Question

public class TabBooklist extends Fragment {

/* <DB> */
//variable use in DB->
int nCount=1;
SQLiteDatabase db;
BookListDBHelper helper;
ListView listview ;
BookListShowAdapter adapter;

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    View rootView = inflater.inflate(R.layout.tab_booklist, container, false);


    /* (XML) <Book list> */

    adapter = new BookListShowAdapter(getContext()) ;

    listview = (ListView) rootView.findViewById (R.id.lv_book_list);
    listview.setAdapter(adapter);

    adapter.addItem(ContextCompat.getDrawable(getActivity(), R.drawable.ic_empty),
            "name1", "author1", 110, 1200) ; //work
    adapter.addItem(ContextCompat.getDrawable(getActivity(), R.drawable.ic_empty),
            "name21", "author21", 210, 1003) ; //work
    adapter.addItem(ContextCompat.getDrawable(getActivity(),  R.drawable.ic_empty),
            "name31", "author31", 101, 1020) ; //work


    //refresh
    Button btn_ref = (Button) rootView.findViewById(R.id.btn_refresh);
    btn_ref.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) { //click to add
            select();
        }
    });

    return rootView;
}


//select
public void select() {
    nCount = 1;

    db = helper.getReadableDatabase();
    Cursor c = db.query("booklist", null, null, null, null, null, null);

    while (c.moveToNext()) {
        int int_idBook = c.getInt(c.getColumnIndex("id_book"));
        int int_idTree = c.getInt(c.getColumnIndex("id_tree"));
        String str_title = c.getString(c.getColumnIndex("title"));
        String str_author = c.getString(c.getColumnIndex("author"));
        String str_imageLink = c.getString(c.getColumnIndex("image_link"));
        int n_pageTotal = c.getInt(c.getColumnIndex("page_total"));

        //add
        adapter.addItem(ContextCompat.getDrawable(getActivity(), R.drawable.ic_empty),
                str_title, str_author, 0, n_pageTotal); //not work

        adapter.addItem(ContextCompat.getDrawable(getActivity(), R.drawable.ic_empty),
                "name31", "author31", 101, 1020) ; //not work

        nCount ++;
    }
}
}

如果点击刷新按钮，然后将项目添加到列表视图，我想这样做。
adapter.addItem中的onCreateView function 工作但在select function中，adapter.addItem 无法正常工作 （并且没有错误。）
数据在DB中。（我用日志检查了一下）
为什么adapter.addItem中的select function 无法正常工作，解决方案是什么？

Answer 1

原因

adapter.addItem(ContextCompat.getDrawable(getActivity(), R.drawable.ic_empty),
        "name1", "author1", 110, 1200) ; //work
adapter.addItem(ContextCompat.getDrawable(getActivity(), R.drawable.ic_empty),
        "name21", "author21", 210, 1003) ; //work
adapter.addItem(ContextCompat.getDrawable(getActivity(),  R.drawable.ic_empty),
        "name31", "author31", 101, 1020) ; //work

在 onCreateView（）中工作是因为 onCreateView（）在呈现视图之前运行，允许ListView呈现项目。< / p>

但是，在 select（）方法中，您要在之后添加项目

。

因为我不知道您的 BookListShowAdapter.addItem（）方法是什么样的，所以我只能假设您没有调用 notifyDataSetChanged（）。如果您调用此方法在 BookListShowAdapter.addItem（）方法结束时的方法，您的适配器将告诉任何反映您的数据的视图以刷新自身（包括渲染）。

适配器addItem无法正常工作

1 个答案: