Come ascoltare le modifiche alle preferenze all'interno di PreferenceFragment?

Question

Come descritto in here, sottoclassi PreferenceFragment e lo visualizzo in un'attività. Questo documento spiega come ascoltare le modifiche delle preferenze here, ma solo se si sottoclasse PreferenceActivity. Dal momento che non lo sto facendo, come posso ascoltare le modifiche alle preferenze?

Ho provato a implementare OnSharedPreferenceChangeListener nel mio PreferenceFragment ma non sembra funzionare (onSharedPreferenceChanged non sembra mai essere chiamato).

Questo è il mio codice finora:

SettingsActivity.java

public class SettingsActivity extends Activity 
{ 
    @Override 
    protected void onCreate(Bundle savedInstanceState) 
    { 
     super.onCreate(savedInstanceState); 

     // Display the fragment as the main content. 
     getFragmentManager().beginTransaction().replace(android.R.id.content, new SettingsFragment()).commit(); 
    } 
} 

SettingsFragment.java

public class SettingsFragment extends PreferenceFragment implements OnSharedPreferenceChangeListener 
{ 
    public static final String KEY_PREF_EXERCISES = "pref_number_of_exercises"; 

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

     // Load the preferences from an XML resource 
     addPreferencesFromResource(R.xml.preferences); 
    } 

    @Override 
    public void onSharedPreferenceChanged(SharedPreferences sharedPreferences, String key) 
    { 
     //IT NEVER GETS IN HERE! 
     if (key.equals(KEY_PREF_EXERCISES)) 
     { 
      // Set summary to be the user-description for the selected value 
      Preference exercisesPref = findPreference(key); 
      exercisesPref.setSummary(sharedPreferences.getString(key, "")); 
     } 
    } 
} 

preferences.xml

<?xml version="1.0" encoding="utf-8"?> 
<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android" > 

    <EditTextPreference 
     android:defaultValue="15" 
     android:enabled="true" 
     android:key="pref_number_of_exercises" 
     android:numeric="integer" 
     android:title="Number of exercises" /> 

</PreferenceScreen> 

Inoltre, il PreferenceFragment è anche il posto giusto dove ascoltare le modifiche alle preferenze o devo farlo all'interno dell'attività?

Answer 1

Credo che sia sufficiente registrare/annullare la registrazione del Listener nel PreferenceFragment e funzionerà.

@Override 
public void onResume() { 
    super.onResume(); 
    getPreferenceManager().getSharedPreferences().registerOnSharedPreferenceChangeListener(this); 

} 

@Override 
public void onPause() { 
    getPreferenceManager().getSharedPreferences().unregisterOnSharedPreferenceChangeListener(this); 
    super.onPause(); 
} 

A seconda di ciò che si desidera, potrebbe non essere necessario utilizzare un listener. Le modifiche alle preferenze vengono assegnate automaticamente a SharedPreferences.

Answer 2

La soluzione di antew funziona bene, qui potete vedere un'attività preferenza completa per android v11 in poi:

import android.app.Activity; 
import android.content.SharedPreferences; 
import android.content.SharedPreferences.OnSharedPreferenceChangeListener; 
import android.os.Bundle; 
import android.preference.ListPreference; 
import android.preference.PreferenceFragment; 

public class UserPreferencesV11 extends Activity { 

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

    // Display the fragment as the main content. 
    getFragmentManager().beginTransaction().replace(android.R.id.content, 
      new PrefsFragment()).commit(); 
} 

public static class PrefsFragment extends PreferenceFragment implements OnSharedPreferenceChangeListener { 

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

     // Load the preferences from an XML resource 
     addPreferencesFromResource(R.xml.preferences); 

     // set texts correctly 
     onSharedPreferenceChanged(null, ""); 

    } 

    @Override 
    public void onResume() { 
     super.onResume(); 
     // Set up a listener whenever a key changes 
     getPreferenceScreen().getSharedPreferences().registerOnSharedPreferenceChangeListener(this); 
    } 

    @Override 
    public void onPause() { 
     super.onPause(); 
     // Set up a listener whenever a key changes 
     getPreferenceScreen().getSharedPreferences().unregisterOnSharedPreferenceChangeListener(this); 
    } 

    @Override 
    public void onSharedPreferenceChanged(SharedPreferences sharedPreferences, String key) { 
     // just update all 
     ListPreference lp = (ListPreference) findPreference(PREF_YOUR_KEY); 
     lp.setSummary("dummy"); // required or will not update 
     lp.setSummary(getString(R.string.pref_yourKey) + ": %s"); 

    } 
} 
} 

Answer 3

Tutte le altre risposte sono corrette. Ma mi piace questa alternativa meglio perché hai immediatamente l'istanza Preferenza che ha causato il cambiamento.

@Override 
public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    Preference pref = findPreference(getString(R.string.key_of_pref));   
    pref.setOnPreferenceChangeListener(new Preference.OnPreferenceChangeListener() { 
     @Override 
     public boolean onPreferenceChange(Preference preference, Object newValue) { 
      // do whatever you want with new value 

      // true to update the state of the Preference with the new value 
      // in case you want to disallow the change return false 
      return true; 
     } 
    }); 
} 

Answer 4

questo ha lavorato per me da PreferenceFragment.onCreate()

OnSharedPreferenceChangeListener listener = 
    new SharedPreferences.OnSharedPreferenceChangeListener() 
    { 
     public void onSharedPreferenceChanged(SharedPreferences prefs, String key) 
     { 
     showDialog(); 
     } 
    }; 

Answer 5

Un altro esempio completo in modo da vedere l'intera immagine.

public class SettingsActivity extends AppCompatPreferenceActivity { 


    /** 
    * A preference value change listener that updates the preference's summary 
    * to reflect its new value. 
    */ 
    private static Preference.OnPreferenceChangeListener 
      sBindPreferenceSummaryToValueListener = 
      new Preference.OnPreferenceChangeListener() { 

       @Override 
       public boolean onPreferenceChange(Preference preference, Object value) { 
        String stringValue = value.toString(); 

        if (preference instanceof ListPreference) { 
         // For list preferences, look up the correct display value in 
         // the preference's 'entries' list. 
         ListPreference listPreference = (ListPreference) preference; 
         int index = listPreference.findIndexOfValue(stringValue); 

         // Set the summary to reflect the new value. 
         preference.setSummary(
           index >= 0 
             ? listPreference.getEntries()[index] 
             : null); 

        } else if (preference instanceof RingtonePreference) { 
         // For ringtone preferences, look up the correct display value 
         // using RingtoneManager. 
         if (TextUtils.isEmpty(stringValue)) { 
          // Empty values correspond to 'silent' (no ringtone). 
          preference.setSummary(R.string.pref_ringtone_silent); 
         } else { 
          Ringtone ringtone = RingtoneManager.getRingtone(
            preference.getContext(), Uri.parse(stringValue)); 
          if (ringtone == null) { 
           // Clear the summary if there was a lookup error. 
           preference.setSummary(null); 
          } else { 
           // Set the summary to reflect the new ringtone display 
           // name. 
           String name = ringtone.getTitle(preference.getContext()); 
           preference.setSummary(name); 
          } 
         } 

        } else { 
         // For all other preferences, set the summary to the value's 
         // simple string representation. 
         preference.setSummary(stringValue); 
        } 
        return true; 
       } 
      }; 

    /** 
    * Helper method to determine if the device has an extra-large screen. For 
    * example, 10" tablets are extra-large. 
    */ 
    private static boolean isXLargeTablet(Context context) { 
     return (context.getResources().getConfiguration().screenLayout 
       & Configuration.SCREENLAYOUT_SIZE_MASK) >= Configuration.SCREENLAYOUT_SIZE_XLARGE; 
    } 

    /** 
    * Binds a preference's summary to its value. More specifically, when the 
    * preference's value is changed, its summary (line of text below the 
    * preference title) is updated to reflect the value. The summary is also 
    * immediately updated upon calling this method. The exact display format is 
    * dependent on the type of preference. 
    * 
    * @see #sBindPreferenceSummaryToValueListener 
    */ 
    private static void bindPreferenceSummaryToValue(Preference preference) { 
     // Set the listener to watch for value changes. 
     preference.setOnPreferenceChangeListener(sBindPreferenceSummaryToValueListener); 

