Android-SQLite 使用 SQLiteOpenHelper (六)_查詢資料( Select )

此篇說明如何查詢對應的結果

1 . 全部結果查詢

private static final String TABLE_CONTACTS = "counter";
private static final String KEY_DATE = "count_date";
private static final String KEY_NUMBER = "count_number";
private static final String KEY_NOTE = "count_note";

/**
 * 取得所有資料
 *
 * @return
 */
public List<Map<String, Object>> getAllData() {
    
    List<Map<String, Object>> listData = new ArrayList<Map<String, Object>>();
    // 查詢條件
    String strSelect = "SELECT  * FROM " + TABLE_CONTACTS;
    SQLiteDatabase db = this.getWritableDatabase();
    Cursor cursor = db.rawQuery(strSelect, null);
    if (cursor.moveToFirst()) {
        do {
            Map<String, Object> mapData = new HashMap<String, Object>();
            mapData.put(KEY_ID, cursor.getString(0));
            mapData.put(KEY_DATE, cursor.getString(1));
            mapData.put(KEY_NUMBER, cursor.getString(2));
            mapData.put(KEY_NOTE, cursor.getString(3));
            listData.add(mapData);
        } while (cursor.moveToNext());
    }

    return listData;
}

2 . 查詢條件結果

private static final String TABLE_CONTACTS = "counter";
private static final String KEY_DATE = "count_date";
private static final String KEY_NUMBER = "count_number";
private static final String KEY_NOTE = "count_note";

/**
 * 取得當日資料
 *
 * @return
 */
public Map<String, Object> getCurrentData(@NonNull Date mDate) {

    DateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
    Map<String, Object> mapData = new HashMap<String, Object>();
    // 查詢條件
    String selectQuery = "SELECT  * FROM " + TABLE_CONTACTS + " WHERE " + KEY_DATE + " = ? ";
    String[] strVal = new String[]{sdf.format(mDate)};
    SQLiteDatabase db = this.getWritableDatabase();
    Cursor cursor = db.rawQuery(selectQuery, strVal);
    if (cursor.moveToFirst()) {
        do {
            mapData.put(KEY_ID, cursor.getString(0));
            mapData.put(KEY_DATE, cursor.getString(1));
            mapData.put(KEY_NUMBER, cursor.getString(2));
            mapData.put(KEY_NOTE, cursor.getString(3));
        } while (cursor.moveToNext());
    }

    return mapData;
}

查詢結果出來的容器 Cursor 是什麼？我要怎麼藉由此東西取出我要的值？
官方說明為

還是不懂怎辦？
可以把它想成是一種 Map
取出來的順序必須依照欄位的順序
不然會取不到對應的值

參考資料：時間區間格式

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