Question

我是SQLite的新手，我试图按降序对我的COLUMN_PRICE进行排序并显示结果。我已经搜索了有关该主题的答案，但是到目前为止，对于我的情况，仍然没有帮助（甚至使用原始查询String selectQuery = "SELECT * FROM "+ TABLE_NAME + " ORDER BY " + COLUMN_PRICE + " DESC";）。

或者，如何在列表视图中对SQLite输出进行排序-更好的选择。

请在下面查看我当前的方法：

private void sortByPrice() {
    Cursor rowsOrdered = getContentResolver().query(Contract.Entry.CONTENT_URI, null, null, null,  COLUMN_PRICE + " DESC", null);
    Log.v("CatalogActivity", rowsOrdered + " rows ordered by price from database");
}

在这里从以下位置调用该方法：

   @Override
    public boolean onOptionsItemSelected(MenuItem item) {
       //sort by price from lowest upon the button click
            case R.id.action_sort_by_price:
                sortByPrice();
              return true;
        }
        return super.onOptionsItemSelected(item);
    }

我在Provider中的游标查询如下：

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

        boolean useAuthorityUri = false;

// Get readable database
        SQLiteDatabase database = mDbHelper.getReadableDatabase();
// This cursor will hold the result of the query
        Cursor cursor;
// Figure out if the URI matcher can match the URI to a specific code
        int match = sURIMatcher.match(uri);
        switch (match) {
            case PRODUCT:
// For the PRODUCT code, query the table directly with the given
// projection, selection, selection arguments, and sort order. The cursor
// could contain multiple rows of table.
                cursor = database.query(InventoryEntry.TABLE_NAME,
                        projection, selection, selectionArgs, null, null,
                        sortOrder);
                break;
            case PRODUCT_ID:
                // For the PRODUCT_ID code, extract out the ID from the URI.
// For every "?" in the selection, we need to have an element in the selection
// arguments that will fill in the "?". Since we have 1 question mark in the
                // selection, we have 1 String in the selection arguments' String array.

                selection = Entry._ID + "=?";
                selectionArgs = new String[]{String.valueOf((ContentUris.parseId(uri)))};
//query

                cursor = database.query(Entry.TABLE_NAME,
                        projection,
                        selection,
                        selectionArgs,
                        null,
                        null,
                        sortOrder);
                break;
            default:
                throw new IllegalArgumentException("No match found");
        }


        // notify all listeners of changes:
        // getContext().getContentResolver().notifyChange(uri, null);
        // if we want to be notified of any changes:
        if (useAuthorityUri) {
            cursor.setNotificationUri(
                    getContext().getContentResolver(),
                    InventoryContract.BASE_CONTENT_URI);
        } else {
            cursor.setNotificationUri(
                    getContext().getContentResolver(),
                    uri);
        }

        return cursor;

    }

日志中没有错误（Log.v.中的消息按预期显示，尽管在应用程序中单击按钮时未发生任何事情。）

我在哪里做错了什么？

非常感谢您的帮助！

P.S。如我所知，我在Catalog Activity中的方法不起作用，因为它在Provider中没有覆盖主要方法（如果我在那进行排序，它可以工作，但是默认情况下是排序，而不是单击按钮）。如何在单击按钮时添加我的排序方法，并在提供者中保留默认顺序？

ORDER BY DESC-按钮单击时的SQLite查询-使用getContentResolver（）-Java Android

0 个答案: