android - 如何从行号获取游标

Question

我在 android 开发中使用 SQLite。当我使用 insert 插入一行时，我得到了行号。但是，我想要作为表主键的 KEY_ID。我使用了下面的函数，但我得到了:

Caused by: java.lang.IllegalStateException: get field slot from row 0 col -1 failed
    at android.database.CursorWindow.getLong_native(Native Method)
    at android.database.CursorWindow.getInt(CursorWindow.java:434)
    at android.database.AbstractWindowedCursor.getInt(AbstractWindowedCursor.java:93)
    at winterfarmer.timemama.DataBaseAdapter.insertData(DataBaseAdapter.java:89)
    at winterfarmer.timemama.ManagerActivity.addNewRecord2DB(ManagerActivity.java:106)
    at winterfarmer.timemama.ManagerActivity.addNewRecord(ManagerActivity.java:100)
    at winterfarmer.timemama.ManagerActivity.addNewRecord2DB(ManagerActivity.java:106)
    at winterfarmer.timemama.ManagerActivity.addNewRecord(ManagerActivity.java:100)
    at winterfarmer.timemama.ManagerActivity.setRecordOK(ManagerActivity.java:92)
    at winterfarmer.timemama.ManagerActivity.setRecord(ManagerActivity.java:78)
    at winterfarmer.timemama.ManagerActivity.onActivityResult(ManagerActivity.java:64)
    at android.app.Activity.dispatchActivityResult(Activity.java:3890)
    at android.app.ActivityThread.deliverResults(ActivityThread.java:3511)

我该如何修复这个错误？

public int insertData(RecordInfo recordInfo) {
    Log.d(TAG, "insertData");

    ContentValues initialValues = new ContentValues();

    initialValues.put(KEY_HOUR, recordInfo.hour);
    initialValues.put(KEY_MINUTE, recordInfo.minute);
    initialValues.put(KEY_REPEAT, recordInfo.repeat);

    long rowId = db.insert(DB_ALARM_TABLE, null, initialValues);
    assert rowId >= 0 : "insertData failed";
    Log.d(TAG, "insertData, rowId = " + rowId);
    Cursor cur = db.rawQuery("SELECT last_insert_rowid() from "
            + DB_ALARM_TABLE, null);
    cur.moveToFirst();
    int colId = cur.getColumnIndex(KEY_ID);
    Log.d(TAG, "insertData, colId = " + colId);
    assert colId >= 0 : "insertData failed";
    return cur.getInt(colId);
}

Answer 1

来自游标文档:

public abstract int getColumnIndex (String columnName)

Since: API Level 1 Returns the zero-based index for the given column name, or -1 if the column doesn't exist. If you expect the column to exist use getColumnIndexOrThrow(String) instead, which will make the error more clear

这样可以更好地解释问题。

无论如何，回到您的实际问题:

问题是 KEY_ID 不是您选择查询的结果列(结果不会命名为 KEY_ID，即使该值最初来自 KEY_ID 列)。它只有一列结果，因此要求列索引没有意义。 colId 将为 0。您可以直接执行:

Cursor cur = db.rawQuery("SELECT last_insert_rowid() from "
        + DB_ALARM_TABLE, null);
cur.moveToFirst();
return cur.getInt(0);