how to clear RecyclerView adapter data

问题

Here in my UI, i have used two buttons to load different data to a RecyclerView. First time the data is displaying properly on click of each button. But if i click the button for the second time the data is adding to the adapter twice. I mean the the adapter is not cleared. it is keep on adding the data on click of button. I Think i have to do something with the adapter on click of a button. Can anyone pls let me know how to clear the adapter or where i am going wrong..

Here is the code.

public class GstVendorLocRetrieve extends AppCompatActivity {

    private String vault;

    private TextView txt;
    public static final String DATA_URL = "http://oursite.com/getgstvendorlocation.php?vault_no=";
    public static final String DATA_URL1 = "http://oursite.com/getgstcustomerlocation.php?vault_no=";

    //Tags for my JSONRes
    public static final String TAG_VendorID = "VendorID";
    public static final String TAG_CustomerID = "Customer_ID";
    public static final String TAG_ADDRESS = "Address";

    private Button vendor;
    private Button customer;

    //Creating a List of superheroes
    private List<GstVendLoc> listSuperHeroes;
    private List<GstCustLoc> listSuperHeroes1;

    //Creating Views
    private RecyclerView recyclerView;
    private RecyclerView.LayoutManager layoutManager;
    private RecyclerView.Adapter adapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.locationretrieve);

        SharedPreferences sharedPreferences = getSharedPreferences(GstLogin.SHARED_PREF_NAME, MODE_PRIVATE);
        vault = sharedPreferences.getString(GstLogin.EMAIL_SHARED_PREF,"Not Available");

        vendor = (Button) findViewById(R.id.login);
        customer = (Button) findViewById(R.id.login1);

        recyclerView = (RecyclerView) findViewById(R.id.recyclerView);
        recyclerView.setHasFixedSize(true);
        layoutManager = new LinearLayoutManager(this);
        recyclerView.setLayoutManager(layoutManager);

        //Initializing our superheroes list
        listSuperHeroes = new ArrayList<>();
        listSuperHeroes1 = new ArrayList<>();

        vendor.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                recyclerView.setAdapter(null);
                getData();
            }
        });

        customer.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                recyclerView.setAdapter(null);
                getData1();
            }
        });

    }

    //This method will get data from the web api
    private void getData(){
        //Showing a progress dialog
        final ProgressDialog loading = ProgressDialog.show(this,"Loading Data", "Please wait...",false,false);

        //Creating a json array request
        JsonArrayRequest jsonArrayRequest = new JsonArrayRequest(DATA_URL+vault,
                new Response.Listener<JSONArray>() {
                    @Override
                    public void onResponse(JSONArray response) {
                        //Dismissing progress dialog
                        loading.dismiss();

                        //calling method to parse json array
                        parseData(response);
                    }
                },
                new Response.ErrorListener() {
                    @Override
                    public void onErrorResponse(VolleyError error) {

                    }
                });

        //Creating request queue
        RequestQueue requestQueue = Volley.newRequestQueue(this);

        //Adding request to the queue
        requestQueue.add(jsonArrayRequest);
    }

    //This method will parse json data
    private void parseData(JSONArray array){
        for(int i = 0; i<array.length(); i++) {
            GstVendLoc gst1 = new GstVendLoc();
            JSONObject json = null;
            try {

                json = array.getJSONObject(i);
                gst1.setVendorID(json.getString(TAG_VendorID));
                gst1.setAddress(json.getString(TAG_ADDRESS));


            } catch (JSONException e) {
                e.printStackTrace();
            }
            listSuperHeroes.add(gst1);
        }

        //Finally initializing our adapter
        adapter = new CardAdapter17(listSuperHeroes, this);

        //Adding adapter to recyclerview
        recyclerView.setAdapter(adapter);

    }

    private void getData1(){
        //Showing a progress dialog
        final ProgressDialog loading = ProgressDialog.show(this,"Loading Data", "Please wait...",false,false);

        //Creating a json array request
        JsonArrayRequest jsonArrayRequest = new JsonArrayRequest(DATA_URL1+vault,
                new Response.Listener<JSONArray>() {
                    @Override
                    public void onResponse(JSONArray response) {
                        //Dismissing progress dialog
                        loading.dismiss();

                        //calling method to parse json array
                        parseData1(response);
                    }
                },
                new Response.ErrorListener() {
                    @Override
                    public void onErrorResponse(VolleyError error) {

                    }
                });

        //Creating request queue
        RequestQueue requestQueue = Volley.newRequestQueue(this);

        //Adding request to the queue
        requestQueue.add(jsonArrayRequest);
    }

    //This method will parse json data
    private void parseData1(JSONArray array){
        for(int i = 0; i<array.length(); i++) {
            GstCustLoc gst1 = new GstCustLoc();
            JSONObject json = null;
            try {

                json = array.getJSONObject(i);
                gst1.setCustomer_ID(json.getString(TAG_CustomerID));
                gst1.setAddress(json.getString(TAG_ADDRESS));


            } catch (JSONException e) {
                e.printStackTrace();
            }
            listSuperHeroes1.add(gst1);
        }

        //Finally initializing our adapter
        adapter = new CardAdapter18(listSuperHeroes1, this);

        //Adding adapter to recyclerview
        recyclerView.setAdapter(adapter);
    }

}

回答1:

You need to clear your Array List before you get data second time.

Do this inside parseData1 method before for loop.

listSuperHeroes.clear();

listSuperHeroes1.clear();

回答2:

Use this code for clear RecycleView items

public void clear() {
    int size = listSuperHeroes.size();
    listSuperHeroes.clear();
    notifyItemRangeRemoved(0, size);
}

回答3:

you dont need to set adapter after geting data from the online

//Finally initializing our adapter
    adapter = new CardAdapter18(listSuperHeroes1, this);

    //Adding adapter to recyclerview
    recyclerView.setAdapter(adapter);

you can initialize of set the adapter in the on create and add data in the 'listSuperHeroes1' and after parse data you can do adapter.notifyDataSetChanged(); this will change the list data.

and the solution for the getting the previous data you have to remove the all data from the listsuperHeroes1 this will help you if you getting any problem please comment .

回答4:

What you have to do is Update RecyclerView on button Click , Put below method in your adapter

public void updateData(ArrayList<ViewModel> viewModels) {
   items.clear();
   items.addAll(viewModels);
   notifyDataSetChanged();
}

Than call this method with new data

ArrayList<ViewModel> viewModelsWithNewData = new ArrayList<ViewModel>();
adapter.updateData(viewModelsWithNewData );

来源：https://stackoverflow.com/questions/41843758/how-to-clear-recyclerview-adapter-data