Getting started with Stringee Call API using Flutter Plugin

Step 1: Prepare

Before using Stringee Call API for the first time, you must have a Stringee account.

If you do not have a Stringee account, sign up for free here: https://developer.stringee.com/account/register
Create a Project on Stringee Dashboard
Buy a Number (optional)

For app-to-phone, phone-to-app calling, buy a Number from Dashboard. If you only need app-to-app calling, skip this step.
Configure answer_url

For more information about answer_url, read Stringee Call API Overview. You can view the answer_url sample code.
- Configure Project's answer_url: To make an app-to-app, app-to-phone call, configure your Project's answer_url
If you do not have answer_url, you can use the following Project's answer_url to speed up the process:

Project's answer_url for App-to-App call:
```
https://developer.stringee.com/scco_helper/simple_project_answer_url?record=false&appToPhone=false
```
Project's answer_url for App-to-Phone call:
```
https://developer.stringee.com/scco_helper/simple_project_answer_url?record=false&appToPhone=true
```
(Source code: https://github.com/stringeecom/server-samples/blob/master/answer_url/php/project_answer_url.php)

When building an application, you should use your own answer_url.
- Configure Number's answer_url: To receive a phone-to-app call, configure your Number's answer_url
If you do not have answer_url, you can use the following Number's answer_url to speed up the process:

Number's answer_url for Phone-to-App call (The call is routed to Your App, which is authenticated by USER_ID):
```
https://developer.stringee.com/scco_helper/simple_number_answer_url?record=true&phoneToPhone=false&to_number=USER_ID
```
Number's answer_url for Phone-to-Phone call (The call is routed to TO_NUMBER):
```
https://developer.stringee.com/scco_helper/simple_number_answer_url?record=true&phoneToPhone=true&stringeeNumber=STRINGEE_NUMBER&to_number=TO_NUMBER
```
(Source code: https://github.com/stringeecom/server-samples/blob/master/answer_url/php/number_answer_url.php)

When building an application, you should use your own answer_url.

Step 2: Install stringee-plugin

Install stringee-plugin from pub.dev by running the following command from the project root:

$ flutter pub add stringee_plugin:^1.3.2

Check out plugin's documentation for more information.

Step 3: Setup

Android

The latest plugin requires JDK 17, Android minSdk 21 or later, and is compiled with Android API 36. If your application declares its own compileSdk, set it to 36 or later:

   android {
      compileSdk = 36

      defaultConfig {
         minSdk = 21
      }
   }

Permissions

The Stringee Android SDK requires some permissions from your AndroidManifest. Open up android/app/src/main/AndroidManifest.xml then add the following lines:

<!--Internet-->
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
<uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />
<!--Record-->
<uses-permission android:name="android.permission.RECORD_AUDIO" />
<!--Audio-->
<uses-permission android:name="android.permission.MODIFY_AUDIO_SETTINGS" />
<!--Camera-->
<uses-permission android:name="android.permission.CAMERA" />
<uses-feature
    android:name="android.hardware.camera"
    android:required="false" />
<uses-feature
    android:name="android.hardware.camera.autofocus"
    android:required="false" />
<!--Bluetooth-->
<uses-permission
    android:name="android.permission.BLUETOOTH"
    android:maxSdkVersion="30" />
<uses-permission android:name="android.permission.BLUETOOTH_CONNECT" /> <!--Require for android 12 or higher-->
<uses-feature
    android:name="android.hardware.bluetooth"
    android:required="false" />
<uses-feature
    android:name="android.hardware.bluetooth_le"
    android:required="false" />
<!-- Graphic -->
<uses-feature
    android:glEsVersion="0x00020000"
    android:required="false" />

Request camera, microphone, and BLUETOOTH_CONNECT at runtime on Android versions where they are dangerous permissions.

ProGuard/R8 rules for Stringee and WebRTC are included in the plugin. Keep your application's existing minification configuration; you do not need to enable minification specifically for Stringee.

iOS

The latest plugin requires iOS 13.0 or later.

From the command line run following command:
```
pod install --repo-update
```
After running CocoaPods, open the generated .xcworkspace file.
Right-click the information property list file (Info.plist) and select Open As → Source Code. Then insert the following XML snippet into the body of your file just before the final element:
```
<key>NSCameraUsageDescription</key>
<string>$(PRODUCT_NAME) uses Camera</string>
<key>NSMicrophoneUsageDescription</key>
<string>$(PRODUCT_NAME) uses Microphone</string>
```
In the "Build Settings" tab → "Allow Non-modular includes in Framework Modules" select "YES"

Step 4: Connect to Stringee Server

To connect to Stringee Server, 3-party authentication is required as described here: Client authentication

For testing, go to Dashboard -> Tools -> Generate Access token and generate an access_token. In production, your server should generate the access_token. See the access token examples.

Initialize StringeeClient:

import 'dart:async';
import 'package:stringee_plugin/stringee_plugin.dart';
...
final StringeeClient _client = StringeeClient();
StreamSubscription? _clientSubscription;
StreamSubscription? _callSubscription;

// Listen for the StringeeClient event
_clientSubscription = _client.eventStreamController.stream.listen((event) {
 Map<dynamic, dynamic> map = event;
 switch (map['eventType']) {
   case StringeeClientEvents.didConnect:
     handleDidConnectEvent();
     break;
   case StringeeClientEvents.didDisconnect:
     handleDiddisconnectEvent();
     break;
   case StringeeClientEvents.didFailWithError:
     int code = map['body']['code'];
     String msg = map['body']['message'];
     handleDidFailWithErrorEvent(code,msg);
     break;
   case StringeeClientEvents.requestAccessToken:
     handleRequestAccessTokenEvent();
     break;
   case StringeeClientEvents.didReceiveCustomMessage:
     handleDidReceiveCustomMessageEvent(map['body']);
     break;
   case StringeeClientEvents.incomingCall:
     StringeeCall call = map['body'];
     handleIncomingCallEvent(call);
     break;
   default:
     break;
 }
});

...
/// Invoked when the StringeeClient is connected
void handleDidConnectEvent() {}

/// Invoked when the StringeeClient is disconnected
void handleDiddisconnectEvent() {}

/// Invoked when the StringeeClient connection fails
void handleDidFailWithErrorEvent(int code, String message) {}

/// Invoked when your token is expired
void handleRequestAccessTokenEvent() {}

/// Invoked when get Custom message
void handleDidReceiveCustomMessageEvent(Map<dynamic, dynamic> map) {}

/// Invoked when an incoming StringeeCall is received
void handleIncomingCallEvent(StringeeCall call) {}

Connect

String token = 'PUT YOUR TOKEN HERE';
_client.connect(token);

Step 5: Make an outgoing call

After the client connects to Stringee server, follow these steps to make a call:

Initialize StringeeCall

import 'package:stringee_plugin/stringee_plugin.dart';
...
late StringeeCall _call;
...
_call = StringeeCall(_client);

// Register this listener for every outgoing or incoming StringeeCall object.
void registerCallEvents(StringeeCall call) {
 _callSubscription?.cancel();
 _callSubscription = call.eventStreamController.stream.listen((event) {
   Map<dynamic, dynamic> map = event;
   switch (map['eventType']) {
   case StringeeCallEvents.didChangeSignalingState:
     handleSignalingStateChangeEvent(map['body']);
     break;
   case StringeeCallEvents.didChangeMediaState:
     handleMediaStateChangeEvent(map['body']);
     break;
   case StringeeCallEvents.didReceiveCallInfo:
     handleReceiveCallInfoEvent(map['body']);
     break;
   case StringeeCallEvents.didHandleOnAnotherDevice:
     handleHandleOnAnotherDeviceEvent(map['body']);
     break;
   case StringeeCallEvents.didReceiveLocalStream:
     handleReceiveLocalStreamEvent(map['body']);
     break;
   case StringeeCallEvents.didReceiveRemoteStream:
     handleReceiveRemoteStreamEvent(map['body']);
     break;
   default:
     break;
   }
 });
}
registerCallEvents(_call);
...
/// Invoked when get Signaling state
void handleSignalingStateChangeEvent(StringeeSignalingState state) {}

/// Invoked when get Media state
void handleMediaStateChangeEvent(StringeeMediaState state) {}

/// Invoked when get Call info
void handleReceiveCallInfoEvent(Map<dynamic, dynamic> info) {}

/// Invoked when an incoming call is handle on another device
void handleHandleOnAnotherDeviceEvent(StringeeSignalingState state) {}

/// Invoked when get Local stream in video call
void handleReceiveLocalStreamEvent(String callId) {}

/// Invoked when get Remote stream in video call
void handleReceiveRemoteStreamEvent(String callId) {}

Make a call

Option 1: Using our MakeCallParams for easily to make a call

MakeCallParams params = MakeCallParams(
 'caller_userId', /// caller id
 'callee_userId', /// callee id
 isVideoCall: false, /// true - video call, false - not video call, default is 'false'
 videoQuality: VideoQuality.normal, /// video quality in video call, default is 'normal'
);

