如何使用notifyDataSetChanged和Volley

Question

我有屏幕Book，如果要在屏幕上重新加载数据，我想添加FloatingActionButton，我必须单击该按钮。 我在Book_Fragment中添加了notifydatasetchanged来检查更改。 但是单击后，按钮将重新加载列表视图不变的数据。 我不知道该如何解决。 请帮我。 谢谢

这是我的源代码：

Book_Fragment.java

public class Book_Fragment extends Fragment {
    String urlJsonArry = "https://book.com/json.json";
    Constants constants;
    ListView listView;
    ListAdapter_Book listAdapter_Book;
    public ArrayList<Constants> book_data_list = new ArrayList<Constants>();
    View rootView;

    public Book_Fragment() {}

    @Override public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
    }

    @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        rootView = inflater.inflate(R.layout.book, container, false);
        listView = (ListView)rootView.findViewById(R.id.data);
        listAdapter_Book = new ListAdapter_Book(this);
        listView.setAdapter(listAdapter_Book);
        listView.setDivider(null);
        book_data_list.clear();
        getData();
        return rootView;
    }

    private void getData() {
        String tag_string_req1 = "request";
        StringRequest strReq1 = new StringRequest(Request.Method.GET, urlJsonArry, new Response.Listener<String>() {
            @Override public void onResponse(String response) {
                try {
                    JSONObject jsonObject_main = new JSONObject(response);
                    JSONArray stories = jsonObject_main.getJSONArray("data");
                    for (int i = 0; i < stories.length(); i ++) {
                        constants = new Constants();
                        JSONObject jsonObject = stories.getJSONObject(i);
                        constants.book_id = jsonObject.getString("id");
                        constants.book_name = jsonObject.getString("book_name");
                        book_data_list.add(constants);
                    }
                    book_data_list.notifyDataSetChanged();
                } catch (JSONException e) {
                    e.printStackTrace();
                    Toast.makeText(getContext(), "Error: " + e.getMessage(), Toast.LENGTH_LONG).show();
                }

                pDialog.hide();
            }
        }, new Response.ErrorListener() {
            @Override
            public void onErrorResponse(VolleyError error) {
                pDialog.hide();
            }
        }) {};

        AppController.getInstance().addToRequestQueue(strReq1, tag_string_req1);
    }
}

Mainactivity.java

public class MainActivity extends AppCompatActivity implements FragmentDrawer.FragmentDrawerListener {

    public ViewPager viewPager;
    private Toolbar mToolbar;
    FrameLayout ly;
    private FragmentDrawer drawerFragment;
    private FloatingActionButton floatingbutton;

    @Override protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mToolbar = (Toolbar)findViewById(R.id.toolbar);
        setSupportActionBar(mToolbar);
        ly = (FrameLayout)findViewById(R.id.container_body);
        ly.setVisibility(View.GONE);
        floatingbutton = (FloatingActionButton)findViewById(R.id.fab);
        final TabLayout tabLayout = (TabLayout)findViewById(R.id.tab_layout);
        tabLayout.addTab(tabLayout.newTab().setText("Book"));
        getSupportActionBar().setElevation(0);
        tabLayout.setTabMode(TabLayout.MODE_SCROLLABLE);
        tabLayout.setTabGravity(TabLayout.GRAVITY_FILL);
        viewPager = (ViewPager)findViewById(R.id.pager);
        final PagerAdapter adapter = new PagerAdapter(getSupportFragmentManager(), tabLayout.getTabCount());
        viewPager.setAdapter(adapter);
        viewPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout));
        tabLayout.setOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
            @Override
            public void onTabSelected(TabLayout.Tab tab) {
                viewPager.setCurrentItem(tab.getPosition());
                viewPager.setVisibility(View.VISIBLE);
                ly.setVisibility(View.GONE);
                viewPager.setCurrentItem(tab.getPosition());
                if (tab.getPosition() == 0) {
                    mToolbar.setTitle("Book");
                }
            }

            @Override
            public void onTabUnselected(TabLayout.Tab tab) {}

            @Override
            public void onTabReselected(TabLayout.Tab tab) {}
        });
        floatingbutton.setOnClickListener(new View.OnClickListener() {
            Fragment fragment = null;

            @Override
            public void onClick(View v) {
                int current_tab = viewPager.getCurrentItem();

                switch (current_tab) {
                    case 0:
                        fragment = new Book_Fragment();
                        break;
                    default:
                        break;
                }

                if (fragment != null) {
                    FragmentManager fragmentManager = getSupportFragmentManager();
                    FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
                    fragmentTransaction.replace(R.id.container_body, fragment);
                    fragmentTransaction.commit();
                }
            }
        });

        drawerFragment = (FragmentDrawer)getSupportFragmentManager().findFragmentById(R.id.fragment_navigation_drawer);
        drawerFragment.setUp(R.id.fragment_navigation_drawer, (DrawerLayout)findViewById(R.id.drawer_layout), mToolbar);
        drawerFragment.setDrawerListener(this);
        displayView(0);
    }

    @Override public void onDrawerItemSelected(View view, int position) {
        displayView(position);
        ly.setVisibility(View.GONE);
        viewPager.setVisibility(View.VISIBLE);
    }

    private void displayView(int position) {
        switch (position) {
            case 0:
                viewPager.setCurrentItem(0);
                break;
            default:
                break;
        }
    }
}

ListAdapter_Book.java

public class ListAdapter_Book extends BaseAdapter {

    Book_Fragment main;

    public ListAdapter_Book(Book_Fragment main) {
        this.main = main;
    }

    @Override public int getCount() {
        return main.book_data_list.size();
    }

    @Override public Object getItem(int position) {
        return null;
    }

    @Override public long getItemId(int position) {
        return 0;
    }

    public static class ViewHolderItem {
        public TextView book_name;
    }

    @Override public View getView(final int position, View convertView, ViewGroup parent) {
        ViewHolderItem holder = new ViewHolderItem();

        if (convertView == null) {
            LayoutInflater inflater = (LayoutInflater)main.getActivity().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            convertView = inflater.inflate(R.layout.book_list_cell, null);

            holder.book_name = (TextView)convertView.findViewById(R.id.book_name);
            holder.book_name = this.main.book_data_list.get(position).data_book_name;
        } else {
            holder = (ViewHolderItem)convertView.getTag();
        }
        final ViewHolderItem finalHolder = holder;
        convertView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent opn = new Intent(main.getContext(), Book_Details.class).setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
                opn.putExtra("id", main.book_data_list.get(position).data_id);
                main.getContext().startActivity(opn);
            }
        });

        return convertView;
    }
}

Answer 1

您的适配器应该是这样的：

 public class ListAdapter_Book extends BaseAdapter {

    Book_Fragment main;
    List<Constants> book_data_list=new ArrayList<>();

    public ListAdapter_Book(Book_Fragment main) {

        this.main = main;

    }

    @Override
    public int getCount() {
        return book_data_list.size();
    }

    @Override
    public Object getItem(int position) {
        return book_data_list.get(position);
    }

    @Override
    public long getItemId(int position) {
        return position;
    }

    public static class ViewHolderItem {
        public TextView book_name;
    }

    public void addItems(List<Constant> items){
       book_data_list.addAll(items);
       notifyDataSetChanged();
    }

    @Override
    public View getView(final int position, View convertView, ViewGroup parent) {
        ViewHolderItem holder = new ViewHolderItem();

        if (convertView == null) {
            LayoutInflater inflater = (LayoutInflater) main.getActivity().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            convertView = inflater.inflate(R.layout.book_list_cell, null);

            holder.book_name = (TextView) convertView.findViewById(R.id.book_name);
        holder.book_name = this.main.book_data_list.get(position).data_book_name;
           } else {
            holder = (ViewHolderItem) convertView.getTag();
        }
        final ViewHolderItem finalHolder = holder;
        convertView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                Intent opn = new Intent(main.getContext(), Book_Details.class).setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
                opn.putExtra("id", main.book_data_list.get(position).data_id);
                main.getContext().startActivity(opn);
            }
        });

        return convertView;
    }
}

现在在您进行网络呼叫的片段中：

public class Book_Fragment extends Fragment {
    String urlJsonArry = "https://book.com/json.json";
    Constants constants;
    ListView listView;
    ListAdapter_Book listAdapter_Book;
    public ArrayList<Constants> book_data_list = new ArrayList<Constants>();
    View rootView;

    public Book_Fragment() {

    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        rootView = inflater.inflate(R.layout.book, container, false);
        listView = (ListView) rootView.findViewById(R.id.data);
        listAdapter_Book = new ListAdapter_Book(this);
        listView.setAdapter(listAdapter_Book);
        listView.setDivider(null);

        getData();

        return rootView;
    }

    private void getData() {
        String tag_string_req1 = "request";
        StringRequest strReq1 = new StringRequest(Request.Method.GET,
                                                  urlJsonArry, new Response.Listener<String>() {

            @Override
            public void onResponse(String response) {

                try {
                    JSONObject jsonObject_main = new JSONObject(response);
                    JSONArray stories = jsonObject_main.getJSONArray("data");
                    for (int i = 0; i < stories.length(); i++) {
                        constants = new Constants();
                        JSONObject jsonObject = stories.getJSONObject(i);
                        constants.book_id = jsonObject.getString("id");
                        constants.book_name = jsonObject.getString("book_name");


                  book_data_list.add(constants);
                    }
                    listAdapter_Book.addItems(book_data_list);
                } catch (
                    JSONException e
                ) {
                    e.printStackTrace();
                    Toast.makeText(getContext(),
                                   "Error: " + e.getMessage(),
                                   Toast.LENGTH_LONG).show();
                }

                pDialog.hide();
            }
        }

            , new Response.ErrorListener() {

            @Override
            public void onErrorResponse(VolleyError error) {

                pDialog.hide();
            }
        }

        ) {

        };


        AppController.getInstance().

            addToRequestQueue(strReq1, tag_string_req1);
    }

}

Answer 2

修改您的代码为此

private void getData() {

    String tag_string_req1 = "request";
    StringRequest strReq1 = new StringRequest(Request.Method.GET, urlJsonArry, new Response.Listener<String>() {

        @Override public void onResponse(String response) {

            try {
                JSONObject jsonObject_main = new JSONObject(response);
                JSONArray stories = jsonObject_main.getJSONArray("data");
                for (int i = 0; i < stories.length(); i ++) {
                    constants = new Constants();
                    JSONObject jsonObject = stories.getJSONObject(i);
                    constants.book_id = jsonObject.getString("id");
                    constants.book_name = jsonObject.getString("book_name");

                    book_data_list.add(constants);
                }
                listAdapter_Book = new ListAdapter_Book(this);
                listView.setAdapter(listAdapter_Book);
                listView.setDivider(null);
                listAdapter_Book.notifyDataSetChanged();
            } catch (JSONException e) {
                e.printStackTrace();
                Toast.makeText(getContext(), "Error: " + e.getMessage(), Toast.LENGTH_LONG).show();
            }

            pDialog.hide();
        }
    }, new Response.ErrorListener() {

        @Override
        public void onErrorResponse(VolleyError error) {
            pDialog.hide();
        }
    }) {};

    AppController.getInstance().addToRequestQueue(strReq1, tag_string_req1);
}

并将其从onCreate方法中删除

listAdapter_Book = new ListAdapter_Book(getActivity());
listView.setAdapter(listAdapter_Book);
listView.setDivider(null);