java - 哈希表列表更新所有字符串值

Question

我正在使用可扩展 ListView 并需要标题列表和每个标题的子项...我在下面的代码中面临的问题是它正在更新所有字符串/键值而不是目标值...

    private void prepareListData() {
        listDataHeader = new ArrayList<String>();
        listDataChild = new HashMap<String, List<String>>();
        databaseProjects = new ArrayList<>();
        arrayListTagNames=new ArrayList<String>();
        arrayListTagNames.clear();
        int countheaders = 0;


        for(int i = 0; i < databasePositions.size(); i++) {


            if (!(databasePositions.get(i).equals("None"))) {

                listDataHeader.add(databasePositions.get(i));

                databaseProjects = databaseAdapter.getAllProjectsNameOnlyDBusingserverID(databasePositionsid.get(i));

                for (int j = 0; j < databaseProjects.size(); j++) {
                    if (!(databaseProjects.get(j).equals("None"))) {
                        arrayListTagNames.add( databaseProjects.get(j));
                    }
                }

                listDataChild.put(listDataHeader.get(countheaders), arrayListTagNames);


                countheaders++;
                arrayListTagNames.clear();
            }
        }
    }

Answer 1

当您使用 arrayListTagNames.clear() 清除 arrayList 时，它会影响放入 hashmap 的内容，而不是清除创建一个新的数组列表并放入 HashMap，尝试这样的事情

private void prepareListData() {
            listDataHeader = new ArrayList<String>();
            listDataChild = new HashMap<String, List<String>>();
            databaseProjects = new ArrayList<>();
            int countheaders = 0;


            for(int i = 0; i < databasePositions.size(); i++) {


                if (!(databasePositions.get(i).equals("None"))) {
                    arrayListTagNames=new ArrayList<String>();

                    listDataHeader.add(databasePositions.get(i));

                    databaseProjects = databaseAdapter.getAllProjectsNameOnlyDBusingserverID(databasePositionsid.get(i));

                    for (int j = 0; j < databaseProjects.size(); j++) {
                        if (!(databaseProjects.get(j).equals("None"))) {
                            arrayListTagNames.add( databaseProjects.get(j));
                        }
                    }

                    listDataChild.put(listDataHeader.get(countheaders), arrayListTagNames);


                    countheaders++;
                }
            }
        }