Question

问题

我已经使用外部库为回收者视图实现了多选行为。现在，为了从回收者视图中删除项目，我实现了两个for循环。第一个for循环从SQLite中删除项目，第二个for循环从适配器中删除相应的视图。但是，从适配器删除视图时会出现问题。

         for (i in selectedCardItems!!.indices)  //selectedCardItems stores selected card position.
            {
                val index = selectedCardItems!![i]
                val noteRowID = listItems!![index]  //list items contains references to items in SQLite and is fed to recyclerview.setadapter = myAdapter(context,listitems)


                dbHandler!!.deleteNote(noteRowID.noteID!!)
            }




            for(i in selectedCardItems!!.indices)
            {
                val index = selectedCardItems!![i]
                listItems!!.removeAt(i)  //problem starts here, due to mismatched indexes.

                adapter!!.notifyItemRemoved(i)
            }

            if(dbHandler!!.trashedNotesCount() == 0)
            {
                trashedRecyclerView!!.visibility = View.GONE
                emptyTrashImg!!.visibility = View.VISIBLE
                emptyTrashMsg!!.visibility = View.VISIBLE
            }

            selectedCardItems!!.clear()  //once all operation is done,remove card positions from this ArrayList.
        }

列表项和selectedCardPosition均为ArrayList类型。我知道一旦将ArrayList中的项目从索引中删除，则较高索引的项目索引会自动移至较低索引。解决此问题的有效方法是什么？

我尝试过的事情： BAD 的一项修复是基本上删除第二个for循环，该循环删除视图，然后将其替换为adapter.notifyDataSetChanged（），该循环还删除删除的动画。

Answer 1

如果我正确理解了您的问题，则会出现问题，因为从列表中删除会破坏初始索引。如果是这种情况，则必须先从较高索引处开始删除，然后向下进行。因此，对循环之前降序的列表进行排序：

private static Scanner sc;
private static String firstIp;
private static String secondIp;

private static long first;
private static long second;

private static final long lastIP = 255255255255L;

private static String convertHexToIp(long hex){
   String result = "";
   result += (hex>>24 & 0xFF) + ".";
   result += (hex>>16 & 0xFF) + ".";
   result += (hex>>8 & 0xFF) + ".";
   result += (hex & 0xFF);
   return result;
}

private static void ipSort() {

    sc = new Scanner(System.in);

    System.out.println("Firtst IP");
    firstIp = sc.nextLine().replaceAll("\\.", "");
    first = Long.parseLong(firstIp);

    if (first > lastIP || first < 1111) throw new RuntimeException("incorrect IP");


    System.out.println("Second IP");
    secondIp = sc.nextLine().replaceAll("\\.", "");
    second = Integer.parseInt(secondIp);

    if (second > 255255255 || second < 1111) throw new RuntimeException("incorrect IP");


    for (long i = second; i <lastIP ; i++) {
        System.out.println(convertHexToIp(second++));
    }


}

public static void main(String[] args) {
    ipSort();
   }
}

索引越界：ArrayList

1 个答案: