Question

我试图从URL检索数据并将其存储在本地数据库中，然后将该数据附加到listview。我想尝试新的，所以请不要介意代码有大错误或错误的程序...建议我怎么做。

我的数据库类是

public class DatabaseHandler extends SQLiteOpenHelper {
private static final int DATABASE_VERSION = 1;

// Database Name
private static final String DATABASE_NAME = "placesmanager";

// Contacts table name
private static final String TABLE_PLACES = "places";
public DatabaseHandler(Context context) {
    super(context, DATABASE_NAME, null, DATABASE_VERSION);
}

@Override
public void onCreate(SQLiteDatabase db) {
    db.execSQL("create table if not exists TABLE_PLACES(name varchar(50),rating varchar(50),icon varchar(50))");

}

@Override
public void onUpgrade(SQLiteDatabase db, int i, int i1) {
    db.execSQL("DROP TABLE IF EXISTS " + TABLE_PLACES);

    // Create tables again
    onCreate(db);

}
//adding contact
public void addContact(PlacesData data) {
    SQLiteDatabase db = this.getWritableDatabase();

    ContentValues values = new ContentValues();
    values.put("name", data.getName());
    values.put("rating", data.getRating());
    values.put("icon", data.getIcon());

    // Inserting Row
    db.insert(TABLE_PLACES, null, values);
    db.close(); // Closing database connection
}

// Getting All Contacts
public ArrayList<PlacesData> getAllContacts() {
    ArrayList<PlacesData> contactList = new ArrayList<>();
    // Select All Query
    String selectQuery = "SELECT  * FROM " + TABLE_PLACES;

    SQLiteDatabase db = this.getWritableDatabase();
    Cursor cursor = db.rawQuery(selectQuery, null);

    // looping through all rows and adding to list
    if (cursor.moveToFirst()) {
        do {
            PlacesData contact = new PlacesData();
            contact.setName(cursor.getString(0));
            contact.setRating(cursor.getString(1));
            contact.setIcon(cursor.getString(2));
            // Adding contact to list
            contactList.add(contact);
        } while (cursor.moveToNext());
    }

    // return contact list
    return contactList;
}

以及我想附加到数据库并尝试检索它的recyclelerview方法

 public void onBindViewHolder(MyRecycler holder, final int position) {

    DatabaseHandler handler = new DatabaseHandler(activity);
    handler.addContact(new PlacesData(data.get(position).getName(),data.get(position).getRating(),data.get(position).getIcon()));
  //  Log.i("Database",handler+"");

    ArrayList<PlacesData> contacts = handler.getAllContacts();

    for (PlacesData cn : contacts) {
        String log = "Name: "+cn.getName()+" ,Rating: " + cn.getRating() + " ,Icon: " + cn.getIcon();
        Log.i("Name: ", log);
        holder.tvName.setText(cn.getName());
        holder.tvRating.setText(cn.getRating());
        Picasso.with(activity).load(cn.getIcon()).into(holder.imgIcon);
    }
        }
    });

将数据库数据附加到recyclerview已完成，但字段在视图中重复的方式不正确。在Android监视器中显示以下错误。

我这样做是通过跟踪一些谷歌示例建议我可能的更改。

最后输出是

Answer 1

使你的适配器类像这样

public class PlacesDataAdapter extends RecyclerView.Adapter<PlacesDataAdapter.Viewholder>
{

    ArrayList<PlacesData> PlacesDatalist;
    Context context;
    LayoutInflater inflater;

    public PlacesDataAdapter(Context context,ArrayList<PlacesData> PlacesDatalist){
        this.context=context;
        this.surveylist=PlacesDatalist;
        inflater= LayoutInflater.from(context);

    }
    @Override
    public Viewholder onCreateViewHolder(ViewGroup parent, int viewType) {

        final View view=inflater.inflate(R.layout.single_row,parent,false);
        return new Viewholder(view);
    }

    @Override
    public void onBindViewHolder(Viewholder holder, int position)
    {
            final PlacesData placedata=surveylist.get(position);

            holder.tvName.setText(placedata.getName());
            holder.tvRating.setText(placedata.getRating());

    }

    @Override
    public int getItemCount() {
        return PlacesDatalist.size();
    }


}

从您的活动中的本地数据库中获取数据（每次清除arraylist以使值不会在列表中重复表示执行＆＃34; contacts.clear＆＃34;）

ArrayList<PlacesData> contacts = handler.getAllContacts();

之后只需创建适配器类的对象并在其中传递arraylist并执行notifydatasetchange。

PlacesDataAdapter adapter=new SurveyAdapter(this,contacts);
adapter.notifyDataSetChanged();

Answer 2

在数据库的onCreate中声明一个ID。我认为这就是问题所在。每个表必须包含一个ID（主键），每个行都是唯一的。

尝试从URL检索数据并存储在本地数据库中，然后附加到列表视图

2 个答案: