尽管我使用了Adapter.notifyDataSetChanged（），但在更改数据集后，Android ListView不会刷新

Question

I know similar questions had been asked here a couple of times, but none of them could help me with my problem, so I will just have to ask again.

What I have is an app that has a fragment that holds a ListView in the main activity and I used a PullableListView so that when I drag the ListView up, it will trigger the onLoadMore() callback method to load more data from the server. Once data loaded, the data will be saved to a SQLiteDB and then used by the ListView to show the updated data.

The is my PullableListViewFragment.java:

public class PullableListViewFragment extends Fragment implements
    OnItemClickListener {

private ListView listView;
private PullToRefreshLayout ptrl;

private MissionDB mMissionDB;
private List<MissionEntity> mData;

private MissionListAdapter mAdapter;

/**
 * Specify the exact mission that will be displayed in MissionDetailActivity
 */
private int mIndexOfMission;

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {
    View pullableLayout = inflater.inflate(R.layout.pullable_layout, container, false);
    listView = (ListView) pullableLayout.findViewById(R.id.content_view);
    listView.setDivider(null);
    ptrl = (PullToRefreshLayout) pullableLayout.findViewById(R.id.refresh_view);
    ptrl.setOnRefreshListener(new RefreshListener());
    loadData();

    Log.d(Constants.LOG_TAG, "onCreateView Called from PullableListViewFragment");

    return pullableLayout;
}

/**
 * Initialise ListView
 */
@Override
public void onActivityCreated(Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);
    mAdapter = new MissionListAdapter(getActivity(), mData);
    listView.setAdapter(mAdapter);
    listView.setOnItemClickListener(this);
    mAdapter.notifyDataSetChanged();
    Log.d(Constants.LOG_TAG, "onActivityCreated Called from PullableListViewFragment");
}

/**
 * Load data from db
 */
private void loadData() {
    mData = new ArrayList<>();
    mMissionDB = MissionDB.getInstance(MyApplication.getContext());
    mData = mMissionDB.loadMission();
}

/**
 * OnItemClick event
 */
@Override
public void onItemClick(AdapterView<?> parent, View view, int position,
        long id) {
    Intent intent = new Intent(getActivity(), MissionDetailActivity.class);
    mIndexOfMission = mData.get((int) id).getId();
    intent.putExtra("Position", mIndexOfMission);
    startActivity(intent);
}

}

And this is the RefreshListener.java:

public class RefreshListener implements PullToRefreshLayout.OnRefreshListener {

private MissionDB mMissionDB = MissionDB.getInstance(MyApplication.getContext());

@Override
public void onLoadMore(final PullToRefreshLayout pullToRefreshLayout) {
    // LoadMore
    new Handler() {

        @Override
        public void handleMessage(Message msg) {

            /** When drag up, load more mission that is older and not out of date */
            mMissionDB.open();
            int id = mMissionDB.getMaxOrMinId("MIN");
            final JSONObject oldMission = new JSONObject();
            try {
                oldMission.put("platform", "1");
                oldMission.put("more", 0);
                oldMission.put("id", id);
                oldMission.put("size", 1);
            } catch (JSONException e) {
                e.printStackTrace();
            }

            Thread t = new Thread(new Runnable() {

                @Override
                public void run() {
                    HttpRequest.sendHttpRequest(Constants.PULLORDRAG_TO_LOAD_MISSION_URL, oldMission, new HttpCallbackListener() {

                        @Override
                        public void onFinish(String response) {
                            MissionEntity mMission = new MissionEntity();

                            /** Save new mission to mission database */
                            try {
                                JSONObject jsonObject = new JSONObject(response);
                                JSONArray missionList = jsonObject.getJSONArray("taskList");
                                for (int i = 0; i < missionList.length(); i++) {
                                    JSONObject mission = missionList.getJSONObject(i);
                                    mMission.setId(mission.getInt("id"));
                                    mMission.setDownloadUrl(mission.getString("appPath"));
                                    mMission.setCreateTime(mission.getString("taskId"));
                                    mMission.setImageUrl(mission.getString("appImg"));
                                    mMission.setTitleName(mission.getString("appName"));
                                    mMission.setRemainTime("Remain： 1d 11h 23m 36s");
                                    mMission.setParticipant("135");
                                    mMission.setCreator("Google");
                                    mMission.setRequirement(mission.getString("description"));
                                    mMission.setRewards("TODO");
                                    mMission.setAttention("TODO");
                                    mMission.setValidDate(mission.getString("deadline"));
                                    mMission.setAccepted("0");
                                    mMission.setCollected("0");
                                    mMission.setAccomplished("0");
                                    mMissionDB.saveMission(mMission);
                                }
                            } catch (JSONException e) {
                                e.printStackTrace();
                            }
                        }

                        @Override
                        public void onError(Exception e) {
                            e.printStackTrace();
                            Log.e(Constants.LOG_TAG, "Error while loading more");
                        }
                    });
                }
            });

            try {
                t.start();
                t.join();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }

            pullToRefreshLayout.loadmoreFinish(PullToRefreshLayout.SUCCEED);

            //==================Update 1==================
            ListView list = (ListView) pullToRefreshLayout.findViewById(R.id.content_view);
            List<MissionEntity> missionList = mMissionDB.loadMission();
            Log.d(Constants.LOG_TAG, "mission size" + missionList.size());
            MissionListAdapter adapter = (MissionListAdapter) list.getAdapter();
            adapter.setData(missionList);
            adapter.notifyDataSetChanged();
            list.setAdapter(adapter);
            //==================Update 1==================
        }
    }.sendEmptyMessageDelayed(0, 1000);
}

}

The PullToRefreshLayout is a custom RelativeLayout that defined a inner interface OnRefreshListener that will be called once the onLoadMore() callback method is called.

The ListView I use in the Fragment is a PullableListView that implemented a Pullable interface that can drag up.

My Pullable.java:

public interface Pullable
{
    /**
     * If pull up is not needed, set canPullUp to false
     * 
     * @return true if the View can pull up
     */
    boolean canPullUp();
}

This is the fragment's layout.xml:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
          android:layout_width="match_parent"
          android:layout_height="match_parent"
          android:background="#f2f2f2"
          android:orientation="vertical">

<View
    android:layout_width="match_parent"
    android:layout_height="5dp" />

<pulltorefresh.PullToRefreshLayout
    android:id="@+id/refresh_view"
    android:layout_marginLeft="8dp"
    android:layout_marginRight="8dp"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <include layout="@layout/refresh_head"/>

    <!-- Supports all view that implemented the Pullable interface -->
    <pulltorefresh.PullableListView
        android:id="@+id/content_view"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>

    <include layout="@layout/load_more"/>

</pulltorefresh.PullToRefreshLayout>

</LinearLayout>

The problem is when the data in the SQLiteDB is changed after the onLoadMore() method, the ListView in the fragment doesn't refresh itself unless I navigate to another fragment within the same main activity and then navigate back.

I tired all the ways I can find here and none of them help.

Could anyone tell me how can I make the ListView refresh itself when the data in the SQLiteDB changed.

[Update 1] I've added some code in the onLoadMore() callback, the size of the data remains the same after I get some data from the server, i think this is the problem why the ListVie is not refreshing, what's interesting is if I put a Thread.sleep(500) before mMission.loadMission() the size of the data is correct and everything is fine. Any idea why?

Answer 1

In onLoadMore method, you just only load data and save into database. After load data, you should update the data source of the adapter and call adapter.notifyDataSetChanged() to refresh the listview. or you can notify the fragment to reload data from database.

Answer 2

Make sure it get data when load more first. And I think your mMissionDB is changed indeed, but what about mData? Your adapter is use mData as datasource actually, so you should update mData, and call adapter.notifyDataSetChanged() to refresh the listview. Hope it can help you.