在Android中刷新ListAdapter

Question

我在嘗試刷新Android中的列表視圖時遇到了一些問題。這是我的onCreate方法：

protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.transaction_rec); 
    context = this; 
    listview = (ListView) findViewById(R.id.listview); 
    builtListView(); 
} 

public void builtListView() { 
    DatabaseAdapter mDbHelper = new DatabaseAdapter(this); 
    mDbHelper.createDatabase(); 
    mDbHelper.open(); 
    TransactionRecController trc = new TransactionRecController(
      mDbHelper.open()); 

    ArrayList<TransactionRecModel> trans_list = trc 
      .getTransactionRec(session_userID); 

    for (int i = 0; i < trans_list.size(); i++) { 
     String date = trans_list.get(i).getDate(); 
     String categoryName = trans_list.get(i).getCategory(); 
     String transDesc = trans_list.get(i).getTransDescription(); 

     TransactionRecModel _TransModel = new TransactionRecModel(); 

     _TransModel.setDate(date); 
     _TransModel.setCategory(categoryName); 
     _TransModel.setTransDescription(transDesc); 

     _translist.add(_TransModel); 
    } 
    // Set the data into listview 
    listview.setAdapter(new ListAdapter(this)); 

    mDbHelper.close(); 
} 

我創建一個rebuildListView方法來設置listAdapter爲空，然後再次調用buildListView方法：

public void rebuildListView() { 
    listview.setAdapter(null); 
    builtListView(); 
} 

當我成功地插入記錄到數據庫中，我刷新

TransactionRecController trc = new TransactionRecController(
       mDbHelper.open()); 
     if (trc.addTransactionRec(trm)) { 
      Toast.makeText(TransactionRec.this, 
        "Transaction Record Added successfully.", 
        Toast.LENGTH_LONG).show(); 
      mDbHelper.close(); 
      txtTransDesc.setText(""); 
      txtAmount.setText(""); 
      txtDate.setText(""); 

      // Refresh the list view after record added 
      rebuildListView(); 

這是我listAdapter類：

致電rebuildListView列表視圖

private class ListAdapter extends BaseAdapter { 
    LayoutInflater inflater; 
    ViewHolder viewHolder; 

    public ListAdapter(Context context) { 
     // TODO Auto-generated constructor stub 
     inflater = LayoutInflater.from(context); 
    } 

    // Bind the data to different textView for each rows 
    @Override 
    public View getView(int position, View convertView, ViewGroup parent) { 
     // TODO Auto-generated method stub 
     if (convertView == null) { 

      convertView = inflater.inflate(R.layout.trans_listview_row, 
        null); 
      viewHolder = new ViewHolder(); 

      viewHolder.txt_ddate = (TextView) convertView 
        .findViewById(R.id.txtDisplayDate); 

      viewHolder.txt_ddesc = (TextView) convertView 
        .findViewById(R.id.txtDisplayDesc); 

      viewHolder.txt_dcat = (TextView) convertView 
        .findViewById(R.id.txtDisplayCat); 

     } else { 
      viewHolder = (ViewHolder) convertView.getTag(); 
     } 

     viewHolder.txt_ddate.setText(_translist.get(position).getDate() 
       .trim()); 

     viewHolder.txt_ddesc.setText(_translist.get(position) 
       .getTransDescription().trim()); 

     viewHolder.txt_dcat.setText(_translist.get(position).getCategory() 
       .trim()); 

     return convertView; 
    } 
} 

但是，我現在的問題是讓我們說，我先得到記錄1,2和3。然後當我添加另一個記錄是4時，列表視圖應該只顯示1-4。但用我的代碼，我得到的是1,2,3,1,2,3,4。我想知道爲什麼listAdapter繼續堆疊記錄，儘管我將它設置爲null並重新構建它。

在此先感謝。

Answer 1

您不清除舊的列表數據。您已從列表中刪除舊記錄。

public void builtListView() { 
    _translist.clear(); 
    DatabaseAdapter mDbHelper = new DatabaseAdapter(this); 
    mDbHelper.createDatabase(); 
    mDbHelper.open(); 
    TransactionRecController trc = new TransactionRecController(
      mDbHelper.open()); 

    ArrayList<TransactionRecModel> trans_list = trc 
      .getTransactionRec(session_userID); 

    for (int i = 0; i < trans_list.size(); i++) { 
     String date = trans_list.get(i).getDate(); 
     String categoryName = trans_list.get(i).getCategory(); 
     String transDesc = trans_list.get(i).getTransDescription(); 

     TransactionRecModel _TransModel = new TransactionRecModel(); 

     _TransModel.setDate(date); 
     _TransModel.setCategory(categoryName); 
     _TransModel.setTransDescription(transDesc); 

     _translist.add(_TransModel); 
    } 
    // Set the data into listview 
    listview.setAdapter(new ListAdapter(this)); 

    mDbHelper.close(); 
} 

，或者您可以重新分配的值

public void builtListView() { 
    _translist.clear(); 
    DatabaseAdapter mDbHelper = new DatabaseAdapter(this); 
    mDbHelper.createDatabase(); 
    mDbHelper.open(); 
    TransactionRecController trc = new TransactionRecController(
      mDbHelper.open()); 

    _translist = trc 
      .getTransactionRec(session_userID); 

    // Set the data into listview 
    listview.setAdapter(new ListAdapter(this)); 

    mDbHelper.close(); 
}