GROUP BY与CursorLoader [英] GROUP BY with CursorLoader

问题描述

如何定义一个 GROUP BY 查询我CursorLoader？

How do I define a GROUP BY query for my CursorLoader?

这两个构造为 CursorLoader 我看拿一个单上下文或背景，乌里，预测，选择， selectionArgs两个和排序顺序。

The two constructors for a CursorLoader I see take either a single Context or a Context, Uri, projection, selection, selectionArgs and sortOrder.

但是，没有 GROUPBY 。

（我用的是Android 2.3设备的支持包）

(I'm using the support package for a Android 2.3 device)

推荐答案

不是真的...

您可以定义一个特定的URI您的具体GROUP BY子句。

You can define a specific URI to your specific GROUP BY clause.

例如，如果你有一个表mPersonTable，可能是按性别分组，您可以定义以下的URI：

For example, if you have a table mPersonTable, possibly grouped by gender, you can define the following URIs:

PERSON
PERSON/#
PERSON/GENDER

您查询的查询时，切换使您可以通过参数添加组：

When querying, switch between your queries so you can add your group by parameter:

public Cursor query(Uri uri, String[] projection, String selection,
            String[] selectionArgs, String sortOrder) {
   String groupBy = null;
   switch (mUriMatcher.match(uri)) {
      case PERSON_ID:
         ...
         break;
      case PERSON_GENDER:
         groupBy = GENDER_COLUMN;
      case PERSON:
        SQLiteQueryBuilder builder = new SQLiteQueryBuilder();
        builder.setTables(mPersonTable);
        builder.setProjectionMap(mProjectionMap);
        return builder.query(db, projection, selection, selectionArgs, groupBy, having, sortOrder, limit);
      default:
         break;
   }
}

在事实上，你可以任何类型的参数传递到您的查询

In fact, you could pass any sort of parameters to your query

观测：使用UriMatcher到URI与您的查询实现匹配。

Obs.: Use a UriMatcher to match the uri with your query implementation.

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