游标、SQLite 和查询 [英] Cursors, SQLite, and queries
问题描述
我在我的应用程序中实现了一个 sqlite 数据库，并且在启动时不断收到 IllegalStateException.
I have a sqlitedatabase I'm implementing within my app and I keep receiving an IllegalStateException when launching.
09-21 22:48:26.749 15762-16277/nz.co.exium.panther E/AndroidRuntime﹕ FATAL EXCEPTION: SyncAdapterThread-2
java.lang.IllegalStateException: Couldn't read row 0, col 4 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 android.database.CursorWrapper.getString(CursorWrapper.java:114)
at nz.co.exium.panther.sync.PantherSyncAdapter.getRegistrationId(PantherSyncAdapter.java:269)
at nz.co.exium.panther.sync.PantherSyncAdapter.onPerformSync(PantherSyncAdapter.java:64)
at android.content.AbstractThreadedSyncAdapter$SyncThread.run(AbstractThreadedSyncAdapter.java:254)
我相信这是由于查询返回一个相当空的表(自动递增的 _ID 除外)，然后当我尝试从游标中获取字符串时引起的.
I believe this is caused by the query returning a fairly empty table (except for _ID that is autoincremented) and then when I attempt to get a String from the cursor.
String registrationID = "";
Uri uri = CustomerEntry.CONTENT_URI;
Cursor cursor = mContext.getContentResolver().query(uri, CUSTOMER_PROJECTION, null, null, null);
if (cursor.moveToFirst()) {
registrationID = cursor.getString(INDEX_CUST_REGID);
}
SQL 创建表调用:
final String SQL_CREATE_CUSTOMER_TABLE = "CREATE TABLE " + CustomerEntry.TABLE_NAME + " (" +
CustomerEntry._ID + " INTEGER PRIMARY KEY AUTOINCREMENT, " +
CustomerEntry.COLUMN_CUST_NAME + " TEXT NOT NULL, " +
CustomerEntry.COLUMN_CUST_EMAIL + " TEXT NOT NULL, " +
CustomerEntry.COLUMN_CUST_QRHASH + " TEXT NOT NULL," +
CustomerEntry.COLUMN_CUST_REGID + " TEXT NOT NULL)";
在这种情况下，INDEX_CUST_REGID 是与 String[] 投影中的位置相关的最终静态 int，在这种情况下是第三个位置.这会抛出是有道理的，但是是否有一种方法或方法可以查询 SyncAdapter 以获取特定列(如 CUST_REGID)，或者在尝试使用 cursor.getString() 之前检查请求的列是否已返回的方法?
In this case, the INDEX_CUST_REGID is a final static int related to the position in the String[] projection, 3rd position in this case. It makes sense this would throw but is there a method or way to query the SyncAdapter for a specific column like the CUST_REGID or a method to check if the Column requested was returned before attempting a cursor.getString()?
这也可能解决我在知道 EMAIL、NAME、QRHASH 之前保存 Reg ID 的另一个问题.不能只插入一列而其余列也没有值(NOT NULL)，即使它是毫无价值的数据并尽快被覆盖.
This also might solve another problem I have with saving the Reg ID before knowing the EMAIL, NAME, QRHASH. Can't insert just one column without the rest having a value as well (NOT NULL), even though it would be worthless data and overwritten asap.
尝试存储注册 ID 的方法.
Method attempting to store Reg ID.
private void storeRegistrationID(Context context, String regID) {
//DB insert regid
ContentValues cValues = new ContentValues();
cValues.put(CustomerEntry.COLUMN_CUST_NAME, "");
cValues.put(CustomerEntry.COLUMN_CUST_EMAIL, "");
cValues.put(CustomerEntry.COLUMN_CUST_QRHASH, "");
cValues.put(CustomerEntry.COLUMN_CUST_REGID, regID);
mContext.getContentResolver().insert(CustomerEntry.CONTENT_URI, cValues);
}
按要求投影:
String[] CUSTOMER_PROJECTION = new String[]{
CustomerEntry._ID,
CustomerEntry.COLUMN_CUST_NAME,
CustomerEntry.COLUMN_CUST_EMAIL,
CustomerEntry.COLUMN_CUST_QRHASH,
CustomerEntry.COLUMN_CUST_REGID
};
推荐答案
您确定该表是实际创建的吗?SQL_CREATE_CUSTOMER_TABLE 文本字符串的末尾缺少一个分号 - 尽管我不确定是否必须运行 sql 来创建表.我建议在 Eclipse 模拟器上运行它，然后从 DDMS 的角度来看，在某个地方复制数据库，在那里你可以使用 Firefox 的 SQLite Manager 插件打开它 - 这将显示数据库表.
Are you certain the table was actually created? There's a semi-colon mising from the end of your SQL_CREATE_CUSTOMER_TABLE text string - although I'm not sure if it is mandatory to run the sql for creating the table. I would suggest running it on the Eclipse emulator, then from the DDMS perspective, take a copy of the database somewhere where you can open it with the SQLite Manager plugin for Firefox - this will show you the database tables.
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