我使用 sqllite.i 成功创建了 sql 数据库,我也可以插入一些值并在 ListView 中显示它。现在我想编写函数女巫返回标题,其中 ServerID 喜欢我的值 我写了函数但是这个函数没有返回计数器
public class DatabaseHandler extends SQLiteOpenHelper {
private static final int DATABASE_VERSION = 1;
private static final String DATABASE_NAME = "lv_db4";
private static final String TABLE_CONTACTS = "CardTable1";
public static final String KEY_ID = "id";
private static final String KEY_Tittle = "title";
private static final String KEY_Description = "description";
private static final String KEY_Price = "price";
private static final String KEY_Counter = "counter";
private static final String KEY_ServerId = "serverid";
private static final String KEY_Image = "image";
private final ArrayList<Contact> contact_list = new ArrayList<Contact>();
public static SQLiteDatabase db;
public DatabaseHandler(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db) {
String CREATE_CONTACTS_TABLE = "CREATE TABLE " + TABLE_CONTACTS + "("
+ KEY_ID + " INTEGER PRIMARY KEY,"
+ KEY_Tittle + " TEXT,"
+ KEY_Description + " TEXT,"
+ KEY_Price + " TEXT,"
+ KEY_Counter + " TEXT,"
+ KEY_ServerId + " TEXT,"
+ KEY_Image + " TEXT"
+ ");";
db.execSQL(CREATE_CONTACTS_TABLE);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS " + TABLE_CONTACTS);
onCreate(db);
}
// Adding new contact
public void Add_Contact(Contact contact) {
db = this.getWritableDatabase();
ContentValues values = new ContentValues();
values.put(KEY_Tittle, contact.getTitle());
values.put(KEY_Description, contact.getDescription());
values.put(KEY_Price, contact.getPrice());
values.put(KEY_Counter, contact.getCounter());
values.put(KEY_ServerId, contact.getServerId());
values.put(KEY_Image, contact.getImage());
db.insert(TABLE_CONTACTS, null, values);
db.close();
}
public void deleteUser(String userName) {
db = this.getWritableDatabase();
try {
db.delete(TABLE_CONTACTS, "title = ?", new String[] { userName });
} catch (Exception e) {
e.printStackTrace();
} finally {
db.close();
}
}
public String GetCounterFromServerID(String value) {
db = this.getWritableDatabase();
Cursor cursor = db.rawQuery("select " + KEY_Counter+ " from " + TABLE_CONTACTS
+ " where serverid like '%" + value + "%'", null);
cursor.close();
return KEY_Counter;
}
public int Update_Contact(Contact contact) {
db = this.getWritableDatabase();
ContentValues values = new ContentValues();
values.put(KEY_Counter, contact.getCounter());
// updating row
return db.update(TABLE_CONTACTS, values, KEY_ID + " = ?",
new String[] { String.valueOf(contact.getID()) });
}
// Getting single contact
Contact Get_Contact(int id) {
SQLiteDatabase db = this.getReadableDatabase();
Cursor cursor = db.query(TABLE_CONTACTS, new String[] { KEY_ID,
KEY_Tittle, KEY_Description, KEY_Price, KEY_Counter,
KEY_ServerId, KEY_Image }, KEY_ID + "=?",
new String[] { String.valueOf(id) }, null, null, null);
if (cursor != null)
cursor.moveToFirst();
Contact contact = new Contact(cursor.getString(0), cursor.getString(1),
cursor.getString(2), cursor.getString(3), cursor.getString(4),
cursor.getString(5));
cursor.close();
db.close();
return contact;
}
public boolean DublicateValues(String S_title) {
db = this.getWritableDatabase();
Cursor cursor = db.rawQuery("select * from " + TABLE_CONTACTS
+ " where title like '%" + S_title + "%'", null);
boolean exists = (cursor.getCount() > 0);
cursor.close();
return exists;
}
我的 GetCounterFromServerID 函数只返回“计数器”,我想返回例如 2 或 4 等
我在另一个 Activity 中这样调用我的函数:
String counter;
counter=dbHandler.GetCounterFromServerID(intentServerId);
System.out.println(counter );
dbHandler.close();
日志结果只有计数器 我究竟做错了什么?如果有人知道解决方案请帮助我
最佳答案
你可以这样做。
public String GetCounterFromServerID(String value)
{
Cursor cursor = db.rawQuery("SELECT " + KEY_Counter + " FROM " + TABLE_CONTACTS + " WHERE serverid like '%" + value + "%'", null);
if (!cursor.moveToFirst())
{
return null;
}
if(-1 == cursor.getColumnIndex(KEY_Counter))
{
return null;
}
String counter = cursor.getString(cursor.getColumnIndex(KEY_Counter));
cursor.close();
return counter;
}
关于Android sqlite 选择不工作,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/24777664/