     // Trigger the listener immediately with the preference's current value. 
     sBindPreferenceSummaryToValueListener.onPreferenceChange(preference, 
       PreferenceManager 
         .getDefaultSharedPreferences(preference.getContext()) 
         .getString(preference.getKey(), "")); 
    } 

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

    /** 
    * Set up the {@link android.app.ActionBar}, if the API is available. 
    */ 
    private void setupActionBar() { 
     ActionBar actionBar = getSupportActionBar(); 
     if (actionBar != null) { 
      // Show the Up button in the action bar. 
      actionBar.setDisplayHomeAsUpEnabled(true); 
     } 
    } 

    @Override 
    public boolean onMenuItemSelected(int featureId, MenuItem item) { 
     int id = item.getItemId(); 
     if (id == android.R.id.home) { 
      if (!super.onMenuItemSelected(featureId, item)) { 
       NavUtils.navigateUpFromSameTask(this); 
      } 
      return true; 
     } 
     return super.onMenuItemSelected(featureId, item); 
    } 

    /** 
    * {@inheritDoc} 
    */ 
    @Override 
    public boolean onIsMultiPane() { 
     return isXLargeTablet(this); 
    } 

    /** 
    * {@inheritDoc} 
    */ 
    @Override 
    @TargetApi(Build.VERSION_CODES.HONEYCOMB) 
    public void onBuildHeaders(List<Header> target) { 
     loadHeadersFromResource(R.xml.pref_headers, target); 
    } 

    /** 
    * This method stops fragment injection in malicious applications. 
    * Make sure to deny any unknown fragments here. 
    */ 
    protected boolean isValidFragment(String fragmentName) { 
     return PreferenceFragment.class.getName().equals(fragmentName) 
       || GPSLocationPreferenceFragment.class.getName().equals(fragmentName) 
       || DataSyncPreferenceFragment.class.getName().equals(fragmentName) 
       || NotificationPreferenceFragment.class.getName().equals(fragmentName); 
    } 

    ////////////////// NEW PREFERENCES //////////////////////////// 

    @TargetApi(Build.VERSION_CODES.HONEYCOMB) 
    public static class GPSLocationPreferenceFragment extends PreferenceFragment { 

     Preference prefGPSServerAddr, prefGPSASDID, prefIsGPSSwitch; 

     @Override 
     public void onCreate(Bundle savedInstanceState) { 
      super.onCreate(savedInstanceState); 
      addPreferencesFromResource(R.xml.pref_gps_location); 
      setHasOptionsMenu(true); 

      // Bind the summaries of EditText/List/Dialog/Ringtone preferences 
      // to their values. When their values change, their summaries are 
      // updated to reflect the new value, per the Android Design 
      // guidelines. 

      bindPreferenceSummaryToValue(findPreference("gpsServer_Addr")); 
      bindPreferenceSummaryToValue(findPreference("gpsASD_ID")); 


      prefGPSServerAddr = findPreference("gpsServer_Addr"); 
      prefGPSServerAddr.setOnPreferenceChangeListener(new Preference.OnPreferenceChangeListener() { 
       @Override 
       public boolean onPreferenceChange(Preference preference, Object newValue) { 

        try { 
         // do whatever you want with new value 

        } 
        catch (Exception ex) 
        { 
         Log.e("Preferences", ex.getMessage()); 
        } 

        // true to update the state of the Preference with the new value 
        // in case you want to disallow the change return false 
        return true; 
       } 
      }); 

      prefGPSASDID = findPreference("gpsASD_ID"); 
      prefGPSASDID.setOnPreferenceChangeListener(new Preference.OnPreferenceChangeListener() { 
       @Override 
       public boolean onPreferenceChange(Preference preference, Object newValue) { 

        try { 
         // do whatever you want with new value 

        } 
        catch (Exception ex) 
        { 
         Log.e("Preferences", ex.getMessage()); 
        } 

