Question

我正处于制作应用程序的中间位置，通过排球请求获取一些数据，并在ListFragment上的ListView中设置数据。

我的问题是，当我使用我的后退按钮转换回上一个活动并退出应用程序时（onStop），当我从appdrawer重新打开应用程序并转到ListFragment时，它显示的列表是复制。

参考下面的图片：

代码：

ListFragment类：

package lassebjoerklund.easyfridge;

import android.app.Activity;
import android.app.Fragment;
import android.app.ListFragment;
import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.Toast;

/**
 * Created by lassebjorklund on 17/02/16.
 */
public class ProductsList extends ListFragment {
    ProductListListnerInteface productListListnerInteface;


    public interface ProductListListnerInteface {
        public void onProductSelected(int pos);
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        Log.d(getActivity().getClass().getSimpleName(), "onCreate");
        super.onCreate(savedInstanceState);
        if(savedInstanceState == null) {
            setListAdapter(new ProductAdapter(getActivity(), BootActivity.getProductsToDisplayInlist()));
        }else{

        }
    }

    @Override
    public void onAttach(Context context) {
        Log.d(getActivity().getClass().getSimpleName(), "onAttach");
        super.onAttach(context);
        try {
            productListListnerInteface = (ProductListListnerInteface) context;
        } catch (ClassCastException e) {
            throw new ClassCastException(context.toString() + "must implement ProductListListnerInteface");
        }
    }

    @Override
    public void onStart() {
        Log.d(getActivity().getClass().getSimpleName(), "onStart");
        super.onStart();
        if (getFragmentManager().findFragmentById(R.id.fragment_container_list) != null) {
            getListView().setChoiceMode(ListView.CHOICE_MODE_SINGLE);
        }


    }

    @Override
    public void onListItemClick(ListView l, View v, int position, long id) {
        productListListnerInteface.onProductSelected(position);
    }




}

Activity将ListFragment与DetailFragment绑定（不是问题的一部分）

package lassebjoerklund.easyfridge;

import android.app.Activity;
import android.app.FragmentTransaction;
import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
import android.view.KeyEvent;

/**
 * Created by lassebjorklund on 17/02/16.
 */
public class ProductViewController extends FragmentActivity implements ProductsList.ProductListListnerInteface {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.products_list_layout);
            if (findViewById(R.id.fragment_container_list) != null) {
                if (savedInstanceState != null) {
                    return;
                }
                ProductsList productsList = new ProductsList();
                productsList.setArguments(getIntent().getExtras());
                getFragmentManager().beginTransaction().add(R.id.fragment_container_list, productsList).commit();

            }

    }

    @Override
    public void onProductSelected(int pos) {
            ProductDetail productDetail = (ProductDetail) getFragmentManager().findFragmentById(R.id.details_fragment_container);

        if (productDetail != null) {

            productDetail.updateProductOnPos(pos);

        } else {
            ProductDetail newProductDetail = new ProductDetail();
            Bundle args = new Bundle();
            args.putInt("Position", pos);
            newProductDetail.setArguments(args);
            FragmentTransaction fragmentTransaction = getFragmentManager().beginTransaction();
            fragmentTransaction.replace(R.id.fragment_container_list, newProductDetail);
            fragmentTransaction.addToBackStack("ProductList");
            fragmentTransaction.commit();
        }
    }

}

启动器活动

package lassebjoerklund.easyfridge;

import android.app.Activity;
import android.app.Fragment;
import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.ImageButton;
import android.widget.Toast;

import com.android.volley.Request;
import com.android.volley.RequestQueue;
import com.android.volley.Response;
import com.android.volley.VolleyError;
import com.android.volley.VolleyLog;
import com.android.volley.toolbox.JsonArrayRequest;
import com.android.volley.toolbox.Volley;

import org.json.JSONArray;
import org.json.JSONObject;

import java.util.ArrayList;

public class BootActivity extends Activity {
    private static ArrayList<Products> productsToDisplayInlist = new ArrayList<>();
    private String TAG = BootActivity.class.getSimpleName();
    private String url = "XXXXXXXXXXXXXXXXXXXX";
    private String jsonRespons = "";
    private RequestQueue rQueue;


