Question

如何在另一个类中以及在此页中调用该类之后移动诸如getData（）之类的方法？
我尝试做某事，但是没用。
您能帮忙创建一个新班吗？



package it.example.app.fragment_2;

import android.content.Context;
import android.net.Uri;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ProgressBar;
import android.widget.Toast;

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

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

import java.util.ArrayList;
import java.util.List;


public class Tab1 extends Fragment  implements RecyclerView.OnScrollChangeListener {

  View v;
    private Tab1.OnFragmentInteractionListener mListener;

    private List<SuperHero> listSuperHeroes;

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

    //Volley Request Queue
    private RequestQueue requestQueue;

    //The request counter to send ?page=1, ?page=2  requests
    private int requestCount = 1;

    public Tab1() {
        // Required empty public constructor
    }



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

}

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        v = inflater.inflate(R.layout.fragment_tab1, container, false);
        recyclerView = (RecyclerView) v.findViewById(R.id.recyclerView);
        recyclerView.setHasFixedSize(true);


        listSuperHeroes = new ArrayList<>();
        requestQueue = Volley.newRequestQueue(getContext());

        getData();
        adapter = new CardAdapter(listSuperHeroes, getContext());
        layoutManager = new LinearLayoutManager(getActivity());
        recyclerView.setLayoutManager(layoutManager);
        recyclerView.setOnScrollChangeListener(this);
        recyclerView.setAdapter(adapter);
        return v;
    }

    //This integer will used to specify the page number for the request ?page = requestcount
    //This method would return a JsonArrayRequest that will be added to the request queue
    private JsonArrayRequest getDataFromServer(int requestCount) {
        //Initializing ProgressBar
        //final ProgressBar progressBar = (ProgressBar) findViewById(R.id.progressBar1);

        //Displaying Progressbar
        //progressBar.setVisibility(View.VISIBLE);
        //setProgressBarIndeterminateVisibility(true);

        //JsonArrayRequest of volley
        JsonArrayRequest jsonArrayRequest = new JsonArrayRequest(Config.DATA_URL + String.valueOf(requestCount),
                new Response.Listener<JSONArray>() {
                    @Override
                    public void onResponse(JSONArray response) {
                        //Calling method parseData to parse the json response
                        parseData(response);
                        //Hiding the progressbar
                        //progressBar.setVisibility(View.GONE);
                    }
                },
                new Response.ErrorListener() {
                    @Override
                    public void onErrorResponse(VolleyError error) {
                       // progressBar.setVisibility(View.GONE);
                        //If an error occurs that means end of the list has reached
                       // Toast.makeText(Hero_main_activity.this, "No More Items Available", Toast.LENGTH_SHORT).show();
                    }
                });

        //Returning the request
        return jsonArrayRequest;
    }

    //This method will get data from the web api
    private void getData() {
        //Adding the method to the queue by calling the method getDataFromServer
        requestQueue.add(getDataFromServer(requestCount));
        //Incrementing the request counter
        requestCount++;
    }

    //This method will parse json data
    private void parseData(JSONArray array) {
        for (int i = 0; i < array.length(); i++) {
            //Creating the superhero object
            SuperHero superHero = new SuperHero();
            JSONObject json = null;
            try {
                //Getting json
                json = array.getJSONObject(i);

                //Adding data to the superhero object
                superHero.setImageUrl(json.getString(Config.TAG_IMAGE_URL));
                superHero.setName(json.getString(Config.TAG_NAME));
                superHero.setPublisher(json.getString(Config.TAG_PUBLISHER));
            } catch (JSONException e) {
                e.printStackTrace();
            }
            //Adding the superhero object to the list
            listSuperHeroes.add(superHero);
        }

        //Notifying the adapter that data has been added or changed
        adapter.notifyDataSetChanged();
    }

    //This method would check that the recyclerview scroll has reached the bottom or not
    private boolean isLastItemDisplaying(RecyclerView recyclerView) {
        if (recyclerView.getAdapter().getItemCount() != 0) {
            int lastVisibleItemPosition = ((LinearLayoutManager) recyclerView.getLayoutManager()).findLastCompletelyVisibleItemPosition();
            if (lastVisibleItemPosition != RecyclerView.NO_POSITION && lastVisibleItemPosition == recyclerView.getAdapter().getItemCount() - 1)
                return true;
        }
        return false;
    }

    //Overriden method to detect scrolling
    @Override
    public void onScrollChange(View v, int scrollX, int scrollY, int oldScrollX, int oldScrollY) {
        //Ifscrolled at last then
        if (isLastItemDisplaying(recyclerView)) {
            //Calling the method getdata again
            getData();
        }
    }
    public interface OnFragmentInteractionListener {
        // TODO: Update argument type and name
        void onFragmentInteraction(Uri uri);
    }
}

Answer 1

如果我对您的理解正确，那么您想在其他类/活动/片段中调用getData（）函数。

这不是最好的方法，但是，您可以创建另一个具有静态变量的类（公共静态Tab1 tab1;），并在Tab1.onCreateView（...）中设置此变量（OtherClass.tab1 = this; ）。（此外，您还必须公开getData函数。）

但是有一个问题，如果一个类/活动/片段试图在Tab1之前到达getData函数，它将给出NullPointEx ...

我不知道您真正想要什么，但是，我认为您必须更改架构。

Answer 2

这可能不是最好的出路，但您可以肯定......

只需创建TAB1片段类实例即可，该实例应有帮助   如果还没开始之前就实例化该课程

private static Tab1 single_instance = null;
        public static Tab1 getInstance(){
            if (single_instance == null)
                single_instance = new Tab1();
            return single_instance;
        }

我将假设这是需要调用getData（）的其他任何类通过仅使用TAB1实例变量就可以完成TAB1，就像我们仅在下面删除。

public class ClassCaller{
    Tab1 tab1 = Tab1.getInstance();

这可以是调用程序类中的任何方法，可以是onCreate（）或其他任何人。

@Override
    protected void onResume() {
        super.onResume();
       if(something_is_true)
         tab1.getData();
    }

}

请记住，我没有测试此代码，只是希望您尝试一下。

使用Java在另一个类中移动方法getData（）？

2 个答案: