Listview從數據庫中每次啓動活動時都會彈出

Question

我正在將一些json數據提取到EventApp中，並且我試圖在SQLite數據庫中存儲一些事件。我在另一個活動中顯示事件，而不是主要事件，每當我從該活動返回到主活動時，我都會返回帶有列表視圖的活動，每次都會複製數據。所以如果我點擊10次進入該活動，我的數據在列表視圖和數據庫中也會獲得10次。我怎樣才能解決這個問題？

SQLiteDatabase db = getWritableDatabase(); 

public DatabaseHelper(Context context) { 
    super(context, DATABASE_NAME, null, DATABASE_VERSION); 
} 

@Override 
public void onCreate(SQLiteDatabase db) { 
    db.execSQL(CREATE_TABLE); 
} 

@Override 
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { 
    db.execSQL("DROP TABLE IF EXISTS " + TABLE_NAME); 
    onCreate(db); 
} 

//Add new row to the database 
public void addEvent(Event ev){ 
    ContentValues contentValues = new ContentValues(); 
    contentValues.put(DatabaseHelper.TITLE, ev.getTitle()); 
    contentValues.put(DatabaseHelper.START_DATE, ev.getStartTime()); 
    contentValues.put(DatabaseHelper.END_DATE, ev.getEndTime()); 
    contentValues.put(DatabaseHelper.IMAGE_URL, ev.getImageURL()); 
    contentValues.put(DatabaseHelper.URL, ev.getUrl()); 
    contentValues.put(DatabaseHelper.SUBTITLE, ev.getSubtitle()); 
    contentValues.put(DatabaseHelper.DESCRIPTION, ev.getDescription()); 
    db.insert(TABLE_NAME, null, contentValues); 
    //db.close(); 
} 

//Delete event from database 
public void deleteEvent(String eventTitle){ 
    db.execSQL("DELETE FROM " + TABLE_NAME + "WHERE " + TITLE + "=\"" + eventTitle + "\";"); 
} 

public int deleteEvents() { 
    return db.delete(DatabaseHelper.TABLE_NAME, null, null); 
} 

//Print the database as string 
public String databaseToString(){ 
    String dbString=""; 

    //points to a location in results 
    Cursor c = getEvents(); 

    while (c.moveToNext()){ 
     if(c.getString(c.getColumnIndex("Title")) != null){ 
      dbString += c.getString(c.getColumnIndex("Title")); 
      dbString += "\n"; 
     } 
    } 
    //db.close(); 
    return dbString; 
} 

public Cursor getEvents(){ 
    return db.query(TABLE_NAME, ALL_COLUMNS, null, null, null, null, null, null); 
} 

}

這是我顯示從數據庫中

public class StoredEventsActivity extends AppCompatActivity { 

@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 

    setContentView(R.layout.stored_events); 

    ListView listView = (ListView) findViewById(R.id.lv_stored_events); 

    Intent intent = getIntent(); 
    ArrayList<Event> events = new ArrayList<Event>(); 

    events = (ArrayList<Event>) intent.getSerializableExtra("storedEvents"); 

    EventAdapter adapter = new EventAdapter(this, R.layout.list_view_row, R.id.stored, events); 
    listView.setAdapter(adapter); 
} 

}

這裏的數據活動，返回的存儲事件的方法

public static ArrayList<Event> returnStoredEvents(){ 
    long id = -1; 
    //getStoredEvents(); 
    Cursor c = eventsDB.getEvents(); 

    while (c.moveToNext()){ 
     id = c.getInt(c.getColumnIndex(eventsDB.ID)); 
     String title = c.getString(c.getColumnIndex(eventsDB.TITLE)); 
     String start = c.getString(c.getColumnIndex(eventsDB.START_DATE)); 
     String end = c.getString(c.getColumnIndex(eventsDB.END_DATE)); 
     organizeEvents.add(new Event(title, start, end, true)); 
    } 
    c.close(); 
    Log.d("DATABASE", organizeEvents.toString()); 
    return organizeEvents; 
} 

這裏是我實際添加一些事件：

private void readEvents(String str){ 
    Event ev = null; 
    try { 
     JSONObject geoJSON = new JSONObject(str); 
     JSONArray jsonEvents = geoJSON.getJSONArray("events"); 
     for (int i = 0; i < jsonEvents.length(); i++) { 
      JSONObject event = jsonEvents.getJSONObject(i); 
      JSONArray timeJsonEvent = event.getJSONArray("datelist"); 
      JSONObject time = timeJsonEvent.getJSONObject(0); 

      title = event.getString("title_english"); 

      Date date = new Date(time.getLong("start")); 
      startDate = dateFormat.format(date); 

      date = new Date(time.getLong("end")); 
      endDate = dateFormat.format(date); 

      imageURL = event.getString("picture_name"); 
      url = event.getString("url"); 
      subtitle = event.getString("subtitle_english"); 
      description = event.getString("description_english"); 

      if (title.charAt(0) == 'T') { 
       ev = new Event(title, startDate, endDate, true); 
       eventsDB.addEvent(ev); 
      }else { 
        ev = new Event(title, startDate, endDate, false); 
      } 

      // Process a newly found event 
      final Event finalEv = ev; 
      handler.post(new Runnable() { 
       public void run() { 
        addNewEvent(finalEv); 
       } 
      }); 
     } 
    }catch (Exception e) { 
     Log.d(null, e.getMessage()); 
    } 
} 

這裏是我的主：

public class MainActivity extends AppCompatActivity{ 
DatabaseHelper eventsDB; 
ListFragment listFragment; 
SimpleCursorAdapter adapter; 
Intent intent; 

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

    eventsDB = new DatabaseHelper(this); 
    //storedEvents.addAll(EventsListFragment.returnStoredEvents()); 
} 

@Override 
public boolean onCreateOptionsMenu(Menu menu) { 
    getMenuInflater().inflate(R.menu.main_menu, menu); 
    return true; 
} 

@Override 
public boolean onOptionsItemSelected(MenuItem item) { 

    if (item.getTitle().equals("Sort by name")){ 
     Toast.makeText(this, "ITEM 2 CLICKED", Toast.LENGTH_LONG).show(); 
     EventsListFragment.sort(-1); 
    }else if (item.getTitle().equals("Sort by date")) { 
     EventsListFragment.sort(1); 
    }else if (item.getTitle().equals("Stored events")){ 
     showSavedEvents(); 
     Toast.makeText(this, "ITEM 3 CLICKED", Toast.LENGTH_LONG).show(); 
    } 
    return true; 
} 

public void showSavedEvents(){ 
    intent = new Intent(this, StoredEventsActivity.class); 
    intent.putExtra("storedEvents", EventsListFragment.returnStoredEvents()); 
    startActivity(intent); 
} 

}

Answer 1

你需要從運行時間，即插入數據，需要存儲用戶輸入的文本 否則如果您硬編碼的數據，它會添加每次刷新活動

試試這個存儲數據只有一次

https://stackoverflow.com/a/37449709/6312749