我正在尝试更新我的RecyclerView，因为数据集中的元素数量会发生变化
PlaceHolderFragment
public class PlaceholderFragment extends Fragment {
private static final String ARG_SECTION_NUMBER = "section_number";
public static final String HOME_ADAPTER = "HOME";
public static final String TRENDING_ADAPTER = "TREND";
public static int P_START = -1;
public static int P_END = -1;
public static int T_START = -1;
public static int T_END = -1;
List<Posts> mNewsFeeds = new ArrayList<>();
List<Posts> mTrending = new ArrayList<>();
List<ChatList> mChatList = new ArrayList<>();
List<Online> mOnline = new ArrayList<>();
HomeAdapter homeAdapter;
HomeAdapter TrendAdapter;
ChatListAdapter chatListAdapter;
OnlineListAdapter onlineAdapter;
RecyclerView recyclerViewT1;
RecyclerView recyclerViewT2;
RecyclerView recyclerViewT3;
RecyclerView recyclerViewT4;
private SwipeRefreshLayout swipeRefreshLayoutT1;
private SwipeRefreshLayout swipeRefreshLayoutT2;
private SwipeRefreshLayout swipeRefreshLayoutT3;
private SwipeRefreshLayout swipeRefreshLayoutT4;
private int visibleThreshold = 2;
private int PlastVisibleItem, PtotalItemCount;
private boolean Ploading;
private int TlastVisibleItem, TtotalItemCount;
private boolean Tloading;
public static PlaceholderFragment newInstance(int sectionNumber) {
PlaceholderFragment fragment = new PlaceholderFragment();
Bundle args = new Bundle();
args.putInt(ARG_SECTION_NUMBER, sectionNumber);
fragment.setArguments(args);
return fragment;
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_main, container, false);
Bundle args = new Bundle(getArguments());
int TabID = args.getInt(ARG_SECTION_NUMBER);
if (TabID == 1) {
recyclerViewT1 = (RecyclerView) rootView.findViewById(R.id.rv_numbers);
swipeRefreshLayoutT1 = (SwipeRefreshLayout) rootView.findViewById(R.id.refresh);
final LinearLayoutManager layoutManager = new LinearLayoutManager(getContext());
recyclerViewT1.setLayoutManager(layoutManager);
recyclerViewT1.setHasFixedSize(false);
try {
OnlineltPosts();
} catch (JSONException e) {
e.printStackTrace();
}
recyclerViewT1.addOnScrollListener(new RecyclerView.OnScrollListener() {
@Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
PtotalItemCount = layoutManager.getItemCount();
PlastVisibleItem = layoutManager.findLastVisibleItemPosition();
if (!Ploading && PtotalItemCount <= (PlastVisibleItem + visibleThreshold)) {
Ploading = true;
OnlineltPosts();
Log.e("coool","yeeeeeeeeeeeeee");
}
}
});
} else if (TabID == 2) {
} else if (TabID == 3) {
} else {
}
return rootView;
}
.........
Onlineltpost
void OnlineltPosts() {
String url = ApiUtil.getltPostUrl(P_END);
StringRequest stringRequest = new StringRequest(Request.Method.GET, url,
new Response.Listener<String>() {
@Override
public void onResponse(String response) {
try {
JSONArray arr = new JSONArray(response);
for (int i = 0; i < arr.length(); i++) {
mNewsFeeds.add(postHelper(arr, i));
}
if (recyclerViewT1.getAdapter() == null) {
homeAdapter = new HomeAdapter(mNewsFeeds, mNewsFeeds.size() + 1, HOME_ADAPTER);
recyclerViewT1.setAdapter(homeAdapter);
}else
homeAdapter.notifyDataSetChanged();
// getActivity().runOnUiThread(new Runnable() {
// public void run() {
// homeAdapter.notifyDataSetChanged();
// }
// });
// Log.e("coool", String.valueOf(mNewsFeeds.size()));
} catch (JSONException | MalformedURLException | URISyntaxException e) {
e.printStackTrace();
}
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
}
});
RequestManager.getInstance(getContext()).addToRequestQueue(stringRequest);
}
postHelper
public static Posts postHelper(JSONArray arr, int i) throws JSONException, URISyntaxException, MalformedURLException {
JSONObject obj = new JSONObject(String.valueOf(arr.get(i)));
int id = obj.getInt("post_id");
// SharedPreferences pref = getContext().getSharedPreferences(Preferences.POST, 0);
// SharedPreferences.Editor editor = pref.edit();
//
// int start = pref.getInt(Preferences.POST_LATEST_START, -1);
// int end = pref.getInt(Preferences.POST_LATEST_END, -1);
//
// if (start == -1 || id > start)
// editor.putInt(Preferences.POST_LATEST_START, id);
//
// if (end == -1 || id < end)
// editor.putInt(Preferences.POST_LATEST_END, id);
//
// editor.putString(Preferences.POST_PREFEX + id, obj.toString());
//
// editor.apply();
if (P_START == -1 || id > P_START)
