HarmonyOS鸿蒙Next中录屏开启时app能自动返回桌面录制，并且能输出原始码流，最好有demo

以下分析仅供参考：

在鸿蒙系统上实现桌面分享功能，需要结合多模态交互和系统底层能力。以下是基于ArkTS的核心实现方案：

1. 权限申请（必须首先处理）

// 在module.json5中添加权限
{
  "module": {
    "requestPermissions": [
      {
        "name": "ohos.permission.CAPTURE_SCREEN",
        "reason": "$string:screen_capture_desc"
      }
    ]
  }
}

// 动态权限申请
import abilityAccessCtrl from '@ohos.abilityAccessCtrl';

async function requestPermissions() {
  const atManager = abilityAccessCtrl.createAtManager();
  try {
    const status = await atManager.requestPermissionsFromUser(
      this.context,
      ['ohos.permission.CAPTURE_SCREEN']
    );
    return status.authResults[0] === 0;
  } catch (err) {
    console.error(`Request permission failed: ${err}`);
    return false;
  }
}

1. 屏幕捕获核心逻辑（使用XComponent+NDK）

// ArkTS组件
@Component
struct ScreenCaptureView {
  @State surfaceId: string = "";

  build() {
    XComponent({
      id: 'xcomponent_id',
      type: 'surface',
      controller: this.xcomponentController
    })
    .onLoad(() => {
      this.surfaceId = this.xcomponentController.getXComponentSurfaceId();
      this.startCapture();
    })
  }

  private startCapture() {
    // 调用Native层进行屏幕捕获
    nativeCapture.startScreenCapture(this.surfaceId, (errCode) => {
      if (errCode === 0) {
        console.log('Screen capture started');
      }
    });
  }
}

1. 视频编码传输（建议使用硬件编码）

// 使用鸿蒙媒体库进行H.264编码
import media from '@ohos.multimedia.media';

class VideoEncoder {
  private mediaCodec: media.Codec;

  async initEncoder() {
    const codecMime = media.CodecMimeType.VIDEO_AVC;
    this.mediaCodec = await media.createCodec(codecMime);
    
    const format = {
      audioSampleRate: 48000,
      audioChannels: 2,
      width: 1920,
      height: 1080,
      colorFormat: media.ColorFormat.YUV420P,
      frameRate: 30,
      bitrate: 4000000
    };
    
    await this.mediaCodec.configure(format);
    this.mediaCodec.start();
  }

  async encodeFrame(data: ArrayBuffer) {
    const inputBuffer = await this.mediaCodec.getInputBuffer();
    inputBuffer.write(data);
    await this.mediaCodec.queueInputBuffer();
    
    const outputBuffer = await this.mediaCodec.getOutputBuffer();
    // 处理编码后的数据
    this.sendNetworkPacket(outputBuffer);
  }
}

1. 网络传输优化方案

// 使用WebSocket进行低延迟传输（生产环境建议使用RTP）
class NetworkManager {
  private webSocket: WebSocket;

  connect(url: string) {
    this.webSocket = new WebSocket(url);
    this.webSocket.onopen = () => {
      console.log('WebSocket connected');
    };
    this.webSocket.onmessage = (event) => {
      this.handleControlMessage(event.data);
    };
  }

  sendNetworkPacket(data: ArrayBuffer) {
    if (this.webSocket.readyState === WebSocket.OPEN) {
      this.webSocket.send(data);
    }
  }

  private handleControlMessage(message: string) {
    // 处理网络质量反馈、码率调整等
  }
}

1. 接收端渲染优化

// 使用XComponent进行高效渲染
@Component
struct RemoteScreenView {
  @State surfaceId: string = "";

  build() {
    XComponent({
      id: 'remote_screen',
      type: 'surface',
      controller: this.xcomponentController
    })
    .onLoad(() => {
      this.surfaceId = this.xcomponentController.getXComponentSurfaceId();
      this.startRendering();
    })
  }

  private startRendering() {
    // 绑定Native层渲染表面
    nativeRender.bindSurface(this.surfaceId);
  }
}

实现注意事项：

1. 性能优化关键点：

• 使用双缓冲机制减少画面撕裂
• 动态调整编码参数（根据网络质量）

class QualityController {
  private currentBitrate = 4000000;

  adjustQuality(networkQuality: number) {
    if (networkQuality < 50) {
      this.currentBitrate = 2000000;
    } else if (networkQuality < 80) {
      this.currentBitrate = 3000000;
    } else {
      this.currentBitrate = 4000000;
    }
    videoEncoder.setBitrate(this.currentBitrate);
  }
}