使用 BaseAdapter 重复项自定义列表视图答案

【问题标题】：Duplicate item custom listview with BaseAdapter使用 BaseAdapter 重复项自定义列表视图
【发布时间】：2014-07-17 12:21:29
【问题描述】：

我尝试使用自定义 ListView 扩展 BaseAdapter 将数据从数据库 mysql 显示到列表视图。数据库中的数据如：

tbl_userbook：

    id   | username  |  title          | category
   ------+-----------+-----------------+-------------
    1    | A         |  Java           | 1
    2    | B         |  VB.NET         | 1
    3    | C         |  Swing Java     | 1
    4    | D         |  Java Hibernate | 1
    5    | E         |  C#             | 1
    6    | F         |  Ruby           | 1
    7    | G         |  MySQL          | 1
    8    | H         |  Sqlite         | 1
    9    | I         |  PHP            | 1
    10   | J         |  MsSQL          | 1

我的问题是为什么 listview 显示从 id 1 到 6 的重复项和数据 id 7、8、9、10 未显示在 listview 中。

Listview 中显示的数据如下：

    | username  |  title          | 
    +-----------+-----------------+
    | A         |  Java           |
    | B         |  VB.NET         |
    | C         |  Swing Java     |
    | D         |  Java Hibernate |
    | E         |  C#             |
    | F         |  Ruby           |
    | A         |  Java           | < ----  duplicate starting from here
    | B         |  VB.NET         |
    | C         |  Swing Java     |
    | D         |  Java Hibernate |

基础适配器：

public class HomeListViewAdapter extends BaseAdapter {

Context context;
ArrayList<HashMap<String, String>> userList;
HashMap<String, String> map = new HashMap<String, String>();

public HomeListViewAdapter(Context context,
        ArrayList<HashMap<String, String>> arraylist) {
    this.context = context;
    userList = arraylist;
}

@Override
public int getCount() {
    // TODO Auto-generated method stub
    return userList.size();
}

@Override
public Object getItem(int position) {
    // TODO Auto-generated method stub
    return null;
}

@Override
public long getItemId(int position) {
    // TODO Auto-generated method stub
    return 0;
}

@Override
public View getView(int position, View convertView, ViewGroup parent) {
    // TODO Auto-generated method stub

    TextView tvUsername, tvTitle;

    if (convertView == null) {
        LayoutInflater layoutInflator = (LayoutInflater) context
                .getSystemService(Context.LAYOUT_INFLATER_SERVICE);

        convertView = layoutInflator.inflate(R.layout.custom_listview_home, parent, false);

        map = membersList.get(position);

        tvUsername = (TextView) convertView.findViewById(R.id.tvUsername);
        tvTitle = (TextView) convertView.findViewById(R.id.tvTitle);

        tvUsername.setText(map.get(FragmentHome.USERNAME));
        tvTitle.setText(map.get(FragmentHome.TITLE));

    }
    return convertView;

片段

public class FragmentHome extends SherlockFragment {

public static String USERNAME = "username";
public static String TITLE = "title";

private ProgressDialog pDialog; 
JSONPostGet jPostget = new JSONPostGet();
JSONArray users = null;
ArrayList<HashMap<String, String>> userList;

private static String url_getbook = "http://....../get_userbook.php";

ListView list;
HomeListViewAdapter homeadapter;

private static final String KEY_SUCCESS = "success";
private static final String KEY_USERS = "users";
private static final String KEY_USERNAME = "username";
private static final String KEY_TITLE = "title";

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {
    View rootView = inflater.inflate(R.layout.fragment_home, container, false);
    userList = new ArrayList<HashMap<String,String>>();
    new LoadUserBook().execute();
    return rootView;
}

class LoadUserBook extends AsyncTask<String, String, String> {

    @Override
    protected void onPreExecute() {
        // TODO Auto-generated method stub
        super.onPreExecute();
        pDialog = new ProgressDialog(getActivity());
        pDialog.setMessage("Please wait....");
        pDialog.setIndeterminate(false);
        pDialog.setCancelable(true);
        pDialog.show();
    }

    @Override
    protected String doInBackground(String... args) {
        // TODO Auto-generated method stub
        List<NameValuePair> params = new ArrayList<NameValuePair>();
        params.add(new BasicNameValuePair("category", "1"));
        JSONObject json = jPostget.makeHttpRequest(url_getbook, "GET", params);
        Log.d("All News Feed: ", json.toString());
        try {
            int success = json.getInt(KEY_SUCCESS);
            if (success == 1) {
                users = json.getJSONArray(KEY_USERS);
                for (int i = 0; i < users.length(); i++) {
                    JSONObject c = users.getJSONObject(i);

