Programmatically obtain the phone number of the Android phone

Code:

TelephonyManager tMgr = (TelephonyManager)mAppContext.getSystemService(Context.TELEPHONY_SERVICE);
String mPhoneNumber = tMgr.getLine1Number();

Required Permission:

<uses-permission android:name="android.permission.READ_PHONE_STATE"/> 

Caveats:

According to the highly upvoted comments, there are a few caveats to be aware of. This can return null or "" or even "???????", and it can return a stale phone number that is no longer valid. If you want something that uniquely identifies the device, you should use getDeviceId() instead.

There is no guaranteed solution to this problem because the phone number is not physically stored on all SIM-cards, or broadcasted from the network to the phone. This is especially true in some countries which requires physical address verification, with number assignment only happening afterwards. Phone number assignment happens on the network - and can be changed without changing the SIM card or device (e.g. this is how porting is supported).

I know it is pain, but most likely the best solution is just to ask the user to enter his/her phone number once and store it.

Update: This answer is no longer available as Whatsapp had stopped exposing the phone number as account name, kindly disregard this answer.

There is actually an alternative solution you might want to consider, if you can't get it through telephony service.

As of today, you can rely on another big application Whatsapp, using AccountManager. Millions of devices have this application installed and if you can't get the phone number via TelephonyManager, you may give this a shot.

Permission:

<uses-permission android:name="android.permission.GET_ACCOUNTS" />

Code:

AccountManager am = AccountManager.get(this);
Account[] accounts = am.getAccounts();

for (Account ac : accounts) {
    String acname = ac.name;
    String actype = ac.type;
    // Take your time to look at all available accounts
    System.out.println("Accounts : " + acname + ", " + actype);
}

Check actype for WhatsApp account

if(actype.equals("com.whatsapp")){
    String phoneNumber = ac.name;
}

Of course you may not get it if user did not install WhatsApp, but its worth to try anyway. And remember you should always ask user for confirmation.

So that's how you request a phone number through the Play Services API without the permission and hacks. Source and Full example.

In your build.gradle (version 10.2.x and higher required):

compile "com.google.android.gms:play-services-auth:$gms_version"

In your activity (the code is simplified):

@Override
protected void onCreate(Bundle savedInstanceState) {
    // ...
    googleApiClient = new GoogleApiClient.Builder(this)
            .addApi(Auth.CREDENTIALS_API)
            .build();
    requestPhoneNumber(result -> {
        phoneET.setText(result);
    });
}

public void requestPhoneNumber(SimpleCallback<String> callback) {
    phoneNumberCallback = callback;
    HintRequest hintRequest = new HintRequest.Builder()
            .setPhoneNumberIdentifierSupported(true)
            .build();

    PendingIntent intent = Auth.CredentialsApi.getHintPickerIntent(googleApiClient, hintRequest);
    try {
        startIntentSenderForResult(intent.getIntentSender(), PHONE_NUMBER_RC, null, 0, 0, 0);
    } catch (IntentSender.SendIntentException e) {
        Logs.e(TAG, "Could not start hint picker Intent", e);
    }
}

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);
    if (requestCode == PHONE_NUMBER_RC) {
        if (resultCode == RESULT_OK) {
            Credential cred = data.getParcelableExtra(Credential.EXTRA_KEY);
            if (phoneNumberCallback != null){
                phoneNumberCallback.onSuccess(cred.getId());
            }
        }
        phoneNumberCallback = null;
    }
}

This will generate a dialog like this:

As posted in my earlier answer

Use below code :

TelephonyManager tMgr = (TelephonyManager)mAppContext.getSystemService(Context.TELEPHONY_SERVICE);
String mPhoneNumber = tMgr.getLine1Number();

In AndroidManifest.xml, give the following permission:

 <uses-permission android:name="android.permission.READ_PHONE_STATE"/> 

But remember, this code does not always work, since Cell phone number is dependent on the SIM Card and the Network operator / Cell phone carrier.

Also, try checking in Phone--> Settings --> About --> Phone Identity, If you are able to view the Number there, the probability of getting the phone number from above code is higher. If you are not able to view the phone number in the settings, then you won't be able to get via this code!

Suggested Workaround:

1. Get the user's phone number as manual input from the user.
2. Send a code to the user's mobile number via SMS.
3. Ask user to enter the code to confirm the phone number.
4. Save the number in sharedpreference.

Do the above 4 steps as one time activity during the app's first launch. Later on, whenever phone number is required, use the value available in shared preference.