[英]Updated table, but isn't returning the correct value
可能很簡單,但花了我很長時間才能弄清楚。
我想保存等級欄等級,然后在重新打開活動時加載該等級。 但是它總是返回0。
我有一個帶有評分列的配方表:
final String CREATE_TABLE_RECIPES = "CREATE TABLE IF NOT EXISTS " +
TABLE_RECIPES + "(" +
RECIPE_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, " +
RECIPE_NAME + " TEXT, " +
RECIPE_INSTRUCTIONS + " TEXT, " +
RECIPE_RATING + " FLOAT " +
")";
我有一個onRatingBarChange偵聽器,將評分保存到表中:
(id和rating的值正確)
ratingbar.setOnRatingBarChangeListener(new RatingBar.OnRatingBarChangeListener() {
@Override
public void onRatingChanged(RatingBar ratingBar, float rating, boolean fromUser) {
db.addRating(id, rating);
}
});
db類中的addRating方法:
public void addRating(int id, float rating) {
String SET_RATING =
"UPDATE " + TABLE_RECIPES +
" SET " + RECIPE_RATING + " = " + rating +
" WHERE " + RECIPE_ID + " = " + id;
SQLiteDatabase db = this.getWritableDatabase();
db.rawQuery(SET_RATING, null);
db.close();
}
最后是db類中的getRating方法:
public float getRating(int id) {
String GET_RATING =
"SELECT " + RECIPE_RATING +
" FROM " + TABLE_RECIPES +
" WHERE " + RECIPE_ID + " = " + id;
SQLiteDatabase db = this.getReadableDatabase();
Cursor c = db.rawQuery(GET_RATING, null);
c.moveToFirst();
float rating = c.getFloat(0);
Log.i("getRating", "gotRating: " + rating);
return rating;
}
返回的等級始終為0,因此它未正確保存或未正確獲得該值。
db.rawQuery(SET_RATING, null);
您應該將execSQL()
用於UPDATE
查詢,而不是rawQuery()
。 (或便捷包裝之一,例如update()
。)
rawQuery()
編譯基礎SQL但不執行它; execSQL()
編譯並運行SQL。
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