I am working on a method that queries a content provider using a cursor. After I delete a record, it calls the loadfromProvider method and refreshes the arraylist. The content provider normally has records in it however, when I delete all the records and the query runs automatically it throws exceptions. Here is my method:
private void loadFromProvider() {
// Clear the existing array list
EQlist.clear();
ContentResolver cr = getContentResolver();
// Return all the saved records
Cursor c = cr.query(EQProvider.CONTENT_URI, null, null, null, null);
if (c.moveToFirst()) {
do {
String details = c.getString(EQProvider.DETAILS_COLUMN);
String linkString = c.getString(EQProvider.LINK_COLUMN);
EQli q = new EQli(details, linkString);
addEQToArray(q);
} while(c.moveToNext());
}
c.close();
}
When I run this with no records in the content provider it throws the following:
java.lang.IndexOutOfBoundsException: Invalid index 1, size is 1
at java.util.ArrayList.throwIndexOutOfBoundsException(ArrayList.java:257)
I think this is due to the cursor trying to parse a null value. I am trying to figure out a way that if the cursor does not come back with any records, it bypasses the rest of the code and does nothing happens.
Any help would be appreciated. Thanks
If there are no records your cursor should be empty. If the cursor is empty then c.moveToFirst() will return false and you are not going to enter the do-while loop.
Debug your application and make sure that the cursor is empty.
Related
in my android application i used the following function to retrieve the column from the table..the table contains value but it has an exception.
public String[] getactivelist(){
Log.v("ppp","getactivelist");
String[] actname=new String[50];
SQLiteDatabase db = this.getWritableDatabase();
Log.v("ppp","dbcrtd");
Cursor cursor = db.rawQuery("SELECT name FROM activelist ORDER BY time ASC", null);
Log.v("ppp","aftrcurser");
int i=0;
Log.v("ppp crsr",cursor.getString(0));
if (cursor.moveToFirst()) {
do {
actname[i]=cursor.getString(0);
Log.v("ppp crsr",cursor.getString(0));
} while (cursor.moveToNext());
}
cursor.close();
db.close();
return actname;
}
the log cat shows the following error
04-04 01:19:41.170 2581-2601/com.example.pranavtv.loudspeaker V/pppīš tryandroid.database.CursorIndexOutOfBoundsException: Index -1 requested, with a size of 2
In your line
Log.v("ppp crsr", cursor.getString(0));
You try to get a string from the cursor. If there aren't any lines, it should throw the error observed.
You are calling the following line...
Log.v("ppp crsr",cursor.getString(0));
...before you have moved the position of your Cursor using...
if (cursor.moveToFirst()) {
By default, the position of a Cursor is initially set to be -1 which is before the first valid position as the first position which contains data is position 0.
Simply remove that line (the one before the if(...)) and you should be good to go.
On another note, in your do...while loop you are using...
actname[i]=cursor.getString(0);
...but you never increment i. Consequentially you will only ever modify actname[0] regardless of how many results are returned to the Cursor.
I am a programming newbie
and I found this piece of code in the internet and it works fine
Cursor c=db.query(DataBase.TB_NAME, new String[] {DataBase.KEY_ROWID,DataBase.KEY_RATE}, DataBase.KEY_ROWID+"= 1", null, null, null, null);
if(c!=null)
{
c.moveToFirst();
}
but I am not able to understand the use of the
if(c!=null)
{
c.moveToFirst();
}
part. What does it do exactly , and if I remove the
if(c!=null) { c.moveToFirst(); }
part, the code doesn't work.
The docs for SQLiteDatabase.query() say that the query methods return:
"A Cursor object, which is positioned before the first entry."
Calling moveToFirst() does two things: it allows you to test whether the query returned an empty set (by testing the return value) and it moves the cursor to the first result (when the set is not empty). Note that to guard against an empty return set, the code you posted should be testing the return value (which it is not doing).
Unlike the call to moveToFirst(), the test for if(c!=null) is useless; query() will either return a Cursor object or it will throw an exception. It will never return null.
if (c.moveToFirst()) {
while(!c.isAfterLast()) { // If you use c.moveToNext() here, you will bypass the first row, which is WRONG
...
c.moveToNext();
}
}
Cursor is not a Row of the result of query. Cursor is an object that can iterate on the result rows of your query. Cursor can moves to each row. .moveToFirst() method move it to the first row of result table.
moveToFirst() method moves the cursor to the first row. It allows to perform a test whether the query returned an empty set or not. Here is a sample of its implementation,
if (cursor.getCount() == 0 || !cursor.moveToFirst()) {
return cursor.getLong(cursor.getColumnIndexOrThrow(ID_COLUMN));
cursor.close();
what macio.Jun says is right!
we have code like below:
String sql = "select id,title,url,singer,view,info from cache where id=" + id;
SQLiteDatabase db = getMaintainer().getReadableDatabase();
Cursor query = db.rawQuery(sql, null);
query.moveToFirst();
while(query.moveToNext()){
DBMusicData entity = new DBMusicData();
entity.setId(query.getString(query.getColumnIndex(FIELD_ID)));
entity.setTitle(query.getString(query.getColumnIndex(FIELD_TITLE)));
entity.setSinger(query.getString(query.getColumnIndex(FIELD_SINGER)));
entity.setTitlepic(query.getString(query.getColumnIndex(FIELD_PICURL)));
entity.setInfoUrl(query.getString(query.getColumnIndex(FIELD_INFO)));
entity.setViews(query.getString(query.getColumnIndex(FIELD_VIEW)));
Log.w(tag, "cache:"+ entity.toString());
}
query.close();
query=null;
db.close();
db=null;
If we have only one record in the cache table, query.moveToFirst(); will cause that no record returns.
So I'm trying to get the values from a SQLite database into a cursor, then pick a random value. I can read the cursor with getString() as I normally would in the method, but after it returns the cursor it doesn't work correctly. I don't know why..
Here's my method for getting the cursor from the database. It seems to work correctly.
public Cursor getRandomText(String Rating)
{
Cursor cursor = myDatabase.query("Elec0RandTexts", new String[] {"Message"}, "Rating=?",
new String[]{Rating}, null, null, null);
cursor.moveToFirst();
cursor.close();
return cursor;
}
Here's my code for reading the cursor after it's returned.
Cursor result = dbh.getRandomText(Rating);
result.moveToFirst();
int RandText = rand.nextInt(result.getCount());
result.moveToPosition(RandText);
Toast.makeText(getApplicationContext(), "" + result.getString(RandText), Toast.LENGTH_LONG).show();
result.close();
I'm probably making a stupid mistake and not realizing it, but I can't figure this out.
Thanks,
~Elec0
cursor.close(); // in getRandomText()
after that you cannot obtain any data from the cursor - it is closed. Remove this line.
You close() your Cursor before you return it. From where it is returned to, you are then attempting to call moveToFirst(). This cannot be done if the Cursor is closed.
In your getRandomText(String) method, you should return the meaningful data from your Cursor, rather than the Cursor object itself. That way, the method that created the Cursor can continue to close the Cursor as it should. (It should just happen at the end of the method)
I am an android novice and have been experimenting with SQLite and Android. I am able to get queries and use the cursor results, but I can't seem to get this the following code to work:
This is my Query statement, where queryWhere = "MyObject="1"" and DATABASE_TABLE_TOQUERY = "FavoriteObjects". These are all okay when viewed in an SQLite database viewer and it also returns a correct result if I execute the query using my SQLite database viewer.
public long findObject(String[] keys, String[] values,String DATABASE_TABLE_TOQUERY){
try {
if(keys.length<0 || keys.length!=values.length)
System.exit(-1);
String queryWhere = keys[0]+"=\""+values[0]+"\"";
for(int i=1;i<keys.length;i++) {
queryWhere+=" AND "+keys[i]+"=\""+values[i]+"\"";
}
Cursor mCursor = mDb.query(true, DATABASE_TABLE_TOQUERY, null,
queryWhere, null, null, null, null, null);
if (mCursor != null && mCursor.getCount()>0)
return Long.parseLong(mCursor.getString(mCursor.getColumnIndex(KEY_ROWID)));
}catch (SQLException e) {
return -1;
}
return -1;
}
When I get the results after executing the query statement, Cursor mCursor has at least one row, but when I access that row using mCursor.getString(X), it throws a weird error:
android.database.CursorIndexOutOfBoundsException: Index -1 requested, with a size of 1
If I check mCursor.getColumnIndex(KEY_ROWID), I get a 0 value (which is correct). Anyone have any suggestions?
Thanks!
Jon
Try
mCursor.moveToNext();
I query the table by using this function below
public Cursor getTableInfo() throws SQLException
{
return db.query(TableName, null,
null,
null,
null,
null,
null);
}
I got the error "View Root.handleMessage(Message)line:1704". I could insert the data but can't query the data. I called this function below
Cursor c = db.getTableInfo();
int cRow = c.getCount();
if (cRow == 0)
{
Toast.makeText(NewContact.this,
"No Record",
Toast.LENGTH_LONG).show();
}
In SQLite, is there any case-sensitive in the name of database, table, column?
Please help me.
Your db request looks ok and it should return all records from your table.
So maybe there are just no records in the table?
Also it's unclear whether you have problem with db related stuff or with smth else, because the code provided looks ok.
I would rather evaluate the outcome of c.moveToFirst() instead of c.getCount(). The latter means the cursor iterates over the whole dataset which is a more costly operation.