问题
I am trying to implement Endless Infinite Scrolling with RecyclerView, but I am only getting first 10 records, not getting next 10 records and even not getting any progress while trying to scroll at bottom.
Whereas I was suppose to get next 10 records on scroll and so on... But getting only first 10 records
Here I have uploaded copy of my JSON - But i am not able to fetch data from same url, that's why i am using client's url and local host.
I am following this tutorial
Here is my complete code, May I know where I am doing mistake ?
JSON :
{
"names": [
{
"name": "Name 1"
},
{
"name": "Name 2"
},
....
{
"name": "Name 60"
}
]
}
Log:
D/name -(13759): Name 1
D/name -(13759): Name 2
.......................
D/name -(13759): Name 60
Here is my updated code, which i am using to parse JSON data
MainActivity.java: UPDATED
public class MainActivity extends AppCompatActivity {
private Toolbar toolbar;
private TextView tvEmptyView;
private RecyclerView mRecyclerView;
private DataAdapter mAdapter;
private LinearLayoutManager mLayoutManager;
private ArrayList<Student> studentList;
protected Handler handler;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
toolbar = (Toolbar) findViewById(R.id.toolbar);
tvEmptyView = (TextView) findViewById(R.id.empty_view);
mRecyclerView = (RecyclerView) findViewById(R.id.my_recycler_view);
studentList = new ArrayList<Student>();
handler = new Handler();
if (toolbar != null) {
setSupportActionBar(toolbar);
getSupportActionBar().setTitle("Android Students");
}
loadData();
}
// load initial data
private void loadData() {
new Parser().execute("http://10.0.2.2/jsons/mytest.txt");
}
class Parser extends AsyncTask<String, Void, Boolean> {
ProgressDialog dialog;
@Override
protected void onPreExecute() {
super.onPreExecute();
dialog = new ProgressDialog(MainActivity.this);
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 = EntityUtils.toString(entity);
JSONObject jsono = new JSONObject(data);
JSONArray jarray = jsono.getJSONArray("names");
for (int i = 0; i < jarray.length(); i++) {
JSONObject object = jarray.getJSONObject(i);
Student actor = new Student();
actor.setName(object.getString("name"));
Log.d("name - ", object.getString("name"));
studentList.add(actor);
}
Log.d("MainActivity:StudentList ", "The size "+studentList.size());
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();
Log.d("MainActivity:StudentList ", "The size "+studentList.size());
ArrayList< Student > temArray =
new ArrayList< Student >(studentList.subList(0, 10));
mAdapter = new DataAdapter(temArray, mRecyclerView);
Log.d("MainActivity:TempList ", "The size "+temArray.size());
// set the adapter object to the Recyclerview
mRecyclerView.setAdapter(mAdapter);
// 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(MainActivity.this);
// use a linear layout manager
mRecyclerView.setLayoutManager(mLayoutManager);
if (studentList.isEmpty()) {
mRecyclerView.setVisibility(View.GONE);
tvEmptyView.setVisibility(View.VISIBLE);
} else {
mRecyclerView.setVisibility(View.VISIBLE);
tvEmptyView.setVisibility(View.GONE);
}
mAdapter.setOnLoadMoreListener(new OnLoadMoreListener() {
@Override
public void onLoadMore() {
//add null , so the adapter will check view_type and show progress bar at bottom
studentList.add(null);
mAdapter.notifyItemInserted(studentList.size() - 1);
handler.postDelayed(new Runnable() {
@Override
public void run() {
// remove progress item
studentList.remove(studentList.size() - 1);
mAdapter.notifyItemRemoved(studentList.size());
//add items one by one
int start = studentList.size();
int end = start + 10;
for (int i = start + 1; i < end; i++) {
mAdapter.notifyItemInserted(studentList.size());
}
mAdapter.setLoaded();
//or you can add all at once but do not forget to call mAdapter.notifyDataSetChanged();
}
}, 2000);
}
});
}
}
}
DataAdapter.java:
public class DataAdapter extends RecyclerView.Adapter {
private final int VIEW_ITEM = 1;
private final int VIEW_PROG = 0;
private List<Student> studentList;
// 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 DataAdapter(List<Student> students, RecyclerView recyclerView) {
studentList = students;
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 studentList.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.list_row, parent, false);
vh = new StudentViewHolder(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 StudentViewHolder) {
Student singleStudent= (Student) studentList.get(position);
((StudentViewHolder) holder).tvName.setText(singleStudent.getName());
((StudentViewHolder) holder).student= singleStudent;
} else {
((ProgressViewHolder) holder).progressBar.setIndeterminate(true);
}
}
public void setLoaded() {
loading = false;
}
@Override
public int getItemCount() {
return studentList.size();
}
public void setOnLoadMoreListener(OnLoadMoreListener onLoadMoreListener) {
this.onLoadMoreListener = onLoadMoreListener;
}
//
public static class StudentViewHolder extends RecyclerView.ViewHolder {
public TextView tvName;
public Student student;
public StudentViewHolder(View v) {
super(v);
tvName = (TextView) v.findViewById(R.id.tvName);
v.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
Toast.makeText(v.getContext(),
"OnClick :" + student.getName(),
Toast.LENGTH_SHORT).show();
}
});
}
}
public static class ProgressViewHolder extends RecyclerView.ViewHolder {
public ProgressBar progressBar;
public ProgressViewHolder(View v) {
super(v);
progressBar = (ProgressBar) v.findViewById(R.id.progressBar1);
}
}
}
OnLoadMoreListener.java:
public interface OnLoadMoreListener {
void onLoadMore();
}
回答1:
I had the same issue once an I solve it using this code ... First .. create this class
public abstract class EndlessOnScrollListener extends OnScrollListener {
public static String TAG = EndlessOnScrollListener.class.getSimpleName();
// use your LayoutManager instead
private LinearLayoutManager llm;
public EndlessOnScrollListener(LinearLayoutManager sglm) {
this.lm = llm;
}
@Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
if (!recyclerView.canScrollVertically(1)) {
onScrolledToEnd();
}
}
public abstract void onScrolledToEnd();
}
Second .. in you activity use this
recyclerView.addOnScrollListener(new EndlessOnScrollListener() {
@Override
public void onScrolledToEnd() {
if (!loading) {
loading = true;
// add 10 by 10 to tempList then notify changing in data
}
loading = false;
}
});
This works for me .... I hope it works for you to.
回答2:
Try notifyItemRangeChanged
yourCurrentList.addAll(newData);
mAdapter.notifyItemRangeChanged(yourCurretList.size() + 1, newDataSize);
I think this'll help you.
回答3:
1.
Getting first 11 recyclerview Items blank (And showing progress bar continuously), see below screenshot:
Change loadData method as:
private void loadData() {
new Parser().execute("http://clienturl.com/jsons/mytest.txt");
}
2.
Whereas I was suppose to get first 10 records, and on scroll next 10 records and so on...
Change onPostExecute method of Parser as:
protected void onPostExecute(Boolean result) {
dialog.cancel();
ArrayList< Student > temArray =
new ArrayList< Student >(studentList.subList(0, 10));
mAdapter = new DataAdapter(temArray, mRecyclerView);
// set the adapter object to the Recyclerview
mRecyclerView.setAdapter(mAdapter);
}
And also remove following lines from onCreate method:
mAdapter = new DataAdapter(studentList, mRecyclerView);
// set the adapter object to the Recyclerview
mRecyclerView.setAdapter(mAdapter);
回答4:
Try changing the
int i = start + 1; i <= end; i++
in the for loop to
int i = start + 1; i < end; i++
The <= validation adds an extra item.
回答5:
Issue-1: You have created a new instance of mAdapter before setting the LayoutManager for RecyclerView. Thereby the constructor code in the DataAdapter to add ScrollListener is not executed since recyclerView.getLayoutManager() returns null:
if (recyclerView.getLayoutManager() instanceof LinearLayoutManager){
// code to add ScrollListener is never executed
}
Fix: First set the LayoutManager for the Recyclerview and then create the adapter like below:
// use a linear layout manager
mRecyclerView.setLayoutManager(mLayoutManager);
mAdapter = new DataAdapter(temArray, mRecyclerView);
// set the adapter object to the Recyclerview
mRecyclerView.setAdapter(mAdapter);
Issue-2: You have used temArray to create DataAdapter but in onLoadMore() you are using the studentList to add/remove new items, since studentList is not binded with mAdapter your changes doesn't reflect in the UI.
Fix: Declare temArray as a class level variable and use temArray to manipulate the items.
//class variable
private ArrayList<Student> temArray = new ArrayList<Student>();
handler.postDelayed(new Runnable() {
@Override public void run() {
// remove progress item
temArray.remove(temArray.size() - 1);
mAdapter.notifyItemRemoved(temArray.size());
//add items one by one
int start = temArray.size();
int end = start + 10;
if(end<=studentList.size()){
temArray.addAll(studentList.subList(start,end));
}
mAdapter.setLoaded();
}
}, 2000);
回答6:
replace
private List<Student> studentList;
with
private List<Object> list;
also replace
@Override
public int getItemViewType(int position) {
return studentList.get(position) != null ? VIEW_ITEM : VIEW_PROG;
}
with
@Override
public int getItemViewType(int position) {
return list.get(position) instanceof Student ? VIEW_ITEM : VIEW_PROG;
}
for detect end of List you can using
@Override
public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
super.onScrollStateChanged(recyclerView, newState);
// When went to the end of the list, load more posts
if (newState == RecyclerView.SCROLL_STATE_IDLE) {
if (linearLayoutManager.findLastVisibleItemPosition() >= linearLayoutManager.getItemCount() - 1) {
// Grow List
}
}
}
Also for Add Loading Item. add this code in adapter
public void addLoadingView(){
list.add(new Object());
notifyDataSetChanged();
}
回答7:
for (int i = start + 1; i < end; i++) {
studentList.add(add data here) ;
mAdapter.notifyItemInserted(studentList.size());
}
回答8:
mAdapter.setOnLoadMoreListener(new OnLoadMoreListener() {
@Override
public void onLoadMore() {
//add null , so the adapter will check view_type and show progress bar at bottom
studentList.add(null);
mAdapter.notifyItemInserted(studentList.size() - 1);
handler.postDelayed(new Runnable() {
@Override
public void run() {
// remove progress item
studentList.remove(studentList.size() - 1);
mAdapter.notifyItemRemoved(studentList.size());
//add items one by one
int start = studentList.size();
int end = start + 10;
for (int i = start + 1; i < end; i++) {
// studentList.add();
mAdapter.notifyItemInserted(studentList.size());
}
mAdapter.setLoaded();
//or you can add all at once but do not forget to call mAdapter.notifyDataSetChanged();
}
}, 2000);
}
});
ok so you inserted progress bar, and then you've removed it as well but you never inserted the next student to show... something like studentList.add();
I hope that solved your problem... good luck..
来源：https://stackoverflow.com/questions/32946441/recyclerview-endless-infinite-scrolling-issue