android java.lang.IllegalStateException : Couldn't read row 0, col 0 来自 CursorWindow

Question

我正在开发一个应用程序，它下载一些文件并将它们的文本保存在 file_content 字段到数据库中。文件大小可以从几 KB 到 10 MB 不等。该应用程序适用于所有尺寸，同时保存。对长 file_content 记录使用 select 语句时会出现问题。它给了

java.lang.IllegalStateException: Couldn't read row 0, col 0 from CursorWindow

在获取此类行时。字段内容大小是否有任何限制？如果是这样，那么为什么它让我们在检索时保存并给出错误？这是我截取的获取行的代码:

public String getFileContent(MyFile gc) {
        if(!isDBOpen()) {
            open();
        }
        try {
            String mQuery = "SELECT * FROM " + DBOpenHelper.TABLE_SAVED_FILES + " WHERE " + DBOpenHelper.COLUMN_ID + " = " + gc.id;
            Cursor mCursor = database.rawQuery(mQuery, null);
            if(mCursor.getCount() <= 0) {
                return null;
            }
            if(mCursor.moveToFirst()) {
                return getCursorRowContent(mCursor);
            }
        } catch (Exception e) {
            e.getMessage();
        }
        return null;
    }

    private String getCursorRowContent(Cursor mCursor) throws Exception {
        return mCursor.getString(mCursor.getColumnIndex(DBOpenHelper.COLUMN_FILE_CONTENT));
    }

知道发生了什么吗？我已经在 2 到 3 台设备上对其进行了测试。

Logcat 输出:

01-29 13:41:56.520: W/CursorWindow(4121): Window is full: requested allocation 5140987 bytes, free space 2096617 bytes, window size 2097152 bytes
01-29 13:41:56.520: E/CursorWindow(4121): Failed to read row 0, column 0 from a CursorWindow which has 0 rows, 9 columns.

01-29 13:43:30.932: W/System.err(4121): java.lang.IllegalStateException: Couldn't read row 0, col 0 from CursorWindow.  Make sure the Cursor is initialized correctly before accessing data from it. 
01-29 13:43:30.932: W/System.err(4121):     at android.database.CursorWindow.nativeGetLong(Native Method) 
01-29 13:43:30.932: W/System.err(4121):     at android.database.CursorWindow.getLong(CursorWindow.java:507) 
01-29 13:43:30.932: W/System.err(4121):     at android.database.AbstractWindowedCursor.getLong(AbstractWindowedCursor.java:75) 
01-29 13:43:30.936: W/System.err(4121):     at android.database.AbstractCursor.moveToPosition(AbstractCursor.java:220) 
01-29 13:43:30.936: W/System.err(4121):     at android.database.AbstractCursor.moveToNext(AbstractCursor.java:245) 
01-29 13:43:30.940: W/System.err(4121):     at com.nxb.cachehead.bl.PocketQueryDataSource.getGeoCacheContent(PocketQueryDataSource.java:97) 01-29 13:43:30.940: W/System.err(4121):     at com.nxb.cachehead.bl.GPXFileCopyAsyncTask.doInBackground(GPXFileCopyAsyncTask.java:27) 
01-29 13:43:30.940: W/System.err(4121):     at com.nxb.cachehead.bl.GPXFileCopyAsyncTask.doInBackground(GPXFileCopyAsyncTask.java:1) 
01-29 13:43:30.940: W/System.err(4121):     at android.os.AsyncTask$2.call(AsyncTask.java:287) 
01-29 13:43:30.944: W/System.err(4121):     at java.util.concurrent.FutureTask.run(FutureTask.java:234) 
01-29 13:43:30.944: W/System.err(4121):     at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:230) 
01-29 13:43:30.948: W/System.err(4121):     at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1080) 
01-29 13:43:30.948: W/System.err(4121):     at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:573) 
01-29 13:43:30.948: W/System.err(4121):     at java.lang.Thread.run(Thread.java:856)

Answer 1

01-29 13:41:56.520: W/CursorWindow(4121): Window is full: requested allocation 5140987 bytes, free space 2096617 bytes, window size 2097152 bytes

Android SQLite 在光标窗口中返回最大大小为 2MB 的行，由 config_cursorWindowSize 指定。 .如果您的行超过此限制，您将收到此错误。

无论如何，在 sqlite 数据库中存储大数据并不是一个好主意。将文件存储在文件系统中，将路径存储在数据库中。