Question

我尝试从android中的SQLite数据库中检索一些数据，但是我收到了一些错误。

首先，这是我的数据库代码片段：

private static final String TABLE_NAME_UrlCache = "UrlCache";
private static final String COLUMN_NAME_UrlCache_ID = "id";
private static final String COLUMN_NAME_UrlCache_TIME = "time";
private static final String COLUMN_NAME_UrlCache_DATE = "date";
private static final String COLUMN_NAME_UrlCache_CLIENTIP = "clientip";
private static final String COLUMN_NAME_UrlCache_CLIENTMAC = "clientmac";
private static final String COLUMN_NAME_UrlCache_REQUESTEDURL = "requestedurl";
private static final String COLUMN_NAME_UrlCache_FILENAME = "filename";
private static final String CREATE_TABLE_UrlCache = "CREATE TABLE " +TABLE_NAME_UrlCache+ " (" + COLUMN_NAME_UrlCache_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, " + COLUMN_NAME_UrlCache_TIME +" text, " + COLUMN_NAME_UrlCache_DATE + " text, "+ COLUMN_NAME_UrlCache_CLIENTIP + " text, "+ COLUMN_NAME_UrlCache_CLIENTMAC + " text, "+ COLUMN_NAME_UrlCache_REQUESTEDURL +" text, "+COLUMN_NAME_UrlCache_FILENAME+" text "+");";


 public boolean addRequestedURL(String time,String date,String client_ip,String client_mac,String url,String file_name)
{
    Log.d("Client mac db", client_mac);

    SQLiteDatabase db = this.getWritableDatabase();
    ContentValues contentValues = new ContentValues();
    contentValues.put(this.COLUMN_NAME_UrlCache_TIME, time);
    contentValues.put(this.COLUMN_NAME_UrlCache_DATE, date);
    contentValues.put(this.COLUMN_NAME_UrlCache_CLIENTIP, client_ip);
    contentValues.put(this.COLUMN_NAME_UrlCache_CLIENTMAC, client_mac);
    contentValues.put(this.COLUMN_NAME_UrlCache_REQUESTEDURL, url);
    contentValues.put(this.COLUMN_NAME_UrlCache_FILENAME, file_name);
    db.insert(TABLE_NAME_UrlCache, null, contentValues);

    return true;
}


public boolean FileFromUrlAlreadyRequested(String url)
    {

        SQLiteDatabase db = this.getReadableDatabase();

        try
        {
            Cursor cursor = db.rawQuery("select requestedurl from "+ TABLE_NAME_UrlCache, null);


            try {

                if (cursor.moveToFirst())
                {
                    do
                    {

                        String retrieved_url = cursor.getString(cursor.getColumnIndex(DBManager.COLUMN_NAME_UrlCache_REQUESTEDURL));
                        String retrieved_id = cursor.getString(cursor.getColumnIndex(DBManager.COLUMN_NAME_UrlCache_CLIENTMAC));

                        if (retrieved_url.equals(url))
                        {
                            this.setID(retrieved_id);
                            return true;
                        }

                    } while (cursor.moveToNext());
                }

            }
            finally
            {
                try
                {
                    cursor.close();
                }
                catch (Exception ignore) {}
            }

        }
        finally
        {
            try
            {
                db.close();
            } catch (Exception ignore) {}
        }

        return false;

    }

这是错误：

java.lang.IllegalStateException: Couldn't read row 0, col -1 from CursorWindow.  Make sure the Cursor is initialized correctly before accessing data from it.
                                                                      at android.database.CursorWindow.nativeGetString(Native Method)
                                                                      at android.database.CursorWindow.getString(CursorWindow.java:438)
                                                                      at android.database.AbstractWindowedCursor.getString(AbstractWindowedCursor.java:51)
                                                                      at com.android.python27.DBManager.FileFromUrlAlreadyRequested(DBManager.java:427)
                                                                      at com.android.python27.Download$GetRequestedURLAsyncTask.onPostExecute(Download.java:267)
                                                                      at com.android.python27.Download$GetRequestedURLAsyncTask.onPostExecute(Download.java:193)
                                                                      at android.os.AsyncTask.finish(AsyncTask.java:631)
                                                                      at android.os.AsyncTask.access$600(AsyncTask.java:177)
                                                                      at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:644)
                                                                      at android.os.Handler.dispatchMessage(Handler.java:99)
                                                                      at android.os.Looper.loop(Looper.java:137)
                                                                      at android.app.ActivityThread.main(ActivityThread.java:4867)
                                                                      at java.lang.reflect.Method.invokeNative(Native Method)
                                                                      at java.lang.reflect.Method.invoke(Method.java:511)
                                                                      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1007)
                                                                      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:774)
                                                                      at dalvik.system.NativeStart.main(Native Method)

当我尝试在这里检索mac地址时它崩溃了：

String retrieved_id = cursor.getString(cursor.getColumnIndex(DBManager.COLUMN_NAME_UrlCache_CLIENTMAC));

我检查了Lod.d以查看我是否成功传递了变量，因为我可以看到新记录是成功创建的。

任何建议都会有所帮助并深表感激。

Answer 1

您尝试阅读DBManager.COLUMN_NAME_UrlCache_CLIENTMAC列，但不在投影列表中。

更改您的SQL查询以同时选择DBManager.COLUMN_NAME_UrlCache_CLIENTMAC和DBManager.COLUMN_NAME_UrlCache_REQUESTEDURL。

Answer 2

您的变量被声明为“私有”，这意味着它只能在课程中访问，请尝试将其更改为“公共”。

SQLite错误：无法从CursorWindow读取第0行，col -1

2 个答案: