问题
How Do I show progress bar at bottom when user reached to items those are visible in a list.
I have written a code in which i am getting data using web service, now i would like to populate partial records, because i have around 630 records in my JSON.
Here is my whole code which i am using to get data from JSON and to populate into RecyclerView.
Here is how my JSON looks, but real JSON contains over 600 records:
http://walldroidhd.com/api.php
Can someone guide me where i have to make changes in my code ?
I want to populate more records whenever user do scroll to bottom using progressbar, still i am showing all the records.
RecyclerViewFragment.java:
public class RecyclerViewFragment extends Fragment {
RecyclerView mRecyclerView;
LinearLayoutManager mLayoutManager;
RecyclerView.Adapter mAdapter;
ArrayList<NatureItem> actorsList;
private int previousTotal = 0;
private boolean loading = true;
private int visibleThreshold = 5;
int firstVisibleItem, visibleItemCount, totalItemCount;
public static RecyclerViewFragment newInstance() {
return new RecyclerViewFragment();
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
return inflater.inflate(R.layout.fragment_recyclerview_advance, container, false);
}
@Override
public void onViewCreated(View view, Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
actorsList = new ArrayList<NatureItem>();
new JSONAsyncTask().execute(\"my JSON url\");
mRecyclerView = (RecyclerView) view.findViewById(R.id.recycler_view);
mRecyclerView.setHasFixedSize(true);
mLayoutManager = new GridLayoutManager(getActivity(), 2);
mRecyclerView.setLayoutManager(mLayoutManager);
mRecyclerView.setOnScrollListener(new RecyclerView.OnScrollListener() {
@Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
visibleItemCount = mRecyclerView.getChildCount();
totalItemCount = mLayoutManager.getItemCount();
firstVisibleItem = mLayoutManager.findFirstVisibleItemPosition();
if (loading) {
if (totalItemCount > previousTotal) {
loading = false;
previousTotal = totalItemCount;
}
}
if (!loading && (totalItemCount - visibleItemCount)
<= (firstVisibleItem + visibleThreshold)) {
// End has been reached
Log.i(\"...\", \"end called\");
// Do something
loading = true;
}
}
});
// mAdapter = new CardAdapter();
mAdapter = new RecyclerViewMaterialAdapter(new CardAdapter(getActivity(), actorsList), 2);
mRecyclerView.setAdapter(mAdapter);
MaterialViewPagerHelper.registerRecyclerView(getActivity(), mRecyclerView, null);
mRecyclerView.addOnItemTouchListener(
new RecyclerItemClickListener(getActivity(), new RecyclerItemClickListener.OnItemClickListener() {
@Override
public void onItemClick(View view, int position) {
Toast.makeText(getActivity(), String.valueOf(position), Toast.LENGTH_LONG).show();
}
})
);
}
class JSONAsyncTask extends AsyncTask<String, Void, Boolean> {
ProgressDialog dialog;
@Override
protected void onPreExecute() {
super.onPreExecute();
dialog = new ProgressDialog(getActivity());
dialog.setMessage(\"Loading, please wait\");
dialog.setTitle(\"Connecting server\");
dialog.show();
dialog.setCancelable(false);
}
@Override
protected Boolean doInBackground(String... urls) {
try {
//------------------>>
HttpGet httppost = new HttpGet(urls[0]);
HttpClient httpclient = new DefaultHttpClient();
HttpResponse response = httpclient.execute(httppost);
// StatusLine stat = response.getStatusLine();
int status = response.getStatusLine().getStatusCode();
if (status == 200) {
HttpEntity entity = response.getEntity();
String data = null;
try {
data = EntityUtils.toString(entity);
} catch (IOException e) {
e.printStackTrace();
}
JSONObject jsono = null;
try {
jsono = new JSONObject(data);
} catch (JSONException e) {
e.printStackTrace();
}
JSONArray jarray = jsono.getJSONArray(\"wallpapers\");
for (int i = 0; i < jarray.length(); i++) {
JSONObject object = jarray.getJSONObject(i);