                    String suname = c.getString(KEY_USERNAME);
                    String stitle = c.getString(KEY_TITLE);

                    HashMap<String, String> map = new HashMap<String, String>();
                    map.put(KEY_USERNAME, suname);
                    map.put(KEY_TITLE, stitle);

                    userList.add(map);
                }
            } else {
                // ...
            }
        } catch (JSONException e) {
            // TODO: handle exception
            e.printStackTrace();
        }
        return null;
    }

    @Override
    protected void onPostExecute(String result) {
        // TODO Auto-generated method stub
        pDialog.dismiss();
        try {
            getActivity().runOnUiThread(new Runnable() {

                @Override
                public void run() {
                    // TODO Auto-generated method stub      
                    list = (ListView) getView().findViewById(R.id.listview1);
                    homeadapter = new HomeListViewAdapter(getActivity(), userList);
                    list.setAdapter(homeadapter);
                    homeadapter.notifyDataSetChanged();
                }
            });
        } catch (Exception e) {
            // TODO: handle exception
        }
    }
}

}

请帮忙。感谢提前

【问题讨论】：

在 doInBackground() 方法中使用 userList.clear() ，例如 . @Override protected String doInBackground(String... args) { userList.clear()
哈哈。我只是删除它“ if (convertView == null) ”问题解决了，但请你给我一个为什么会发生这种情况的原因。
你不应该删除它..它有助于保持顺利
如果在 doInBackground() 中使用，我必须将代码“userList.clear()”放在哪里，数据不显示？
@eric : 那我该怎么办？

标签： android mysql listview android-listview baseadapter

【解决方案1】：

您的getView 实现不正确。试试这个 -

  @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        // TODO Auto-generated method stub

        TextView tvUsername, tvTitle;

        if (convertView == null) {
            LayoutInflater layoutInflator = (LayoutInflater) context
                    .getSystemService(Context.LAYOUT_INFLATER_SERVICE);

            convertView = layoutInflator.inflate(R.layout.custom_listview_home, parent, false);   
        }


            map = membersList.get(position);

            tvUsername = (TextView) convertView.findViewById(R.id.tvUsername);
            tvTitle = (TextView) convertView.findViewById(R.id.tvTitle);

            tvUsername.setText(map.get(FragmentHome.USERNAME));
            tvTitle.setText(map.get(FragmentHome.TITLE));

        return convertView;
}

【讨论】：

@Kshitij : 谢谢你，我用你的建议..我的问题解决了

【解决方案2】：

我认为您没有将 else 添加到为 convertView 指定的条件为 null。

所以现在你的代码只是为那些当前显示的视图设置数据，对于剩余的数据它重复之前已经初始化的视图。

就这样试试吧，我相信你会得到解决方案的：

if(convertView == null){
// some code here 
} 
else{
     holder = (ViewHolder) row.getTag();
}

【讨论】：

谢谢你的解释，现在我明白了。

【解决方案3】：

我认为 getItem() 应该返回 userlist.get(position) 并在 onCreateView
地图 = membersList.get(位置);
应该是
ap = userlist.get(位置);

另一件事是当转换视图不为空时缺少 else 子句。

【讨论】：

【解决方案4】：

试试这个：

@Override
public View getView(int position, View convertView, ViewGroup parent) {
    // TODO Auto-generated method stub

    TextView tvUsername, tvTitle;

    if (convertView == null) {
        LayoutInflater layoutInflator = (LayoutInflater) context
                .getSystemService(Context.LAYOUT_INFLATER_SERVICE);

        convertView = layoutInflator.inflate(R.layout.custom_listview_home, parent, false);




    }else{
       LayoutInflater layoutInflator = convertView;

    }

     map = membersList.get(position);

        tvUsername = (TextView) convertView.findViewById(R.id.tvUsername);
        tvTitle = (TextView) convertView.findViewById(R.id.tvTitle);

        tvUsername.setText(map.get(FragmentHome.USERNAME));
        tvTitle.setText(map.get(FragmentHome.TITLE));

    return convertView;
}

【讨论】：

【解决方案5】：

解决方案：-

您没有正确实现 Base 适配器。 android出于性能原因回收视图，因此您需要初始化文本图像等。每次。所以你只需要将初始化代码放在 convertview 空检查之外。只需这样做：--

@Override
public View getView(int position, View convertView, ViewGroup parent) {
// TODO Auto-generated method stub

TextView tvUsername, tvTitle;

if (convertView == null) {
    LayoutInflater layoutInflator = (LayoutInflater) context
            .getSystemService(Context.LAYOUT_INFLATER_SERVICE);

    convertView = layoutInflator.inflate(R.layout.custom_listview_home, parent, false);



    tvUsername = (TextView) convertView.findViewById(R.id.tvUsername);
    tvTitle = (TextView) convertView.findViewById(R.id.tvTitle);



}
map = membersList.get(position);
tvUsername.setText(map.get(FragmentHome.USERNAME));
    tvTitle.setText(map.get(FragmentHome.TITLE));
return convertView;
}

【讨论】：

【解决方案6】：

public View getView(int position, View view, ViewGroup parent) { // TODO 自动生成的方法存根

            // get the layout inflater

            LayoutInflater mLayoutInflater = (LayoutInflater) getApplicationContext()
                    .getSystemService(Context.LAYOUT_INFLATER_SERVICE);

            // create a ViewHolder reference
            ViewHolder holder = null;

            // check to see if the reused view is null or not, if is not
            // null then reuse it

            if (view == null) {
                holder = new ViewHolder();
                // check to see if the reused view is null or not, if is not
                // null then reuse it
                if (view == null) {
                    holder = new ViewHolder();

                    view = mLayoutInflater.inflate(
                            R.layout.listview_values, null);
                    holder.txt_date = (TextView) view
                            .findViewById(R.id.t_date);
                    holder.txt_intime = (TextView) view
                            .findViewById(R.id.txt_intime);
                    holder.txt_outtime = (TextView) view
                            .findViewById(R.id.txt_outtime);

                    // the setTag is used to store the data within this view
                    view.setTag(holder);
                } else {
                    // the getTag returns the viewHolder object set as a tag
                    // to the view
                    holder = (ViewHolder) view.getTag();
                    view = mLayoutInflater.inflate(
                            R.layout.listview_values, parent, false);
                }

            }
            // get the string item from the position "position" from array
            // list to put it on the TextView
            String date = attendence_webdata.get(position).get("A_date")
                    .toString();
            String intime = attendence_webdata.get(position)
                    .get("Ain_time").toString();
            String outtime = attendence_webdata.get(position)
                    .get("out_time").toString();
            if (date != null) {
                if (holder.txt_date != null) {
                    // set the item name on the TextView
                    holder.txt_date.setText(date);
                }
            }
            if (intime != null) {
                if (holder.txt_intime != null) {
                    // set the item name on the TextView
                    holder.txt_intime.setText(intime);
                }
            }
            if (outtime != null) {
                if (holder.txt_outtime != null) {
                    // set the item name on the TextView
                    holder.txt_outtime.setText(outtime);
                }
            }

            // this method must return the view corresponding to the data at
            // the specified position.
            return view;

        }
    }

}

/**
 * Static class used to avoid the calling of "findViewById" every time the
 * getView() method is called, because this can impact to your application
 * performance when your list is too big. The class is static so it cache
 * all the things inside once it's created.
 */
private static class ViewHolder {
    private TextView txt_outtime;
    private TextView txt_intime;
    private TextView txt_date;

}

@Override
public void onBackPressed() {
    // TODO Auto-generated method stub
    super.onBackPressed();
    attendence_webdata.clear();// where attendence_webdata is arraylistname
    list.setAdapter(null);     //where list is your listview name
}

检查此代码以了解您何时返回父活动并通过 .clear() 方法清除数据。我在我的应用程序和它的工作中使用了这段代码，所以你可以从这段代码中了解如何管理列表视图中的重复条目

【讨论】：

【解决方案7】：

public View getView(int position, View convertView, ViewGroup parent) {
    LayoutInflater inflater = (LayoutInflater) context
        .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    View gridView;
    if (convertView == null) {
        gridView = new View(context);
    } else {
        gridView = (View) convertView;
    }
    gridView = inflater.inflate(R.layout.worker_listmain, null);
    // your source code here!!! Run 100%
    return gridView;
}

【讨论】：

我也遇到了这个问题，我想办法解决！请使用我的源代码：D 简单就是完美：D

【解决方案8】：

我认为您应该在活动类的清单文件中添加这一行。 android:windowSoftInputMode="adjustPan"

【讨论】：