = l;
this.filteredList = l;
}
@Override
public CardViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.card, null);
return new CardViewHolder(view);
}
@Override
public void onBindViewHolder(final CardViewHolder holder, int position) {
Card card = cardList.get(position);
holder.currentItem = cardList.get(position);
holder.cardName.setText(card.getCardName());
}
@Override
public int getItemCount() {
return filteredList.size();
}
@Override
public Filter getFilter() {
return new Filter() {
@Override
protected FilterResults performFiltering(CharSequence query) {
FilterResults results = new FilterResults();
if (query != null && query.length() > 0) {
query = query.toString().toUpperCase();
ArrayList<Card> searchResults = new ArrayList<Card>();
for (int i = 0; i < filteredList.size(); i++) {
if (filteredList.get(i).getCardName().toUpperCase().contains(query)) {
searchResults.add(filteredList.get(i));
}
else if (filteredList.get(i).getDescription().toUpperCase().contains(query)) {
searchResults.add(filteredList.get(i));
}
}
results.count = searchResults.size();
results.values = searchResults;
}
else {
results.count = filteredList.size();
results.values = filteredList;
}
return results;
}
@Override
protected void publishResults(CharSequence query, FilterResults results) {
filteredList = (ArrayList<Card>) results.values;
notifyDataSetChanged();
System.out.println(filteredList);
}
};
}
}
答案 0 :(得分：1)
在CardAdapter cardAdapter = new CardAdapter(this, cardArrayList); this行中的代码不是Context，而是Fragment。将行更改为：
CardAdapter cardAdapter = new CardAdapter(getActivity(), cardArrayList);