如何将 WebRTC 集成到 Android 应用程序中

使用 Kotlin 和 MVVM 架构将 WebRTC 集成到 Android 应用程序中，可实现代码的可扩展性和可维护性。通过将应用程序结构化为模型（Models）、视图模型（ViewModels）和视图（View），您可以有效地管理实时通信功能，并确保清晰的关注点分离。

将 WebRTC 集成到 Android 移动应用中，按照以下步骤操作：

1. 设置 Android 项目

确保拥有必要的工具：

Android Studio：用于管理和构建 Android 项目。
Gradle：用于管理依赖关系。

2. 添加 WebRTC 依赖项

在 build.gradle 文件中添加 WebRTC 依赖项。您可以使用 WebRTC 项目提供的预编译二进制文件，也可以从源代码构建它们。

implementation("org.webrtc:google-webrtc:1.0.32006")

3. 实现 WebRTC 管理器（模型）

创建一个 WebRTCManager 类来处理 WebRTC 操作。

WebRTCManager.kt：

import org.webrtc.*

class WebRTCManager {
    private var peerConnectionFactory: PeerConnectionFactory? = null
    private var peerConnection: PeerConnection? = null
    private var localStream: MediaStream? = null

    init {
        PeerConnectionFactory.initialize(
            PeerConnectionFactory.InitializationOptions.builder().createInitializationOptions()
        )
        peerConnectionFactory = PeerConnectionFactory.builder().createPeerConnectionFactory()
    }

    fun createPeerConnection(iceServers: List<PeerConnection.IceServer>) {
        val rtcConfig = PeerConnection.RTCConfiguration(iceServers)
        rtcConfig.iceTransportsType = PeerConnection.IceTransportsType.ALL
        rtcConfig.bundlePolicy = PeerConnection.BundlePolicy.BALANCED
        rtcConfig.rtcpMuxPolicy = PeerConnection.RtcpMuxPolicy.REQUIRED

        peerConnection = peerConnectionFactory?.createPeerConnection(rtcConfig, object : PeerConnection.Observer {
            override fun onIceCandidate(candidate: IceCandidate) {
                // Handle ICE candidates
            }

            override fun onAddStream(stream: MediaStream) {
                // Handle added stream
            }

            override fun onRemoveStream(stream: MediaStream) {
                // Handle removed stream
            }

            // Implement other PeerConnection.Observer methods as needed
        })
    }

    fun startMediaStream() {
        val audioConstraints = MediaConstraints()
        val videoConstraints = MediaConstraints()

        val audioSource = peerConnectionFactory?.createAudioSource(audioConstraints)
        val videoSource = peerConnectionFactory?.createVideoSource(false)

        val audioTrack = peerConnectionFactory?.createAudioTrack("audioTrack", audioSource)
        val videoTrack = peerConnectionFactory?.createVideoTrack("videoTrack", videoSource)

        localStream = peerConnectionFactory?.createLocalMediaStream("localStream")
        localStream?.addTrack(audioTrack)
        localStream?.addTrack(videoTrack)

        peerConnection?.addStream(localStream)
    }

    fun setRemoteDescription(offer: SessionDescription) {
        peerConnection?.setRemoteDescription(object : SdpObserver() {
            override fun onSetSuccess() { /* Handle success */ }
            override fun onSetFailure(error: String) { /* Handle failure */ }
        }, offer)
    }

    fun createAnswer() {
        peerConnection?.createAnswer(object : SdpObserver() {
            override fun onCreateSuccess(description: SessionDescription) {
                peerConnection?.setLocalDescription(object : SdpObserver() {
                    override fun onSetSuccess() { /* Handle success */ }
                    override fun onSetFailure(error: String) { /* Handle failure */ }
                }, description)
            }

            override fun onCreateFailure(error: String) { /* Handle failure */ }
        }, MediaConstraints())
    }
}

4. 实现 ViewModel

创建 WebRTCViewModel 以管理 WebRTC 相关数据并与 WebRTCManager 交互。

WebRTCViewModel.kt：

import androidx.lifecycle.LiveData
import androidx.lifecycle.MutableLiveData
import androidx.lifecycle.ViewModel
import org.webrtc.*

class WebRTCViewModel : ViewModel() {
    private val webRTCManager = WebRTCManager()
    private val _localStream = MutableLiveData<MediaStream>()
    val localStream: LiveData<MediaStream> get() = _localStream

    fun startStream() {
        webRTCManager.startMediaStream()
        _localStream.value = webRTCManager.localStream
    }

    fun createPeerConnection(iceServers: List<PeerConnection.IceServer>) {
        webRTCManager.createPeerConnection(iceServers)
    }

    fun setRemoteDescription(offer: SessionDescription) {
        webRTCManager.setRemoteDescription(offer)
    }

    fun createAnswer() {
        webRTCManager.createAnswer()
    }
}

5. 实现视图

View 负责与用户交互，并根据 ViewModel 的数据更新用户界面。

MainActivity.kt：

import android.os.Bundle
import androidx.activity.viewModels
import androidx.appcompat.app.AppCompatActivity
import org.webrtc.VideoTrack

class MainActivity : AppCompatActivity() {
    private val viewModel: WebRTCViewModel by viewModels()

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        viewModel.localStream.observe(this) { stream ->
            // Handle the local stream, e.g., display video on a SurfaceViewRenderer
        }

        viewModel.startStream()

        // Example setup of ICE servers
        val iceServers = listOf(PeerConnection.IceServer.builder("stun:stun.l.google.com:19302").createIceServer())
        viewModel.createPeerConnection(iceServers)
    }
}

activity_main.xml:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <!-- Define UI components such as a SurfaceViewRenderer for video display -->

</RelativeLayout>

6. 处理权限

在 AndroidManifest.xml 中申请摄像头和麦克风访问权限：

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

处理活动中的运行权限：

if (checkSelfPermission(Manifest.permission.CAMERA) != PackageManager.PERMISSION_GRANTED ||
    checkSelfPermission(Manifest.permission.RECORD_AUDIO) != PackageManager.PERMISSION_GRANTED) {
    requestPermissions(arrayOf(Manifest.permission.CAMERA, Manifest.permission.RECORD_AUDIO), PERMISSION_REQUEST_CODE)
}

7. 测试应用程序

在不同设备和网络条件下测试应用程序，以确保可靠性和性能。WebRTC 对网络变化非常敏感，因此全面测试至关重要。