android - 在 Android Studio 中用数据库中的两个表填充 ListView

Question

我有两张 table 。 tblsubject 和 tbltopics。我想列出所有主题以及每个主题的主题数。

getSubject()

public Cursor getAllSubject() {
    String where = null;
    Cursor c =  db.query(true, DATABASE_TABLE, ALL_KEYS, where, null, null, null, null, null);
    if (c != null) {
        c.moveToFirst();
    }
    return c;
}

countTopics()

public int countTopics(long subjectid) {
    String where = KEY_TOPICSUBJECTID + " = " +  subjectid;
    Cursor c = db.query(true, DATABASE_TABLE2, ALL_KEYS2,
            where, null, null, null, null, null);
    if (c != null) {
        c.moveToFirst();
    }
    return c.getCount();
}

viewList() 这是我填充 ListView 的地方

@TargetApi(Build.VERSION_CODES.HONEYCOMB)
public void viewList() {
    Cursor cursor = myDb.getAllSubject();
    String[] fromFieldNames = new String[]{DBAdapter.KEY_SUBJECTID, DBAdapter.KEY_SUBJECT, DBAdapter.KEY_DATESUBJECT};
    int[] toViewIds = new int[]{R.id.txtViewSubjectId, R.id.txtViewSubject, R.id.txtSubjectDateCreated};
    SimpleCursorAdapter myCursorAdapter;
    myCursorAdapter = new SimpleCursorAdapter(getBaseContext(), R.layout.activity_view_the_list, cursor, fromFieldNames, toViewIds, 0);
    ListView myList = (ListView) findViewById(R.id.listView);
    myList.setAdapter(myCursorAdapter);
}

我的问题是如何添加每个主题的主题数。我可以显示主题。谢谢。

Answer 1

您可以使用表中的 UNION 运行直接原始 sql。像这样:

String select = "Select * FROM table1 UNION Select * FROM table2";

Cursor c = return db.rawQuery(select, new String[]{});