[英]Recycler View adapter not working properly when the list is big enough to scroll
[英]Recycler View infinite scroll not working properly
我正在从TMDB获取数据并将其显示在回收者视图中。 我想使用无限滚动回收器视图,所以我看了一些教程并实现了它。 问题在于,在第一次加载后,在前五个元素中滚动后,整个数据将被新数据刷新。 我该如何解决?
EndlessRecyclerViewScrollListener.java
public abstract class EndlessRecyclerViewScrollListener extends RecyclerView.OnScrollListener {
/ The minimum amount of items to have below your current scroll position
// before loading more.
private int visibleThreshold = 15;
// The current offset index of data you have loaded
private int currentPage = 1;
// The total number of items in the dataset after the last load
private int previousTotalItemCount = 0;
// True if we are still waiting for the last set of data to load.
private boolean loading = true;
// Sets the starting page index
private int startingPageIndex = 1;
RecyclerView.LayoutManager mLayoutManager;
public EndlessRecyclerViewScrollListener(LinearLayoutManager layoutManager) {
this.mLayoutManager = layoutManager;
}
public EndlessRecyclerViewScrollListener(GridLayoutManager layoutManager) {
this.mLayoutManager = layoutManager;
visibleThreshold = visibleThreshold * layoutManager.getSpanCount();
}
public EndlessRecyclerViewScrollListener(StaggeredGridLayoutManager layoutManager) {
this.mLayoutManager = layoutManager;
visibleThreshold = visibleThreshold * layoutManager.getSpanCount();
}
public int getLastVisibleItem(int[] lastVisibleItemPositions) {
int maxSize = 0;
for (int i = 0; i < lastVisibleItemPositions.length; i++) {
if (i == 0) {
maxSize = lastVisibleItemPositions[i];
}
else if (lastVisibleItemPositions[i] > maxSize) {
maxSize = lastVisibleItemPositions[i];
}
}
return maxSize;
}
// This happens many times a second during a scroll, so be wary of the code you place here.
// We are given a few useful parameters to help us work out if we need to load some more data,
// but first we check if we are waiting for the previous load to finish.
@Override
public void onScrolled(RecyclerView view, int dx, int dy) {
int lastVisibleItemPosition = 0;
int totalItemCount = mLayoutManager.getItemCount();
if (mLayoutManager instanceof StaggeredGridLayoutManager) {
int[] lastVisibleItemPositions = ((StaggeredGridLayoutManager) mLayoutManager).findLastVisibleItemPositions(null);
// get maximum element within the list
lastVisibleItemPosition = getLastVisibleItem(lastVisibleItemPositions);
} else if (mLayoutManager instanceof GridLayoutManager) {
lastVisibleItemPosition = ((GridLayoutManager) mLayoutManager).findLastVisibleItemPosition();
} else if (mLayoutManager instanceof LinearLayoutManager) {
lastVisibleItemPosition = ((LinearLayoutManager) mLayoutManager).findLastVisibleItemPosition();
}
// If the total item count is zero and the previous isn't, assume the
// list is invalidated and should be reset back to initial state
if (totalItemCount < previousTotalItemCount) {
this.currentPage = this.startingPageIndex;
this.previousTotalItemCount = totalItemCount;
if (totalItemCount == 0) {
this.loading = true;
}
}
// If it’s still loading, we check to see if the dataset count has
// changed, if so we conclude it has finished loading and update the current page
// number and total item count.
if (loading && (totalItemCount > previousTotalItemCount)) {
loading = false;
previousTotalItemCount = totalItemCount;
}
// If it isn’t currently loading, we check to see if we have breached
// the visibleThreshold and need to reload more data.
// If we do need to reload some more data, we execute onLoadMore to fetch the data.
// threshold should reflect how many total columns there are too
if (!loading && (lastVisibleItemPosition + visibleThreshold) > totalItemCount) {
currentPage++;
onLoadMore(currentPage, totalItemCount, view);
loading = true;
}
}
// Call this method whenever performing new searches
public void resetState() {
this.currentPage = this.startingPageIndex;
this.previousTotalItemCount = 0;
this.loading = true;
}
// Defines the process for actually loading more data based on page
public abstract void onLoadMore(int page, int totalItemsCount, RecyclerView view);/ The minimum amount of items to have below your current scroll position
// before loading more.
private int visibleThreshold = 15;
// The current offset index of data you have loaded
private int currentPage = 1;
// The total number of items in the dataset after the last load
private int previousTotalItemCount = 0;
// True if we are still waiting for the last set of data to load.
private boolean loading = true;
// Sets the starting page index
private int startingPageIndex = 1;
RecyclerView.LayoutManager mLayoutManager;
public EndlessRecyclerViewScrollListener(LinearLayoutManager layoutManager) {
this.mLayoutManager = layoutManager;
}
public EndlessRecyclerViewScrollListener(GridLayoutManager layoutManager) {
this.mLayoutManager = layoutManager;
visibleThreshold = visibleThreshold * layoutManager.getSpanCount();
}
public EndlessRecyclerViewScrollListener(StaggeredGridLayoutManager layoutManager) {
this.mLayoutManager = layoutManager;
visibleThreshold = visibleThreshold * layoutManager.getSpanCount();
}
public int getLastVisibleItem(int[] lastVisibleItemPositions) {
int maxSize = 0;
for (int i = 0; i < lastVisibleItemPositions.length; i++) {
if (i == 0) {
maxSize = lastVisibleItemPositions[i];
}
else if (lastVisibleItemPositions[i] > maxSize) {
maxSize = lastVisibleItemPositions[i];
}
}
return maxSize;
}
// This happens many times a second during a scroll, so be wary of the code you place here.
// We are given a few useful parameters to help us work out if we need to load some more data,
// but first we check if we are waiting for the previous load to finish.
@Override
public void onScrolled(RecyclerView view, int dx, int dy) {
int lastVisibleItemPosition = 0;
int totalItemCount = mLayoutManager.getItemCount();
if (mLayoutManager instanceof StaggeredGridLayoutManager) {
int[] lastVisibleItemPositions = ((StaggeredGridLayoutManager) mLayoutManager).findLastVisibleItemPositions(null);
// get maximum element within the list
lastVisibleItemPosition = getLastVisibleItem(lastVisibleItemPositions);
} else if (mLayoutManager instanceof GridLayoutManager) {
lastVisibleItemPosition = ((GridLayoutManager) mLayoutManager).findLastVisibleItemPosition();
} else if (mLayoutManager instanceof LinearLayoutManager) {
lastVisibleItemPosition = ((LinearLayoutManager) mLayoutManager).findLastVisibleItemPosition();
}
// If the total item count is zero and the previous isn't, assume the
// list is invalidated and should be reset back to initial state
if (totalItemCount < previousTotalItemCount) {
this.currentPage = this.startingPageIndex;
this.previousTotalItemCount = totalItemCount;
if (totalItemCount == 0) {
this.loading = true;
}
}
// If it’s still loading, we check to see if the dataset count has
// changed, if so we conclude it has finished loading and update the current page
// number and total item count.
if (loading && (totalItemCount > previousTotalItemCount)) {
loading = false;
previousTotalItemCount = totalItemCount;
}
// If it isn’t currently loading, we check to see if we have breached
// the visibleThreshold and need to reload more data.
// If we do need to reload some more data, we execute onLoadMore to fetch the data.
// threshold should reflect how many total columns there are too
if (!loading && (lastVisibleItemPosition + visibleThreshold) > totalItemCount) {
currentPage++;
onLoadMore(currentPage, totalItemCount, view);
loading = true;
}
}
// Call this method whenever performing new searches
public void resetState() {
this.currentPage = this.startingPageIndex;
this.previousTotalItemCount = 0;
this.loading = true;
}
// Defines the process for actually loading more data based on page
public abstract void onLoadMore(int page, int totalItemsCount, RecyclerView view);}}
MainActivity.java
public class MainActivity extends AppCompatActivity implemens ConnectivityReceiver.ConnectivityReceiverListener {
private static final String API_KEY = "***************";
private static final String TAG = "MainActivity";
private int page = 1;
private TextView no_data_tv;
private RecyclerView mainMoviesView;
private View noInternetLayout;
private ProgressBar progressBar;
private EndlessRecyclerViewScrollListener scrollListener;
private LinearLayoutManager llm;
List<Movies> movies;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
no_data_tv = (TextView) findViewById(R.id.text_no_data);
movies = new ArrayList<>();
llm = new LinearLayoutManager(this);
mainMoviesView = (RecyclerView) findViewById(R.id.main_recycler_view);
mainMoviesView.setLayoutManager(llm);
// This is the layout which is displayed if there is no internet connection. It is currently set to View.INVISIBLE
noInternetLayout = findViewById(R.id.no_internet_layout);
noInternetLayout.setVisibility(View.INVISIBLE);
progressBar = (ProgressBar) findViewById(R.id.loading_main_activity);
if(checkConnetion())
{
getDataFromServer(page);
progressBar.setVisibility(View.INVISIBLE);
}else
{
noInternetLayout.setVisibility(View.VISIBLE);
progressBar.setVisibility(View.INVISIBLE);
}
scrollListener = new EndlessRecyclerViewScrollListener(llm) {
@Override
public void onLoadMore(int page, int totalItemsCount, RecyclerView view) {
getDataFromServer(page);
Log.v(TAG,"Page loaded is"+page);
}
};
mainMoviesView.addOnScrollListener(scrollListener);
}
private boolean checkConnetion() {
return ConnectivityReceiver.isConnected();
}
private void getDataFromServer(int page)
{
// These are the retrofit codes to get the data from TMDB API
ApiInterface apiService = ApiClient.getClient().create(ApiInterface.class);
Call<Response> call = apiService.getPopularMovies(API_KEY , page);
call.enqueue(new Callback<Response>() {
@Override
public void onResponse(Call<Response> call, retrofit2.Response<Response> response) {
List<Movies> movies = response.body().getMovies();
progressBar.setVisibility(View.INVISIBLE);
if(movies.size() == 0)
{
no_data_tv.setVisibility(View.VISIBLE);
}else{
mainMoviesView.setAdapter(new MoviesAdapter(movies,MainActivity.this));
}
}
@Override
public void onFailure(Call<Response> call, Throwable t) {
Log.e(TAG,t.toString());
}
});
}
@Override
protected void onResume() {
super.onResume();
// register connection status listener
MyApplication.getInstance().setConnectivityListener(this);
}
@Override
public void onNetworkConnectionChanged(boolean isConnected) {
if(isConnected)
{
getDataFromServer(page);
}else{
progressBar.setVisibility(View.INVISIBLE);
noInternetLayout.setVisibility(View.VISIBLE);
}
}}
我哪里出问题了?
杜德,您每次调用都会分配新的值,
看这行-
List<Movies> movies = response.body().getMovies();
您必须将元素添加到数据集中,
movies.addAll(response.body().getMovies());
这行总是用新数据初始化yourview
mainMoviesView.setAdapter(new MoviesAdapter(movies,MainActivity.this));
它可以在onCreate(),onCreateView()或其他初始化方法中。
MoviesAdapter moviesAdapter = new MoviesAdapter(movies,MainActivity.this);
mainMoviesView.setAdapter(moviesAdepter);
然后您的新呼叫入队。
call.enqueue(new Callback<Response>() {
@Override
public void onResponse(Call<Response> call, retrofit2.Response<Response> response) {
movies.addAll(response.body().getMovies()); // this line updated your movies list.
progressBar.setVisibility(View.INVISIBLE);
if(movies.size() == 0)
{
no_data_tv.setVisibility(View.VISIBLE);
}else{
moviesAdapter.notifyDataSetChanged(); // this new line.
}
}
@Override
public void onFailure(Call<Response> call, Throwable t) {
Log.e(TAG,t.toString());
}
});
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