Android屏幕共享+WebSocket实现传输截图

发布于：2025-07-06 ⋅ 阅读:(21) ⋅ 点赞:(0)

大致流程为：客户端通过MediaProjectionManager进行屏幕共享，获取屏幕的截图，然后通过WebSocket发送到服务端，然后通过浏览器访问服务端查看传输的截图。

客户端代码分为3部分：

  1. ScreenShotShareActivity：作用用户的交互界面，有2个按钮，一个是开启屏幕共享，另一个是结束屏幕共享，开启后会启动一个前台服务（这个是系统要求的，屏幕共享的逻辑必须在Service进行）
  2. ScreenShotEncoder：用于实现屏幕共享的图片截图处理，并设置结果回调，相当于一个工具类，会在Service中调用。
  3. ScreenCaptureService：前台服务，启动后会监听ScreenShotEncoder的结果，然后通过WebSocket将结果同步给远端服务器。

服务端代码分为2部分：
服务端通过Node js来实现，需要安装socket.io，2个代码文件：

  1. server.js：作为服务响应
  2. index.html：前端页面，用来展示客户端截图结果

客户端实现

清单文件配置

ScreenShotShareActivity + ScreenCaptureService 声明

<activity android:name=".demo.sharescreen.ScreenShotShareActivity" />

 <service
    android:name=".demo.sharescreen.ScreenCaptureService"
    android:exported="false"
    android:foregroundServiceType="mediaProjection" />

权限声明

<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.FOREGROUND_SERVICE" />
<uses-permission android:name="android.permission.FOREGROUND_SERVICE_MEDIA_PROJECTION" />

ScreenShotShareActivity

class ScreenShotShareActivity : AppCompatActivity() {
    private var isBound = false
    private var binder: ScreenCaptureService.LocalBinder? = null
    private var imageView: ImageView? = null


    private val screenCaptureLauncher = registerForActivityResult(
        ActivityResultContracts.StartActivityForResult()
    ) { result ->
        if (result.resultCode == Activity.RESULT_OK && result.data != null) {
            startScreenEncoding(result.resultCode, result.data!!)
        } else {
            Toast.makeText(this, "屏幕录制权限被拒绝", Toast.LENGTH_SHORT).show()
        }
    }


    private val connection = object : ServiceConnection {
        override fun onServiceConnected(name: ComponentName?, service: IBinder?) {
            binder = service as? ScreenCaptureService.LocalBinder
            binder?.setImageCallback(object : ScreenShotCaptureCallback {
                override fun onJpegImageReady(jpegData: String) {
                    // 采集端本地测试
                    val decodedBytes = Base64.decode(jpegData, Base64.NO_WRAP)
                    val bitmap = BitmapFactory.decodeByteArray(decodedBytes, 0, decodedBytes.size)
                    runOnUiThread {
                        imageView?.setImageBitmap(bitmap)
                    }
                }
            })
            isBound = true
        }

        override fun onServiceDisconnected(name: ComponentName?) {
            isBound = false
        }
    }

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        imageView = ImageView(this).apply {
            scaleType = ImageView.ScaleType.FIT_CENTER
        }

        setContentView(LinearLayout(this).apply {
            orientation = LinearLayout.VERTICAL

            addView(
                Button(this@ScreenShotShareActivity).apply {
                    text = "开始屏幕录制"
                    click {
                        requestScreenCapture()
                    }
                }
            )

            addView(
                Button(this@ScreenShotShareActivity).apply {
                    text = "停止屏幕录制"
                    click {
                        stopScreenCapture()
                    }
                }
            )

            addView(imageView, LinearLayout.LayoutParams(
                LinearLayout.LayoutParams.MATCH_PARENT,
                LinearLayout.LayoutParams.MATCH_PARENT
            ))
        })

    }

    private fun stopScreenCapture() {
        if (isBound) unbindService(connection)
        val intent = Intent(this@ScreenShotShareActivity, ScreenCaptureService::class.java)
        stopService(intent)
    }

    /**
     * 请求屏幕共享权限
     */
    private fun requestScreenCapture() {
        val projectionManager = getSystemService(Context.MEDIA_PROJECTION_SERVICE) as MediaProjectionManager
        val intent = projectionManager.createScreenCaptureIntent()
        screenCaptureLauncher.launch(intent)
    }

    /**
     * 开始屏幕共享，启动前台服务 ScreenCaptureService
     */
    private fun startScreenEncoding(resultCode: Int, data: Intent) {
        val serviceIntent = Intent(this, ScreenCaptureService::class.java).apply {
            putExtra("resultCode", resultCode)
            putExtra("data", data)
        }
        ContextCompat.startForegroundService(this, serviceIntent)
        bindService(serviceIntent, connection, Context.BIND_AUTO_CREATE)
    }
}

ScreenCaptureService


/**
 * 前台服务，需要添加权限：
 *   <uses-permission android:name="android.permission.FOREGROUND_SERVICE" />
 *   <uses-permission android:name="android.permission.FOREGROUND_SERVICE_MEDIA_PROJECTION" />
 */
class ScreenCaptureService : Service() {

    private var screenShotEncoder:ScreenShotEncoder? = null
    private var screenShotCallback: ScreenShotCaptureCallback? = null

    private val socket by lazy {
        val opts = IO.Options().apply {
            transports = arrayOf("websocket") // ⭐ 避免 xhr-poll 错误
            reconnection = true
            reconnectionAttempts = 5
            timeout = 5000
        }
        IO.socket("http://192.168.28.101:3000",opts)
    }

    private fun startForeground(notification: Notification) {
        if (VERSION.SDK_INT >= Build.VERSION_CODES.Q) {
            startForeground(
                1,
                notification,
                ServiceInfo.FOREGROUND_SERVICE_TYPE_MEDIA_PROJECTION
            )
        } else {
            startForeground(1, notification)
        }
    }


    override fun onStartCommand(intent: Intent?, flags: Int, startId: Int): Int {
        startForeground(createNotification())
        val resultCode = intent?.getIntExtra("resultCode", Activity.RESULT_CANCELED) ?: return START_NOT_STICKY
        val data = intent.getParcelableExtra<Intent>("data") ?: return START_NOT_STICKY
        initSocketIO()

        screenShotEncoder = ScreenShotEncoder(this, resultCode, data)
        screenShotEncoder?.startCapturing { base64Jpeg ->
        	// 回调给外部activity，可以用做测试或者打印log
            screenShotCallback?.onJpegImageReady(base64Jpeg)
            // 发送给远端服务器
            socket.emit("frame", base64Jpeg)
        }

        return START_STICKY
    }

    private fun initSocketIO() {
        try {
            // 连接状态监听
            socket.on(Socket.EVENT_CONNECT) {
                Log.d("ScreenCaptureService", "✅ Socket 已连接到服务器")
            }

            socket.on(Socket.EVENT_CONNECT_ERROR) { args ->
                Log.e("ScreenCaptureService", "❌ Socket 连接失败: ${args.getOrNull(0)}")
            }

            socket.on(Socket.EVENT_DISCONNECT) {
                Log.w("ScreenCaptureService", "⚠️ Socket 已断开连接")
            }

            socket.connect()
        } catch (e: URISyntaxException) {
            Log.e("ScreenCaptureService", "❌ Socket URI 格式错误", e)
        }
    }


    private fun createNotification(): Notification {
        val channelId = "screen_capture"
        val manager = getSystemService(Context.NOTIFICATION_SERVICE) as NotificationManager
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            val channel = NotificationChannel(channelId, "屏幕共享", NotificationManager.IMPORTANCE_LOW)
            manager.createNotificationChannel(channel)
        }
        return NotificationCompat.Builder(this, channelId)
            .setContentTitle("屏幕共享中")
            .setContentText("正在采集屏幕内容")
            .setSmallIcon(android.R.drawable.ic_menu_camera)
            .build()
    }

    override fun onBind(intent: Intent?): IBinder? {
        return LocalBinder()
    }

    override fun onDestroy() {
        super.onDestroy()
        screenEncoder?.stopEncoding()
        screenShotEncoder?.stopCapturing()
        socket.disconnect()
        Log.d("ScreenCaptureService","服务销毁")
    }

    inner class LocalBinder : Binder() {
        fun stopCapture() {
            stopSelf()
        }

        fun setImageCallback(callback: ScreenShotCaptureCallback) {
            screenShotCallback  = callback
        }
    }
}


interface ScreenShotCaptureCallback {
    fun onJpegImageReady(jpegData: String)
}

ScreenShotEncoder


class ScreenShotEncoder(
    private val context: Context,
    private val resultCode: Int,
    private val data: Intent,
    private val width: Int = 720,
    private val height: Int = 1280,
    private val dpi: Int = 320
) {

    private lateinit var mediaProjection: MediaProjection
    private var imageReader: ImageReader? = null
    private var handlerThread: HandlerThread? = null
    private var handler: Handler? = null
    private var isCapturing = false

    fun startCapturing(onFrameReady: (String) -> Unit) {
        setupMediaProjection()
        setupImageReader(onFrameReady)
        isCapturing = true
    }

    fun stopCapturing() {
        isCapturing = false
        imageReader?.close()
        mediaProjection.stop()
        handlerThread?.quitSafely()
    }

    private fun setupMediaProjection() {
        val projectionManager = context.getSystemService(Context.MEDIA_PROJECTION_SERVICE) as MediaProjectionManager
        mediaProjection = projectionManager.getMediaProjection(resultCode, data)
    }

    private fun setupImageReader(onFrameReady: (String) -> Unit) {
        imageReader = ImageReader.newInstance(width, height, PixelFormat.RGBA_8888, 2)
        handlerThread = HandlerThread("ScreenShotThread").also { it.start() }
        handler = Handler(handlerThread!!.looper)

        mediaProjection.createVirtualDisplay(
            "ScreenShotCapture",
            width,
            height,
            dpi,
            0,
            imageReader!!.surface,
            null,
            handler
        )

        handler?.post(object : Runnable {
            override fun run() {
                if (!isCapturing) return

                val image = imageReader?.acquireLatestImage()
                if (image != null) {
                    val planes = image.planes
                    val buffer = planes[0].buffer
                    val pixelStride = planes[0].pixelStride
                    val rowStride = planes[0].rowStride
                    val rowPadding = rowStride - pixelStride * width
                    val bitmap = createBitmap(width + rowPadding / pixelStride, height)
                    bitmap.copyPixelsFromBuffer(buffer)
                    image.close()

                    val outputStream = ByteArrayOutputStream()
                    bitmap.compress(Bitmap.CompressFormat.JPEG, 70, outputStream)
                    val byteArray = outputStream.toByteArray()
                    val base64Image = Base64.encodeToString(byteArray, Base64.NO_WRAP)

                    onFrameReady(base64Image)
                    bitmap.recycle()
                }

                handler?.postDelayed(this, 100) // 每 100ms 截图一帧（约10帧/s）
            }
        })
    }
}

启动App后，看到界面如下：
在这里插入图片描述

点击开始录制，会弹一个权限弹窗
在这里插入图片描述
同意后，进入录制
在这里插入图片描述

服务端实现

第一步：准备环境

安装 Node.js
如果你尚未安装，请去 https://nodejs.org/ 下载并安装 LTS 版本。
安装完成后，打开终端输入：

node -v
npm -v

确认安装成功。

第二步：创建项目文件夹

mkdir webrtc-server
cd webrtc-server
npm init -y
npm install express socket.io

第三步：创建信令服务器 server.js

在webrtc-server文件夹下创建server.js文件，代码如下：

// server.js
const express = require('express');
const app = express();
const http = require('http').createServer(app);
const io = require('socket.io')(http);  // v2.4.1 不需要 CORS 配置

app.use(express.static(__dirname + '/public'));

io.on('connection', socket => {
  console.log('🟢 Client connected:', socket.id);

  socket.on('frame', (data) => {
    console.log(`📥 接收到 frame，长度=${data.length}`);
    socket.broadcast.emit('frame', data);
  });

  socket.on('offer', (data) => {
    socket.broadcast.emit('offer', data);
  });

  socket.on('answer', (data) => {
    socket.broadcast.emit('answer', data);
  });

  socket.on('ice-candidate', (data) => {
    socket.broadcast.emit('ice-candidate', data);
  });

  socket.on('disconnect', () => {
    console.log('🔴 Client disconnected:', socket.id);
  });
});

const PORT = 3000;
http.listen(PORT, '0.0.0.0', () => {
  console.log(`🚀 Server running at http://0.0.0.0:${PORT}`);
});

第四步：创建接收端前端页面

在 webrtc-server 目录下创建一个 public/index.html 文件：

<!DOCTYPE html>
<html lang="zh">
<head>
  <meta charset="UTF-8">
  <title>屏幕共享画面</title>
  <style>
    #log {
      background: #f4f4f4;
      border: 1px solid #ccc;
      padding: 10px;
      margin-top: 10px;
      height: 100px;
      overflow-y: auto;
      font-family: monospace;
      font-size: 14px;
    }
  </style>
</head>
<body>
<h2>接收到的屏幕共享图像</h2>
<img id="screenImg"
     style="max-width: 100%; max-height: 600px; border: 1px solid #ccc; object-fit: contain;" />


<div id="log"></div>

<script src="/socket.io/socket.io.js"></script>
<script>
  const socket = io();
  const img = document.getElementById("screenImg");
  const logEl = document.getElementById("log");

  function log(message) {
    const time = new Date().toLocaleTimeString();
    const entry = `[${time}] ${message}`;
    console.log(entry);
    logEl.innerText += entry + "\n";
    logEl.scrollTop = logEl.scrollHeight;
  }

  socket.on("connect", () => {
    log("✅ 已连接到服务器");
  });

  socket.on("disconnect", () => {
    log("❌ 与服务器断开连接");
  });

  socket.on("frame", (base64) => {
    log("🖼️ 收到一帧图像");
    img.src = "data:image/jpeg;base64," + base64;
  });

  socket.on("connect_error", (err) => {
    log("⚠️ 连接错误: " + err.message);
  });
</script>
</body>
</html>

第五步：运行服务器

node server.js

你会看到：
在这里插入图片描述
说明服务端运行成功了，并且有一个客户端加入了，这个就是我们的客户端发起的屏幕共享加入的。

验证效果

打开浏览器输入地址：http://192.168.28.101:3000/index.html
注意：这里的地址是局域网地址，我本机电脑的地址，和我手机是在同一个局域网内。

成功的话，可以看到客户端的共享内容：
在这里插入图片描述

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