通过活动传递和保存数据

Question

I have three activities.

• Settings activity [A] // where you input a number that will be used in the main activity
• Main activity [B] // where it uses the number inputted by the settings activity
• Pause activity [C] // which is dialog that pauses the main activity and gives you the option to reset it

My problem is that i cant find a way to pass that number from A to B and that number to be saved for when the user resets B from CI have tried some methods but i cant make it work. My code:

A:

long npsum = npint * 60000 + np3int * 1000;
Intent cardintent = new Intent(getApplicationContext(), card_game_2.class);
cardintent.putExtra("card2string",npsum);
startActivity(cardintent);

B:

Bundle card2extras = getIntent().getExtras();
    if (card2extras != null) {
        String startcardstring = card2extras.getString("card2string");
        startcard = Long.parseLong(startcardstring);

    }

C:

Intent resetintent = new Intent(card_2_pause.this, card_game_2.class);
startActivity(resetintent);

Thanks for any help

Answer 1

您可以在启动暂停活动C时使用startActivityForResult（）。startActivityForResult（）使您可以将数据发送到接收活动，在您的情况下为MainActivityC。请参见此处的教程。

Answer 2

Fixed it. New code:

A:

 Intent timerdintent = new Intent(timer_settings.this, timer_2.class);
 Bundle timer2extras = new Bundle();
 timer2extras.putString("timer2string", String.valueOf(npsum));
 timerdintent.putExtras(timer2extras);
 startActivity(timerdintent);

B:

SharedPreferences pref = getApplicationContext().getSharedPreferences("timer2stringpref", MODE_PRIVATE);
    Bundle timer2extras = getIntent().getExtras();
    if (timer2extras != null) {
        String timer2string = timer2extras.getString("timer2string");
        starttimer = Integer.parseInt(timer2string);
        SharedPreferences.Editor editor = pref.edit();
        editor.putInt("value", starttimer);
        editor.apply();

    } else {
        int starttimerx = pref.getInt("value", 0);
        starttimer = starttimerx;
    }

C:

Intent resetintent = new Intent(timer_2_pause.this, timer_2.class);
startActivity(resetintent);

Answer 3

You can also set up a (Data)Fragment for exchanging data?

in its onCreate set setRetainInstance(true);

ad some setter/getters to it, for your card2string

and in the different Activities get an instance of it through:

in eg MainActivity

  public final static String DATAFRAG = "DATA";//public so you can use it from any Activity

and in the eg onCreate or where you need the data:

 FragmentManager fm = getFragmentManager();
    dataFrag = (DataFragment) fm.findFragmentByTag(MainActivity.DATAFRAG);
    if (dataFrag == null)
    {
        dataFrag = new DataFragment();
        dataFrag.setCard2String("something");
        fm.beginTransaction().add(dataFrag, MainActivity.DATAFRAG).commit();
    }

make sure to override in the DataFragment the

    @Override
public void onSaveInstanceState(Bundle outState)
{
    super.onSaveInstanceState(outState);
}

and in the onCreate use the Bundle to save & restore your data in case the Fragment was destroyed...

HTH