NatureItem actor = new NatureItem();
actor.setName(object.getString(\"id\"));
actor.setThumbnail(object.getString(\"thumb_url\"));
actorsList.add(actor);
}
return true;
}
//------------------>>
} catch (ParseException e1) {
e1.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (JSONException e) {
e.printStackTrace();
}
return false;
}
protected void onPostExecute(Boolean result) {
dialog.cancel();
mAdapter.notifyDataSetChanged();
if (result == false) {
Toast.makeText(getActivity(), \"Unable to fetch data from server\", Toast.LENGTH_LONG).show();
}
else {
}
}
}
}
CardAdapter.java:
public class CardAdapter extends RecyclerView.Adapter<CardAdapter.ViewHolder> {
private ArrayList<NatureItem> mItems;
private Context mContext;
public CardAdapter(Context context, ArrayList<NatureItem> feedItemList) {
this.mItems = feedItemList;
this.mContext = context;
}
@Override
public ViewHolder onCreateViewHolder(ViewGroup viewGroup, int i) {
View v = LayoutInflater.from(viewGroup.getContext())
.inflate(R.layout.recycler_view_card_item, viewGroup, false);
ViewHolder viewHolder = new ViewHolder(v);
return viewHolder;
}
@Override
public void onBindViewHolder(ViewHolder viewHolder, int i) {
NatureItem nature = mItems.get(i);
viewHolder.tvNature.setText(nature.getName());
Picasso.with(mContext).load(nature.getThumbnail())
.error(R.mipmap.ic_launcher)
.placeholder(R.mipmap.ic_launcher)
.into(viewHolder.imgThumbnail);
}
@Override
public int getItemCount() {
return mItems.size();
}
class ViewHolder extends RecyclerView.ViewHolder{
public ImageView imgThumbnail;
public TextView tvNature;
public ViewHolder(View itemView) {
super(itemView);
imgThumbnail = (ImageView)itemView.findViewById(R.id.img_thumbnail);
tvNature = (TextView)itemView.findViewById(R.id.tv_nature);
}
}
}
Here is how i have implemented Endless as well, using this:
mRecyclerView.setOnScrollListener(new EndlessRecyclerOnScrollListener(linearLayoutManager) {
@Override
public void onLoadMore(int current_page) {
// do something...
}
});
Note: I would personally prefer RecyclerView onScroll functionality to get my work done.
回答1:
Activity Class with recylcerview in xml layout file
public class WallpaperActivity extends AppCompatActivity implements OnTaskCompleted {
private static final String TAG = "WallpaperActivity";
private Toolbar toolbar;
private RecyclerView mRecyclerView;
private WallPaperDataAdapter mAdapter;
private LinearLayoutManager mLayoutManager;
// to keep track which pages loaded and next pages to load
public static int pageNumber;
private List<WallPaper> wallpaperImagesList;
protected Handler handler;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.wallpaper_main);
toolbar = (Toolbar) findViewById(R.id.toolbar);
mRecyclerView = (RecyclerView) findViewById(R.id.my_recycler_view);
pageNumber = 1;
wallpaperImagesList = new ArrayList<WallPaper>();
handler = new Handler();
if (toolbar != null) {
setSupportActionBar(toolbar);
getSupportActionBar().setTitle("WallPapers");
}
// use this setting to improve performance if you know that changes
// in content do not change the layout size of the RecyclerView
mRecyclerView.setHasFixedSize(true);
mLayoutManager = new LinearLayoutManager(this);
// use a linear layout manager
mRecyclerView.setLayoutManager(mLayoutManager);
// create an Object for Adapter
mAdapter = new WallPaperDataAdapter(wallpaperImagesList, mRecyclerView);
// set the adapter object to the Recyclerview
mRecyclerView.setAdapter(mAdapter);
getWebServiceData();
mAdapter.setOnLoadMoreListener(new OnLoadMoreListener() {
@Override
public void onLoadMore() {
//add null , so the adapter will check view_type and show progress bar at bottom
wallpaperImagesList.add(null);
mAdapter.notifyItemInserted(wallpaperImagesList.size() - 1);
++pageNumber;
getWebServiceData();
}
});
}
public void getWebServiceData() {