P_START = id;
if (P_END == -1 || id < P_END)
P_END = id;
int user_id = obj.getInt("user_id");
String user_name = (String) obj.get("user_name");
String pic = (String) obj.get("user_picture");
URI uri = new URI(pic);
URL user_picture = uri.toURL();
String post_text = (String) obj.get("post_text");
String post_time = (String) obj.get("post_time");
int likes = (int) obj.get("likes");
int dislikes = (int) obj.get("dislikes");
int comments = (int) obj.get("comments");
int isliked = (int) obj.get("isliked");
int isdisliked = (int) obj.get("isdisliked");
int iscommented = (int) obj.get("iscommented");
int isfollow = (int) obj.get("isfollow");
JSONObject abc = obj.getJSONArray("post_data").getJSONObject(0);
String post_image = (String) abc.get("source");
int type = abc.getInt("type");
if (type == 4) {
String youtube = "www.youtube.com/embed/";
int x = post_image.indexOf(youtube);
post_image = post_image.substring(x + youtube.length(), post_image.length());
int x1 = post_image.indexOf("?");
post_image = post_image.substring(0, x1);
post_image = "http://img.youtube.com/vi/" + post_image + "/0.jpg";
}
List<Like> postLikes = new ArrayList<>();
List<Comment> postComments = new ArrayList<>();
JSONArray likeList = obj.getJSONArray("like_all");
for (int j = 0; j < likeList.length(); j++) {
JSONObject obj1 = new JSONObject(String.valueOf(likeList.get(j)));
int Luser_id = obj1.getInt("user_id");
String Luser_name = obj1.getString("user_name");
String Lusername = obj1.getString("username");
String Lpic = obj1.getString("user_picture");
URI uri1 = new URI(Lpic);
URL Luser_picture = uri1.toURL();
Like mlike = new Like(Luser_id, Luser_name, Lusername, Luser_picture);
postLikes.add(mlike);
}
JSONArray CommentList = obj.getJSONArray("post_comment");
for (int j = 0; j < CommentList.length(); j++) {
JSONObject obj1 = new JSONObject(String.valueOf(CommentList.get(j)));
int Lpost_id = obj1.getInt("post_id");
int Lcomment_id = obj1.getInt("comment_id");
String Lusername = obj1.getString("username");
String Lcomment = obj1.getString("comment");
String Lcomment_time = obj1.getString("comment_time");
int Luser_id = obj1.getInt("user_id");
String Luser_name = obj1.getString("user_name");
String Lpic = obj1.getString("user_picture");
URI uri1 = new URI(Lpic);
URL Luser_picture = uri1.toURL();
Comment mlike = new
Comment(Lpost_id, Lcomment_id, Luser_id, Luser_name,
Lusername, Lcomment, Lcomment_time, Luser_picture);
postComments.add(mlike);
}
return new Posts(id, user_id, user_name, user_picture,
post_text, post_time, likes, dislikes, comments,
isliked, isdisliked, iscommented, isfollow, post_image, type,
postLikes, postComments);
}
我尝试过recyclerViewT1.setHasFixedSize(false);，但一切都没有改变。我注意到的是数据集正在成功更改，但recyclerview未显示新项目。
当我尝试：
homeAdapter = new HomeAdapter(mNewsFeeds, mNewsFeeds.size() + 1, HOME_ADAPTER);
recyclerViewT1.setAdapter(homeAdapter);
而不是：
homeAdapter.notifyDataSetChanged();
它显示正确的项目数，但随后用户被推回到顶部，用户需要再次滚动，这是我不想要的。我只想用新项目更新数据集。
答案 0 :(得分：2)
您应该始终向HomeAdapter提供新的mNewsFeeds并调用homeAdapter.notifyDataSetChanged（）;改变数据
try {
JSONArray arr = new JSONArray(trending);
for (int i = 0; i < arr.length(); i++) {
mNewsFeeds.add(postHelper(arr, i));
}
if (recyclerViewT1.getAdapter() == null) {
homeAdapter = new HomeAdapter(mNewsFeeds, mNewsFeeds.size() + 1, HOME_ADAPTER);
recyclerViewT1.setAdapter(homeAdapter);
}else {
homeAdapter.setNewsFeeds(mNewsFeeds)
}
homeAdapter.notifyDataSetChanged();
// getActivity().runOnUiThread(new Runnable() {
// public void run() {
// homeAdapter.notifyDataSetChanged();
// }
// });
// Log.e("coool", String.valueOf(mNewsFeeds.size()));
} catch (JSONException | MalformedURLException | URISyntaxException e) {
e.printStackTrace();
}
答案 1 :(得分：2)
更新getItemCount＆amp;设置notifyDataSetChanged
之前的数据在适配器中：
private int mListSize;
public void setItemCount(int listsize){
mListSize=listsize;
}
@Override
public int getItemCount() {
return mListSize;
}
在notifydataset改变之前：
if (recyclerViewT1.getAdapter() == null) {
homeAdapter = new HomeAdapter(mNewsFeeds, mNewsFeeds.size() + 1, HOME_ADAPTER);
recyclerViewT1.setAdapter(homeAdapter);
}else{
homeAdapter.setData(mNewsFeeds, mNewsFeeds.size() + 1, HOME_ADAPTER);
homeAdapter.setItemCount(yourlist.size());
homeAdapter.notifyDataSetChanged();
}
也可以尝试这个答案