    @Override
    protected void onCreate(Bundle savedInstanceState) {

        //Layout
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_boot_layout);

        //Custom Adapter for list view, for ref.
        //final ProductAdapter adapter = new ProductAdapter(this, productsToDisplayInlist);

        //RequestQueue
        rQueue = Volley.newRequestQueue(this);

        //Methode to populate Arralist


        //Intent to switch to activity
        final Intent dispalyProductsIntent = new Intent(BootActivity.this, ProductViewController.class);

        getRequest();

        final ImageButton updateViewButton = (ImageButton) findViewById(R.id.bViewProducts);
        updateViewButton.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                startActivity(dispalyProductsIntent);
            }

        });

    }

    public void getRequest() {
        JsonArrayRequest jsonArrayRequest = new JsonArrayRequest(Request.Method.GET, url, null, new Response.Listener<JSONArray>() {
            @Override
            public void onResponse(JSONArray response) {
                Log.d(TAG, response.toString());
                try {
                    for (int i = 0; i < response.length(); i++) {
                        JSONObject productToBuild = (JSONObject) response.get(i);
                        String name = productToBuild.getString("name");
                        String type = productToBuild.getString("type");
                        int id = productToBuild.optInt("id");
                        String removalDate = productToBuild.getString("removal_date");
                        String placementDate = productToBuild.getString("placement_date");
                        Products product = new Products(name, placementDate, removalDate, type);
                        productsToDisplayInlist.add(product);
                    }

                } catch (Exception e) {
                    e.printStackTrace();
                }

            }
        }, new Response.ErrorListener() {
            @Override
            public void onErrorResponse(VolleyError error) {
                VolleyLog.d("Volly", "Error");
                error.printStackTrace();
            }
        });

        rQueue.add(jsonArrayRequest);
    }

    public void postRequest() {

    }

    public static ArrayList<Products> getProductsToDisplayInlist() {
        return productsToDisplayInlist;
    }

    @Override
    protected void onResume() {
        Log.d("onResume", "onResume");
        /*Toast toast = Toast.makeText(this, "onResume", Toast.LENGTH_LONG);
        toast.show();*/
        super.onResume();

    }

    @Override
    protected void onRestart() {
        Log.d("onRestart", "onRestart");
        /*Toast toast = Toast.makeText(this, "onRestart", Toast.LENGTH_SHORT);
        toast.show();*/
        super.onRestart();
    }

    @Override
    protected void onStop() {
        Log.d("onStop", "onStop");
       // productsToDisplayInlist.clear();
        super.onStop();
    }

    @Override
    protected void onPause() {
        Log.d("onPause", "onPause");
        super.onPause();
    }
}

我似乎无法找到问题..任何人都可以帮忙吗？

Answer 1

productsToDisplayInlist是静态的，每次返回BootActivity时都不会重新创建，直到重新创建应用程序本身。

当您收到回复时，您只会添加到收藏中，因此每次收到回复时您都会添加重复项。

有许多方法可以解决这个问题，最简单的方法就是将productsToDisplayInlist.clear()添加到onResponse()的开头，因为无论如何都要完全重新填充列表。

Answer 2

我认为问题在于，在BootActivity中，您不会在向HTTP响应中添加产品之前清除productsToDisplayInList（productsToDisplay.clear();）。 productsToDisplayInList是静态的，这意味着它在整个应用程序的生命周期中保持其状态。我对此并不是百分之百确定，但是当你将底部活动留在堆栈中时（退出应用程序），它仍然可以包含数据，因为应用程序仍然在后台运行。

Android ListFragment项目重复

2 个答案: