Question

无法将列表添加到自定义列表视图。我在使用String []时遇到问题，我正试图从Firebase数据库中获取用户并将其存储到我的 private ArrayList<UserInfo> userInfos; userInfos=new ArrayList<>(); 但是当运行它进行仿真时，我的列表视图显示为空白，我试图检查List<String> friends = new ArrayList<>();并且我的用户可用。有人可以帮助我吗？

我的MainActivityCustonlistViewnew.java

import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ListView;
import android.widget.Toast;

import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.ValueEventListener;

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

import androidx.appcompat.app.AppCompatActivity;
import androidx.appcompat.widget.SearchView;
import androidx.appcompat.widget.Toolbar;



public class MainActivityCustonlistViewnew extends AppCompatActivity {



    private ArrayList<UserInfo> userInfos;
    private CustomListAdapter customListAdapter;
    private ListView customListView;



    private FirebaseDatabase firebaseDatabase = FirebaseDatabase.getInstance();
    private DatabaseReference databaseReference = firebaseDatabase.getReference();

    private  DatabaseReference UserData = databaseReference.child("Users");


    private List<String> friends = new ArrayList<>();

    private String[] names ;


    private String[] professions={
            "Rank 1",
            "Rank 2",
            "Rank 3"

    };
    private int[] photos={
            R.drawable.sample_5,
            R.drawable.sample_1,
            R.drawable.sample_6

    };



    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_maincustomlistview);
        setSupportActionBar((Toolbar)findViewById(R.id.toolbar));


       // ArrayList arrayList = new ArrayList(friends);

        ValueEventListener eventListener = new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {

                for(DataSnapshot ds : dataSnapshot.getChildren()) {
                    String friend = ds.getKey();

                    friends.add(friend);



                }

        }

            @Override
            public void onCancelled(DatabaseError databaseError) {}
        };
        UserData.addListenerForSingleValueEvent(eventListener);




        customListView=(ListView)findViewById(R.id.custom_list_view);
        userInfos=new ArrayList<>();
        Arrays.sort(names, String.CASE_INSENSITIVE_ORDER);
        customListAdapter=new CustomListAdapter(userInfos,MainActivityCustonlistViewnew.this);
        customListView.setAdapter(customListAdapter);
        getDatas();
        customListView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
                Toast.makeText(MainActivityCustonlistViewnew.this, "Name : " + names[i] + "\n Profession : " + professions[i], Toast.LENGTH_SHORT).show();
            }
        });



//sample-----












    }

    // getting all the datas
    private void getDatas(){




        for(int count=0;count<names.length;count++){

            userInfos.add(new UserInfo(names[count],professions[count],photos[count]));

        }
    }



    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.search_option,menu);
        MenuItem menuItem=menu.findItem(R.id.search);
        SearchView searchView=(SearchView)menuItem.getActionView();
        searchView.setOnQueryTextListener(new SearchView.OnQueryTextListener() {
            @Override
            public boolean onQueryTextSubmit(String query) {
                return true;
            }

            @Override
            public boolean onQueryTextChange(String newText) {
                newText=newText.toString();
                ArrayList<UserInfo> newUserInfos=new ArrayList<>();

                for(UserInfo userInfo:userInfos){
                    String name=userInfo.getName().toLowerCase();
                    String profession=userInfo.getProfession().toLowerCase();
                    if(name.contains(newText) || profession.contains(newText)){
                        newUserInfos.add(userInfo);
                    }
                }
                customListAdapter.filterResult(newUserInfos);
                customListAdapter.notifyDataSetChanged();
                return false;
            }
        });
        return super.onCreateOptionsMenu(menu);
    }
}

我的Userinfo.java

public class UserInfo {
    private String name,profession;
    private int photo;

    public UserInfo(){}

    public UserInfo(String name, String profession, int photo) {
        this.name = name;
        this.profession = profession;
        this.photo = photo;
    }

    public String getName() {
        return name;
    }

    public String getProfession() {
        return profession;
    }

    public int getPhoto() {
        return photo;
    }
}

我的customlistAdapter

import android.view.LayoutInflater;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.PopupMenu;
import android.widget.TextView;
import android.widget.Toast;

import java.util.ArrayList;

public class CustomListAdapter extends BaseAdapter implements View.OnClickListener{
    private ArrayList<UserInfo> userInfos;
    private Context context;

    public CustomListAdapter(ArrayList<UserInfo> userInfos, Context context) {
        this.userInfos = userInfos;
        this.context = context;
    }

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

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

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

    @Override
    public View getView(int i, View view, ViewGroup viewGroup) {
        LayoutInflater layoutInflater=(LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        view=layoutInflater.inflate(R.layout.custom_list_view_layout,null);
        ImageView photo,option;
        if(view==null){
            photo=new ImageView(context);
        }
        UserInfo userInfo=userInfos.get(i);
        photo=(ImageView)view.findViewById(R.id.photo);
        option=(ImageView)view.findViewById(R.id.option);
        TextView name=(TextView)view.findViewById(R.id.name);
        TextView profession=(TextView)view.findViewById(R.id.profession);
        photo.setImageResource(userInfo.getPhoto());
        name.setText(userInfo.getName());
        profession.setText(userInfo.getProfession());
        option.setOnClickListener(this);
        return view;
    }

    @Override
    public void onClick(View view) {
        switch (view.getId()){
           case R.id.option:
               showPopupMenu(view);
                break;
        }
    }

    // getting the popup menu
    private void showPopupMenu(View view){
        PopupMenu popupMenu=new PopupMenu(context,view);
        popupMenu.getMenuInflater().inflate(R.menu.option_menu,popupMenu.getMenu());
        popupMenu.show();
        popupMenu.setOnMenuItemClickListener(new PopupMenu.OnMenuItemClickListener() {
            @Override
            public boolean onMenuItemClick(MenuItem menuItem) {
                switch (menuItem.getItemId()){
                    case R.id.edit:
                        Toast.makeText(context, "Edit !", Toast.LENGTH_SHORT).show();
                        return true;
                    case R.id.remove:
                        Toast.makeText(context, "Remove !", Toast.LENGTH_SHORT).show();
                        return true;
                    default:
                        return false;
                }
            }
        });
    }

    //file search result
    public void filterResult(ArrayList<UserInfo> newUserInfos){
        userInfos=new ArrayList<>();
        userInfos.addAll(newUserInfos);
        notifyDataSetChanged();
    }
}

Answer 1

  customListAdapter=new CustomListAdapter(userInfos,MainActivityCustonlistViewnew.this);
        customListView.setAdapter(customListAdapter);
        getDatas();

您在这里做错了。您正在调用customListAdapter并将此处的cusrom data（userInfos）设置为空。因为getDatas（）方法在customListAdapter之后调用。因此，列表将为空。只需交换正电子即可。

getDatas();
customListAdapter=new CustomListAdapter(userInfos,MainActivityCustonlistViewnew.this);
customListView.setAdapter(customListAdapter);

希望有帮助。

谢谢索拉卜祝您编码愉快！

Answer 2

您正在从getDatas()添加数据，但是您的适配器已经被初始化为空数据。因此，有两种方法：

1：在getDatas()调用后初始化并设置适配器

    getDatas();
    customListAdapter=new CustomListAdapter(userInfos,MainActivityCustonlistViewnew.this);
    customListView.setAdapter(customListAdapter);

2：使用notifyDataSetChanged()方法向适配器通知数据集更改

    customListView.setAdapter(customListAdapter);
    getDatas();
    customListAdapter.notifyDataSetChanged();

添加List <String> friends = new ArrayList <>（）;到customlistview

2 个答案: