java - ListView 项目未在 BaseExpandableListAdapter 中删除

Question

我有一个 expandablelistView。单击列表时，将显示两个按钮。单击删除按钮时，它假设删除子项和父项。不幸的是，没有任何东西被删除。

 ArrayList<ListObj> groupList= new ArrayList<ListObj>();
     listview = (ExpandableListView) findViewById(R.id.exlistView);
     expListAdapter = new ExpandableListAdapter(AddMonthlyExpenses.this,getApplication(), groupList);
     listview.setAdapter(expListAdapter);
     retrieveList(name);

public void retrieveList(String name) {
        groupList.clear();
        database = mdb.getReadableDatabase();
        Cursor cursor = database.rawQuery("SELECT * FROM " + MyDatabaseHelper.TABLE__TASK + " WHERE Name = ? ", new String[]{name}, null);
        if (cursor != null && cursor.getCount() > 0) {
            groupList = new ArrayList<ListObj>();
            while (cursor.moveToNext()) {
                int iD = cursor.getInt(cursor.getColumnIndex("ID"));
                String month = cursor.getString(cursor.getColumnIndex("Month"));
                double budget = cursor.getDouble(cursor.getColumnIndex("Budget"));
                groupList.add(new ListObj(iD,month,budget));
                if (expListAdapter != null) {
                    expListAdapter.add(iD, month, budget,"edit");
                   listview.deferNotifyDataSetChanged();
                }
            }
        }
    }

适配器类

 public class ExpandableListAdapter extends BaseExpandableListAdapter {

    private Context context;
    private ArrayList<ListObj> laptops;
    Activity parentActivity;
    private LayoutInflater mInflater;
    SQLiteDatabase database;
    MyDatabaseHelper mdb;

    public ExpandableListAdapter(Activity parentActivity, Context context, ArrayList<ListObj> laptops) {
        this.parentActivity= parentActivity;
        this.context = context;
        this.laptops = laptops;
        mInflater = LayoutInflater.from(context);
        mdb= new MyDatabaseHelper(context);
    }

    public Object getChild(int groupPosition, int childPosition) {
        ArrayList<ItemDetails> productList =
                laptops.get(groupPosition).getProductList();
        return productList.get(childPosition);
    }


    public void add(int id, String month, double budget) {
        String[] splited = month.split("\\s+");
        ListObj obj = new ListObj(id, month, budget);
        obj.setYear(splited[1]);
        obj.setMonth(splited[0]);
        obj.setBudget(budget);
        obj.setID(id);
//        mySection.put(obj);
        laptops.add(obj);
        this.notifyDataSetChanged();

        ArrayList<ItemDetails> productList = obj.getProductList();

        ItemDetails detailInfo = new ItemDetails();
        productList.add(detailInfo);
        obj.setProductList(productList);
    }

    public long getChildId(int groupPosition, int childPosition) {
        return childPosition;
    }

    public int getCount() {
        return laptops.size();
    }

    public void removeItem(long position) {
        laptops.remove(position);
        notifyDataSetChanged();
    }


    public ListObj getItem(int position) {
        return laptops.get(position);
    }

    public View getChildView(final int groupPosition, final int childPosition,
                             boolean isLastChild, View convertView, ViewGroup parent) {
        if (convertView == null) {
            LayoutInflater infalInflater = (LayoutInflater)
                    context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            convertView = infalInflater.inflate(R.layout.child_item, null);
        }

        Button editButton = (Button)convertView.findViewById(R.id.editButton);
        Button deleteButton = (Button)convertView.findViewById(R.id.deleteButton);

        deleteButton.setOnClickListener(new View.OnClickListener() {

            public void onClick(View v) {
                AlertDialog.Builder builder = new AlertDialog.Builder(parentActivity);
                builder.setMessage("Do you want to remove?");
                builder.setCancelable(false);
                builder.setPositiveButton("Yes",
                        new DialogInterface.OnClickListener() {
                            public void onClick(DialogInterface dialog, int id) {
//                                Toast.makeText(context,"button clicked  "+ groupPosition,Toast.LENGTH_LONG).show();
                                ListObj headerInfo = laptops.get(groupPosition);
                                deleteData(headerInfo.getID());
                                removeItem(groupPosition);
                                Toast.makeText(context,"list deleted",Toast.LENGTH_LONG).show();
                                notifyDataSetChanged();
                            }
                        });
                builder.setNegativeButton("No",
                        new DialogInterface.OnClickListener() {
                            public void onClick(DialogInterface dialog, int id) {
                                dialog.cancel();
                            }
                        });
                AlertDialog alertDialog = builder.create();
                alertDialog.show();
            }
        });


        return convertView;
    }

    public void deleteData(long id)
    {
        database = mdb.getWritableDatabase();
        database.delete(MyDatabaseHelper.TABLE_EXPENSES, MyDatabaseHelper.ID2 + "=?", new String[]{id + ""});
    }

    public int getChildrenCount(int groupPosition) {
        ArrayList<ItemDetails>itemDetails=laptops.get(groupPosition).getProductList();
        return itemDetails.size();
    }

    public Object getGroup(int groupPosition) {
        return laptops.get(groupPosition);
    }

    public int getGroupCount() {
        return this.laptops.size();
    }

    public long getGroupId(int groupPosition) {
        return groupPosition;
    }

    public View getGroupView(int groupPosition, boolean isExpanded,
                             View convertView, ViewGroup parent) {
        convertView = mInflater.inflate(R.layout.expenses_adapter, null);
        TextView month = (TextView) convertView.findViewById(R.id.textMonth);
        TextView budget = (TextView) convertView.findViewById(R.id.textAmount);
        TextView year = (TextView) convertView.findViewById(R.id.textYear);
        month.setText(laptops.get(groupPosition).getMonth());
        budget.setText(laptops.get(groupPosition).getBudget()+"");
        year.setText(laptops.get(groupPosition).getYear());
        return convertView;
    }


    public boolean hasStableIds() {
        return true;
    }

    public boolean isChildSelectable(int groupPosition, int childPosition) {
        return true;
    }
}

我的适配器类正在扩展 BaseExpandableListAdapter

Answer 1

首先:您需要更改hasStableIds，因为对列表的删除和添加操作会更改列表的索引，所以true意味着，可扩展 ListView 可以重用对应的 View ID，它可能会导致不必要地重用脏(已删除) View 的问题

public boolean hasStableIds() {
    return false;
}

第二:正如您提到的，您需要使用 int 而不是 long 因为这样做

 laptops.remove(position);

long 位置将被AutoBoxed 放入Long 因此它将调用覆盖版本的remove 对象即ArrayList#remove(Object)这导致

 laptops.remove(LongObject); 

因此它将尝试从 ArrayList 中搜索并删除一个 Long 对象(其值是位​​置)，尽管没有 Long对象存在于列表中。

为什么是拳击？

按照规则

Widening Primitive Conversion

int will be promoted to long but inverse is not automatically allowed (result in lost of data)

因此 long 将被装箱 为 Long 以调用更具体的删除方法 ArrayList#remove(Object)

解决方案:使用 int 或在使用 remove as

时将转换应用于 int

 laptops.remove((int)position);