如何将 3 个数据库合并为一个并在 ListView 上显示；答案

【问题标题】：How a merge 3 database lists to one and show it on a ListView;如何将 3 个数据库合并为一个并在 ListView 上显示；
【发布时间】：2019-12-05 19:16:15
【问题描述】：

我有 3 个数据库列表，我想将它们合并为一个并将数据显示到列表视图中，如下所示：

vathmoss + " " firstnames + " " +lastnames

现在我只显示名字...

Cursor c = database.rawQuery("Select * From " + PDFDatabaseManager.DATABASE_USERS_TABLE + ";", null);

        ArrayList<String> vathmoss = new ArrayList<>();
        ArrayList<String> firstnames = new ArrayList<>();
        ArrayList<String> lastnames = new ArrayList<>();

        while (c.moveToNext()) {
            vathmoss.add(c.getString(0));
            firstnames.add(c.getString(1));
            lastnames.add(c.getString(2));
        }
        c.close();

        final ListView listUser = (ListView) popup.findViewById(R.id.listview_user);

        if (!vathmoss.isEmpty() && !firstnames.isEmpty() && !lastnames.isEmpty()) {
            ArrayAdapter<String> adapter = new ArrayAdapter<String>(this.context, android.R.layout.simple_list_item_1,firstnames);
            listUser.setAdapter(adapter);

        }

【问题讨论】：

标签： android sql listview merge

【解决方案1】：

做这样的事情：

Cursor c = database.rawQuery("Select * From " + 
PDFDatabaseManager.DATABASE_USERS_TABLE + ";", null);

    ArrayList<String> vathmoss = new ArrayList<>();
    ArrayList<String> firstnames = new ArrayList<>();
    ArrayList<String> lastnames = new ArrayList<>();

    ArrayList<String> mergednames = new ArrayList<>();

    while (c.moveToNext()) {
        vathmoss.add(c.getString(0));
        firstnames.add(c.getString(1));
        lastnames.add(c.getString(2));

        mergednames.add(c.getString(0) + " " + c.getString(1) + " " + c.getString(2))
    }
    c.close();

    final ListView listUser = (ListView) popup.findViewById(R.id.listview_user);

    if (!vathmoss.isEmpty() && !firstnames.isEmpty() && !lastnames.isEmpty()) {

        //In the below line, pass mergednames instead of firstname as last parameter
        ArrayAdapter<String> adapter = new ArrayAdapter<String>(this.context, android.R.layout.simple_list_item_1,mergednames);
        listUser.setAdapter(adapter);

    }

【讨论】：