데이터베이스에서 데이터를 가져올 수 없습니다.

Question

데이터베이스에 데이터를 저장,로드 및 삭제하는 데 3 가지 버튼이 있습니다.

TotalResults.java

package com.example.simplegame; 

android.os.Bundle; 
import android.app.Activity; 
import android.content.Intent; 
import android.util.Log; 
import android.view.Menu; 
import android.view.View; 
import android.view.View.OnClickListener; 
import android.widget.Button; 
import android.widget.TextView; 

public class TotalResults extends Activity { 

DatabaseManager db = new DatabaseManager(this); 
String name; 
int score; 
TextView result; 
TextView saved; 
@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_total_results); 

    result = (TextView) findViewById (R.id.textResult); 
    saved = (TextView) findViewById (R.id.textLoad); 
    Button save = (Button) findViewById (R.id.buttonSave); 
    Button load = (Button) findViewById (R.id.buttonLoad); 

     Intent intent = getIntent(); 
     name = intent.getExtras().getString("name"); 
     score = intent.getExtras().getInt("score"); 

     result.setText("Name: "+name+" , Score: "+score); 

     save.setOnClickListener(new OnClickListener(){ 

      public void onClick(View v) { 

       db.addContact(new PlayerData(name,score)); 
       Log.d("Insert: ", "Inserting .."); 

      } 
     }); 



      load.setOnClickListener(new OnClickListener(){ 

       public void onClick(View v) { 

        String showName = db.getContact(0).getName(); 
        int showScore = db.getContact(0).getscore(); 
        saved.setText("Player Name: "+showName+" Player Score: "+showScore); 

       } 
      }); 





} 

@Override 
public boolean onCreateOptionsMenu(Menu menu) { 
    // Inflate the menu; this adds items to the action bar if it is present. 
    getMenuInflater().inflate(R.menu.total_results, menu); 
    return true; 
} 

} 

및 DatabaseManager.java는

package com.example.simplegame; 

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

import android.content.ContentValues; 
import android.content.Context; 
import android.database.Cursor; 
import android.database.sqlite.SQLiteDatabase; 
import android.database.sqlite.SQLiteOpenHelper; 

public class DatabaseManager extends SQLiteOpenHelper { 

// All Static variables 
// Database Version 
private static final int DATABASE_VERSION = 1; 

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

// Contacts table name 
private static final String TABLE_CONTACTS = "contacts"; 

// Contacts Table Columns names 
private static final String KEY_ID = "id"; 
private static final String KEY_NAME = "name"; 
private static final String KEY_PH_NO = "phone_number"; 

public DatabaseManager(Context context) { 
    super(context, DATABASE_NAME, null, DATABASE_VERSION); 
} 

// Creating Tables 
@Override 
public void onCreate(SQLiteDatabase db) { 
    String CREATE_CONTACTS_TABLE = "CREATE TABLE " + TABLE_CONTACTS + "(" 
      + KEY_ID + " INTEGER PRIMARY KEY," + KEY_NAME + " TEXT," 
      + KEY_PH_NO + " TEXT" + ")"; 
    db.execSQL(CREATE_CONTACTS_TABLE); 
} 

// Upgrading database 
@Override 
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { 
    // Drop older table if existed 
    db.execSQL("DROP TABLE IF EXISTS " + TABLE_CONTACTS); 

    // Create tables again 
    onCreate(db); 
} 

/** 
* All CRUD(Create, Read, Update, Delete) Operations 
*/ 

// Adding new contact 
void addContact(PlayerData contact) { 
    SQLiteDatabase db = this.getWritableDatabase(); 

    ContentValues values = new ContentValues(); 
    values.put(KEY_NAME, contact.getName()); // Contact Name 
    values.put(KEY_PH_NO, contact.getscore()); // Contact Phone 

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

// Getting single contact 
PlayerData getContact(int id) { 
    SQLiteDatabase db = this.getReadableDatabase(); 

    Cursor cursor = db.query(TABLE_CONTACTS, new String[] { KEY_ID, 
      KEY_NAME, KEY_PH_NO }, KEY_ID + "=?", 
      new String[] { String.valueOf(id) }, null, null, null, null); 
    if (cursor != null) 
     cursor.moveToFirst(); 

    PlayerData contact = new PlayerData(Integer.parseInt(cursor.getString(0)), 
      cursor.getString(1), cursor.getInt(2)); 

    cursor.close(); 
    // return contact 
    return contact; 
} 

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

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

    // looping through all rows and adding to list 
    if (cursor.moveToFirst()) { 
     do { 
      PlayerData contact = new PlayerData(); 
      contact.setID(Integer.parseInt(cursor.getString(0))); 
      contact.setName(cursor.getString(1)); 
      contact.setscore(cursor.getInt(2)); 
      // Adding contact to list 
      contactList.add(contact); 
     } while (cursor.moveToNext()); 
    } 

    // return contact list 
    return contactList; 
} 

// Updating single contact 
public int updateContact(PlayerData contact) { 
    SQLiteDatabase db = this.getWritableDatabase(); 

    ContentValues values = new ContentValues(); 
    values.put(KEY_NAME, contact.getName()); 
    values.put(KEY_PH_NO, contact.getscore()); 

    // updating row 
    return db.update(TABLE_CONTACTS, values, KEY_ID + " = ?", 
      new String[] { String.valueOf(contact.getID()) }); 
} 

// Deleting single contact 
public void deleteContact(PlayerData contact) { 
    SQLiteDatabase db = this.getWritableDatabase(); 
    db.delete(TABLE_CONTACTS, KEY_ID + " = ?", 
      new String[] { String.valueOf(contact.getID()) }); 
    db.close(); 
} 


// Getting contacts Count 
public int getContactsCount() { 
    String countQuery = "SELECT * FROM " + TABLE_CONTACTS; 
    SQLiteDatabase db = this.getReadableDatabase(); 
    Cursor cursor = db.rawQuery(countQuery, null); 
    cursor.close(); 

    // return count 
    return cursor.getCount(); 
} 

} 

이 데이터를 삽입하지만 부하 버튼을 클릭하면 그것은 중지를 강제하고, 로그 캣는 말한다 :

08-30 18:48:41.616: E/AndroidRuntime(760): android.database.CursorIndexOutOfBoundsException: Index 0 requested, with a size of 0 
08-30 18:48:41.616: E/AndroidRuntime(760): at com.example.simplegame.DatabaseManager.getContact(DatabaseManager.java:79) 

도와주세요. 미리 감사드립니다!

Answer 1

로드는 데이터베이스의 첫 번째 항목이 아닌 id가 0 인 요소 만 가져옵니다. 따라서 데이터베이스에 대한 첫 번째 항목을 삭제 한 경우이 작업은 항상 실패합니다.

당신이해야 할 일은 getAllContacts() 함수에서 첫 번째 사용자를 얻는 것입니다. 사용자 확인 후 사용자 세부 정보를 확인할 수 있습니다.

List<PlayerData> contacts = db.getAllContacts(); 
//check to ensure there are users 
if(contacts.size()==0) throw new Exception(); 
PlayerData player = contacts.get(0); 
String showName = player.getName(); 
int showScore = player.getscore(); 

Answer 2

커서를 사용하여 데이터를 검색하기 전에 항상 커서를 확인해야합니다. 편도는 cursor.isAfterLast()과 cursor.isBeforeFirst()입니다.