Question

我在数据库中有24行，从1到24，但是当我尝试在recyclerview上显示项目时， EndlessRecyclerViewScrollListener 类的问题就变成了随机项目。

ScreenShot

绿色圆圈 =＃20 红色圆圈 =＃11

为什么是＃11而不是＃21？

我要显示从＃1到＃24的项目

PostsActivity

public class PostsActivity extends AppCompatActivity {

    @BindView(R.id.rv_posts)
    RecyclerView rv_posts;
    SaveSystem saveSystem;
    List<PostsModels> postsModels = new ArrayList<>();
    PostsAdapter postsAdapter;
    EndlessRecyclerViewScrollListener scrollListener;
    int page = 0;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_posts);
        ButterKnife.bind(this);
        saveSystem = new SaveSystem(this);
        //check first time
        if (saveSystem.LoadBooleanData("FirstTime")) {
            saveSystem.SaveStringData("language", "en");
            saveSystem.SaveBooleanData("FirstTime", false);
        }
        //setData
        setData();
    }

    void setData() {
        postsAdapter = new PostsAdapter(PostsActivity.this, postsModels);
        LinearLayoutManager linearLayoutManager = new LinearLayoutManager(PostsActivity.this, LinearLayoutManager.VERTICAL, false);
        rv_posts.setLayoutManager(linearLayoutManager);
        rv_posts.setAdapter(postsAdapter);
        scrollListener = new EndlessRecyclerViewScrollListener(linearLayoutManager) {
            @Override
            public void onLoadMore(int i, int totalItemsCount, RecyclerView view) {
                page = page + 10;
                Toast.makeText(PostsActivity.this, "" + page, Toast.LENGTH_SHORT).show();
                retrofit(page);
            }
        };
        rv_posts.addOnScrollListener(scrollListener);
        retrofit(page);
    }

    void retrofit(int number) {
        Retrofit retrofit = new Retrofit.Builder().baseUrl("http://***").addConverterFactory(GsonConverterFactory.create()).build();
        HTTP http = retrofit.create(HTTP.class);
        Call<List<PostsModels>> call = http.get_posts(saveSystem.LoadStringData("language"), number);
        call.enqueue(new Callback<List<PostsModels>>() {
            @Override
            public void onResponse(Call<List<PostsModels>> call, Response<List<PostsModels>> response) {
                List<PostsModels> list = response.body();
                for (PostsModels i : list) {
                    postsModels.add(new PostsModels(i.id, i.user_id, i.user_name, i.word, i.description, i.sound, i.level, i.shortcut));
                }
                postsAdapter.notifyItemRangeInserted(postsAdapter.getItemCount(), list.size() - 1);
            }

            @Override
            public void onFailure(Call<List<PostsModels>> call, Throwable t) {

            }
        });
    }

}

PostsModels

public class PostsModels {

    @SerializedName("id")
    String id;
    @SerializedName("user_id")
    String user_id;
    @SerializedName("user_name")
    String user_name;
    @SerializedName("word")
    String word;
    @SerializedName("description")
    String description;
    @SerializedName("sound")
    String sound;
    @SerializedName("level")
    String level;
    @SerializedName("shortcut")
    String shortcut;

    public PostsModels(String id, String user_id, String user_name, String word, String description, String sound, String level, String shortcut) {
        this.id = id;
        this.user_id = user_id;
        this.user_name = user_name;
        this.word = word;
        this.description = description;
        this.sound = sound;
        this.level = level;
        this.shortcut = shortcut;
    }
}

PostsAdapter

public class PostsAdapter extends RecyclerView.Adapter<PostsAdapter.posts> {

    Context context;
    List<PostsModels> postsModels;
    int lastCheckedPosition = -1;

    public PostsAdapter(Context context, List<PostsModels> postsModels) {
        this.context = context;
        this.postsModels = postsModels;
    }

    @NonNull
    @Override
    public posts onCreateViewHolder(@NonNull ViewGroup viewGroup, int i) {
        View view = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.row_posts, viewGroup, false);
        posts viewHolder = new posts(view);
        return viewHolder;
    }

    @Override
    public void onBindViewHolder(@NonNull posts posts, int i) {
        PostsModels list = postsModels.get(i);
        //set photo
        Picasso.get().load("http://graph.facebook.com/" + list.user_id + "/picture?type=large").into(posts.img_profile);
        //set word
        posts.txt_word.setText(list.word);
        //set id
        posts.txt_id.setText("#" + list.id);
        //set description
        posts.txt_description.setText(list.description);
        //if checked
        if (lastCheckedPosition == i) {
            posts.linear_layout.setBackgroundColor(context.getResources().getColor(R.color.posts_item_selected_1));
            posts.frame_pink.setVisibility(View.VISIBLE);
        } else {
            posts.linear_layout.setBackgroundColor(0x000000000);
            posts.frame_pink.setVisibility(View.INVISIBLE);
        }
    }

    @Override
    public int getItemCount() {
        return postsModels.size();
    }

    class posts extends RecyclerView.ViewHolder {

        @BindView(R.id.linear_layout)
        LinearLayout linear_layout;
        @BindView(R.id.frame_pink)
        FrameLayout frame_pink;
        @BindView(R.id.img_profile)
        CircleImageView img_profile;
        @BindView(R.id.txt_word)
        TextViewFont txt_word;
        @BindView(R.id.txt_id)
        TextViewFont txt_id;
        @BindView(R.id.txt_description)
        TextViewFont txt_description;

        @OnClick(R.id.linear_layout)
        public void onClick() {
            lastCheckedPosition = getAdapterPosition();
            notifyDataSetChanged();
        }

        public posts(View view) {
            super(view);
            ButterKnife.bind(this, view);
        }

    }
}

EndlessRecyclerViewScrollListener

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 = 5;
    // The current offset index of data you have loaded
    private int currentPage = 0;
    // 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 = 0;

    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);

希望您能帮助我找到解决方法。

Answer 1

EndlessRecyclerViewScrollListener用LayoutManager检查最后一个可见位置。当它检测到最后一个（在这种情况下）时，请调用onLoadMore()方法。我注意到的一件奇怪的事情是，您在活动中管理page，但随后忽略了使用监听器的currentPage值。

问题可能出在于此。在EndlessRecyclerViewScrollListener内放置一个断点，并检查调用“ onLoadMore（）”方法的次数以及使用哪些参数。

希望有帮助。

EndlessRecyclerViewScrollListener不会在recyclerview上显示所有项目

1 个答案: