SharedPreferences无法跨活动工作

Question

I'm trying to save some filters/state in one activity, and then use that data in the next activity.

I'm using SharedPreferences, but it isn't working as I'd expected it to.

public class FilterActivity extends Activity {

  private static final String TAG = FilterActivity.class.getName();

  EditText distanceEditor;

  @Override
  public void onPause() {
    super.onPause();
    SharedPreferences preferences = getSharedPreferences(PreferenceKey.FILTER_PREFERENCES_NAME, MODE_WORLD_READABLE);
    String distance = distanceEditor.getText().toString();
    preferences.edit().putString(PreferenceKey.DISTANCE, distance);
    preferences.edit().commit();
    Log.i(TAG, "Wrote max-distance=" + distance);

    Log.i(TAG, "Preferences contains distance=" + preferences.getString(PreferenceKey.DISTANCE, "FAIL"));
  }


  public static class PreferenceKey {
    public static final String FILTER_PREFERENCES_NAME = "FilterActivity:" + "Filter_Preference_File";
    public static final String DISTANCE = "FilterActivity:" + "DISTANCE";
  }
}

Then, the Activity that should use this preference:

public class MapActivity  extends MapActivity {
  @Override
  public void onResume() {
    super.onResume();

    SharedPreferences preferences = getSharedPreferences(FilterActivity.PreferenceKey.FILTER_PREFERENCES_NAME, MODE_WORLD_READABLE);
    String maxDistance = preferences.getString(FilterActivity.PreferenceKey.DISTANCE, "FAIL");

    Log.i(TAG, "Read max-distance=" + maxDistance);
  }
}

But the output I get is:

.FilterActivity( 4847): Wrote max-distance=99.9
.FilterActivity( 4847): Preferences contains distance=FAIL
.MapActivity( 4847): Read max-distance=FAIL

Can anyone tell me what I'm doing wrong here?

I am developing against API Level-8.

Answer 1

In the following two lines,

preferences.edit().putString(PreferenceKey.DISTANCE, distance);
preferences.edit().commit();

two different SharedPreferences.Editor s are being returned. Hence the value is not being committed. Instead, you have to use:

SharedPreferences.Editor spe = preferences.edit();
spe.putString(PreferenceKey.DISTANCE, distance);
spe.commit();