Somehow while debugging a little Location based android app I get a strange exception. Have a look and share your ideas:
I have connected a ListActivity with an sqlite3 database through a ContentProvider. Now always when I start the ListActivity the program dies with an Exception telling me
column '_id' does not exist
(without a table name) for the line where I create the SimpleCursorAdapter object for my ListActivity.
Cursor cursor = managedQuery(intent.getData(), new String[] {TrackTable.START_LOC, TrackTable.END_LOC}, null, null,
TrackTable.DEFAULT_SORT_ORDER);
SimpleCursorAdapter adapter = new SimpleCursorAdapter(this,
R.layout.gps_track_entry, cursor, new String[] {
TrackTable.COLUMN_NAME_TIME_START,
TrackTable.COLUMN_NAME_TIME_END
}, new int[] { R.id.l_start, R.id.l_end });
My database looks like that:
sqlite> .tables
.tables
android_metadata ocation track
sqlite> . schema track
.schema track
CREATE TABLE track (
_id INTEGER PRIMARY KEY,
start_location INTEGER,
end_location INTEGER,
start_time TEXT,
end_time TEXT
);
sqlite> .schema location
.schema location
CREATE TABLE location (
_id INTEGER PRIMARY KEY,
long TEXT,
lat TEXT,
alt TEXT,
accu TEXT,
bear TEXT,
sped TEXT,
time TEXT);
sqlite> .schema android_metadata
.schema android_metadata
CREATE TABLE android_metadata (locale TEXT);
I mean, it is quite unlikely that the mistake is an Android bug, but it definitely looks like one, because the only table without an _id is the android_metadata. But maybe I wrote something in a strange way, that the VM now thinks I want to use android_metadata and not track, which I actually want to use.
Erich is right above; the problem is that your SELECT query needs to include BaseColumns._ID as part of the projection. Something like:
Cursor cursor = getContentResolver().query(TrackTable.CONTENT_URI,
new String[] { TrackTable._ID, TrackTable.COLUMN_NAME_TIME_START,
TrackTable.COLUMN_NAME_TIME_END }, null, null, null);
BTW, see the javadoc for CursorAdapter:
The Cursor must include a column named "_id" or this class will not work.
Related
I'm having trouble with something that works in the Notepad example.
Here's the code from the NotepadCodeLab/Notepadv1Solution:
String[] from = new String[] { NotesDbAdapter.KEY_TITLE };
int[] to = new int[] { R.id.text1 };
SimpleCursorAdapter notes = new SimpleCursorAdapter(this,
R.layout.notes_row, c, from, to);
This code seems to work fine. But just to be clear, I ran the ADB
utility and run SQLite 3. I inspected the schema as follows:
sqlite> .schema
CREATE TABLE android_metadata (locale TEXT);
CREATE TABLE notes (_id integer primary key autoincrement, title text
not null, body text not null);
All seems good to me.
Now on to my application, which, as far as I can see, is basically the same with
a few minor changes. I've simplified and simplified my code, but the
problem persists.
String[] from = new String[] { "x" };
int[] to = new int[] { R.id.x };
SimpleCursorAdapter adapter = null;
try
{
adapter = new SimpleCursorAdapter(this, R.layout.circle_row, cursor, from, to);
}
catch (RuntimeException e)
{
Log.e("Circle", e.toString(), e);
}
When I run my application, I get a RuntimeException and the following prints
in LogCat from my Log.e() statement:
LogCat Message:
java.lang.IllegalArgumentException: column '_id' does not exist
So, back to SQLite 3 to see what's different about my schema:
sqlite> .schema
CREATE TABLE android_metadata (locale TEXT);
CREATE TABLE circles (_id integer primary key autoincrement, sequence
integer, radius real, x real, y real);
I don't see how I'm missing the '_id'.
What have I done wrong?
One thing that's different between my application and the Notepad example is
that I started by creating my application from scratch using the
Eclipse wizard while the sample application comes already put together. Is
there some sort of environmental change I need to make for a new application
to use a SQLite database?
I see, the documentation for CursorAdapter states:
The Cursor must include a column named _id or this class will not
work.
The SimpleCursorAdapter is a derived class, so it appears this statement applies. However, the statement is technically wrong and somewhat misleading to a newbie. The result set for the cursor must contain _id, not the cursor itself.
I'm sure this is clear to a DBA because that sort of shorthand documentation is clear to them, but for those newbies, being incomplete in the statement causes confusion. Cursors are like iterators or pointers, they contain nothing but a mechanism for transversing the data, they contain no columns themselves.
The Loaders documentation contains an example where it can be seen that the _id is included in the projection parameter.
static final String[] CONTACTS_SUMMARY_PROJECTION = new String[] {
Contacts._ID,
Contacts.DISPLAY_NAME,
Contacts.CONTACT_STATUS,
Contacts.CONTACT_PRESENCE,
Contacts.PHOTO_ID,
Contacts.LOOKUP_KEY,
};
public Loader<Cursor> onCreateLoader(int id, Bundle args) {
// ...
return new CursorLoader(getActivity(), baseUri,
CONTACTS_SUMMARY_PROJECTION, select, null,
Contacts.DISPLAY_NAME + " COLLATE LOCALIZED ASC");
}
This has been answered and I would like to make it more comprehensive here.
SimpleCursorAdapter requires that the Cursor's result set must include a column named exactly "_id". Don't haste to change schema if you didn't define the "_id" column in your table.
SQLite automatically added an hidden column called "rowid" for every table. All you need to do is that just select rowid explicitly and alias it as '_id' Ex.
SQLiteDatabase db = mHelper.getReadableDatabase();
Cursor cur = db.rawQuery( "select rowid _id,* from your_table", null);
Tim Wu's code really works...
If you are using db.query, then it would be like this...
db.query(TABLE_USER, new String[] {
"rowid _id",
FIELD_USERNAME,
},
FIELD_USERNAME + "=" + name,
null,
null,
null,
null);
Yes , I also change the SELECT string query to fix this issue.
String query = "SELECT t.*,t.id as _id FROM table t ";
What solved my issue with this error was that I had not included the _id column in my DB query. Adding that solved my problem.
This probably isn't relevant anymore, but I just hit the same problem today. Turns out column names are case sensitive. I had an _ID column, but Android expects an _id column.
If you read the docs on sqlite, creating any column of type INTEGER PRIMARY KEY will internally alias the ROWID, so it isn't worth the trouble of adding an alias in every SELECT, deviating from any common utilities that might take advantage of something like an enum of columns defining the table.
http://www.sqlite.org/autoinc.html
It is also more straightforward to use this as the ROWID instead of the AUTOINCREMENT option which can cause _ID can deviate from the ROWID. By tying _ID to ROWID it means that the primary key is returned from insert/insertOrThrow; if you are writing a ContentProvider you can use this key in the returned Uri.
Another way of dealing with the lack of an _id column in the table is to write a subclass of CursorWrapper which adds an _id column if necessary.
This has the advantage of not requiring any changes to tables or queries.
I have written such a class, and if it's of any interest it can be found at https://github.com/cmgharris/WithIdCursorWrapper
I'm having trouble with something that works in the Notepad example.
Here's the code from the NotepadCodeLab/Notepadv1Solution:
String[] from = new String[] { NotesDbAdapter.KEY_TITLE };
int[] to = new int[] { R.id.text1 };
SimpleCursorAdapter notes = new SimpleCursorAdapter(this,
R.layout.notes_row, c, from, to);
This code seems to work fine. But just to be clear, I ran the ADB
utility and run SQLite 3. I inspected the schema as follows:
sqlite> .schema
CREATE TABLE android_metadata (locale TEXT);
CREATE TABLE notes (_id integer primary key autoincrement, title text
not null, body text not null);
All seems good to me.
Now on to my application, which, as far as I can see, is basically the same with
a few minor changes. I've simplified and simplified my code, but the
problem persists.
String[] from = new String[] { "x" };
int[] to = new int[] { R.id.x };
SimpleCursorAdapter adapter = null;
try
{
adapter = new SimpleCursorAdapter(this, R.layout.circle_row, cursor, from, to);
}
catch (RuntimeException e)
{
Log.e("Circle", e.toString(), e);
}
When I run my application, I get a RuntimeException and the following prints
in LogCat from my Log.e() statement:
LogCat Message:
java.lang.IllegalArgumentException: column '_id' does not exist
So, back to SQLite 3 to see what's different about my schema:
sqlite> .schema
CREATE TABLE android_metadata (locale TEXT);
CREATE TABLE circles (_id integer primary key autoincrement, sequence
integer, radius real, x real, y real);
I don't see how I'm missing the '_id'.
What have I done wrong?
One thing that's different between my application and the Notepad example is
that I started by creating my application from scratch using the
Eclipse wizard while the sample application comes already put together. Is
there some sort of environmental change I need to make for a new application
to use a SQLite database?
