在Android中使用游标表联盟 [英] Union of Tables with Cursor in Android

问题描述

我试图联合与同一领域的两个表创建我使用创建我的ListView单个光标（通过内容提供商）。

  @覆盖
 公共光标查询（URI URI，字符串[]投影，字符串的选择，
   的String [] selectionArgs两个，字符串中将sortOrder）{  SQLiteQueryBuilder QB =新SQLiteQueryBuilder（）;
  字符串GROUPBY = NULL;  开关（sUriMatcher.match（URI））{  案例清单：
   StringBuilder的SB =新的StringBuilder（）;   对于（一个String：投影）
    sb.append（多个）.append（，）;   串projectionStr = sb.toString（）;
   projectionStr = projectionStr.substring（0，
     projectionStr.length（） -  1）;   的String [] =子查询新的String [] {
     SELECT+ projectionStr +FROM+ Customer.TABLE_NAME，
     SELECT+ projectionStr +FROM
       + IndividualCustomer.TABLE_NAME};
   SQL字符串= qb.buildUnionQuery（子查询中将sortOrder，NULL）;
   SQLiteDatabase分贝= mDatabaseHelper.getReadableDatabase（）;
   光标mCursor = db.rawQuery（SQL，NULL）;   mCursor.setNotificationUri（的getContext（）getContentResolver（），URI）;   返回mCursor;
 

即使两个表是空的，我得到两个空行，这在我的列表视图创建两行。我该如何摆脱这个问题的？

此外，当我从ListView中删除一行，光标没有得到尽管setNotificationUri的更新（）

任何指针，将AP最多preciated

解决方案

解决 - 我不得不子句中的列之一，提供一组（投影）有一个TOTAL（...）功能<。 / p>

I am trying to UNION two tables with the same fields to create a single cursor (through a content provider) that I am using to create my ListView.

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

  SQLiteQueryBuilder qb = new SQLiteQueryBuilder();
  String groupBy = null;

  switch (sUriMatcher.match(uri)) {

  case LIST:
   StringBuilder sb = new StringBuilder();

   for (String s : projection)
    sb.append(s).append(",");

   String projectionStr = sb.toString();
   projectionStr = projectionStr.substring(0,
     projectionStr.length() - 1);

   String[] subQueries = new String[] {
     "SELECT " + projectionStr + " FROM " + Customer.TABLE_NAME,
     "SELECT " + projectionStr + " FROM "
       + IndividualCustomer.TABLE_NAME };
   String sql = qb.buildUnionQuery(subQueries, sortOrder, null);
   SQLiteDatabase db = mDatabaseHelper.getReadableDatabase();
   Cursor mCursor = db.rawQuery(sql, null);

   mCursor.setNotificationUri(getContext().getContentResolver(), uri);

   return mCursor;

Even if the two tables are empty, I get two null rows, which creates two rows in my listview. How do I get rid of this problem?

Additionally, when I delete a row from the ListView, the cursor is not getting updated in spite of setNotificationUri()

Any pointers, will be most appreciated

解决方案

Solved - I had to supply a group by clause as one of the columns (of the projection) had a "TOTAL(...)" function.

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