Flutter使用Agora实现应用关闭时呼起视频通话界面方案咨询

核心前提 #

• 首先要申请系统*悬浮窗（出现在其他应用上层）*权限，这是在应用外显示通话界面的基础
• 集成Agora RTM（实时消息）组件做呼叫信令监听，即使主应用进程被回收，也要通过保活的后台服务/推送通道唤醒信令监听
• 音视频流的初始化可以放到独立的Service组件中，不和主应用页面生命周期绑定

Android端实现代码 #

首先在AndroidManifest.xml中添加必要权限：

<!-- 悬浮窗权限 -->
<uses-permission android:name="android.permission.SYSTEM_ALERT_WINDOW" />
<!-- 前台服务权限 -->
<uses-permission android:name="android.permission.FOREGROUND_SERVICE" />
<uses-permission android:name="android.permission.FOREGROUND_SERVICE_MEDIA_PROJECTION" />
<uses-permission android:name="android.permission.FOREGROUND_SERVICE_CAMERA" />
<uses-permission android:name="android.permission.FOREGROUND_SERVICE_MICROPHONE" />

编写后台监听呼叫信令的前台服务代码：

public class CallMonitorService extends Service {
    private RtmClient mRtmClient;
    private final String APP_ID = "替换为你的Agora App ID";

    @Override
    public void onCreate() {
        super.onCreate();
        // 初始化RTM客户端监听呼叫信令
        try {
            mRtmClient = RtmClient.createInstance(this, APP_ID, new RtmClientListener() {
                @Override
                public void onMessageReceived(RtmMessage rtmMessage, String peerId) {
                    // 匹配自定义呼叫信令，收到后唤起通话界面
                    if ("invite_call".equals(rtmMessage.getText())) {
                        showCallNotification(peerId);
                        launchFloatingCallActivity(peerId);
                    }
                }
            });
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    // 启动前台服务保活，避免被系统回收
    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        Notification notification = buildForegroundNotification();
        startForeground(1001, notification);
        return START_STICKY;
    }

    // 唤起悬浮窗通话页面
    private void launchFloatingCallActivity(String callerId) {
        Intent intent = new Intent(this, FloatingCallActivity.class);
        intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_REORDER_TO_FRONT);
        intent.putExtra("caller_id", callerId);
        startActivity(intent);
    }
}

给悬浮窗通话页面添加特殊配置，在AndroidManifest.xml中声明对应属性：

<activity
    android:name=".FloatingCallActivity"
    android:exported="true"
    android:showOnLockScreen="true"
    android:turnScreenOn="true"
    android:theme="@style/Theme.Transparent.Floating" />

iOS端实现代码 #

首先在Info.plist中添加必要权限和后台模式：

<key>NSMicrophoneUsageDescription</key>
<string>需要麦克风权限进行语音通话</string>
<key>NSCameraUsageDescription</key>
<string>需要摄像头权限进行视频通话</string>
<key>UIBackgroundModes</key>
<array>
    <string>audio</string>
    <string>voip</string>
</array>

基于PushKit实现后台呼叫唤醒逻辑：

import PushKit
import AgoraRtmKit

class CallHandler: NSObject, PKPushRegistryDelegate {
    let rtmKit: AgoraRtmKit? = AgoraRtmKit(appId: "替换为你的Agora App ID", delegate: nil)
    
    func registerVoIPPush() {
        let pushRegistry = PKPushRegistry(queue: DispatchQueue.main)
        pushRegistry.delegate = self
        pushRegistry.desiredPushTypes = [.voIP]
    }
    
    func pushRegistry(_ registry: PKPushRegistry, didReceiveIncomingPushWith payload: PKPushPayload, for type: PKPushType, completion: @escaping () -> Void) {
        guard type == .voIP else {
            completion()
            return
        }
        // 收到VoIP推送后唤起通话界面
        let callVC = FloatingCallViewController()
        callVC.callerId = payload.dictionaryPayload["caller_id"] as? String
        // 获取当前顶层窗口展示通话页面
        if let keyWindow = UIApplication.shared.windows.first(where: { $0.isKeyWindow }) {
            keyWindow.rootViewController?.present(callVC, animated: true)
        }
        completion()
    }
}

注意事项 #

• 不同Android厂商的后台权限限制不同，需要额外引导用户开启应用的自启动、后台活动权限，否则服务被杀死后无法监听呼叫
• iOS端必须使用VoIP推送来唤醒应用，普通推送无法直接唤起通话界面，且需要符合苹果的VoIP推送规范，否则会被拒审
• Agora的音视频引擎不需要和主进程绑定，放到独立的服务/模块中即可保证通话流程不被主应用生命周期影响

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