android - 如何在滾動時為recycleView加載更多項目

Question

我正在使用循環視圖，我通過json從net獲取數據並使用適配器將項添加到我的循環視圖中。 我想在用戶到達回收視圖的末尾時獲取新項目。

我正在使用GridLayoutManager作為循環視圖。 這是代碼：

    int pastVisiblesItems, visibleItemCount, totalItemCount;
    GridLayoutManager mLayoutManager;
    private boolean loading = true;

recycle=(RecyclerView)findViewById(R.id.recycle);
        mLayoutManager = new GridLayoutManager(this, 3);
        // (Context context, int spanCount)
        recycle.setLayoutManager(mLayoutManager);

recycle.addOnScrollListener(new RecyclerView.OnScrollListener() {
            @Override
            public void onScrolled(RecyclerView recyclerView, int dx, int dy) {

                visibleItemCount = mLayoutManager.getChildCount();
                totalItemCount = mLayoutManager.getItemCount();
                pastVisiblesItems = mLayoutManager.findFirstVisibleItemPosition();
                if (loadmore) {
                    if ((visibleItemCount + pastVisiblesItems) >= totalItemCount) {
                        page = page + 1;
                        Toast.makeText(Cats.this, "test", Toast.LENGTH_SHORT);
                    }
                }
            }
        });

我結束了recycleview，但它沒有向我展示任何吐司，所以我認為它不明白我到達了循環視圖的末尾。

這段代碼有什么問題？

Answer 1

很長一段時間我對此感到沮喪。 但終於找到了解決方法。 如果您使用的是RecyclerView ，則必須使用自定義適配器。 在您填充視圖的位置，只需檢查您是否填充了列表中的最后一個元素。

public abstract class Adapter extends RecyclerView.Adapter<VH> {

    protected final List<String> items;
    protected final Context context;

    protected Adapter(Context context) {
        this.context = context;
        this.items = new ArrayList<>();
    }

    @SuppressWarnings("unused")
    public final void add(String item) {
        items.add(item);
        notifyDataSetChanged();
    }

    @Override
    public final void onBindViewHolder(VH holder, int position) {
        holder.textView.setText(items.get(position).toString());
        if (position == items.size() - 1) 
            // Reached End of List
    }

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

}

Answer 2

試試這個完整的android示例，在滾動時為recycleView加載更多項目

第1步：

創建一個新Interface ：

public interface OnLoadMoreListener {
    void onLoadMore();
}

第2步：

創建一個新的模型類並將其放在Example.java ：

public class Example implements Serializable {

    private static final long serialVersionUID = 1L;
    private String name;

    public Student() {

    }

    public Student(String name) {
        this.name = name;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
}

第3步：

使用xml布局中的RecyclerView創建一個新Activity ：

public class MainActivity extends AppCompatActivity {

    private Toolbar toolbar;

    private TextView tvEmptyView;
    private RecyclerView mRecyclerView;
    private DataAdapter mAdapter;
    private LinearLayoutManager mLayoutManager;
    private List<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();

        mRecyclerView.setHasFixedSize(true);

        mLayoutManager = new LinearLayoutManager(this);
        mRecyclerView.setLayoutManager(mLayoutManager);
        mAdapter = new DataAdapter(studentList, mRecyclerView);
        mRecyclerView.setAdapter(mAdapter);

        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 + 20;

                        for (int i = start + 1; i <= end; i++) {
                            studentList.add(new Student("Student " + i, "AndroidStudent" + i + "@gmail.com"));
                            mAdapter.notifyItemInserted(studentList.size());
                        }
                        mAdapter.setLoaded();
                       //or you can add all at once but do not forget to call mAdapter.notifyDataSetChanged();
                    }
                }, 2000);}
        }); }

    private void loadData() {

        for (int i = 1; i <= 20; i++) {
            studentList.add(new Student("Student " + i, "androidstudent" + i + "@gmail.com"));

        }
    }
}

第四步：

為RecyclerView創建Adapter類：

public class DataAdapter extends RecyclerView.Adapter {
    private final int VIEW_ITEM = 1;
    private final int VIEW_PROG = 0;
    private List < Student > studentList;
    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)) {
                            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);
        }
    }
}

Answer 3

 mRecyclerViewList.setOnScrollListener(new RecyclerView.OnScrollListener() {
        @Override
        public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
            super.onScrolled(recyclerView, dx, dy);

        }

        @Override
        public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
            super.onScrollStateChanged(recyclerView, newState);
            if (newState == RecyclerView.SCROLL_STATE_IDLE) {
               //Call your method here for next set of data
            }
        }
    });

Answer 4

private boolean loading = true;
int pastVisiblesItems, visibleItemCount, totalItemCount;

LinearLayoutManager mLayoutManager;
mLayoutManager = new LinearLayoutManager(this);
mRecyclerView.setLayoutManager(mLayoutManager);

mRecyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
    @Override
    public void onScrolled(RecyclerView recyclerView, int dx, int dy) {

            visibleItemCount = mLayoutManager.getChildCount();
            totalItemCount = mLayoutManager.getItemCount();
            pastVisiblesItems = mLayoutManager.findFirstVisibleItemPosition();

            if (loading) {
                if ( (visibleItemCount + pastVisiblesItems) >= totalItemCount) {
                    loading = false;
                    //Action here
                }
            }
     }
});