        // true to update the state of the Preference with the new value 
        // in case you want to disallow the change return false 
        return true; 
       } 
      }); 

      prefIsGPSSwitch = findPreference("isGPS_Switch"); 
      prefIsGPSSwitch.setOnPreferenceChangeListener(new Preference.OnPreferenceChangeListener() { 
       @Override 
       public boolean onPreferenceChange(Preference preference, Object newValue) { 

        try { 
         // do whatever you want with new value 

        } 
        catch (Exception ex) 
        { 
         Log.e("Preferences", ex.getMessage()); 
        } 

        // true to update the state of the Preference with the new value 
        // in case you want to disallow the change return false 
        return true; 
       } 
      }); 
     } 

     @Override 
     public boolean onOptionsItemSelected(MenuItem item) { 
      int id = item.getItemId(); 
      if (id == android.R.id.home) { 
       boolean tabletSize = getResources().getBoolean(R.bool.isTablet); 
       if (tabletSize) { 
        startActivity(new Intent(getActivity(), MainActivity.class)); 
       } else { 
        startActivity(new Intent(getActivity(), SettingsActivity.class)); 
       } 
       return true; 
      } 
      return super.onOptionsItemSelected(item); 
     } 
    } 

    /////////////////////////////////////////////////////////////// 

    /** 
    * This fragment shows notification preferences only. It is used when the 
    * activity is showing a two-pane settings UI. 
    */ 
    @TargetApi(Build.VERSION_CODES.HONEYCOMB) 
    public static class NotificationPreferenceFragment extends PreferenceFragment { 
     @Override 
     public void onCreate(Bundle savedInstanceState) { 
      super.onCreate(savedInstanceState); 
      addPreferencesFromResource(R.xml.pref_notification); 
      setHasOptionsMenu(true); 

      // Bind the summaries of EditText/List/Dialog/Ringtone preferences 
      // to their values. When their values change, their summaries are 
      // updated to reflect the new value, per the Android Design 
      // guidelines. 
      bindPreferenceSummaryToValue(findPreference("notifications_new_message_ringtone")); 
     } 

     @Override 
     public boolean onOptionsItemSelected(MenuItem item) { 
      int id = item.getItemId(); 
      if (id == android.R.id.home) { 
       boolean tabletSize = getResources().getBoolean(R.bool.isTablet); 
       if (tabletSize) { 
        startActivity(new Intent(getActivity(), MainActivity.class)); 
       } else { 
        startActivity(new Intent(getActivity(), SettingsActivity.class)); 
       } 
       return true; 
      } 
      return super.onOptionsItemSelected(item); 
     } 
    } 

    /** 
    * This fragment shows data and sync preferences only. It is used when the 
    * activity is showing a two-pane settings UI. 
    */ 
    @TargetApi(Build.VERSION_CODES.HONEYCOMB) 
    public static class DataSyncPreferenceFragment extends PreferenceFragment { 
     @Override 
     public void onCreate(Bundle savedInstanceState) { 
      super.onCreate(savedInstanceState); 
      addPreferencesFromResource(R.xml.pref_data_sync); 
      setHasOptionsMenu(true); 

      // Bind the summaries of EditText/List/Dialog/Ringtone preferences 
      // to their values. When their values change, their summaries are 
      // updated to reflect the new value, per the Android Design 
      // guidelines. 
      bindPreferenceSummaryToValue(findPreference("sync_frequency")); 
     } 

     @Override 
     public boolean onOptionsItemSelected(MenuItem item) { 
      int id = item.getItemId(); 
      if (id == android.R.id.home) { 
       boolean tabletSize = getResources().getBoolean(R.bool.isTablet); 
       if (tabletSize) { 
        startActivity(new Intent(getActivity(), MainActivity.class)); 
       } else { 
        startActivity(new Intent(getActivity(), SettingsActivity.class)); 
       } 
       return true; 
      } 
      return super.onOptionsItemSelected(item); 
     } 
    } 
}