无法在Android中第二次从DB检索数据

时间:2013-03-15 10:00:57

标签: android sqlite

我创建了一个可以将联系人从文本框保存到数据库的应用。联系人将是输入的号码或默认联系人。这个应用程序有大约5个编辑文本。

这里的问题是:第一次输入号码并单击“保存”按钮时,号码将被保存并正确检索。当我第二次为新号码做同样的事情。号码正在保存。当我尝试从DB中检索数字时,我看不到该数字。

我使用getter和setter方法存储事务值。

以下是我尝试过并解决问题的方法:

通过getter和setter方法从edittext到数据库。

         Contacts contacts = new Contacts();
      //arrsendcontactsinverse is the arraylist which stores all the numbers

         contacts.setArrcontactsofbean(arrsendcontactsinverse);
         database.addContacts(contacts);

//检索我使用下面代码的数据。

db = new DataBase(this);

    if(db.getContactsCount()>0)
    {
        Contacts contactFromDb = db.getContacts();

        contact1.setText(contactFromDb.getArrcontactsofbean().get(0));
        contact2.setText(contactFromDb.getArrcontactsofbean().get(1));
        contact3.setText(contactFromDb.getArrcontactsofbean().get(2));
        contact4.setText(contactFromDb.getArrcontactsofbean().get(3));
        contact5.setText(contactFromDb.getArrcontactsofbean().get(4));
    }
}

这是DataBase.java中的代码。

public class DataBase extends SQLiteOpenHelper
{
private static final int DATABASE_VERSION = 1;
private static final String TABLE_CONTACTS = "ContactsTable";
private static final String KEY_CONTACT1 = "contact1";  //column name
private static final String KEY_CONTACT2 = "contact2";  //column name
private static final String KEY_CONTACT3 = "contact3";  //column name
private static final String KEY_CONTACT4 = "contact4";  //column name
private static final String KEY_CONTACT5 = "contact5";  //column name

ArrayList<String> arrcontactofdatabasehandler= new ArrayList<String>();

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

public void onCreate(SQLiteDatabase db)
{
    String CREATE_CONTACTS_TABLE = "CREATE TABLE " + TABLE_CONTACTS +"("
            +KEY_CONTACT1+ " TEXT," 
            +KEY_CONTACT2+ " TEXT,"
            +KEY_CONTACT3+ " TEXT,"
            +KEY_CONTACT4+ " TEXT,"
            +KEY_CONTACT5+ " TEXT,"
            + ")";
    db.execSQL(CREATE_CONTACTS_TABLE);
}

// Adding new contact
void addContacts(Contacts contacts)
{
    SQLiteDatabase db = this.getWritableDatabase();
    ContentValues values = new ContentValues();

    values.put(KEY_CONTACT1,contacts.getArrcontactsofbean().get(0));
    values.put(KEY_CONTACT2,contacts.getArrcontactsofbean().get(1));
    values.put(KEY_CONTACT3,contacts.getArrcontactsofbean().get(2));
    values.put(KEY_CONTACT4,contacts.getArrcontactsofbean().get(3));
    values.put(KEY_CONTACT5,contacts.getArrcontactsofbean().get(4));

        db.insert(TABLE_CONTACTS, null, values);
    db.close();
}

// Getting contacts
Contacts getContacts()
{
    String selectQuery = "SELECT  * FROM " + TABLE_CONTACTS;
    SQLiteDatabase db = this.getWritableDatabase();
    Cursor cursor = db.rawQuery(selectQuery, null);
    Contacts contacts = new Contacts();

    // looping through all rows and adding to list
    if (cursor.moveToFirst()) 
    {
        do 
        {
            arrcontactofdatabasehandler.add(cursor.getString(0));       
            arrcontactofdatabasehandler.add(cursor.getString(1));   
            arrcontactofdatabasehandler.add(cursor.getString(2));   
            arrcontactofdatabasehandler.add(cursor.getString(3));   
            arrcontactofdatabasehandler.add(cursor.getString(4));       

