Retrieve Incoming Call's Phone Number in Android

How to get phone number from an incoming call?

Make a Broadcast receiver say ServiceReceiver assign its action in Manifest.

<receiver android:name=".ServiceReceiver" >
    <intent-filter>
        <action android:name="android.intent.action.PHONE_STATE" />
    </intent-filter>
</receiver>

Add a PhoneStateListener to your TelephonyManager, PhoneStateListener having override onCallStateChanged() with Incoming number parameter. Thats it.

ServiceReceiver.Java

public class ServiceReceiver extends BroadcastReceiver {

    @Override
    public void onReceive(final Context context, Intent intent) {
        TelephonyManager telephony = (TelephonyManager)context.getSystemService(Context.TELEPHONY_SERVICE);
        telephony.listen(new PhoneStateListener(){
            @Override
            public void onCallStateChanged(int state, String incomingNumber) {
                super.onCallStateChanged(state, incomingNumber);
                System.out.println("incomingNumber : "+incomingNumber);
            }
        },PhoneStateListener.LISTEN_CALL_STATE);
    }
}

How to get incoming call number? [Android]

Please note you need permission READ_CALL_LOG if you want to get incomingNumber, you can check documents here

String: call phone number. If application does not have READ_CALL_LOG permission or carrier privileges (see TelephonyManager#hasCarrierPrivileges), an empty string will be passed as an argument.

Get incoming call number programmatically on android

Try this way...
permission

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

Make a Broadcast receiver say ServiceReceiver assign its action in Manifest.

<receiver android:name=".ServiceReceiver" >
<intent-filter>
    <action android:name="android.intent.action.PHONE_STATE" />
</intent-filter>

ServiceReceiver.Java

public class ServiceReceiver extends BroadcastReceiver {

@Override
public void onReceive(final Context context, Intent intent) {
    TelephonyManager telephony = (TelephonyManager)context.getSystemService(Context.TELEPHONY_SERVICE);
    telephony.listen(new PhoneStateListener(){
        @Override
        public void onCallStateChanged(int state, String incomingNumber) {
            super.onCallStateChanged(state, incomingNumber);
            System.out.println("incomingNumber : "+incomingNumber);
        }
    },PhoneStateListener.LISTEN_CALL_STATE);
}

}

Get incoming call number programmatically on android 10

Yes, implement the class and add the necessary permission below in the manifest:

  <service
        android:name=".CallScreeningService"
        android:permission="android.permission.BIND_SCREENING_SERVICE">
        <intent-filter>
            <action android:name="android.telecom.CallScreeningService" />
        </intent-filter>
    </service>

Within onScreenCall(Call.Details details) you can call details.getHandle() which returns the telephone number of the incoming call. This will only get called if the number cannot be matched to the contact information existing on the device.

@Override
public void onScreenCall(Call.Details details) {
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {
        if(details.getCallDirection() == Call.Details.DIRECTION_INCOMING) {
            CallResponse.Builder response = new CallResponse.Builder();
            response.setDisallowCall(false);
            response.setRejectCall(false);
            response.setSilenceCall(false);
            response.setSkipCallLog(false);
            response.setSkipNotification(false);
            details.getHandle(); //This is the calling number
            respondToCall(details, response.build());

        }
    }
}