Develop Reference

how to implement settings in android

I want to create a settings class one. I've created one myself right now. For example, I created a key switch called camera. This clicklistener how do I do this?
SettingsActivity Class:
public class SettingsActivity extends PreferenceActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
getFragmentManager().beginTransaction().replace(android.R.id.content, new MyPreferenceFragment()).commit();
}
public static class MyPreferenceFragment extends PreferenceFragment
{
#Override
public void onCreate(final Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
addPreferencesFromResource(R.xml.settings);
}
}
}
Settings Activity XML:
<androidx.preference.PreferenceCategory
android:key="the_key_to_retrieve_the_preference_in_code">
<androidx.preference.SwitchPreference
android:key="camera"
android:summary="...."
android:title="Camera" />
<androidx.preference.SwitchPreference
android:key="reset"
android:summary="..."
android:title="Reset" />
<androidx.preference.Preference
android:key="key"
android:summary="subtitle"
android:title="title" />
<androidx.preference.Preference
android:key="key2"
android:summary="subtitle2"
android:title="title2" />
<androidx.preference.CheckBoxPreference
android:key="key_for_check_box"
android:summary="subtitle"
android:title="title" />
</androidx.preference.PreferenceCategory>
</PreferenceScreen>

Follow that steps
1. In oncreate you should make default setting and put the in shared prefs like this
SharedPreferences preferences =
PreferenceManager.getDefaultSharedPreferences(this);
SharedPreferences.Editor editor = preferences.edit();
editor.putString("Key","Value");
editor.apply();
And here change the flag for if settings are default or not. So first time when user open app everything by default and you set default values when he changed something the flag of default is changing and next time he come back this step ignores
2. On each switcher you have to make check and get value from shared preferences like this.
SharedPreferences preferences = PreferenceManager.getDefaultSharedPreferences(this);
String name = preferences.getString("Key", "Value");
if(!name.equalsIgnoreCase("") && !name.equalsIgnoreCase("default")
{
// Switcher change state
}
Optional: You could optimize it by adding one more flag to check were there any changes after last update in that case just go and update each switcher but this is the easiest way. Either you could check if user open app first time or not by adding on null check
Conclusion: Check if first time just put everything with default values from shared preferences -> than if change switcher state just change the same in shared pref -> when come back to setting activity extract all values from each switcher from shared preferences

How are changes in the Preference ie Checkbox Preference , List Preference etc.. saved in the Shared Preference?

Okay so I'm trying to make sense of how Shared Preference works with Preference.
Below is part of an app that works, but I do not understand how it works for the part of Shared Preference.
I have a UserPrefActivity.java containing the following code
public class UserPrefActivity extends PreferenceActivity {
//a preference value change listener that updates the preference summary
//to reflect its new value
private static Preference.OnPreferenceChangeListener
sBindPreferenceSummaryToValueListerner = new Preference.OnPreferenceChangeListener() {
#Override
public boolean onPreferenceChange(Preference preference, Object newValue) {
//gets string value of object
String value = newValue.toString();
Log.e("in sBind Listener", value);
//if the preference is a list preference, get the value at a given index
if (preference instanceof ListPreference) {
//for list preference look up the correct display value
//in the preference entries array
ListPreference listPreference = (ListPreference) preference;
int index = listPreference.findIndexOfValue(value);
//set the summary to reflect the new value
preference.setSummary(index >= 0 ? listPreference.getEntries()[index] : null);
} else {
//set summary to only value
preference.setSummary(value);
}
return true;
}
};
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
//call the deprecated method to load the preference screen
addPreferencesFromResource(R.xml.user_pref);
//get default Shared preference from preference screen
SharedPreferences settings = PreferenceManager.getDefaultSharedPreferences(this);
Preference saveNumPizza = findPreference("saveNumPizza");
//set the preference change listener to saveNumPizza
saveNumPizza.setOnPreferenceChangeListener(sBindPreferenceSummaryToValueListerner);
sBindPreferenceSummaryToValueListerner.onPreferenceChange(saveNumPizza,
PreferenceManager
.getDefaultSharedPreferences(this)
.getString(saveNumPizza.getKey(), ""));
}
}
In the MainActivity.java, I have the following as part of a bigger piece of code
//gets the default shared preference instance and assign to sharedPrefs for enabled save
// data
SharedPreferences sharedPrefs = PreferenceManager.getDefaultSharedPreferences
(MainActivity.this);
//checks if save order status is true
if (sharedPrefs.getBoolean("saveOrder", false)) {
//do stuff..
}
I have the following UserPref.xml
<?xml version="1.0" encoding="utf-8"?>
<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android">
<CheckBoxPreference
android:defaultValue="false"
android:key="saveOrder"
android:summary="for quick loading of favourite order"
android:title="Enable Saving Order"/>
<PreferenceCategory android:title="ORDER HISTORY">
<CheckBoxPreference
android:defaultValue="false"
android:key="keepHistory"
android:summary="of pizza orders"
android:title="Keep History"/>
<ListPreference
android:defaultValue="3"
android:dialogTitle="Choose how many to save"
android:entries="#array/number_of_pizza"
android:entryValues="#array/number_of_pizza_values"
android:summary="3 pizza orders"
android:key="saveNumPizza"
android:title="Number of Orders"/>
</PreferenceCategory>
</PreferenceScreen>
I know that in the UserPrefsActivity, I believe in the PreferenceManager.getDefaultSharedPreferences(this) call, the shared preferences is created and obtained if it does not exist, if it does its just obtained.
From what I've noticed with the app, is that on first launch when I get to the settings and launch the UserPrefActivity via intent, the shared preference of the UserPrefActivity is created, containing only the saveNumPizza key. However the minute I click on the other preferences (Checkbox preference) when I look at the shared preference file, I immediately see that the saveOrder key and keepHistory key are automatically saved.
I would just like to know how this automatic saving is exactly done since I am not using an editor to save it to the shared preference, nor am I calling apply or commit.
Thank you,

EditTextPreference.setText(value) not updating as expected

I'm trying to prevent the user from entering an empty string into an EditTextPreference (in the example, catName). I use a OnPreferenceChangeListener to detect when a change is made to the EditTextPreference, and if there is a change and the string is blank, I use the EditTextPreference.setText() command to reset to the old value. However, the new value doesn't show up properly if I reopen the EditTextPreference in the GUI (the string is blank), and if I go back into the main app, I can verify that a blank value is being saved to the preferences.
I've verified that the if statement executes as expected, and that my parameter keeping track of the old name (oldCatName) is updating as expected. I can even log the catName.getText() value right before the setOnPreferenceChangeListener finishes execution and I always see the value I expect (the new value set by the user, and when they enter a blank value, it properly resets to the old value). I'm not sure why setting the value to the EditTextPreference isn't saving the value to the preferences file or updating the GUI.
public class SettingsActivity extends PreferenceActivity {
private String oldCatName;
private EditTextPreference catName;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
addPreferencesFromResource(R.xml.settings);
catName = (EditTextPreference) findPreference("cat_name");
oldCatName = catName.getText();
catName.setOnPreferenceChangeListener(new OnPreferenceChangeListener() {
#Override
public boolean onPreferenceChange(Preference preference, Object newVal) {
final String value = (String) newVal;
if (value.equals("")) {
catName.setText(oldCatName);
Log.e("new value", catName.getText());
}
else
oldCatName = value;
return true;
}
});
}
}
Thanks for the help!
-Michael
Edit: A clarification. The logic in the if statement is executing correctly. The string value of the EditTextPreference is even updating correctly. However, the value in the GUI if the user taps on the EditTextPreference again does not correctly update, and the value in the app's shared preferences does not update correctly. It stays blank.

Finally found a solution by doing the following:
I used a SharedPreferences.OnSharedPreferenceChangeListener instead of a Preference.OnPreferenceChangeListener. The Preference.OnPreferenceChangeListener looks for when the user changes a preference through the settings menu, and behaves before the change is committed to the preference data. The SharedPreferences.OnSharedPreferenceChangeListener listens for changes to the actual preference data, not changes in the GUI, so it happens a little later. I noticed that in my first attempt, I could run setText() immediately followed by getText() on my EditTextPreference object, and the getText() value wouldn't match what I had just set the setText() value to. I'm not sure why this happens, but waiting for the changes to actually commit before trying to run setText() led to the correct response. Maybe it was a timing issue?
I run setPreferenceScreen(null) and addPreferencesFromResource(R.xml.settings) after updating the value in the EditTextPreference. If I didn't do this, sometimes when the user would click on the EditTextPreference again, the value in the field would appear blank even though the value in the settings file wasn't. This forces the settings page to, more or less, refresh itself.
The working code is below:
public class SettingsActivity extends PreferenceActivity {
private String oldCatName;
private EditTextPreference catName;
private SharedPreferences.OnSharedPreferenceChangeListener listener;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
addPreferencesFromResource(R.xml.settings);
createListener();
catName = (EditTextPreference) findPreference("cat_name");
oldCatName = catName.getText();
}
private void createListener() {
listener = new SharedPreferences.OnSharedPreferenceChangeListener() {
#Override
public void onSharedPreferenceChanged(
SharedPreferences sharedPreferences, String key) {
String value = sharedPreferences.getString("cat_name", "NULL");
if (value.equals("")) {
catName.setText(oldCatName);
setPreferenceScreen(null);
addPreferencesFromResource(R.xml.settings);
} else {
oldCatName = value;
}
}
};
PreferenceManager.getDefaultSharedPreferences(getApplicationContext())
.registerOnSharedPreferenceChangeListener(listener);
}
}

~9 yrs late, Hope this helps some one else.
I too faced similar issue. It can be done simply by returning false. As the documentation states returning true will update the value and you want to ignore changes.
catName.setOnPreferenceChangeListener(new OnPreferenceChangeListener() {
#Override
public boolean onPreferenceChange(Preference preference, Object newVal) {
final String value = (String) newVal;
if (value.equals("")) {
catName.setText(oldCatName);
Log.e("new value", catName.getText());
return false ; // <----------------------------------
}
else
oldCatName = value;
return true;
}
});

Android: Changing a preference via dialog does not update the value

I'm using a PreferenceActivity in my app. Defined the settings.xml as follows -
<?xml version="1.0" encoding="utf-8"?>
<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android"
android:title="Preferences" >
<PreferenceCategory android:title="Email Options" >
<EditTextPreference
android:dialogTitle="#string/pref_email_user_title"
android:key="pref_email_user"
android:summary="#string/pref_email_user_summary"
android:persistent="true"
android:title="#string/pref_email_user_title" />
<EditTextPreference
android:dialogTitle="#string/pref_email_password_title"
android:key="pref_email_password"
android:summary="#string/pref_email_password_summary"
android:persistent="true"
android:title="#string/pref_email_password_title" />
</PreferenceCategory>
Activity as follows -
public class Prefs extends PreferenceActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
addPreferencesFromResource(R.xml.settings);
}
}
Which is all you need, right? Apparently not though, because what happens is that I click on the 'email user' setting, it brings up a dialog which I use to type in a string value. However what I typed in isn't getting placed on the Settings screen, I still see the default value.
I notice that the values are getting persisted in the preferences file under /data/data/<package>/shared_prefs
I also don't see these persisted values when I relaunch the app - it shows default values. What's the bit of magic I'm missing?

You need an OnPreferenceChangeListener that will listen for changes on your preferences and automatically update the preference summary.
See this code from the samples in the SDK:
/**
* 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;
}
};
You need to bind this to all your preference items, for example like this:
bindPreferenceSummaryToValue(findPreference("username"));
And:
/**
* 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(), ""));
}

Android SharedPreferences How is it mean to be used?

I am struggling to restore the default values I specified in the preferences.xml, Here is my code:
Preference reset = findPreference(res.getString(R.string.DEFAULT_PREFS));
reset.setOnPreferenceClickListener(new Preference.OnPreferenceClickListener() {
public boolean onPreferenceClick(Preference p) {
SharedPreferences sp = PreferenceManager.getDefaultSharedPreferences(Preferences.this);
sp.edit().clear().commit();
PreferenceManager.setDefaultValues(Preferences.this, R.layout.preferences, true);
return true;
}
});
This code is my understanding of the android's developers reference for the function setDefaultValues(context, resId, readAgain):
Parameters
context The context of the shared preferences.
resId The resource ID of the preference hierarchy XML file.
readAgain Whether to re-read the default values.
Note: this will NOT reset preferences back to their default values.
For that functionality, use getDefaultSharedPreferences(Context)
and clear it followed by a call to this method with
this parameter set to true.
Well, it does not work, the preferences values are the same after this code is executed.
Then I looked into the SharedPreferences variable sp, and it points to a system generated file in the path:
/data/data/<packagename>/shared_prefs/<packagename>_preferences.xml
which I can only assume is the same xml I provided when I created the activity.
addPreferencesFromResource(R.layout.preferences);
Also inspecting the sp variable, the hash table has all the preferences, but there is no field for default value.
EDIT:
Before I am asked to, here is an excerpt from the preferences.xml file
<?xml version="1.0" encoding="utf-8"?>
<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android" >
<EditTextPreference
android:defaultValue="5000"
android:key="#string/MAX_MESSAGES"
android:numeric="integer"
android:summary="#string/MAX_MESSAGES_desc"
android:title="#string/MAX_MESSAGES_title" />
<EditTextPreference
android:defaultValue="10"
android:key="#string/VIEW_EDGE_ROWS"
android:numeric="integer"
android:summary="#string/VIEW_EDGE_ROWS_desc"
android:title="#string/VIEW_EDGE_ROWS_title" />
<ListPreference
android:defaultValue="0"
android:entries="#array/level_list"
android:entryValues="#array/level_values"
android:key="#string/INITIAL_ORG"
android:summary="#string/INITIAL_ORG_desc"
android:title="#string/INITIAL_ORG_title" />
<ListPreference
android:defaultValue="2"
android:entries="#array/view_list"
android:entryValues="#array/view_values"
android:key="#string/INITIAL_VIEW"
android:summary="#string/INITIAL_VIEW_desc"
android:title="#string/INITIAL_VIEW_title" />
<CheckBoxPreference
android:defaultValue="true"
android:key="#string/AUTOSCROLL"
android:summary="#string/AUTOSCROLL_desc"
android:title="#string/AUTOSCROLL_title" />
<CheckBoxPreference
android:defaultValue="true"
android:key="#string/SEND_THEN_EXIT"
android:summary="#string/SEND_THEN_EXIT_desc"
android:title="#string/SEND_THEN_EXIT_title" />
<Preference
android:key="#string/DEFAULT_PREFS"
android:summary="#string/DEFAULT_PREFS_desc"
android:title="#string/DEFAULT_PREFS_title" />
</PreferenceScreen>

This is my solution so far. After debugging into the Android source code I find out that setDefaultValues() is not reliable and does not work as intended (at least according to my expectations).
I restore the default values manually now. I have a map where I can fetch from the default values.
Here is an interesting note: Inspecting the Preference class shows it has a field called mDefaultValue which contains the default value for the preference. But this field can only be set by setDefaultValue() method, and there is no method to get it. It would have save me the need for a Map
This is the code I use now, tested and working:
Preference reset = findPreference(getResources().getString(R.string.DEFAULT_PREFS));
reset.setOnPreferenceClickListener(new Preference.OnPreferenceClickListener() {
public boolean onPreferenceClick(Preference p) {
SharedPreferences sp = PreferenceManager.getDefaultSharedPreferences(Preferences.this);
SharedPreferences.Editor editor = sp.edit();
editor.clear();
// PreferenceManager.setDefaultValues(Preferences.this, R.layout.preferences, false);
for(int i = 0; i < getPreferenceScreen().getPreferenceCount(); i++) {
restoreDefault(editor, getPreferenceScreen().getPreference(i));
}
editor.commit();
return true;
}
}
private void restoreDefault(Editor editor, Preference p) {
if(p instanceof PreferenceCategory) {
PreferenceCategory pCat = (PreferenceCategory) p;
for(int i = 0; i < pCat.getPreferenceCount(); i++) {
restoreDefault(editor, pCat.getPreference(i));
}
}
if(p instanceof ListPreference) {
editor.putString(p.getKey(), resMap.get(p.getKey())._default);
}
if(p instanceof EditTextPreference) {
editor.putString(p.getKey(), resMap.get(p.getKey())._default);
}
if(p instanceof CheckBoxPreference) {
editor.putBoolean(p.getKey(), resMap.get(p.getKey())._default.equals("true"));
}
}
Another note: editor.commit() updates the preferences file, but does not update the preferences screen. You have to update each preference by using the listener (OnSharedPreferenceChangeListener()).