failed to read row 0,column -1

问题:

I am trying to copy a database that I made with SQLite manager, in which I did:

CREATE TABLE "android_metadata" ("locale" TEXT DEFAULT 'en_US') 

and

INSERT INTO "android_metadata" VALUES ('en_US')   

And I named all my primary keys _id. My database gets copied(in the first run there are various red messages in the logcat); thereafter, it only gives an error when I query it.

MainActivity

public class MainActivity extends Activity { String CNAME=" ques",TABLE_NAME=" JAVAQ";     @Override public void onCreate(Bundle savedInstanceState) {     super.onCreate(savedInstanceState);     setContentView(R.layout.activity_main);     Setupdb dbobj=new Setupdb(this);       try {              //dbobj.close();         dbobj.createDataBase();      } catch (IOException e) {         // TODO Auto-generated catch block         e.printStackTrace();     }         dbobj.openDataBase();     dbobj.close();       try{          SQLiteDatabase sqdb=dbobj.getReadableDatabase();             Cursor c = sqdb.query(TABLE_NAME,                  new String[] { CNAME },                  null, null, null, null, null);           while (c.moveToNext()) {              String name =             c.getString(c.getColumnIndex(CNAME));             Log.i("LOG_TAG", " HAS NAME " + name);          }}                catch(Exception e){                  Log.e("err", e.toString());             }      }} 

Setupdb

public class Setupdb extends SQLiteOpenHelper {    private static String DB_PATH = "";     private static final String DB_NAME = "camprep.sqlite";     private SQLiteDatabase myDataBase;     private final Context myContext;      private static Setupdb mDBConnection;   public Setupdb(Context context) {     super(context, DB_NAME, null, 3);     this.myContext=context;     DB_PATH="/data/data/"             + context.getApplicationContext().getPackageName()             + "/databases/";     Log.e(DB_NAME, DB_PATH); } public static synchronized Setupdb getDBAdapterInstance(Context context) {     if (mDBConnection == null) {         mDBConnection = new Setupdb(context);     }     return mDBConnection; }       public void createDataBase() throws IOException {          boolean dbExist = checkDataBase();         if (dbExist) {             Log.e("db","exist");             // do nothing - database already exist         } else {             // By calling following method             // 1) an empty database will be created into the default system path of your application             // 2) than we overwrite that database with our database.             this.getReadableDatabase();             try {                 Log.e("calling", "copy");                 copyDataBase();              } catch (IOException e) {                 throw new Error("Error copying database");             }         }      }     private boolean checkDataBase() {         SQLiteDatabase checkDB = null;         try {             String myPath = DB_PATH + DB_NAME;             checkDB = SQLiteDatabase.openDatabase(myPath, null,                     SQLiteDatabase.OPEN_READONLY);          } catch (SQLiteException e) {             // database does't exist yet.         }         if (checkDB != null) {             checkDB.close();         }         return checkDB != null ? true : false;      }      private void copyDataBase() throws IOException {         // Open your local db as the input stream     InputStream myInput = myContext.getAssets().open(DB_NAME);         // Path to the just created empty db     String outFileName = DB_PATH + DB_NAME;          // Open the empty db as the output stream     OutputStream myOutput = new FileOutputStream(outFileName);         // transfer bytes from the inputfile to the outputfile     byte[] buffer = new byte[1024];     int length;     while ((length = myInput.read(buffer)) > 0) {         myOutput.write(buffer, 0, length);     }         // Close the streams     myOutput.flush();     myOutput.close();     myInput.close(); }       public void openDataBase() throws SQLException {         String myPath = DB_PATH + DB_NAME;         myDataBase = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READWRITE);     }     public synchronized void close() {         if (myDataBase != null)             myDataBase.close();         super.close();     }   @Override public void onCreate(SQLiteDatabase db) {     // TODO Auto-generated method stub  }  @Override public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {   }  } 

Stacktrace

 08-31 20:17:05.320: I/dalvikvm(9457): threadid=3: reacting to signal 3 08-31 20:17:05.370: I/dalvikvm(9457): Wrote stack traces to '/data/anr/traces.txt' 08-31 20:17:05.451: E/camprep.sqlite(9457): /data/data/com.example.mydataexplosion/databases/ 08-31 20:17:05.490: E/db(9457): exist 08-31 20:17:05.521: E/CursorWindow(9457): Failed to read row 0, column -1 from a CursorWindow which has 11 rows, 1 columns. 08-31 20:17:05.521: E/err(9457): java.lang.IllegalStateException: Couldn't read row 0, col -1 from CursorWindow.  Make sure the Cursor is initialized correctly before accessing data from it. 08-31 20:17:05.650: D/gralloc_goldfish(9457): Emulator without GPU emulation detected. 08-31 20:17:05.650: I/dalvikvm(9457): threadid=3: reacting to signal 3 08-31 20:17:05.670: I/dalvikvm(9457): Wrote stack traces to '/data/anr/traces.txt' 

回答1:

if you see

failed to read row 0,column -1 

It means you are trying to read from a column which doesn't exist.

If it cannot find the column name that you specify, Cursor.getColumnIndex() returns -1 and hence, is invalid.

There are two reasons for this:

1. The column does not exist.
2. The name of the column is incorrect. (so does not exist).

Note: the name of the column is CASE SENSITIVE when using getColumnIndex()

---

In your scenario:

 c.getString(c.getColumnIndex(CNAME)); 

Check that the CNAME variable is spelt correctly, and that a column of that name exists.

String CNAME=" ques" 

Should that extra leading white space be there for example..

回答2:

Before you start reading the consecutive values by using c.moveToNext() , set the cursor to the initial position, that is the beginning of your database.

c.moveToFirst()

and then start reading form it.

Might solve your problem.

回答3:

Although you can get the content by switching with the method cursor.movetonext() so often until you moved to the right number, it was very annoying and requested a bunch of code.

I guess this should solve the problems for most of you. I guess anything but ASCII is wrong -- spaces, dots, minuses etc., cannot be used either.

You may successfully create a database and you may can see with external sqlite tools but android will always nag.

回答4:

Another Scenario when this can happen:
You are deleting rows from the cursor while the cursor is still in use.

E.g pseudo-coden where it could happen:

while(cursor.moveToNext()){    readCursor(cursor);    deleteRowFromCursor(cursor);  }   

Solution:

Keep list of rows you want to delete; build a batch delete sql statement; execute the statment out side of the while loop ( when you are done with using the cursor anymore or after you close it).

while(cursor.moveToNext()){    readCursor(cursor);    queueRowForDelete(cursor);  }   deleteQueuedRows(queuedRowsList); 

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