Hey there! Let's break down your question about modifying carrier-related settings on Android, including the key SDK classes, their permissions, and practical approaches for each setting type.

Core SDK Classes: TelephonyManager vs CarrierConfigManager #

First, let's clarify the roles and limitations of the two classes you mentioned:

CarrierConfigManager #

• Primary Role: This class is designed to read carrier-specific configuration values pushed by your network provider (like CMAS settings, emergency call rules, etc.).
• Permissions & Access: Most of its data is read-only for regular third-party apps. Modifying these settings requires system-level privileges or a carrier-signed app—regular apps can't write to carrier configs.
• Best For: Checking if CMAS alerts are enabled, retrieving carrier-specific emergency number formats, or other read-only carrier preferences.

TelephonyManager #

• Primary Role: This class handles telephony state, network information, and some limited configuration actions. It doesn't directly modify APN/E911/CMAS settings, but it's useful for retrieving related state info.
• Permissions & Access: For write operations (like APN changes), you'll need to pair it with ContentResolver (more on that below), but even then, the required permissions are restricted to system apps.

Practical Implementation for Each Setting Type #

APN Settings Modification #

APN settings are stored in Android's content provider, so direct modification requires interacting with it via ContentResolver:

• Required Permission: android.permission.WRITE_APN_SETTINGS—this is a signature-protected permission, meaning only apps signed with the system's signature or carrier-specific signatures can use it. Regular third-party apps will get a SecurityException if they try.
• Sample Code (System/Carrier Apps Only):

ContentResolver resolver = getApplicationContext().getContentResolver();
ContentValues apnValues = new ContentValues();
apnValues.put("name", "Custom Carrier APN");
apnValues.put("apn", "carrier.custom.apn");
apnValues.put("type", "default,supl,mms");
// Add other fields like proxy, port, username/password as needed
Uri apnUri = Uri.parse("content://telephony/carriers");
resolver.insert(apnUri, apnValues);

• For Regular Apps: You can't modify APNs directly. The best approach is to redirect users to the system APN settings page:

Intent apnSettingsIntent = new Intent(Settings.ACTION_APN_SETTINGS);
startActivity(apnSettingsIntent);

E911 Settings #

E911 (emergency call location sharing) is tightly controlled at the system level:

• Read Access: Use TelephonyManager.getEmergencyNumberList() to retrieve carrier-specific emergency numbers, but this requires the READ_PHONE_STATE permission.
• Modification: There's no public SDK method for regular apps to modify E911 settings. Only system apps or carrier-customized builds can adjust these configurations (like enabling automatic location sharing for emergency calls). For regular apps, you can guide users to the system's emergency settings page via intent.

CMAS Settings #

CMAS (Commercial Mobile Alert System) handles public safety alerts (e.g., earthquake warnings, Amber Alerts):

• Read Access: Use CarrierConfigManager to check if CMAS is enabled:

CarrierConfigManager configManager = (CarrierConfigManager) getSystemService(Context.CARRIER_CONFIG_SERVICE);
Bundle carrierConfig = configManager.getConfig();
boolean isCmasEnabled = carrierConfig.getBoolean(CarrierConfigManager.KEY_CMAS_MESSAGE_ENABLED_BOOL);

• Modification: Again, regular apps can't modify these settings directly. You can either:
  • Redirect users to the system's alert settings page (intent action varies by manufacturer, but Settings.ACTION_NOTIFICATION_SETTINGS is a starting point)
  • For system/carrier apps: Use CarrierConfigManager with the appropriate privileges to update config values, but this requires carrier-specific integration.

Better Alternatives & Resources #

• For Regular Apps: Focus on guiding users to native system settings instead of trying to modify values directly—this is the only reliable, permission-compliant approach.
• For System/Carrier Apps:
  • Dive into Android's open-source code (specifically the Settings app's APN/emergency alert modules) to see how system-level apps handle these configurations.
  • Refer to official Android API docs for CarrierConfigManager and TelephonyManager to explore all available read/write methods (where permitted).
  • Collaborate with your carrier for their specific configuration guidelines (especially for E911/CMAS).

内容的提问来源于stack exchange，提问作者carlosgmercado