在退出应用程序之前保存Listview

Question

我想保存我的listview及其组件，以便当我退出应用程序并返回时它们仍然可用。目前他们已被清除，我被迫制作新物品。

我一直在研究onSaveInstanceState，但我不确定如何在目前的情况下实现它。

我应该怎么做才能存储我目前的Listview状态？阵列

MAINACTIVITY

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);

    // Check whether we're recreating a previously destroyed instance
    //if (savedInstanceState != null) {
        // Restore value of members from saved state
        //mUser = savedInstanceState.getString(STATE_USER);
    //} else {
        // Probably initialize members with default values for a new
        // instance
        //mUser = "NewUser";
    //}

    // // get detail controls
    tvTitle = (TextView) findViewById(R.id.textViewTitle);
    tvDate = (TextView) findViewById(R.id.textViewDate);
    tvTime = (TextView) findViewById(R.id.textViewTime);
    ivPic = (ImageView) findViewById(R.id.imageView1);

    add = (ImageButton) findViewById(R.id.add);
    add.setOnClickListener(this);

}

@Override
public void onClick(View v) {
    // TODO Auto-generated method stub
    switch (v.getId()) {
    case R.id.add:
        Intent intent = new Intent(this, CreateActivity.class);
        startActivityForResult(intent, 100);
        break;
    }
}

@Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);

    // Create the adapter to convert the array to views
    EventAdapter adapter = new EventAdapter(this, lstEvents);

    // attach adapter to a list view
    listView = (ListView) findViewById(R.id.listViewFragment);
    listView.setAdapter(adapter);

    if (requestCode == 100) {
        if (resultCode == RESULT_OK) {
            Bundle b = data.getExtras();
            title = b.getString("TITLE");
            time = b.getString("TIME");
            date = b.getString("DATE");

            // retrieving bitmap from CreateActivity

            Bitmap bitmap = (Bitmap) b.getParcelable("DRAWABLE");

            // converting from bitmap to drawable
            Drawable drawable = new BitmapDrawable(getResources(), bitmap);

            Log.e("TITLE", title);
            Log.e("TIME", time);
            Log.e("DATE", date);

            Event newEvent = new Event();
            newEvent.set_date(date);
            newEvent.set_title(title);
            newEvent.set_time(time);

            // set drawable
            newEvent.set_drawable(drawable);

            lstEvents.add(newEvent);

            adapter.addAll(lstEvents);
            adapter.notifyDataSetChanged();
        }
    }

}

@Override
protected void onSaveInstanceState(Bundle savedInstanceState) {
    // savedInstanceState.putInt(STATE_USER, mUser);
    // Always call the superclass so it can save the view hierarchy state
    super.onSaveInstanceState(savedInstanceState);
}
}

Answer 1

您可以将列表中的元素保存在SQLite DB内或File内，然后将其读取并将所有内容放入ListView中。

您可以使用Serializable标记Event类，以便您可以从文件中保存/恢复该类，并让Java完成大部分工作

Answer 2

我最终使用了SQLite数据库。下面是我实现的一些代码，我将继续更新，直到应用程序完成。

<强> DBHANDLER

public class DatabaseHandler extends SQLiteOpenHelper {

// All Static variables
// Database Version
private static final int DATABASE_VERSION = 1;

// Database Name
private static final String DATABASE_NAME = "scheduleManager";

// Contacts table name
private static final String TABLE_EVENTS = "events";


// Contacts Table Columns names
private static final String KEY_ID = "id";
private static final String KEY_TITLE = "title";
private static final String KEY_TIME = "time";
private static final String KEY_DATE = "date";
private static final int KEY_DRW = 0;

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

@Override
public void onCreate(SQLiteDatabase db) {
    // TODO Auto-generated method stub
    String CREATE_EVENTS_TABLE = "CREATE TABLE " + TABLE_EVENTS + "("
            + KEY_ID + " INTEGER," + KEY_TITLE + " TEXT,"
            + KEY_TIME + " TEXT," + KEY_DATE + " TEXT" + ")";
    db.execSQL(CREATE_EVENTS_TABLE);

}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    // Drop older table if existed
    db.execSQL("DROP TABLE IF EXISTS " + TABLE_EVENTS);

    // Create tables again
    onCreate(db);

}

/**
 * All CRUD(Create, Read, Update, Delete) Operations
 */


//adding an event (NEEDS TO ADD DRAWABLE)
 public void addEvent(Event event) {
        SQLiteDatabase db = this.getWritableDatabase();

        ContentValues values = new ContentValues();
        values.put(KEY_ID, event.get_Id()); //Event ID
        values.put(KEY_TITLE, event.get_title()); // Event Title
        values.put(KEY_TIME, event.get_time()); // Event Time
        values.put(KEY_DATE, event.get_date()); // Event Date
        //values.put(KEY_DRW, event.get_drawable()); // Event Drawable

        // Inserting Row
        db.insert(TABLE_EVENTS, null, values);
        db.close(); // Closing database connection
    }

   // Getting single contact
   public Event getEvent(int id) {
       SQLiteDatabase db = this.getReadableDatabase();

       Cursor cursor = db.query(TABLE_EVENTS, new String[] { KEY_ID,
               KEY_TITLE, KEY_TIME, KEY_DATE }, KEY_ID + "=?",
               new String[] { String.valueOf(id) }, null, null, null, null);
       if (cursor != null)
           cursor.moveToFirst();

       Event event = new Event(Integer.parseInt(cursor.getString(0)),
               cursor.getString(1), cursor.getString(2), null, null);
       // return contact
       return event;
   }