_call.makeCallFromParams(params).then((result) {
 bool status = result['status'];
 int code = result['code'];
 String message = result['message'];
 print('MakeCall CallBack --- $status - $code - $message - ${_call.id} - ${_call.from} - ${_call.to}');
});

Option 2: Using custom parameters to make a call

final parameters = {
 'from': 'caller_userId',
 'to': 'callee_userId',
 'isVideoCall': false, /// true - video call, false - not video call, default is 'false'
 'videoQuality': VideoQuality.normal, /// video quality in video call, default is 'normal'
};

_call.makeCall(parameters).then((result) {
 bool status = result['status'];
 int code = result['code'];
 String message = result['message'];
 print('MakeCall CallBack --- $status - $code - $message - ${_call.id} - ${_call.from} - ${_call.to}');
});

Step 6: Handle an incoming call

When the client receives an incoming call from handleIncomingCallEvent(), use a StringeeCall received from handleIncomingCallEvent. Then follow these steps:

Initialize the call

/// Invoked when an incoming StringeeCall is received
void handleIncomingCallEvent(StringeeCall call) {
 _call = call;
 registerCallEvents(_call);
 // Must initAnswer before answer a call
 _call.initAnswer();
}

Answer a call
```
_call.answer();
```

Step 7: Make a video call

A StringeeCall is a voice call by default. If you want to make a video call, you must change value of field isVideoCall in your parameters to true

Receive and display the local video

Using our StringeeVideoView to display the local video

void handleReceiveLocalStreamEvent(String callId) {
 setState(() {
   widget.hasLocalStream = true;
   widget.callId = callId;
 });
}
...
Widget localView = widget.hasLocalStream
   ? StringeeVideoView(
       callId, /// callId of StringeeCall
       true, /// true - local video, false - remote video
     )
   : Placeholder();
...
return Scaffold(
        body: Stack(
          children: [
            remoteView,
            localView,
            ],
          ),
        );

Receive and display the remote video

Using our StringeeVideoView to display the remote video

...
void handleReceiveRemoteStreamEvent(String callId) {
 setState(() {
   widget.hasRemoteStream = true;
   widget.callId = callId;
 });
}
...
Widget remoteView = widget.hasRemoteStream
     ? StringeeVideoView(
         callId,  /// callId of StringeeCall
         false, /// true - local video, false - remote video
       )
     : Placeholder();
...
return Scaffold(
        body: Stack(
          children: [
            remoteView,
            localView,
            ],
          ),
        );

Step 8: Hangup

Hang up a call:

_call.hangup();

Step 9: Reject

Reject a call:

_call.reject();

Step 10: Mute

Mute the local sound:

bool mute = true; // true: mute, false: unmute
_call.mute(mute);

Step 11: Manage audio devices

Manager output audio device by using singleton class StringeeAudioManager:

Listening for audio device change events:

AudioDevice? selectedAudioDevice; // Default audio device
List<AudioDevice> availableAudioDevices = []; // List of available audio devices
...
// Create StringeeAudioEvent
StringeeAudioEvent audioEvent = StringeeAudioEvent(onChangeAudioDevice: (selectedAudioDevice, availableAudioDevices) {
  // Save list of available audio devices and selected audio device
  this.availableAudioDevices = availableAudioDevices;
  this.selectedAudioDevice = selectedAudioDevice;
  // For the first time, you need choose an audio device that you want to use in your call. 
  // E.g: Video call get AudioDevice with type is AudioType.speakerPhone from availableAudioDevices or which device you want to use then call selectDevice(AudioDevice device) method
});
// Register the audioEvent to StringeeAudioManager
StringeeAudioManager().addListener(audioEvent);

Start audio manager:

You need to start the audio manager before using it.
```
StringeeAudioManager().start();
```
Select audio device:

To select an audio device, you can use the following code:
```
// Select audio device
StringeeAudioManager().selectDevice(audioDevice);
```
Release audio manager:

Before your app is closed, you should release the audio manager to avoid bugs when the call is ended or the app is closed:
```
// Stop listening for audio events
StringeeAudioManager().removeListener(audioEvent);
// Stop the audio manager
StringeeAudioManager().stop();
```

Step 12: Switch camera

Switch the local camera:

_call.switchCamera();

Step 13: Turn on/off video

Turn on/off video:

bool enableVideo = true; // true: turn on, false: turn off
_call.enableVideo(enableVideo);

Step 14: Handle incoming call notification

In case your app is in the background or terminated, you need to handle call notification by following the Flutter push notification guide.

Sample

You can view a full version of this sample app on GitHub: call_sample

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