        } while (cursor.moveToNext());
    }
    contacts.setArrcontactsofbean(arrcontactofdatabasehandler);
    cursor.close();
    db.close();
    return contacts;
}

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

public void dropTable()
{
    SQLiteDatabase db = this.getWritableDatabase();
    db.execSQL("DROP TABLE IF EXISTS " + TABLE_CONTACTS);
    String CREATE_CONTACTS_TABLE = "CREATE TABLE " + TABLE_CONTACTS +"("
            +KEY_CONTACT1+ " TEXT," 
            +KEY_CONTACT2+ " TEXT,"
            +KEY_CONTACT3+ " TEXT,"
            +KEY_CONTACT4+ " TEXT,"
            +KEY_CONTACT5+ " TEXT,"
            + ")";
    db.execSQL(CREATE_CONTACTS_TABLE);
    db.close();
}

  }

Contacts.java。(这些是getter和setter方法)

 public class Contacts 
{
    ArrayList<String> arrcontactsofbean= new ArrayList<String>();

public Contacts()
{

}

public ArrayList<String> getArrcontactsofbean() 
{   
    return arrcontactsofbean;
}

public void setArrcontactsofbean(ArrayList<String> arrcontactsofbean)
{
    this.arrcontactsofbean = arrcontactsofbean;
}
}

我在这里找不到确切的问题。

1 个答案:

答案 0 :(得分:0)

就我的理解而言。我认为问题在于getContacts方法:

根据您的逻辑,Contacts方法的一个对象将包含五个联系人,因此它将保存在数据库中。

但是你没有以正确的方式检索它们,所以必须创建一个类Contacts的数组,然后每个单独的行将包含五个联系人(这反映了列数)

所以做这样的事情:

   // Getting contacts
   Contacts[] getContacts()
   {
       String selectQuery = "SELECT  * FROM " + TABLE_CONTACTS;
       SQLiteDatabase db = this.getWritableDatabase();
       Cursor cursor = db.rawQuery(selectQuery, null);
       int count = getContactsCount();

       **//here can you check if the count is greater than 0**
       Log.d("Database", "Count: " + count);

       Contacts contacts[] = new Contacts[count];



       int index = 0;
       // looping through all rows and adding to list
       if (cursor.moveToFirst()) 
       {
           do 
           {
               Log.d("Database", "Initializing contacts...");
               contacts[index] = new Contacts(); ///initialize contacts here 
               ArrayList<String> arr = new ArrayList<String>();
               arr.add(cursor.getString(0));       
               arr.add(cursor.getString(1));   
               arr.add(cursor.getString(2));   
               arr.add(cursor.getString(3));   
               arr.add(cursor.getString(4));       
               contacts[index].setArrcontactsofbean(arr);
               index++;

           } while (cursor.moveToNext());
       }

       cursor.close();
       db.close();
       return contacts;
   }

您必须更改在代码中检索结果的方式,即处理数组然后显示。

“我尝试使用你说的arraylist方法检索值,它给了我一个空指针异常。” ?

尝试以下代码来遍历结果:

 Contacts contactsFromDb[];
 contactsFromDB = db.getContacts() /// Note the db is the object of Database class in which the getContacts() method is

 if(contactsDB != null){
    for(int k =0; k < contactsFromDB.length; k++){
    arrforcontactsdb = contactsFromDB[k].getArrcontactsofbean();

    for(int i = 0 ;i < (arrforcontactsdb.size());i++)   //not it should not be -1
    { 
        Log.e("retrieved VALUES ARE",""+arrforcontactsdb.get(i));
    }

“你能让我知道你为什么在database.java中使用数组的arraylist。?”

<强>答案:

它不是Array的ArrayList ....它是包含每个单独联系人的String的ArrayList。它是数组的原因,因为每行将包含5个联系人表示一个Contacts对象,因此多行表示多个对象,因此我在retreiving时将它们存储在Array中。