    // Getting All Contacts
   public List<Event> getAllContacts() {
      List<Event> eventList = new ArrayList<Event>();
      // Select All Query
      String selectQuery = "SELECT  * FROM " + TABLE_EVENTS;

      SQLiteDatabase db = this.getWritableDatabase();
      Cursor cursor = db.rawQuery(selectQuery, null);

      // looping through all rows and adding to list
      if (cursor.moveToFirst()) {
          do {
              Event event = new Event();
              event.set_Id(Integer.parseInt(cursor.getString(0)));
              event.set_title(cursor.getString(1));
              event.set_time(cursor.getString(2));
              event.set_date(cursor.getString(3));
              // Adding contact to list
              eventList.add(event);
          } while (cursor.moveToNext());
      }

      // return contact list
      return eventList;
  }

// Getting event Count
    public int getEventsCount() {
        String countQuery = "SELECT  * FROM " + TABLE_EVENTS;
        SQLiteDatabase db = this.getReadableDatabase();
        Cursor cursor = db.rawQuery(countQuery, null);
        cursor.close();

        // return count
        return cursor.getCount();
    }

 // Updating single contact
    public int updateEvent(Event event) {
        SQLiteDatabase db = this.getWritableDatabase();

        ContentValues values = new ContentValues();
        values.put(KEY_TITLE, event.get_title());
        values.put(KEY_TIME, event.get_time());
        values.put(KEY_DATE, event.get_date());

        // updating row
        return db.update(TABLE_EVENTS, values, KEY_ID + " = ?",
                new String[] { String.valueOf(event.get_Id()) });
    }

    // Deleting single contact
    public void deleteEvent(Event event) {
        SQLiteDatabase db = this.getWritableDatabase();
        db.delete(TABLE_EVENTS, KEY_ID + " = ?",
                new String[] { String.valueOf(event.get_Id()) });
        db.close();
    }

}

<强> MAINACTIVITY

public class MainActivity extends FragmentActivity implements OnClickListener {

ListView listView;
int lastIndex = -1;
ArrayList<Event> lstEvents = new ArrayList<Event>();

// detail view
TextView tvTitle, tvTime, tvDate;
ImageView ivPic;
View vw_master;

boolean _isBack = true;

ImageButton add;

String title;
String date;
String time;
int resId;

static final int PICK_CONTACT_REQUEST = 0;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);

    // // get detail controls
    tvTitle = (TextView) findViewById(R.id.textViewTitle);
    tvDate = (TextView) findViewById(R.id.textViewDate);
    tvTime = (TextView) findViewById(R.id.textViewTime);
    ivPic = (ImageView) findViewById(R.id.imageView1);

    add = (ImageButton) findViewById(R.id.add);
    add.setOnClickListener(this);


    /////////////////////////////////LISTVIEW////////////////////////////////////////
    // Create the adapter to convert the array to views
    EventAdapter adapter = new EventAdapter(this, lstEvents);

    // attach adapter to a list view
    listView = (ListView) findViewById(R.id.listViewFragment);
    listView.setAdapter(adapter);
    /////////////////////////////////LISTVIEW////////////////////////////////////////




    // /////////////////////////////DATABASE/////////////////////////////////////////////
    DatabaseHandler db = new DatabaseHandler(this);
    // /////////////////////////////DATABASE/////////////////////////////////////////////

    List<Event> events = db.getAllContacts();

    adapter.addAll(events);
    adapter.notifyDataSetChanged();






}

@Override
public void onClick(View v) {
    // TODO Auto-generated method stub
    switch (v.getId()) {
    case R.id.add:
        Intent intent = new Intent(this, CreateActivity.class);
        startActivityForResult(intent, 100);
        break;
    }
}

@Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);

    // /////////////////////////////DATABASE/////////////////////////////////////////////
    DatabaseHandler db = new DatabaseHandler(this);
    // /////////////////////////////DATABASE/////////////////////////////////////////////

    // Create the adapter to convert the array to views
    EventAdapter adapter = new EventAdapter(this, lstEvents);

    // attach adapter to a list view
    listView = (ListView) findViewById(R.id.listViewFragment);
    listView.setAdapter(adapter);

    if (requestCode == 100) {
        if (resultCode == RESULT_OK) {
            Bundle b = data.getExtras();
            title = b.getString("TITLE");
            time = b.getString("TIME");
            date = b.getString("DATE");

            // retrieving bitmap from CreateActivity

            Bitmap bitmap = (Bitmap) b.getParcelable("DRAWABLE");

            // converting from bitmap to drawable
            Drawable drawable = new BitmapDrawable(getResources(), bitmap);

            // Event newEvent = new Event();
            // newEvent.set_date(date);
            // newEvent.set_title(title);
            // newEvent.set_time(time);

            // set drawable
            // newEvent.set_drawable(drawable);

            // lstEvents.add(newEvent);

            // adapter.addAll(lstEvents);
            // adapter.notifyDataSetChanged();

            ///////////////////////////////DATABASE/////////////////////////////////////////////
            /**
             * CRUD OPERATIONS
             */

            Log.e("Insert: ", "Inserting ..");
            db.addEvent(new Event(0, title, time, date, drawable));

            // Reading all contacts
            Log.e("Reading: ", "Reading all contacts..");
            // List<Event> events = db.getAllContacts();
            List<Event> events = db.getAllContacts();
            adapter.addAll(events);
            adapter.notifyDataSetChanged();

            //logging all events

            for (Event ev : events) {
                String log = "Id: " + ev.get_Id() + " ,Title: "
                        + ev.get_title() + " ,Date: " + ev.get_date();
                // Writing Contacts to log
                Log.e("Name: ", log);

            }

            ///////////////////////////////DATABASE/////////////////////////////////////////////
        }

    }
}

}