android - 为什么 MediaRecorder 函数不会导致 ANR 错误？

Question

我在 Android 5.1 中使用 MediaRecorder 和 MediaProjection 函数启动了一个重新记录屏幕的服务，我认为代码方法 1 会导致应用程序无响应错误，因为它在主线程中工作。

1. 我测试代码方法1重新编码屏幕很长时间，它没有出现“应用程序无响应错误”，为什么？这是否意味着函数 MediaRecorder 和 MediaProjection 在单独的线程中工作？

2. 在代码方法 2 中，我创建了一个线程来运行 mRecordHelper.StartRecord(mRecordArg,resultCode,mIntent);但我收到错误 java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare(), why?

感谢您的帮助。

调用代码

MPublicPar.RecordArg mRecordArg =new MPublicPar().new RecordArg(mContext);
Intent intent = new Intent(mContext,bll.RecordService.class);
intent.putExtra("resultCode",resultCode);
intent.putExtra("dataIntent",data);
intent.putExtra("mRecordArg",mRecordArg);

startService(intent);

方法一

public class RecordService extends Service { 

    private RecordHelper mRecordHelper;
    private Context mContext;

    @Override
    public void onCreate(){  
        mContext=this;

        mRecordHelper=new RecordHelper(mContext);
    }

    @Override
    public void onDestroy(){
        mRecordHelper.StopRecord();
    }


    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {

       final int resultCode=intent.getIntExtra("resultCode",0);
       final Intent mIntent=(Intent)intent.getParcelableExtra("dataIntent");
       final MPublicPar.RecordArg mRecordArg=(MPublicPar.RecordArg)intent.getSerializableExtra("mRecordArg");

        mRecordHelper.StartRecord(mRecordArg,resultCode,mIntent);
        return super.onStartCommand(intent, flags, startId);
    }

}

方法二

public class RecordService extends Service { 

    private RecordHelper mRecordHelper;
    private Context mContext;

    @Override
    public void onCreate(){  
        mContext=this;

        mRecordHelper=new RecordHelper(mContext);
    }

    @Override
    public void onDestroy(){
        mRecordHelper.StopRecord();
    }


    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {

       final int resultCode=intent.getIntExtra("resultCode",0);
       final Intent mIntent=(Intent)intent.getParcelableExtra("dataIntent");
       final MPublicPar.RecordArg mRecordArg=(MPublicPar.RecordArg)intent.getSerializableExtra("mRecordArg");    

       new Thread(new Runnable() {
            public void run() {    
                mRecordHelper.StartRecord(mRecordArg,resultCode,mIntent);           
            }
        }).start();
        return super.onStartCommand(intent, flags, startId);
    }

}

RecordHelper.cs

public class RecordHelper {

    private  MediaRecorder mMediaRecorder;
    private  MediaProjection mMediaProjection;
    private  VirtualDisplay mVirtualDisplay;
    private  MediaProjectionManager mProjectionManager;

    private Context mContext;
    private Toast mToastText;

    public RecordHelper(Context mContext){
        this.mContext=mContext;
        mProjectionManager = (MediaProjectionManager) mContext.getSystemService(Context.MEDIA_PROJECTION_SERVICE);
        mMediaRecorder = new MediaRecorder();
    }

    public void StartRecord(RecordArg mRecordArg, int resultCode, Intent data){

        initRecorder(mRecordArg);
        prepareRecorder();

        mMediaProjection = mProjectionManager.getMediaProjection(resultCode, data);
        MediaProjectionCallback mMediaProjectionCallback = new MediaProjectionCallback();
        mMediaProjection.registerCallback(mMediaProjectionCallback, null);

        mVirtualDisplay=createVirtualDisplay(mRecordArg);

        DelayStartRecord(mRecordArg);
    }


    public void StopRecord(){
        try {
            mMediaRecorder.stop();
            mMediaRecorder.reset();

            mVirtualDisplay.release();
            mMediaRecorder.release();

            mMediaProjection.stop();
            mMediaProjection = null;

        }catch (Exception e){
            Utility.LogError("StopRecord Error " + e.getMessage() + "  " + e.toString());
        }
    }

    private void DelayStartRecord(RecordArg mRecordArg){
        mMediaRecorder.start();
    }


    private void initRecorder(RecordArg mRecordArg) {
        mMediaRecorder.setAudioSource(MediaRecorder.AudioSource.MIC);
        mMediaRecorder.setVideoSource(MediaRecorder.VideoSource.SURFACE);
        mMediaRecorder.setOutputFormat(MediaRecorder.OutputFormat.MPEG_4);
        mMediaRecorder.setVideoEncoder(MediaRecorder.VideoEncoder.H264);
        mMediaRecorder.setAudioEncoder(MediaRecorder.AudioEncoder.AMR_NB);
        mMediaRecorder.setVideoEncodingBitRate(512 * 1000);
        mMediaRecorder.setVideoFrameRate(30);
        mMediaRecorder.setVideoSize(mRecordArg.screenWidth, mRecordArg.screenHeight);
        mMediaRecorder.setOutputFile(mRecordArg.videoFilename);
    }


    private void prepareRecorder() {
        try {
            mMediaRecorder.prepare();
        } catch (IllegalStateException e) {
            e.printStackTrace();
            Utility.LogError(e.getMessage());

        } catch (IOException e) {
            e.printStackTrace();
            Utility.LogError(e.getMessage());
        }
    }


    private VirtualDisplay createVirtualDisplay(RecordArg mRecordArg) {
          return mMediaProjection.createVirtualDisplay("ScreenRecord",
                 mRecordArg.screenWidth, mRecordArg.screenHeight, mRecordArg.mScreenDensity,
                 DisplayManager.VIRTUAL_DISPLAY_FLAG_AUTO_MIRROR,
                 mMediaRecorder.getSurface(), null /*Callbacks*/, null /*Handler*/);
    }


    //Called when the MediaProjection session is no longer valid.
    private  class MediaProjectionCallback extends MediaProjection.Callback {
        @Override
        public void onStop() {

        }
    }

}

Answer 1

but I get the error java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare(), why?

我猜你知道你的第二个问题。事实上，如果您在主线程上调用 mRecordHelper.StartRecord(mRecordArg,resultCode,mIntent);，并不意味着所有代码函数都在该线程上运行，它所做的只是更新 UI 信息调用线程——这是主线程，在后台线程上努力工作。如果您明确地从不同的线程调用，那么您是在指示它从该线程更改 UI 对象，因此您会得到该异常-想象一个使用异步任务或 SurfaceView 的类，先生，请不要感到困惑，您可以随时去查看源代码，看看它是如何工作的。

这没什么大不了的-(我谦虚地说)

why? Does it mean that the function MediaRecorder and MediaProjection worked in separated thread?

检查上面的-我猜是