我创建了两个字符串变量'questionString'和'answerSetId' - 我已经分配给textview的第一个 - 第二个我要传递给我的db helper类:
public void showNextRandomQuestion3() {
SQLDatabaseHelper db = new SQLDatabaseHelper(this);
//get the data from the database
List<List<String>> listList = db.getAllAnswersByQuestion1();
//Get the question/text/answer Strings
List<String> questionStrings = listList.get(0); //question Strings
List<String> answerSetIds = listList.get(4);
//Generate random index
Random r = new Random();
int rand = Math.abs((r.nextInt() % questionStrings.size()));
//get answer description for randomly selected question
String questionString = questionStrings.get(rand);
String answerSetId = answerSetIds.get(rand);
questionView.setText(questionString);
}
在我的db helper类中,我想使用这个字符串变量作为我的查询的代码:
public List<List<String>> getAnswers() {
List<String> array1 = new ArrayList<String>();
List<String> array2 = new ArrayList<String>();
SQLiteDatabase db = this.getReadableDatabase();
String selectQuery = "SELECT * FROM " + TABLE_ANSWERS + "WHERE " + ASID
+ " = " + ??answerSetId??;
Cursor c = db.rawQuery(selectQuery, null);
if (c.moveToFirst()) {
do {
String textdescr = c.getString(c.getColumnIndex(TDESCR));
String answersdescr = c.getString(c.getColumnIndex(ADESCR));
array1.add(textdescr);
array2.add(answersdescr);;
} while (c.moveToNext());
}
List< List<String> > listArray2 = new ArrayList< List<String> >();
listArray2.add(array1);
listArray2.add(array2);
return listArray2;
}
实现这一目标的最佳方式是什么?
答案 0 :(得分:0)
要执行SELECT,您可以使用this method
query(String table, String[] columns, String selection, String[] selectionArgs, String groupBy, String having, String orderBy)
而不是原始查询。在你的情况下:
String selection = ASID+"=?";
String selectionArgs[] = new String[]{String.valueOf(answerSetId)};
Cursor c = db.query(TABLE_ANSWERS, null, selection, selectionArgs, null, null, null);
您还可以选择一些特定的列,将列名称作为第二个参数传递(insted为null)。此外,您可以替换示例中的最后三个空值,以添加GROUP BY
,HAVING
和ORDER BY
子句。
例如,在您的查询中,您只对两列TDESCR和ADESCR感兴趣。所以你可以使用这个查询:
String[] columns = new String[]{TDESCR, ADESCR};
String selection = ASID+"=?";
String[] selectionArgs = new String[]{String.valueOf(answerSetId)};
Cursor c = db.query(TABLE_ANSWERS, columns, selection, selectionArgs, null, null, null);
还有很多其他覆盖方法查询。请查看文档here
但是,如果您愿意,可以通过以下方式执行原始查询:
String queryString = "SELECT * FROM " + TABLE_ANSWERS +
" WHERE "+ASID+"=?";
String[] selectionArgs = new String[]{String.valueOf(answerSetId)};
sqLiteDatabase.rawQuery(queryString, selectionArgs);