BackGroundTask backGroundTask = new BackGroundTask(this, this, pageNumber);
backGroundTask.execute();
}
@Override
public void onTaskCompleted(String response) {
parsejosnData(response);
}
public void parsejosnData(String response) {
try {
JSONObject jsonObject = new JSONObject(response);
// String json = jsonObject.toString();
JSONArray jsonArray = jsonObject.getJSONArray("wallpapers");
if (jsonArray != null) {
// looping through All albums
if (pageNumber > 1) {
wallpaperImagesList.remove(wallpaperImagesList.size() - 1);
mAdapter.notifyItemRemoved(wallpaperImagesList.size());
}
for (int i = 0; i < jsonArray.length(); i++) {
JSONObject c = jsonArray.getJSONObject(i);
// Storing each json item values in variable
String id = c.getString("id");
String orig_url = c.getString("orig_url");
String thumb_url = c.getString("thumb_url");
String downloads = c.getString("downloads");
String fav = c.getString("fav");
// Creating object for each product
WallPaper singleWall = new WallPaper(id, orig_url, thumb_url, downloads, fav);
// adding HashList to ArrayList
wallpaperImagesList.add(singleWall);
handler.post(new Runnable() {
@Override
public void run() {
mAdapter.notifyItemInserted(wallpaperImagesList.size());
}
});
}
mAdapter.setLoaded();
} else {
Log.d("Wallpapers: ", "null");
}
} catch (JSONException e) {
e.printStackTrace();
}
}
}
Adapter Class
public class WallPaperDataAdapter extends RecyclerView.Adapter {
private final int VIEW_ITEM = 1;
private final int VIEW_PROG = 0;
private List<WallPaper> imagesList;
// The minimum amount of items to have below your current scroll position
// before loading more.
private int visibleThreshold = 5;
private int lastVisibleItem, totalItemCount;
private boolean loading;
private OnLoadMoreListener onLoadMoreListener;
public WallPaperDataAdapter(List<WallPaper> imagesList1, RecyclerView recyclerView) {
imagesList = imagesList1;
if (recyclerView.getLayoutManager() instanceof LinearLayoutManager) {
final LinearLayoutManager linearLayoutManager = (LinearLayoutManager) recyclerView
.getLayoutManager();
recyclerView
.addOnScrollListener(new RecyclerView.OnScrollListener() {
@Override
public void onScrolled(RecyclerView recyclerView,
int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
totalItemCount = linearLayoutManager.getItemCount();
lastVisibleItem = linearLayoutManager
.findLastVisibleItemPosition();
if (!loading
&& totalItemCount <= (lastVisibleItem + visibleThreshold)) {
// End has been reached
// Do something
if (onLoadMoreListener != null) {
onLoadMoreListener.onLoadMore();
}
loading = true;
}
}
});
}
}
@Override
public int getItemViewType(int position) {
return imagesList.get(position) != null ? VIEW_ITEM : VIEW_PROG;
}
@Override
public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent,
int viewType) {
RecyclerView.ViewHolder vh;
if (viewType == VIEW_ITEM) {
View v = LayoutInflater.from(parent.getContext()).inflate(
R.layout.wallpaper_row, parent, false);
vh = new WallPaperViewHolder(v);
} else {
View v = LayoutInflater.from(parent.getContext()).inflate(
R.layout.progress_item, parent, false);
vh = new ProgressViewHolder(v);
}
return vh;
}
@Override
public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
if (holder instanceof WallPaperViewHolder) {
WallPaper singleWallPaper = (WallPaper) imagesList.get(position);
Glide.with(((WallPaperViewHolder) holder).thumbIcon.getContext())
.load(singleWallPaper.getThumbUrl())
.centerCrop()
.placeholder(R.drawable.bg)
.crossFade()
.into(((WallPaperViewHolder) holder).thumbIcon);
} else {
((ProgressViewHolder) holder).progressBar.setIndeterminate(true);
}
}
public void setLoaded() {
loading = false;
}
@Override
public int getItemCount() {
return imagesList.size();
}
public void setOnLoadMoreListener(OnLoadMoreListener onLoadMoreListener) {
this.onLoadMoreListener = onLoadMoreListener;
}
//
public static class WallPaperViewHolder extends RecyclerView.ViewHolder {
public ImageView thumbIcon;
public WallPaperViewHolder(View v) {
super(v);
thumbIcon = (ImageView) v.findViewById(R.id.thumbIcon);
}
}
public static class ProgressViewHolder extends RecyclerView.ViewHolder {
public ProgressBar progressBar;
public ProgressViewHolder(View v) {
super(v);
progressBar = (ProgressBar) v.findViewById(R.id.progressBar1);
}
}
}
wallpaper_row.xml
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="wrap_content">
<ImageView
android:id="@+id/thumbIcon"
android:layout_width="160dp"
android:layout_height="160dp"
android:layout_centerInParent="true"
android:layout_margin="2dp"
android:gravity="center" />
</RelativeLayout>
progress_item.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical" >
<ProgressBar
android:id="@+id/progressBar1"
android:layout_width="wrap_content"
android:layout_gravity="center"
android:layout_height="wrap_content" />
</LinearLayout>
Separate BackGroundTask.java
public class BackGroundTask extends AsyncTask<Object, Void, String> {
private ProgressDialog pDialog;
public OnTaskCompleted listener = null;//Call back interface
Context context;
int pageNumber;
public BackGroundTask(Context context1, OnTaskCompleted listener1, int pageNumber) {
context = context1;
listener = listener1; //Assigning call back interface through constructor
this.pageNumber = pageNumber;
}
@Override
protected void onPreExecute() {
super.onPreExecute();
}
@Override
protected String doInBackground(Object... params) {
//My Background tasks are written here
synchronized (this) {
String url = Const.URL_WALLPAPERS_HD + pageNumber;
String jsonStr = ServiceHandler.makeServiceCall(url, ServiceHandler.GET);
Log.i("Url: ", "> " + url);
Log.i("Response: ", "> " + jsonStr);
return jsonStr;
}
}
@Override
protected void onPostExecute(String result) {
super.onPostExecute(result);
listener.onTaskCompleted(result);
}
}
ServiceHanlder.java
public class ServiceHandler {
static String response = null;
public final static int GET = 1;
public final static int POST = 2;
public ServiceHandler() {
}
/**
* Making service call
*
* @url - url to make request
* @method - http request method
*/
public static String makeServiceCall(String url, int method) {
return makeServiceCall(url, method, null);
}
/**
* Making service call
*
* @url - url to make request
* @method - http request method
* @params - http request params
*/
public static String makeServiceCall(String url, int method,
List<NameValuePair> params) {
try {
// http client
DefaultHttpClient httpClient = new DefaultHttpClient();
HttpEntity httpEntity = null;
HttpResponse httpResponse = null;
// Checking http request method type
if (method == POST) {
HttpPost httpPost = new HttpPost(url);
// adding post params
if (params != null) {
httpPost.setEntity(new UrlEncodedFormEntity(params));
}
Log.e("Selltis Request URL", url);
httpResponse = httpClient.execute(httpPost);
} else if (method == GET) {
// appending params to url
if (params != null) {
String paramString = URLEncodedUtils
.format(params, "utf-8");
url += paramString;
Log.i("Request URL", url);
}
HttpGet httpGet = new HttpGet(url);
httpResponse = httpClient.execute(httpGet);
}
httpEntity = httpResponse.getEntity();
response = EntityUtils.toString(httpEntity);
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
return "Fail";
} catch (ClientProtocolException e) {
e.printStackTrace();
return "Fail";
} catch (IOException e) {
e.printStackTrace();
return "Fail";
}
return response;
}
}
Interface for Load More
public interface OnLoadMoreListener {
void onLoadMore();
}
Interface to know web service data loaded from asynctask
public interface OnTaskCompleted{
void onTaskCompleted(String response);
}
Please let me know if this works or any issues for you. Better to use Volley or okHttp Libraries for Networking.
For ImageLoading i used Glide Library.
回答2:
This is how I detect whether RecyclerView should refresh by OnScrollListener, take a look at it:
recyclerView.setOnScrollListener(new RecyclerView.OnScrollListener() {
int ydy = 0;
@Override
public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
super.onScrollStateChanged(recyclerView, newState);
}
@Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
int offset = dy - ydy;
ydy = dy;
boolean shouldRefresh = (linearLayoutManager.findFirstCompletelyVisibleItemPosition() == 0)
&& (recyclerView.getScrollState() == RecyclerView.SCROLL_STATE_DRAGGING) && offset > 30;
if (shouldRefresh) {
//swipeRefreshLayout.setRefreshing(true);
//Refresh to load data here.
return;
}
boolean shouldPullUpRefresh = linearLayoutManager.findLastCompletelyVisibleItemPosition() == linearLayoutManager.getChildCount() - 1
&& recyclerView.getScrollState() == RecyclerView.SCROLL_STATE_DRAGGING && offset < -30;
if (shouldPullUpRefresh) {
//swipeRefreshLayout.setRefreshing(true);
//refresh to load data here.
return;
}
swipeRefreshLayout.setRefreshing(false);
}
});
Hope you'll be inspired. Good luck~
回答3:
Another example. Set you progress bar at bottom and change its visibility according to scrolling/loading and your records. Note: you need to call notifyDataSetChanged(); method to add/refresh data to adapter
recyclerView.setOnScrollListener(new RecyclerView.OnScrollListener() {
@Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
int total = linearLayoutManager.getItemCount();
int firstVisibleItemCount = linearLayoutManager.findFirstVisibleItemPosition();
int lastVisibleItemCount = linearLayoutManager.findLastVisibleItemPosition();
//to avoid multiple calls to loadMore() method
//maintain a boolean value (isLoading). if loadMore() task started set to true and completes set to false
if (!isLoading) {
if (total > 0)
if ((total - 1) == lastVisibleItemCount){
loadMore();//your HTTP stuff goes in this method
loadingProgress.setVisibility(View.VISIBLE);
}else
loadingProgress.setVisibility(View.GONE);
}
}
@Override
public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
super.onScrollStateChanged(recyclerView, newState);
}
});
回答4:
The idea to implement load-more is :
Get all records in one collection. Take another collection which will populate partial records lets say 10 records. Now, when u reach at bottom, populate next 10 records in the collection and notify the list.
So your code will be something like this :
ArrayList<NatureItem> tempList; // which holds partial records
tempList = getList(limit, 10);
mAdapter = new RecyclerViewMaterialAdapter(new CardAdapter(getActivity(), tempList), 2);
mRecyclerView.setAdapter(mAdapter);
Now, code to load next records :
limit += 10;
tempList.addAll(getList(limit, 10));
mAdapter.notifyDataSetChanged();
To show he loader/progress, better to use load-more library
回答5:
In the onScroll method
if (!loading && (totalItemCount - visibleItemCount)
<= (firstVisibleItem + visibleThreshold)) {
// End has been reached
Log.i("...", "end called");
// Do something
new JSONAsyncTask().execute("http://walldroidhd.com/api.php");
loading = true;
}
回答6:
To implement OnScrollListener in Kotlin for RecyclerView, you can use
recyclerViewChat.addOnScrollListener(object : RecyclerView.OnScrollListener() {
override fun onScrollStateChanged(recyclerView: RecyclerView, newState: Int) {
super.onScrollStateChanged(recyclerView, newState)
if (newState == RecyclerView.SCROLL_STATE_IDLE) {
Log.d("scroll", "idle")
} else if (newState == RecyclerView.SCROLL_STATE_SETTLING) {
Log.d("scroll", "settling")
} else if (newState == RecyclerView.SCROLL_STATE_DRAGGING) {
Log.d("scroll", "dragging")
}
}
override fun onScrolled(recyclerView: RecyclerView, dx: Int, dy: Int) {
super.onScrolled(recyclerView, dx, dy)
Log.d("scroll", "scrolling")
}
})
来源：https://stackoverflow.com/questions/31000964/how-to-implement-setonscrolllistener-in-recyclerview