作为Android的新手,我在处理以下问题时遇到了麻烦:
public String[] getContacts(){
Cursor cursor = getReadableDatabase().rawQuery("SELECT name FROM contacts", null);
String [] names = {""};
for(int i = 0; i < cursor.getCount(); i ++){
names[i] = cursor.getString(i);
}
cursor.close();
return names;
}
以下给了我以下错误:
09-18 10:07:38.616: E/AndroidRuntime(28165): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.sqllitetrial/com.example.sqllitetrial.InsideDB}: android.database.CursorIndexOutOfBoundsException: Index -1 requested, with a size of 5
我正在尝试将光标内的数据提取到数组中。有人可以帮助我实施吗?
names.add(cursor.getString(i));
"i"不是游标行索引,而是列索引。游标已定位到特定行。如果您需要重新定位光标。使用 cursor.move 或 moveToXXXX(请参阅文档)。
对于getString/Int/Long等,你只需要告诉光标你想要哪一列。如果您不知道列索引,可以使用cursor.getColumnIndex("yourColumnName")
。
您的循环应如下所示:
public String[] getContacts(){
Cursor cursor = getReadableDatabase().rawQuery("SELECT name FROM contacts", null);
cursor.moveToFirst();
ArrayList<String> names = new ArrayList<String>();
while(!cursor.isAfterLast()) {
names.add(cursor.getString(cursor.getColumnIndex("name")));
cursor.moveToNext();
}
cursor.close();
return names.toArray(new String[names.size()]);
}
我希望它对你有用。
public static ArrayList<ModelAgents> SelectAll(DbHelper dbaConnection) {
ArrayList<ModelAgents> Agents_aList = new ArrayList<ModelAgents>();
SQLiteDatabase sqldb = dbaConnection.openDataBase();
Cursor cursor = sqldb.rawQuery("SELECT * FROM Agents", null);
if (cursor != null)// If Cursordepot is null then do
// nothing
{
if (cursor.moveToFirst()) {
do {
// Set agents information in model.
ModelAgents Agents = new ModelAgents();
Agents.setID(cursor.getInt(cursor
.getColumnIndex(TblAgents.ID)));
Agents.setCode(cursor.getString(cursor
.getColumnIndex(TblAgents.CODE)));
Agents.setName(cursor.getString(cursor
.getColumnIndex(TblAgents.NAME)));
Agents_aList.add(Agents);
} while (cursor.moveToNext());
}
cursor.close();
}
sqldb.close();
return Agents_aList;
}
当从数据库查询返回游标时,它被放置在游标第一个条目上方的索引 -1 处,因此,在使用游标获取数据之前,已将其移动到其第一个位置。为此添加 cursor.MoveToFirst();
后 Cursor cursor = getReadableDatabase().rawQuery("SELECT name FROM contacts", null);
使用这个:
if (cursor != null && cursor.getCount()>0){
cursor.moveToFirst();
do{
for(int i = 0; i < cursor.getCount(); i ++){
names.add(cursor.getString(i));
}
}while(cursor.moveToNext());
}
cursor.close();
放入ArrayList<String>
中,如下所示:
public ArrayList<String> getContacts(){ Cursor cursor = getReadableDatabase().rawQuery("SELECT name FROM contacts", null); ArrayList<String> names=new ArrayList<String>(); if (cursor != null) { if (cursor.moveToFirst()) { for(int i = 0; i < cursor.getCount(); i ++){ names.add(cursor.getString(i)); } } cursor.close(); } return names; }