Question

如何将数据库中发生的更改（例如delete / add）立即显示在recyclerView中？我试过notifyDataSetChanged（）;并直接从arraylist中删除并重新加载数据库列表。但所有这些似乎都是一个混乱的解决方法，并且不起作用？

以下是我的应用中删除操作的视频，其中显示了它现在的状态。

https://www.youtube.com/watch?v=fCJnunOWBR4

这是用户点击来自recyclerview的活动时开始的活动：

 public class EventActivity extends AppCompatActivity {

   @Override
   public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.event_activity);

    loadDatabaseData(this);
    rvAdapter = new RvAdapter(databaseList, this);


    setSupportActionBar(toolbar);
    toolbar.setTitleTextColor(Color.WHITE);
    toolbar.showOverflowMenu();
    getSupportActionBar().setTitle(getIntent().getStringExtra("TITLE"));

    pos = getIntent().getIntExtra("POS",0);


}

 //Delete or remove happends here:---------------------
@Override
public boolean onOptionsItemSelected(MenuItem item) {
    switch (item.getItemId()) {

        case R.id.menu_saveToDb:
            DbHelper.getInstance(EventActivity.this).saveToDb(eventID, title, description, subtitle, start, end, 1, url, imgURL);
            loadDatabaseData(getApplicationContext());

            break;

        case R.id.delete_from_Db:

            DbHelper.getInstance(EventActivity.this).deleteEvent(eventID);

            //these 3 lines dosn't help either
            loadDatabaseData(this);
            rvAdapter.notifyItemRemoved(pos);
            rvAdapter.notifyDataSetChanged();

            finish();

            break;

        default:
    }
    return super.onOptionsItemSelected(item);
}



public void loadDatabaseData(Context context) {

    databaseList = new ArrayList<>();

    dbHelper = new DbHelper(context);
    sqLiteDatabase = dbHelper.getWritableDatabase();
    Cursor c = sqLiteDatabase.rawQuery("SELECT * FROM " + DbHelper.DATABASE_NAME, null);
    EventCurserWrapper wrapper = new EventCurserWrapper(c);

    if (c.moveToFirst()) {
        while (!c.isAfterLast()) {
            databaseList.add(new Event(wrapper.getEvent().getEventID(),wrapper.getEvent().getTitle(), wrapper.getEvent().subtitle, wrapper.getEvent().getDescrption(), wrapper.getEvent().startTime, wrapper.getEvent().endTime, wrapper.getEvent().url,wrapper.getEvent().getImgURL(), wrapper.getEvent().isDb));
            c.moveToNext();
        }
    }

    wrapper.close();
    c.close();
}

}

这是具有recyclerView的MainActivity：

public class MainActivity extends AppCompatActivity {

private RecyclerView recyclerView;
public RvAdapter rvAdapter;
private List<Event> databaseList, allEventsList, jsonList;
private DbHelper dbHelper;
private SQLiteDatabase sqLiteDatabase;
private Toolbar toolbar;
private SharedPreferences preferences;

private static final String URL = "http://events.makeable.dk/api/getEvents";
private static final String DESCRIPTION = "description_english";
private static final String TITLE = "title_english";
private static final String SUBTITLE = "subtitle_english";
private static final String PICTURE_URL = "picture_name";
private static final String EVENT_ID = "eventid";
private static final String DATES = "datelist";
private static final String EVENT_URL = "url";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    dbHelper = new DbHelper(this);
    preferences = PreferenceManager.getDefaultSharedPreferences(this);
    int showListPref = preferences.getInt("SHOW_LIST", 3);

    databaseList = new ArrayList<>();
    jsonList = new ArrayList<>();


    loadDatabaseData(this);
    new JsonParser().execute();


    toolbar = (Toolbar) findViewById(R.id.toolbar2);
    toolbar.setTitleTextColor(Color.WHITE);
    toolbar.showOverflowMenu();
    setSupportActionBar(toolbar);
    getSupportActionBar().setTitle("Events in Arhus");


public void loadDatabaseData(Context context) {

    dbHelper = new DbHelper(context);
    sqLiteDatabase = dbHelper.getWritableDatabase();
    Cursor c = sqLiteDatabase.rawQuery("SELECT * FROM " + DbHelper.DATABASE_NAME, null);
    EventCurserWrapper wrapper = new EventCurserWrapper(c);

    if (c.moveToFirst()) {
        while (!c.isAfterLast()) {
            databaseList.add(new Event(wrapper.getEvent().getEventID(),wrapper.getEvent().getTitle(), wrapper.getEvent().subtitle, wrapper.getEvent().getDescrption(), wrapper.getEvent().startTime, wrapper.getEvent().endTime, wrapper.getEvent().url,wrapper.getEvent().getImgURL(), wrapper.getEvent().isDb));
            c.moveToNext();
        }
    }

    wrapper.close();
    c.close();
    sqLiteDatabase.close();

}



public void initRecyclerView(List<Event> list) {

    recyclerView = (RecyclerView) findViewById(R.id.recyclerview);
    recyclerView.setLayoutManager(new LinearLayoutManager(this));

    rvAdapter = new RvAdapter(list, this);
    recyclerView.setAdapter(rvAdapter);
    rvAdapter.notifyDataSetChanged();

}

}

Answer 1

在我看来，这并不是解决问题的好办法。您可以拨打startActivityForResult()而不是startActivity()。并将 EventActivity 的一些结果返回到 MainActivity ，如果需要，还可以在RecyclerView中重新加载数据。您可以阅读有关Getting a Result from an Activity

的更多信息

如何更新数据库中的最新更改以立即删除/添加到Recyclerview上？

1 个答案: