Android：如何使用ContextResolver在sqlite中進行內部聯接查詢？

Question

我想創建一個sqlite游標，您可以使用contextResolver處理內部聯接查詢。

這是我當前的光標：

Cursor cursor = getContentResolver().query(Exercise.CONTENT_URI, new String[]{Exercise.Columns._ID, Exercise.Columns.EXERCISE_NAME, Exercise.Columns.DONE_LAST},
            "",null, Exercise.Columns.DONE_LAST);

我的新Cusor應該處理以下內容：

private final String MY_QUERY =
                "SELECT a."+Exercise.Columns.EXERCISE_NAME+", a."+Exercise.Columns.DONE_LAST+", b."+Progress.Columns.WEIGHT+", " +
                "b."+Progress.Columns.SETS+", b."+Progress.Columns.REPITITIONS+" " +
                "FROM "+Exercise.TABLE_NAME+" a " +
                "INNER JOIN "+Progress.TABLE_NAME+" b " +
                "ON a.+"+Exercise.Columns._ID+" = b."+Progress.Columns._ID +
                "WHERE b.+"+Progress.Columns.WHENDONE+" = ( Select MAX (b."+Progress.Columns.WHENDONE+") from b";

如果在SOV中找到了一些解決方案-它們都使用rawQuery，但我的活動中沒有SQLiteOpenHelper對象。 那么還有另一種解決方案，通過getContentResolver（）執行此查詢嗎？

Answer 1

您將在兩個數據庫表上創建一個持久性視圖。 然后從內容提供者訪問視圖。 您也可以創建視圖（如果該視圖不存在），但它的效率不如已構建的視圖。

private static final String VERSION_66_CREATE_VIEW = "CREATE VIEW IF NOT EXISTS "
        + VIEW_MARKERS
        + " AS SELECT "
        + TABLE_MARKERS
        + "."
        + KEY_ID
        + ", "
        + TABLE_MARKERS
        + "."
        + KEY_MARKER_LOCATION_ID
        + ", "
        + TABLE_MARKERS
        + "."
        + KEY_MARKER_IMAGE_ID
        + ", "
        + TABLE_MARKERS
        + "."
        + KEY_MARKER_SNIPPET
        + ", "
        + TABLE_MARKERS
        + "."
        + KEY_MARKER_IMAGE_PROCESSED_ID
        + ", "
        + TABLE_MARKERS
        + "."
        + KEY_MARKER_IMAGE_URL
        + ", "
        + TABLE_MARKERS
        + "."
        + KEY_MARKER_IMAGE_URL_THUMBLARGE
        + ", "
        + TABLE_MARKERS
        + "."
        + KEY_MARKER_IMAGE_URL_THUMBMEDIUM
        + ", "
        + TABLE_MARKERS
        + "."
        + KEY_MARKER_IMAGE_URL_THUMBSMALL
        + ", "
        + TABLE_MARKERS + "." + KEY_MARKER_TITLE + ", "
        + TABLE_MARKERS + "." + KEY_MARKER_ALBUM_ID + ", "
        + TABLE_LOCATIONS
        + "."
        + KEY_LOCATION_LATITUDE
        + ", "
        + TABLE_LOCATIONS
        + "."
        + KEY_LOCATION_LONGITUDE
        + ", "
        + TABLE_LOCATIONS
        + "."
        + KEY_LOCATION_ACCURACY
        + ", "
        + TABLE_LOCATIONS
        + "."
        + KEY_LOCATION_ALTITUDE
        + ", "
        + TABLE_LOCATIONS
        + "."
        + KEY_LOCATION_BEARING
        + ", "
        + TABLE_LOCATIONS
        + "."
        + KEY_LOCATION_PROVIDER
        + ", "
        + TABLE_LOCATIONS
        + "."
        + KEY_LOCATION_SPEED
        + ", "
        + TABLE_LOCATIONS
        + "."
        + KEY_LOCATION_TIME
        + " FROM "
        + TABLE_MARKERS
        + " JOIN "
        + TABLE_LOCATIONS
        + " ON "
        + TABLE_MARKERS
        + "."
        + KEY_MARKER_LOCATION_ID
        + " = "
        + TABLE_LOCATIONS + "." + KEY_ID;

 db.execSQL(VERSION_66_CREATE_VIEW);

訪問ContentProvider中的視圖

@Override
public Cursor query(Uri uri, String[] projection, String selection,
                    String[] selectionArgs, String sortOrder) {


    // Uisng SQLiteQueryBuilder instead of query() method
    SQLiteQueryBuilder queryBuilder = new SQLiteQueryBuilder();

    // check if the caller has requested a column which does not exists

    // Set the table

    int uriType = sURIMatcher.match(uri);
    switch (uriType) {
        case MARKERS:
            // create the view here if you can't change it in the database.
            checkColumns(availableMarkers, projection);
            queryBuilder.setTables(RidesDatabaseHandler.VIEW_MARKERS);
            break;

 ...

 SQLiteDatabase db = database.getWritableDatabase();
    Cursor cursor = queryBuilder.query(db, projection, selection,
            selectionArgs, null, null, sortOrder);
    // make sure that potential listeners are getting notified
    cursor.setNotificationUri(getContext().getContentResolver(), uri);
    return cursor;