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set shared preference default programmatically

I have a shared preference with no default value defined in the xml because I would like to set the default value programmatically when the main activity is created. The preference in question should either be the device language (if that language is available), otherwise the first available language, where the languages are defined in the appropriate xml as a string array.
I currently have, inside the main activity's onCreate method, the following
SharedPreferences preferences = getSharedPreferences(
getString(R.string.shared_prefs_key),
MODE_PRIVATE
);
String detailLanguage = preferences.getString(
getResources().getString(R.string.detail_display_language),
""
);
if (detailLanguage.isEmpty()) {
String deviceLanguage = Locale.getDefault().getLanguage();
String[] availableLanguages = getResources().getStringArray(R.array.pref_entry_values_detail_display_language);
boolean deviceLanguageSupported = false;
for (String availableLanguage : availableLanguages) {
if (deviceLanguage.equals(availableLanguage)) {
deviceLanguageSupported = true;
break;
}
}
preferences.edit()
.putString(
getResources()
.getString(R.string.detail_display_language),
deviceLanguageSupported ? deviceLanguage : availableLanguages[0]
).commit();
Debugging this code on the first run it enters the above if statement and sets the preference but the preference doesn't show as selected in the preference activity first time around (if I then select it myself, from then onward it appears selected as something).
Am I missing something? I am fairly new to Android. I tried the above based on some other similar SO questions.

PreferenceActivity and PreferenceFragment read preferences from a default preference file. To get access to those preferences you should use PreferenceManager.getDefaultSharedPreferences(context) method.
I am guessing that this is the reason you aren't seeing your changes: you write them to getString(R.string.shared_prefs_key) rather than to the default one.
Try changing your first line to this:
SharedPreferences preferences = PreferenceManager.getDefaultSharedPreferences(this);

Android - Show numeric keyboard without an EditText

For my Android app I need to show numeric keyboard when the user clicks on an image, but without showing an EditText.
I want to then be notified when the user pressed a specific key, so that I can handle UI appropiately.
How could it be done?
Thank you

Try this...
InputMethodManager inputMethodManager = (InputMethodManager)getSystemService(INPUT_METHOD_SERVICE);
inputMethodManager.toggleSoftInputFromWindow(imageview_reference.getApplicationWindowToken(), InputMethodManager.SHOW_FORCED, 0);

getString() only returns english values

Here is the code of my onActivityResult method:
#Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
if (resultCode == Activity.RESULT_OK) {
String contents = data.getStringExtra("SCAN_RESULT");
if (contents.length() == 26) {
BillBarcode barcode = new BillBarcode(contents);
edtBillId.setText(barcode.extract(BillBarcode.BarcodePart.BillId));
edtPaymentId.setText(barcode.extract(BillBarcode.BarcodePart.PaymentId));
launchService();
} else {
Dialog dialog = new DialogBuilder()
.setTitle(getString(R.string.dialog_title_global_error))
.setMessage(getString(R.string.unknown_barcode))
.build(getActivity());
dialog.show();
}
}
}
The problem is that getString(R.string.dialog_title_global_error) and getString(R.string.unknown_barcode) always returns english value while I have Farsi value too and the locale is farsi too.
The problem only exist in this method.
Farsi value:
<string name="unknown_barcode">بارکد قابل استفاده نیست.</string>
English value:
<string name="unknown_barcode">Unknown barcode</string>
EDIT
I have a setting page and set my locale when user selects persian from language page by this code:
String languageToLoad = "fa";
Resources res = context.getResources();
// Change locale settings in the app.
android.content.res.Configuration conf = res.getConfiguration();
conf.locale = new Locale(languageToLoad);

Let me try to round up all the comments in an answer. Your problem is a combination of two implementation mistakes:
You are setting the locale of the current Activitys context programmatically. However you are doing so in an unsupported way that may yield incorrect results.
When your activity gets a result from another activity in OnActivityResult(), your Activity either gets restarted completely or the context configuration gets reset to the system's default locale. Either way, the locale you set up in the settings dialog is lost.
Solutions
The proper way of changing the App's locale locally is outlined here: Changing Locale within the app itself.
In particular, while just changing the locale in the configuration class may work for you, it is clearly not the correct way to change an application's locale. Doing it properly requires a little more work:
Locale locale; // set to locale of your choice, i.e. "fa"
Configuration config = getResources().getConfiguration();
config.setLocale(locale); // There's a setter, don't set it directly
getApplicationContext().getResources().updateConfiguration(
config,
getApplicationContext().getResources().getDisplayMetrics()
);
// you might even need to use getApplicationContext().getBaseContext(), here.
Locale.setLocale(locale);
Setting the locale on the application context should survive the restart of an activity, but as per Android's lifecycle guarantees, you should not assume that the locale stays around.
If you really need the ability to locally change the locale of your app, you should save the user specified locale (e.g. in a SharedPreference) and obtain and re-set it when the app or your activity is restarted (i.e. at least in OnCreate()). Remember that Android is free to save and restart your activities at any time outside of your control and it is your responsibility to handle the restart gracefully.

Clear intent action default

I am launching the camera app in normal or secure mode depending on what gesture is performed using my app but once the user selects the app and taps Always then there is no option to change the defaults, even from the settings menu in Android.
camera_intent = new Intent(MediaStore.INTENT_ACTION_STILL_IMAGE_CAMERA);
secure_camera_intent = new Intent(MediaStore.INTENT_ACTION_STILL_IMAGE_CAMERA_SECURE);
camera_intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_REORDER_TO_FRONT);
secure_camera_intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_REORDER_TO_FRONT);
this.startActivity(camera_intent);
//this.startActivity(secure_camera_intent);
Is there a workaround? I want to show the camera selection dialog once again so that the user can change his choice.

If you want to present the app chooser even if the user has a default activity selected for the task, use Intent.createChooser().
From the Android developer guide:
If you call Intent.createChooser(), passing it your Intent object, it
returns a version of your intent that will always display the chooser.
This has some advantages:
Even if the user has previously selected a default action for this intent, the chooser will still be displayed.
If no applications match, Android displays a system message.
You can specify a title for the chooser dialog.
You should also check the documentation for ACTION_CHOOSER for guidelines on where this is appropriate or not (Intent.createChooser() is just a convenience method for this).

startActivity(Intent.createChooser(senderIntent, "Title here"));
It will always display the chooser dialog.

Android disable display off while charging

In my application I need to disable display power off when device is charging. There is an option in Developer Menu to disable it, so I can to send Intent for user to enable it.
Also I've found info about PowerManager and WakeLocks, but it is for Alarms, I think. And I must to handle, is device charging.
What is the better, or is there another way to do this?

I've do this by that code:
final boolean isStayAwake = isStayAwakeEnabled(context);
if (!isStayAwake) {
intent = new Intent(ACTION_APPLICATION_DEVELOPMENT_SETTINGS);
}
context.startActivity(intent);
There user must check 'stay awake' option
I've used my own ACTION_APPLICATION_DEVELOPMENT_SETTINGS constant because of problems with default one, which have not "com." prefix

Perhaps you want to try FLAG_KEEP_SCREEN_ON from the WindowManager.LayoutParams