Question

我有两张桌子。 tblsubject和tbltopics。我想列出所有科目，每个科目都有主题数量。

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量。我可以显示主题。谢谢。

Answer 1

您可以使用子查询更新主题SQL语句，以从数据库返回主题计数。见https://robots.thoughtbot.com/back-to-basics-sql#sub-queries

另外，我建议您使用自己的自定义AsyncTask和ArrayAdapter。

http://developer.android.com/guide/topics/ui/layout/listview.html

这将使您的UI更具响应性，并允许您自定义数据访问和呈现。

通过使用自定义适配器，您可以覆盖getView函数来控制结果并执行其他提取。例如，延迟将图像加载到列表视图显示中。

@Override
public View getView(int position, View convertView, ViewGroup parent) {

    View v = convertView;
    if (v == null) {
        LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        v = inflater.inflate(R.layout.subjectitem, null);
    }

    if (position % 2 == 1) {            
        v.setBackgroundColor(Color.rgb(234, 234, 234));  
    } else {
        v.setBackgroundColor(Color.WHITE);  
    }              

    YOURDATAOBJECT p = itemList.get(position);
    TextView name = (TextView) v.findViewById(R.id.name);
    TextView topcount = (TextView) v.findViewById(R.id.topcount);

    //You can run our additional data fetches here and update the UI

Answer 2

您可以从表中使用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[]{});

在Android Studio

2 个答案: