android - 共享首选项不在 Activity 之间传递数据

Question

我已经有几天遇到这个问题了。当我设置数据时，我的共享偏好似乎不起作用。用户从main开始，显示“oncreate”，然后进入设置页面(自动设置数据的地方(暂时))，当他们回到主Activity时，数据似乎不想过来.我正在使用 joda 时间库，我正在尝试计算两个日期之间的时间差。

Main:(onCreate代码和onResume代码是一样的)

public class MainActivity extends Activity {

    TextView tv; 
    Button set;

    //CONST
    final static long MILLIS_IN_DAY = 86400000;
    final static long MILLIS_IN_HOUR = 3600000;
    final static long MILLIS_IN_MINUTE = 60000;
    long day, hour, minute;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        tv = (TextView) findViewById(R.id.textViewx);
        set = (Button) findViewById(R.id.setting);
        tv.setText("ONCREATE!");

        //LOAD DATA
        SharedPreferences prefs = getPreferences(MODE_PRIVATE);
        long loadedTime = prefs.getLong("quitDate", 0); //Load Settings Data
        boolean test = prefs.getBoolean("test", false);

        //get Comparison Data
        DateTime newDate = new DateTime();
        long updateTime = newDate.getMillis();
        long diffInMillis =  (updateTime-loadedTime);

        //Calculate
        minute = (diffInMillis/MILLIS_IN_MINUTE)%60;
        hour = (diffInMillis/MILLIS_IN_HOUR)%24;
        day = (diffInMillis/MILLIS_IN_DAY);

        tv.setText(""+Long.toString(loadedTime));
        if(test==true){
            tv.setText("" + "\nDay|Hour|Minute: " + Long.toString(day) +":" + Long.toString(hour) + ":" + Long.toString(minute));   
        }


        set.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View arg0) {
                Intent x = new Intent(MainActivity.this, Settings.class);
                startActivity(x);

            }
        });

设置:

import org.joda.time.DateTime;
import android.content.SharedPreferences;

public class Settings extends Activity implements View.OnClickListener {
    Button bAbout,bSettings,bFacebook;
    //(5000);
            final long MILLIS_IN_DAY = 86400000;
            final long MILLIS_IN_HOUR = 3600000;
            final long MILLIS_IN_MINUTE = 60000;
    //Variables
    long loadedTime;
    int packs;
    float cost;
    long day, hour, minute, second;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setTitle("Settings");
        setContentView(R.layout.activity_settings);
        setUpButtons();

        DateTime d1 = new DateTime(2013,9,11,0,0);

        long today = d1.getMillis();        

        //SAVE DATA
        SharedPreferences.Editor editor = getPreferences(MODE_PRIVATE).edit();
         editor.putLong("quitDate", today);
         editor.putBoolean("test", true);
         editor.commit();

        minute = (today/MILLIS_IN_MINUTE)%60;
        hour = (today/MILLIS_IN_HOUR)%24;
        day = (today/MILLIS_IN_DAY);

        TextView tv = (TextView) findViewById(R.id.TEMPDATE);
        TextView tv2 = (TextView) findViewById(R.id.todayis);
    tv2.setText("Today is: " + Long.toString(today));

    }

Answer 1

您正在使用每个 Activity 专用的首选项。这意味着您有两组首选项:一组用于 MainActivity，一组用于设置。

这是相关的文档 fragment :

Activity persistent state is managed with the method getPreferences(int), allowing you to retrieve and modify a set of name/value pairs associated with the activity. To use preferences that are shared across multiple application components (activities, receivers, services, providers), you can use the underlying Context.getSharedPreferences() method to retrieve a preferences object stored under a specific name

http://developer.android.com/reference/android/app/Activity.html#getPreferences(int)

你可以使用类似 getSharedPreferences("MY_PREFERENCES", MODE_PRIVATE) 的东西或者直接调用 PreferenceManager.getDefaultSharedPreferences(Context context)获取默认共享首选项集。