I see, the documentation for CursorAdapter states:
The Cursor must include a column named _id or this class will not
work.
The SimpleCursorAdapter is a derived class, so it appears this statement applies. However, the statement is technically wrong and somewhat misleading to a newbie. The result set for the cursor must contain _id, not the cursor itself.
I'm sure this is clear to a DBA because that sort of shorthand documentation is clear to them, but for those newbies, being incomplete in the statement causes confusion. Cursors are like iterators or pointers, they contain nothing but a mechanism for transversing the data, they contain no columns themselves.
The Loaders documentation contains an example where it can be seen that the _id is included in the projection parameter.
static final String[] CONTACTS_SUMMARY_PROJECTION = new String[] {
Contacts._ID,
Contacts.DISPLAY_NAME,
Contacts.CONTACT_STATUS,
Contacts.CONTACT_PRESENCE,
Contacts.PHOTO_ID,
Contacts.LOOKUP_KEY,
};
public Loader<Cursor> onCreateLoader(int id, Bundle args) {
// ...
return new CursorLoader(getActivity(), baseUri,
CONTACTS_SUMMARY_PROJECTION, select, null,
Contacts.DISPLAY_NAME + " COLLATE LOCALIZED ASC");
}
This has been answered and I would like to make it more comprehensive here.
SimpleCursorAdapter requires that the Cursor's result set must include a column named exactly "_id". Don't haste to change schema if you didn't define the "_id" column in your table.
SQLite automatically added an hidden column called "rowid" for every table. All you need to do is that just select rowid explicitly and alias it as '_id' Ex.
SQLiteDatabase db = mHelper.getReadableDatabase();
Cursor cur = db.rawQuery( "select rowid _id,* from your_table", null);
Tim Wu's code really works...
If you are using db.query, then it would be like this...
db.query(TABLE_USER, new String[] {
"rowid _id",
FIELD_USERNAME,
},
FIELD_USERNAME + "=" + name,
null,
null,
null,
null);
Yes , I also change the SELECT string query to fix this issue.
String query = "SELECT t.*,t.id as _id FROM table t ";
What solved my issue with this error was that I had not included the _id column in my DB query. Adding that solved my problem.
This probably isn't relevant anymore, but I just hit the same problem today. Turns out column names are case sensitive. I had an _ID column, but Android expects an _id column.
If you read the docs on sqlite, creating any column of type INTEGER PRIMARY KEY will internally alias the ROWID, so it isn't worth the trouble of adding an alias in every SELECT, deviating from any common utilities that might take advantage of something like an enum of columns defining the table.
http://www.sqlite.org/autoinc.html
It is also more straightforward to use this as the ROWID instead of the AUTOINCREMENT option which can cause _ID can deviate from the ROWID. By tying _ID to ROWID it means that the primary key is returned from insert/insertOrThrow; if you are writing a ContentProvider you can use this key in the returned Uri.
Another way of dealing with the lack of an _id column in the table is to write a subclass of CursorWrapper which adds an _id column if necessary.
This has the advantage of not requiring any changes to tables or queries.
I have written such a class, and if it's of any interest it can be found at https://github.com/cmgharris/WithIdCursorWrapper
I need to reorder the rowid sequentially after deleting some rows. Vacuum on table seems to be a good fit for the situation but for some reasons its not reordering the rowid.
sqlite> .schema inboxmessages
CREATE TABLE InboxMessages(id text not null, title text not null, text text not null, senders_username text not null, created_at text not null, sender_image text not null, read text not null, Unique(id));
sqlite> select rowid, id from inboxmessages limit 5;
1|746915
3|746540
4|746195
5|745403
6|745371
sqlite> vacuum inboxmessages;
sqlite> select rowid, id from inboxmessages;
1|746915
3|746540
4|746195
5|745403
6|745371
whats wrong ?
VACUUM is not guaranteed to reorder rowid values, and if there is some INTEGER PRIMARY KEY column, it never will.
If you want to have specific values for your rowids, you have to set them manually.
Please note that in most cases, it is a better idea to just leave gaps in the rowid sequence.
Now I have a weird problem, I've done all kinds of test and I believe I'm seeing something weird.
I create three tables in SQLiteOpenHelper:
public void onCreate(SQLiteDatabase db) {
try {
db.execSQL(TABLE_CHANNELS_CREATE);
db.execSQL(TABLE_FEEDS_CREATE);
db.execSQL(TABLE_FEEDMAP_CREATE);
}
catch (SQLiteException e){
Toast.makeText(mContext, e.getMessage(), Toast.LENGTH_LONG).show();
}
}
The CREATE statements for the three tables follow:
CREATE TABLE IF NOT EXISTS IRChannels (
ChannelId INTEGER PRIMARY KEY,
ChannelHash TEXT NOT NULL,
ChannelTitle TEXT NOT NULL,
ChannelDesc TEXT, ChannelLink TEXT);
CREATE TABLE IF NOT EXISTS IRFeeds (
FeedId INTEGER PRIMARY KEY,
FeedHash TEXT NOT NULL,
FeedTitle TEXT NOT NULL,
FeedDescription TEXT,
FeedLink TEXT);
CREATE TABLE IF NOT EXISTS IRFeedMap (
ChannelHash_FK TEXT NOT NULL,
FeedHash_FK TEXT NOT NULL,
FOREIGN KEY (ChannelHash_FK) REFERENCES IRChannels (ChannelHash),
FOREIGN KEY (FeedHash_FK) REFERENCES IRFeeds (FeedHash));
The problem is apparently the column FeedHash in IRFeeds is not created while others are. I'm looking at the output in sqlite3 command prompt;
sqlite> .schema
CREATE TABLE IRChannels (
ChannelId INTEGER PRIMARY KEY,
ChannelHash TEXT NOT NULL,
ChannelTitle TEXT NOT NULL,
ChannelDesc TEXT,
ChannelLink TEXT);
CREATE TABLE IRFeedMap (
ChannelHash_FK TEXT NOT NULL,
FeedHash_FK TEXT NOT NULL,
FOREIGN KEY (ChannelHash_FK) REFERENCES IRChannels (ChannelHash),
FOREIGN KEY (FeedHash_FK) REFERENCES IRFeeds (FeedHash));
CREATE TABLE IRFeeds (
FeedId INTEGER PRIMARY KEY,
FeedHash TEXT NOT NULL,
FeedTitle TEXT NOT NULL,
FeedDescription TEXT,
FeedLink TEXT);
This does list the FeedHash column in IRFeeds. However, when I execute
sqlite> select * from IRFeeds where FeedHash='';
SQL error: no such column: FeedHash
All other columns do not give such errors. This condition is causing my code to fail unexpectedly as well. What could I be missing?
sqlite> select * from IRFeeds where FeedID=1;
sqlite> select * from IRFeeds where FeedTitle='';
sqlite> select * from IRFeeds where FeedDescription='';
sqlite> select * from IRFeeds where FeedLink='';
No errors above when I execute select statement for other columns.
There is no error in your SQL. I tested and everything was created properly. Also your SQL query did not cause no such column error. So try to delete the database with context.deleteDatabase(databaseName); and try again.
After an entire day of struggle, I managed to isolate why the problem triggers. Still don't know why, but it does fix the problem. The problems occurs because of the following table which has foreign keys on the other two tables:
CREATE TABLE IRFeedMap (
ChannelHash_FK TEXT NOT NULL,
FeedHash_FK TEXT NOT NULL,
FOREIGN KEY (ChannelHash_FK) REFERENCES IRChannels (ChannelHash),
FOREIGN KEY (FeedHash_FK) REFERENCES IRFeeds (FeedHash));
Changing the column names of foreign key columns to be the same as the column they reference fixes the problem. I changed the statement above to:
CREATE TABLE IRFeedMap (
ChannelHash TEXT NOT NULL,
FeedHash TEXT NOT NULL,
FOREIGN KEY (ChannelHash) REFERENCES IRChannels (ChannelHash),
FOREIGN KEY (FeedHash) REFERENCES IRFeeds (FeedHash));
And voila! Sanity was restored. Beats me.
In my case I was using a SQLite reserved word (column, that was)
I ended up in this SO question, so maybe it helps others in my situation
I'm having trouble with something that works in the Notepad example.
Here's the code from the NotepadCodeLab/Notepadv1Solution:
String[] from = new String[] { NotesDbAdapter.KEY_TITLE };
int[] to = new int[] { R.id.text1 };
SimpleCursorAdapter notes = new SimpleCursorAdapter(this,
R.layout.notes_row, c, from, to);
This code seems to work fine. But just to be clear, I ran the ADB
utility and run SQLite 3. I inspected the schema as follows:
sqlite> .schema
CREATE TABLE android_metadata (locale TEXT);
CREATE TABLE notes (_id integer primary key autoincrement, title text
not null, body text not null);
All seems good to me.
Now on to my application, which, as far as I can see, is basically the same with
a few minor changes. I've simplified and simplified my code, but the
problem persists.
String[] from = new String[] { "x" };
int[] to = new int[] { R.id.x };
SimpleCursorAdapter adapter = null;
try
{
adapter = new SimpleCursorAdapter(this, R.layout.circle_row, cursor, from, to);
}
catch (RuntimeException e)
{
Log.e("Circle", e.toString(), e);
}
When I run my application, I get a RuntimeException and the following prints
in LogCat from my Log.e() statement:
LogCat Message:
java.lang.IllegalArgumentException: column '_id' does not exist
So, back to SQLite 3 to see what's different about my schema:
sqlite> .schema
CREATE TABLE android_metadata (locale TEXT);
CREATE TABLE circles (_id integer primary key autoincrement, sequence
integer, radius real, x real, y real);
I don't see how I'm missing the '_id'.
What have I done wrong?
One thing that's different between my application and the Notepad example is
that I started by creating my application from scratch using the
Eclipse wizard while the sample application comes already put together. Is
there some sort of environmental change I need to make for a new application
to use a SQLite database?
I see, the documentation for CursorAdapter states:
The Cursor must include a column named _id or this class will not
work.
The SimpleCursorAdapter is a derived class, so it appears this statement applies. However, the statement is technically wrong and somewhat misleading to a newbie. The result set for the cursor must contain _id, not the cursor itself.
I'm sure this is clear to a DBA because that sort of shorthand documentation is clear to them, but for those newbies, being incomplete in the statement causes confusion. Cursors are like iterators or pointers, they contain nothing but a mechanism for transversing the data, they contain no columns themselves.
The Loaders documentation contains an example where it can be seen that the _id is included in the projection parameter.
static final String[] CONTACTS_SUMMARY_PROJECTION = new String[] {
Contacts._ID,
Contacts.DISPLAY_NAME,
Contacts.CONTACT_STATUS,
Contacts.CONTACT_PRESENCE,
Contacts.PHOTO_ID,
Contacts.LOOKUP_KEY,
};
public Loader<Cursor> onCreateLoader(int id, Bundle args) {
// ...
return new CursorLoader(getActivity(), baseUri,
CONTACTS_SUMMARY_PROJECTION, select, null,
Contacts.DISPLAY_NAME + " COLLATE LOCALIZED ASC");
}
This has been answered and I would like to make it more comprehensive here.
SimpleCursorAdapter requires that the Cursor's result set must include a column named exactly "_id". Don't haste to change schema if you didn't define the "_id" column in your table.
SQLite automatically added an hidden column called "rowid" for every table. All you need to do is that just select rowid explicitly and alias it as '_id' Ex.
SQLiteDatabase db = mHelper.getReadableDatabase();
Cursor cur = db.rawQuery( "select rowid _id,* from your_table", null);
Tim Wu's code really works...
If you are using db.query, then it would be like this...
db.query(TABLE_USER, new String[] {
"rowid _id",
FIELD_USERNAME,
},
FIELD_USERNAME + "=" + name,
null,
null,
null,
null);
Yes , I also change the SELECT string query to fix this issue.
String query = "SELECT t.*,t.id as _id FROM table t ";
What solved my issue with this error was that I had not included the _id column in my DB query. Adding that solved my problem.
This probably isn't relevant anymore, but I just hit the same problem today. Turns out column names are case sensitive. I had an _ID column, but Android expects an _id column.
If you read the docs on sqlite, creating any column of type INTEGER PRIMARY KEY will internally alias the ROWID, so it isn't worth the trouble of adding an alias in every SELECT, deviating from any common utilities that might take advantage of something like an enum of columns defining the table.
http://www.sqlite.org/autoinc.html
It is also more straightforward to use this as the ROWID instead of the AUTOINCREMENT option which can cause _ID can deviate from the ROWID. By tying _ID to ROWID it means that the primary key is returned from insert/insertOrThrow; if you are writing a ContentProvider you can use this key in the returned Uri.
Another way of dealing with the lack of an _id column in the table is to write a subclass of CursorWrapper which adds an _id column if necessary.
This has the advantage of not requiring any changes to tables or queries.
I have written such a class, and if it's of any interest it can be found at https://github.com/cmgharris/WithIdCursorWrapper