尝试将数据从Intent迁移到ListView，但出现了一些错误

Posted 2023-04-19

【中文标题】尝试将数据从Intent迁移到ListView，但出现了一些错误

【英文标题】：Try to migrate data from Intent to ListView, but there are some error

【发布时间】：2018-10-21 22:44:50

【问题描述】：

我已经在这个问题上得到了帮助，但是现在，当我运行应用程序时，这个错误就来了。 2小时后一切都很好，但我没有改变任何东西，那是什么？我尝试从 Firestore 中获取数据，并将其传送到 ListView，然后传送到下一个活动。

错误：

进程：com.example.eugene.lafinalproduction，PID：9741 java.lang.IllegalArgumentException: n

这一行有错误：

randomPlaceList.add(placesList.get(randomGenerator.nextInt(placeCount)));

主要活动：

public class ListViewPlaces extends AppCompatActivity 

FirebaseFirestore rootRef = FirebaseFirestore.getInstance();
CollectionReference placesRef = rootRef.collection("Places");

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

    placesRef.get().addOnCompleteListener(new OnCompleteListener<QuerySnapshot>() 
        @Override
        public void onComplete(@NonNull Task<QuerySnapshot> task) 
            if (task.isSuccessful()) 
                List<Places> placesList = new ArrayList<>();
                for (DocumentSnapshot document : task.getResult()) 
                    Places places = document.toObject(Places.class);

                    placesList.add(places);
                
                if (placesList.size() > 0) 
                    int placeCount = placesList.size();
                    System.out.println(placesList.size());
                    Random randomGenerator = new Random();
                    List<Places> randomPlaceList = new ArrayList<>();
                    for (int i = 0; i <= 3; i++) 
                        String randomIndex = randomGenerator.nextInt(randomPlaceList.size());
                        randomPlaceList.add(randomIndex);
                        ListView mListView = (ListView) findViewById(R.id.place_list);
                        PlacesAdapter placesAdapter = new PlacesAdapter(getApplicationContext(), randomPlaceList);
                        mListView.setAdapter(placesAdapter);
                    
                
        
    
);

模型类：

    public class Places 
    private String name;

    public Places() 

    

    public Places(String name) 

        this.name = name;


    


    public String getName()  return name; 

我的适配器：

    class PlaceAdapter extends ArrayAdapter<Places> 

private ArrayList<Places> dataSet;
Context mContext;

private static class ViewHolder 
    TextView name_text;
    ImageView image_text;


public PlaceAdapter(ArrayList<Places> dataSet, Context context ) 
    super(context, R.layout.item_list, dataSet);

    this.dataSet = dataSet;
    this.mContext = context;



@Override
public View getView(int position, View converView, ViewGroup parent) 

    Places places = getItem(position);
    ViewHolder viewHolder;

    final View result;

    if (converView == null) 
        viewHolder = new ViewHolder();
        LayoutInflater inflater = LayoutInflater.from(getContext());
        converView = inflater.inflate(R.layout.item_list, parent, false);
        viewHolder.name_text = (TextView) converView.findViewById(R.id.text_image_id);
        viewHolder.image_text = (ImageView) converView.findViewById(R.id.image_id);

        result = converView;

        converView.setTag(viewHolder);
     else 
        viewHolder = (ViewHolder) converView.getTag();
        result = converView;
    

    viewHolder.name_text.setText(places.getName());
    Glide.with(getContext()).load(places.getImage()).into(viewHolder.image_text);

    return converView;

第二个活动：

public class Card_activity extends AppCompatActivity implements View.OnClickListener

    TextView mTextView;

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

        mTextView = findViewById(R.id.head_name);
        String name = getIntent().getStringExtras("name")
        mTextView.setText(name);
    

【问题讨论】：

更新错误行

我在 Main Activity@Eminem 中更新了答案

是的，现在在我的项目@Eminem 中是错误的

【参考方案1】：

int placeCount = placesList.size();

nextInt(int) 产生一个从 0 到 n 的数字。例如，nextInt(3) 可能会产生 0、1 或 2。因此，值 placecount

bound - 上限（不包括）。必须是正面的。 编辑：

for (int i = 1; i <= 3; i++) 
    if (placeCount >0) 
        randomPlaceList.add(placesList.get(randomGenerator.nextInt(placeCount)));          
    

另一种方法是：

    for (int i = 0; i < 3; i++)  
       int randomIndex = randomGenerator.nextInt(randomPlaceList.size()); 
       Places item = randomPlaceList.get(randomIndex); 
       randomPlaceList.add(item);