android设备间实现无线投屏

前言

Android提供了MediaProjection来实现录屏，通过MediaProjection可以获取当前屏幕的视频流，而视频流需要通过编解码来压缩进行传输，通过MediaCodec可实现视频的编码和解码。视频流的推送和接收可通过Socket或WebSocket来实现，服务端推送编码的视频流，客户端接收视频流并进行解码，然后渲染在SurfaceView上即可显示服务端的画面。
媒体投影MediaProjection的核心是虚拟屏幕，您可以通过对 MediaProjection 实例调用 createVirtualDisplay() 来创建虚拟屏幕（VirtualDisplay）：
Android的媒体投影MediaProjection介绍：媒体投影

投屏服务端的实现

服务端主入口负责请求录屏和启动录屏服务，服务端主入口的实现如下：

package com.example.screenprojection;import android.content.Intent;
import android.media.projection.MediaProjectionManager;
import android.os.Build;
import android.os.Bundle;
import android.view.View;import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;public class MainActivity extends AppCompatActivity {private static final int PROJECTION_REQUEST_CODE = 1;private MediaProjectionManager mediaProjectionManager;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);init();}private void init() {mediaProjectionManager = (MediaProjectionManager) getSystemService(MEDIA_PROJECTION_SERVICE);}public void onClick(View view) {if (view.getId() == R.id.btn_start) {startProjection();}}// 请求开始录屏private void startProjection() {Intent intent = mediaProjectionManager.createScreenCaptureIntent();startActivityForResult(intent, PROJECTION_REQUEST_CODE);}@Overrideprotected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {super.onActivityResult(requestCode, resultCode, data);if (resultCode != RESULT_OK) {return;}if (requestCode == PROJECTION_REQUEST_CODE) {Intent service = new Intent(this, ScreenService.class);service.putExtra("code", resultCode);service.putExtra("data", data);if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {startForegroundService(service);} else {startService(service);}}}@Overrideprotected void onDestroy() {super.onDestroy();}
}

Android8.0后录屏需要开启前台服务通知，录屏服务开启后同时启动WebSocketServer服务端，前台服务代码如下：

package com.example.screenprojection;import android.app.Notification;
import android.app.NotificationChannel;
import android.app.NotificationManager;
import android.app.PendingIntent;
import android.app.Service;
import android.content.Intent;
import android.graphics.BitmapFactory;
import android.media.projection.MediaProjection;
import android.media.projection.MediaProjectionManager;
import android.os.Build;
import android.os.IBinder;public class ScreenService extends Service {private MediaProjectionManager mMediaProjectionManager;private SocketManager mSocketManager;@Overridepublic void onCreate() {super.onCreate();mMediaProjectionManager = (MediaProjectionManager) getSystemService(MEDIA_PROJECTION_SERVICE);createNotificationChannel();}@Overridepublic int onStartCommand(Intent intent, int flags, int startId) {int resultCode = intent.getIntExtra("code", -1);Intent resultData = intent.getParcelableExtra("data");startProject(resultCode, resultData);return super.onStartCommand(intent, flags, startId);}// 录屏开始后进行编码推流private void startProject(int resultCode, Intent data) {MediaProjection mediaProjection = mMediaProjectionManager.getMediaProjection(resultCode, data);if (mediaProjection == null) {return;}// 初始化服务器端mSocketManager = new SocketManager();mSocketManager.start(mediaProjection);}private void createNotificationChannel() {Notification.Builder builder = new Notification.Builder(this.getApplicationContext());Intent nfIntent = new Intent(this, MainActivity.class);builder.setContentIntent(PendingIntent.getActivity(this, 0, nfIntent, 0)).setLargeIcon(BitmapFactory.decodeResource(this.getResources(), R.mipmap.ic_launcher)) // 设置下拉列表中的图标(大图标).setSmallIcon(R.mipmap.ic_launcher) // 设置状态栏内的小图标.setContentText("is running......") // 设置上下文内容.setWhen(System.currentTimeMillis()); // 设置该通知发生的时间if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {builder.setChannelId("notification_id");// 前台服务notification适配NotificationManager notificationManager =(NotificationManager) getSystemService(NOTIFICATION_SERVICE);NotificationChannel channel =new NotificationChannel("notification_id", "notification_name", NotificationManager.IMPORTANCE_LOW);notificationManager.createNotificationChannel(channel);}Notification notification = builder.build();notification.defaults = Notification.DEFAULT_SOUND; // 设置为默认通知音startForeground(110, notification);}@Overridepublic IBinder onBind(Intent intent) {return null;}@Overridepublic void onDestroy() {mSocketManager.close();super.onDestroy();}
}

SocketManager为WebSocketServer的控制类，并同时将录屏对象MediaProjection与视频编码器ScreenEncoder绑定。

package com.example.screenprojection;import android.media.projection.MediaProjection;import java.net.InetSocketAddress;public class SocketManager {private static final String TAG = SocketManager.class.getSimpleName();private static final int SOCKET_PORT = 50000;private final ScreenSocketServer mScreenSocketServer;private ScreenEncoder mScreenEncoder;public SocketManager() {mScreenSocketServer = new ScreenSocketServer(new InetSocketAddress(SOCKET_PORT));}public void start(MediaProjection mediaProjection) {mScreenSocketServer.start();mScreenEncoder = new ScreenEncoder(this, mediaProjection);mScreenEncoder.startEncode();}public void close() {try {mScreenSocketServer.stop();mScreenSocketServer.close();} catch (InterruptedException e) {e.printStackTrace();}if (mScreenEncoder != null) {mScreenEncoder.stopEncode();}}public void sendData(byte[] bytes) {mScreenSocketServer.sendData(bytes);}
}

推流服务端ScreenSocketServer代码如下：

package com.example.screenprojection;import android.util.Log;import org.java_websocket.WebSocket;
import org.java_websocket.handshake.ClientHandshake;
import org.java_websocket.server.WebSocketServer;import java.net.InetSocketAddress;public class ScreenSocketServer extends WebSocketServer {private final String TAG = ScreenSocketServer.class.getSimpleName();private WebSocket mWebSocket;public ScreenSocketServer(InetSocketAddress inetSocketAddress) {super(inetSocketAddress);}@Overridepublic void onOpen(WebSocket conn, ClientHandshake handshake) {Log.d(TAG, "onOpen");mWebSocket = conn;}@Overridepublic void onClose(WebSocket conn, int code, String reason, boolean remote) {Log.d(TAG, "onClose:" + reason);}@Overridepublic void onMessage(WebSocket conn, String message) {}@Overridepublic void onError(WebSocket conn, Exception ex) {Log.d(TAG, "onError:" + ex.toString());}@Overridepublic void onStart() {Log.d(TAG, "onStart");}public void sendData(byte[] bytes) {if (mWebSocket != null && mWebSocket.isOpen()) {// 通过WebSocket 发送数据Log.d(TAG, "sendData:");mWebSocket.send(bytes);}}public void close() {mWebSocket.close();}
}

WebSocketServer启动成功会回调onStart方法。

       @Overridepublic void onStart() {Log.d(TAG, "onStart");}

当有客户端连接回调onOpen方法，通过回调的WebSocket对象即可向客户端发送数据。

      @Overridepublic void onOpen(WebSocket conn, ClientHandshake handshake) {Log.d(TAG, "onOpen");mWebSocket = conn;}

视频编码器ScreenEncoder采用采用H.265编码（H.265/HEVC），需要注意不同手机支持的编码最大分辨率不同。

package com.example.screenprojection;import android.hardware.display.DisplayManager;
import android.media.MediaCodec;
import android.media.MediaCodecInfo;
import android.media.MediaFormat;
import android.media.projection.MediaProjection;
import android.view.Surface;import java.io.IOException;
import java.nio.ByteBuffer;/*** 采用H.265编码 H.265/HEVC的编码架构大致上和H.264/AVC的架构相似 H.265又称为HEVC(全称High Efficiency Video Coding，高效率视频编码)*/
public class ScreenEncoder extends Thread {//不同手机支持的编码最大分辨率不同private static final int VIDEO_WIDTH = 2160;private static final int VIDEO_HEIGHT = 3840;private static final int SCREEN_FRAME_RATE = 20;private static final int SCREEN_FRAME_INTERVAL = 1;private static final long SOCKET_TIME_OUT = 10000;// I帧private static final int TYPE_FRAME_INTERVAL = 19;// vps帧private static final int TYPE_FRAME_VPS = 32;private final MediaProjection mMediaProjection;private final SocketManager mSocketManager;private MediaCodec mMediaCodec;private boolean mPlaying = true;// 记录vps pps spsprivate byte[] vps_pps_sps;public ScreenEncoder(SocketManager socketManager, MediaProjection mediaProjection) {mSocketManager = socketManager;mMediaProjection = mediaProjection;}public void startEncode() {MediaFormat mediaFormat =MediaFormat.createVideoFormat(MediaFormat.MIMETYPE_VIDEO_HEVC, VIDEO_WIDTH, VIDEO_HEIGHT);mediaFormat.setInteger(MediaFormat.KEY_COLOR_FORMAT, MediaCodecInfo.CodecCapabilities.COLOR_FormatSurface);// 比特率（比特/秒）mediaFormat.setInteger(MediaFormat.KEY_BIT_RATE, VIDEO_WIDTH * VIDEO_HEIGHT);// 帧率mediaFormat.setInteger(MediaFormat.KEY_FRAME_RATE, SCREEN_FRAME_RATE);// I帧的频率mediaFormat.setInteger(MediaFormat.KEY_I_FRAME_INTERVAL, SCREEN_FRAME_INTERVAL);try {mMediaCodec = MediaCodec.createEncoderByType(MediaFormat.MIMETYPE_VIDEO_HEVC);mMediaCodec.configure(mediaFormat, null, null, MediaCodec.CONFIGURE_FLAG_ENCODE);Surface surface = mMediaCodec.createInputSurface();mMediaProjection.createVirtualDisplay("screen",VIDEO_WIDTH,VIDEO_HEIGHT,1,DisplayManager.VIRTUAL_DISPLAY_FLAG_PUBLIC,surface,null,null);} catch (IOException e) {e.printStackTrace();}start();}@Overridepublic void run() {mMediaCodec.start();MediaCodec.BufferInfo bufferInfo = new MediaCodec.BufferInfo();while (mPlaying) {int outPutBufferId = mMediaCodec.dequeueOutputBuffer(bufferInfo, SOCKET_TIME_OUT);if (outPutBufferId >= 0) {ByteBuffer byteBuffer = mMediaCodec.getOutputBuffer(outPutBufferId);encodeData(byteBuffer, bufferInfo);mMediaCodec.releaseOutputBuffer(outPutBufferId, false);}}}private void encodeData(ByteBuffer byteBuffer, MediaCodec.BufferInfo bufferInfo) {int offSet = 4;if (byteBuffer.get(2) == 0x01) {offSet = 3;}int type = (byteBuffer.get(offSet) & 0x7E) >> 1;if (type == TYPE_FRAME_VPS) {vps_pps_sps = new byte[bufferInfo.size];byteBuffer.get(vps_pps_sps);} else if (type == TYPE_FRAME_INTERVAL) {final byte[] bytes = new byte[bufferInfo.size];byteBuffer.get(bytes);byte[] newBytes = new byte[vps_pps_sps.length + bytes.length];System.arraycopy(vps_pps_sps, 0, newBytes, 0, vps_pps_sps.length);System.arraycopy(bytes, 0, newBytes, vps_pps_sps.length, bytes.length);mSocketManager.sendData(newBytes);} else {byte[] bytes = new byte[bufferInfo.size];byteBuffer.get(bytes);mSocketManager.sendData(bytes);}}public void stopEncode() {mPlaying = false;if (mMediaCodec != null) {mMediaCodec.release();}if (mMediaProjection != null) {mMediaProjection.stop();}}
}

注意点：
1.需要依赖WebSocket相关jar。

implementation “org.java-websocket:Java-WebSocket:1.5.3”

2.AndroidManifest配置网络和前台服务权限。

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

3.配置前台录屏服务foregroundServiceType属性。

    <serviceandroid:name=".ScreenService"android:enabled="true"android:exported="true"android:foregroundServiceType="mediaProjection" />

投屏客户端的实现

客户端入口负责创建SurfaceView并初始化WebSocket客户端管理器SocketClientManager。

package com.example.screenplayer;import android.os.Bundle;
import android.view.Surface;
import android.view.SurfaceHolder;
import android.view.SurfaceView;import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;public class MainActivity extends AppCompatActivity {private SocketClientManager mSocketClientManager;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);SurfaceView surfaceView = findViewById(R.id.sv_screen);surfaceView.getHolder().addCallback(new SurfaceHolder.Callback() {@Overridepublic void surfaceCreated(@NonNull SurfaceHolder holder) {// 连接到服务端initSocketManager(holder.getSurface());}@Overridepublic void surfaceChanged(@NonNull SurfaceHolder holder, int format, int width, int height) {}@Overridepublic void surfaceDestroyed(@NonNull SurfaceHolder holder) {}});}private void initSocketManager(Surface surface) {mSocketClientManager = new SocketClientManager();mSocketClientManager.start(surface);}@Overrideprotected void onDestroy() {if (mSocketClientManager != null) {mSocketClientManager.stop();}super.onDestroy();}
}

SocketClientManager将Surface与解码器绑定，创建WebSocket客户端并接收服务端推送的视频流。其中URI 需要修改为服务端的IP地址和端口。

package com.example.screenplayer;import android.view.Surface;import java.net.URI;
import java.net.URISyntaxException;public class SocketClientManager implements ScreenSocketClient.SocketCallback {private static final int SOCKET_PORT = 50000;private ScreenDecoder mScreenDecoder;private ScreenSocketClient mSocketClient;public void start(Surface surface) {mScreenDecoder = new ScreenDecoder();mScreenDecoder.startDecode(surface);try {// 需要修改为服务端的IP地址与端口URI uri = new URI("ws://192.168.1.3:" + SOCKET_PORT);mSocketClient = new ScreenSocketClient(this, uri);mSocketClient.connect();} catch (URISyntaxException e) {e.printStackTrace();}}public void stop() {if (mSocketClient != null) {mSocketClient.close();}if (mScreenDecoder != null) {mScreenDecoder.stopDecode();}}@Overridepublic void onReceiveData(byte[] data) {if (mScreenDecoder != null) {mScreenDecoder.decodeData(data);}}
}

ScreenSocketClient代码如下：

package com.example.screenplayer;import android.util.Log;import org.java_websocket.client.WebSocketClient;
import org.java_websocket.handshake.ServerHandshake;import java.net.URI;
import java.nio.ByteBuffer;public class ScreenSocketClient extends WebSocketClient {private static final String TAG = ScreenSocketClient.class.getSimpleName();private final SocketCallback mSocketCallback;public ScreenSocketClient(SocketCallback socketCallback, URI serverUri) {super(serverUri);mSocketCallback = socketCallback;}@Overridepublic void onOpen(ServerHandshake serverHandshake) {Log.d(TAG, "onOpen");}@Overridepublic void onMessage(String message) {}@Overridepublic void onMessage(ByteBuffer bytes) {byte[] buf = new byte[bytes.remaining()];bytes.get(buf);if (mSocketCallback != null) {mSocketCallback.onReceiveData(buf);}}@Overridepublic void onClose(int code, String reason, boolean remote) {Log.d(TAG, "onClose =" + reason);}@Overridepublic void onError(Exception ex) {Log.d(TAG, "onError =" + ex.toString());}public interface SocketCallback {void onReceiveData(byte[] data);}
}

不同手机支持的解码最大分辨率不同，需要设置正确的分辨率才不会报错。投屏解码器ScreenDecoder代码如下：

package com.example.screenplayer;import android.media.MediaCodec;
import android.media.MediaFormat;
import android.view.Surface;import java.io.IOException;
import java.nio.ByteBuffer;public class ScreenDecoder {private static final int VIDEO_WIDTH = 2160;private static final int VIDEO_HEIGHT = 3840;private static final long DECODE_TIME_OUT = 10000;private static final int SCREEN_FRAME_RATE = 20;private static final int SCREEN_FRAME_INTERVAL = 1;private MediaCodec mMediaCodec;public ScreenDecoder() {}public void startDecode(Surface surface) {try {// 配置MediaCodecmMediaCodec = MediaCodec.createDecoderByType(MediaFormat.MIMETYPE_VIDEO_HEVC);MediaFormat mediaFormat =MediaFormat.createVideoFormat(MediaFormat.MIMETYPE_VIDEO_HEVC, VIDEO_WIDTH, VIDEO_HEIGHT);mediaFormat.setInteger(MediaFormat.KEY_BIT_RATE, VIDEO_WIDTH * VIDEO_HEIGHT);mediaFormat.setInteger(MediaFormat.KEY_FRAME_RATE, SCREEN_FRAME_RATE);mediaFormat.setInteger(MediaFormat.KEY_I_FRAME_INTERVAL, SCREEN_FRAME_INTERVAL);mMediaCodec.configure(mediaFormat, surface, null, 0);mMediaCodec.start();} catch (IOException e) {e.printStackTrace();}}public void decodeData(byte[] data) {int index = mMediaCodec.dequeueInputBuffer(DECODE_TIME_OUT);if (index >= 0) {ByteBuffer inputBuffer = mMediaCodec.getInputBuffer(index);inputBuffer.clear();inputBuffer.put(data, 0, data.length);mMediaCodec.queueInputBuffer(index, 0, data.length, System.currentTimeMillis(), 0);}MediaCodec.BufferInfo bufferInfo = new MediaCodec.BufferInfo();int outputBufferIndex = mMediaCodec.dequeueOutputBuffer(bufferInfo, DECODE_TIME_OUT);while (outputBufferIndex > 0) {mMediaCodec.releaseOutputBuffer(outputBufferIndex, true);outputBufferIndex = mMediaCodec.dequeueOutputBuffer(bufferInfo, 0);}}public void stopDecode() {if (mMediaCodec != null) {mMediaCodec.release();}}
}

注意点：
1.需要依赖WebSocket相关jar。

implementation “org.java-websocket:Java-WebSocket:1.5.3”

2.AndroidManifest配置网络权限。

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

效果

左手边为服务端，右手边为客户端，服务端投屏到客户端的效果如下：

遇到的错误

1.WebSocket出现Permission denied的报错：

onerror =java.net.SocketException: socket failed: EACCES (Permission denied)

问题原因：需要网络权限。

<uses-permission android:name=“android.permission.INTERNET”/>

2.WebSocket出现Host unreachable报错：

onerror =java.net.NoRouteToHostException: Host unreachable

问题原因：不在同一局域网内或服务端未正常启动。

3.WebSocket出现failed to connect报错：

failed to connect to /192.168.1.3 (port 50000) from /:: (port 38262):，不在同一局域网内或服务端未正常启动

问题原因：不在同一局域网内或服务端未正常启动。

客户端连接成功回调onOpen方法

      @Overridepublic void onOpen(ServerHandshake handshakedata) {Log.d(TAG,"SocketClient onOpen");}

4.初始化MediaFormat时报IllegalStateException异常：

Caused by: java.lang.IllegalArgumentException
at android.media.MediaCodec.native_configure(Native Method)
at android.media.MediaCodec.configure(MediaCodec.java:2023)
at android.media.MediaCodec.configure(MediaCodec.java:1951)
at com.example.screenprojection.ScreenEncoder.startEncode(ScreenEncoder.java:56)

问题原因：不同手机支持的最大编解码分辨率不同，可通过adb shell cat /system/etc/media_codecs.xml的adb命令查看手机支持的编解码分辨率。未设置编码强制要求的一些配置会抛出 IllegalStateException。

       <MediaCodec name="OMX.hisi.video.decoder.hevc.secure" type="video/hevc" ><Quirk name="needs-flush-on-all-ports" /><Limit name="size" min="128x128" max="4096x2304" /><Limit name="alignment" value="2x2" /><Limit name="block-size" value="16x16" /><Limit name="block-count" range="64-36896" /><Limit name="blocks-per-second" range="99-1106880" /><Limit name="bitrate" range="1-52428800" /><Feature name="adaptive-playback" /><Feature name="secure-playback" required="true" /><Quirk name="requires-allocate-on-input-ports" /><Quirk name="requires-allocate-on-output-ports" /><Limit name="concurrent-instances" max="1" /></MediaCodec><!--config suggestion for hevc --><!--VT:1280x720@1Mbps@30fps，640x360@450kpbps@30fps,640x360@250kbps@30fps，640x360@170kbps@15fps--><!--DestkTop Share: 1280x720@500kbps@3-7fps,720x450@200kbps@3-7fps--><!--Wifi Display:1920x1080@8Mbps@30fps 4Kx2k@27M@30fps--><!--Recoding:1920x1080@12Mbps@30fps，4k2k@30Mbps@30fps,1920x1080@40M@120fps，1280X720@40M@120fps--><MediaCodec name="OMX.hisi.video.encoder.hevc" type="video/hevc" ><Limit name="size" min="176x144" max="3840x2160" /><Limit name="alignment" value="4x4" /><Limit name="block-size" value="64x64" /><Limit name="blocks-per-second" range="99-244800" /><Limit name="bitrate" range="200000-70000000" /><Quirk name="requires-allocate-on-output-ports" /><Limit name="concurrent-instances" max="3" /></MediaCodec>

源码下载地址：无线投屏源码