How can i update my activities after preference changes immediately?

Question

I want to update my activity immediately after a user changes a setting like language or time format. Here is my code:

public class SettingsActivity extends PreferenceActivity implements OnSharedPreferenceChangeListener {
    public static final String HOUR_FORMAT = "hourFormat";
    public static final String LANGUAGE_CHOICE = "languageSelection";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        addPreferencesFromResource(R.xml.preferences);

    }

    @Override
    public void onSharedPreferenceChanged(SharedPreferences sharedPreferences, String key) {
        if (key.equals("hourFormat")) {
            Preference connectionPref = findPreference(key);
            // Set summary to be the user-description for the selected value
            connectionPref.setSummary(Boolean.toString(sharedPreferences.getBoolean(key, true)));
        }
        else if(key.equals("languageSelection")) {
            Preference connectionPref = findPreference(key);
            // Set summary to be the user-description for the selected value
            connectionPref.setSummary(sharedPreferences.getString(key, "English"));
        }
    }

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

    @Override
    protected void onPause() {
        super.onPause();
        // Unregister the listener whenever a key changes
        getPreferenceScreen().getSharedPreferences()
                .unregisterOnSharedPreferenceChangeListener(this);
    }


}

This is preferences.xml

<?xml version="1.0" encoding="utf-8"?>
<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android">
    <CheckBoxPreference
        android:key="hourFormat"
        android:title="@string/hour24"
        android:summary="@string/hour24Explanation"
        android:defaultValue="true" />
    <ListPreference
            android:key="languageSelection"
            android:entries="@array/languageValues"
            android:summary="@string/languageSelection"
            android:entryValues="@array/languageValues"
            android:title="@string/language" />
</PreferenceScreen>

This only works, if i restart the app. However I want to update it immediately just after the change? (If you want, I can provide other source codes in my app, I know there are lots of resources but I couldn't get this thing working.)

I also think I don't really understand the xListener concept in Java. I read about it a lot but can you clarify or provide additional links to me. Thanks, in advance.

Answer 1

You need to receive the system triggers when the user changes them. To do this, you need to have a class to receive the information, for example for the Time change, put this class in the main Activity class:

private final BroadcastReceiver timeChangedReceiver = new BroadcastReceiver() { @Override public void onReceive(Context context, Intent intent) { final String action = intent.getAction();

        if (action.equals(Intent.ACTION_TIME_CHANGED) ||
            action.equals(Intent.ACTION_TIMEZONE_CHANGED))
        {
            doStuffYouNeedToDo();
        }
    }
};

Write a method doStuffYouNeedToDo in the Activity which does whatever you need to when the time or timezone is changed. To make sure it is called, put this in your class:

// For intent filter for catching timezone etc changes
private static IntentFilter timeChangeIntentFilter;
static {
    timeChangeIntentFilter = new IntentFilter();
    timeChangeIntentFilter.addAction(Intent.ACTION_TIMEZONE_CHANGED);
    timeChangeIntentFilter.addAction(Intent.ACTION_TIME_CHANGED);
}

and this in onCreate:

registerReceiver(timeChangedReceiver, timeChangeIntentFilter);

And to stop it when the Activity stops, put this in onDestroy:

unregisterReceiver(timeChangedReceiver);