Android: 如何使用 ContextResolver 在 sqlite 中进行内连接查询？

Question

我想创建一个 sqlite 游标，您可以使用 contextResolver 处理内部连接查询。

这是我当前的光标：

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 应该处理这样的事情：

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 中找到一些解决方案 - 它们都使用 rawQuery，但我的 activity 中没有 SQLiteOpenHelper 对象。那么是否有另一种解决方案，通过 getContentResolver() 执行此查询？

Answer 1

您将在两个数据库表上创建持久视图。然后从内容提供者访问视图。如果视图不存在，您也可以创建它，但效率不如已经构建的视图。

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);

访问 ContentProvider 中的视图

@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;

Android: 如何使用 ContextResolver 在 sqlite 中进行内连接查询？

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