How to implement setOnScrollListener in RecyclerView
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")
}
})
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.
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~