Question

我想对HashMaps的ArrayList进行排序

ArrayList＆lt; HashMap＆lt;串，对象＆gt;＆GT;

在以下课程中：

public class NotificationFragment extends ListFragment {

    private static final String TAG = "NotificationFragment";
    private DatabaseReference mDatabaseReference;
    private ProgressBar mProgressBar;

    String[] from = {"TITLE","BODY","TIME"};
    int[] to = {R.id.single_notification_row_title,
            R.id.single_notification_row_body,
            R.id.single_notification_row_time};

    ArrayList<HashMap<String,Object>> data;

    SimpleAdapter adapter;

    public NotificationFragment() {
        // Required empty public constructor
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        Log.d(TAG, "onCreateView");
        // Inflate the layout for this fragment
        View view = inflater.inflate(R.layout.fragment_notification, container, false);

        return view;
    }

    @Override
    public void onActivityCreated(@Nullable Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);

        //Set Activity title
        getActivity().setTitle(R.string.Notifications);

        mDatabaseReference = FirebaseDatabase.getInstance().getReference()
                .child("Notification").child("Android");

        Query query = mDatabaseReference.orderByChild("title");

        query.addListenerForSingleValueEvent(new ValueEventListener() {
            @Override
            public void onDataChange(final DataSnapshot dataSnapshot) {

                getNewData((Map<String,Object>)dataSnapshot.getValue());
            }

            @Override
            public void onCancelled(DatabaseError databaseError) {

                Toast.makeText(getActivity(), R.string.Something_went_wrong_retry, Toast.LENGTH_SHORT).show();
            }
        });


    }

    private void cancelNotification(Activity activity, int notifyId) {
        String ns = Context.NOTIFICATION_SERVICE;
        NotificationManager nMgr = (NotificationManager) activity.getSystemService(ns);
        nMgr.cancel(notifyId);
    }

    private void getNewData (Map<String,Object> mapDatabase){

        mProgressBar = (ProgressBar)getActivity().findViewById(R.id.progressBarNotifications);

        data = new ArrayList<>();

        try{

            //Iterate through each notification
            for(Map.Entry<String,Object> entry : mapDatabase.entrySet()){
                Log.e(TAG, "ForEach entered");

                Map singleNotification = (Map)entry.getValue();

                //Fill the list
                String title = (String) singleNotification.get("title");
                String body = (String) singleNotification.get("body");
                String time = (String) singleNotification.get("time");
                String timeLong = (String) singleNotification.get("timeStamp");

                HashMap<String,Object> map = new HashMap<>();
                map.put("TITLE", title);
                map.put("BODY", body);
                map.put("TIME", time);
                map.put("timeLong", timeLong);

                data.add(map);
                Log.d(TAG,"data.add(map)");
                Log.d(TAG,"data.size = " + data.size());
            }

            for(HashMap<String, Object> myMap: data) {
                for(Map.Entry<String, Object> mapEntry: myMap.entrySet()) {
                    String key = mapEntry.getKey();
                    String value = (String) mapEntry.getValue();
                    if(key.equals("timeLong")){
                        Log.d(TAG,"timeLong = " + value);
                        //?????????HOW TO SORT by LONG VALUE ??????????
                    }
                }
            }
            //Adapter
            adapter = new SimpleAdapter
                    (getActivity(),data,R.layout.single_notification_row ,from,to);

            setListAdapter(adapter);
            Log.d(TAG,"setListAdapter(adapter)");
        }catch (NullPointerException e){
            Toast.makeText(getActivity(), R.string.No_Notifications, Toast.LENGTH_SHORT).show();
        }
        if(mProgressBar.getVisibility() == View.VISIBLE){
            mProgressBar.setVisibility(View.GONE);
        }
        cancelNotification(getActivity(), 0);
    }
    @Override
    public void onStart() {
        super.onStart();

        getListView().setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {

                Toast.makeText(getActivity(), "HI", Toast.LENGTH_SHORT).show();
            }
        });
    }
}

我得到以下排序顺序：

Screenshot

请注意，我在每个ArrayList项目中都有一个Long项目（称为“timeLong”）。

提前谢谢你，加埃塔诺

Answer 1

，我建议你创建一个包含4个属性的类：

www.mysite.com/2-home

假设该类的名称是Instance。获取数据后，创建此类的实例并设置此实例的属性，而不是具有4个字符串值。

将您的ArrayList更改为此String title; String body; String time; long timeLong;

创建一个类

ArrayList<Instance> myList = ArrayList();

用于排序

public class SortingClass implements Comparator<Instance>
{
     public int compare(Instance left, Instance right){
          return left.timeLong < right.timeLong ? 1 : -1; 
}

排序ArrayList <hashmap <string，object>＆gt;来自Top的最大价值

1 个答案: