preview display in android media recorder

问题

In android how to show preview surface before media recorder start. my app have video recording functionality,when i navigate to video recording fragment it display black screen,when i start recording using start button camera preview is display and recording start.

how to start preview before recording. i have added code that i used in onCreateView() of fragment-

surfaceHolder = mySurfaceView.getHolder();
camera = Camera.open();
if(camera!=null){
    camera.setDisplayOrientation(90);
    Camera.Parameters param;
    param = camera.getParameters();
    param.setPreviewFrameRate(20);
    param.setPreviewSize(176, 144);
    camera.setParameters(param);
    camera.setPreviewDisplay(surfaceHolder);
}

mediaRecorder = new MediaRecorder();
camera.unlock();
mediaRecorder.setCamera(camera);
mediaRecorder.setAudioSource(MediaRecorder.AudioSource.DEFAULT);
mediaRecorder.setVideoSource(MediaRecorder.VideoSource.DEFAULT);
CamcorderProfile camcorderProfile_HQ = CamcorderProfile
            .get(CamcorderProfile.QUALITY_HIGH);
mediaRecorder.setProfile(camcorderProfile_HQ);
String filePath = getOutputMediaFile(MEDIA_TYPE_VIDEO).getPath();
fileUri = getOutputMediaFileUri(MEDIA_TYPE_VIDEO);
mediaRecorder.setOutputFile(filePath);

and the code that i used on start button click-

mediaRecorder.setPreviewDisplay(surfaceHolder.getSurface());
mediaRecorder.prepare();
mediaRecorder.start();

so i am able to recode video by using above code,but not able to show preview before recording start. Please help me where i am missing.for that black screen is displayed before recoding video.

Thanks in advance.

回答1:

public void surfaceCreated(SurfaceHolder holder) {
        if (mCamera != null) {
            Parameters params = mCamera.getParameters();
            mCamera.setParameters(params);
            try {
                //mCamera.setDisplayOrientation(90);
                mCamera.setPreviewDisplay(holder);
            } catch (IOException e) {
                e.printStackTrace();
            }
            mCamera.startPreview();
        }
    }

If you implement SurfaceHolder.Callback, override the surfaceCreated method like this. This worked for me.

回答2:

I ran into the same problem. I looked it up and here's my Activity. It took me a bit of effort to make it not crash, so here's the final result. It displays the preview before the user clicks the REC button. (I am also displaying a countdown, but don't mind that). Notice also that there is too much work done on the main thread in this example (when clicking). There are a few things here that aren't best practices, but for a working example I think it's good enough.

import android.app.Activity;
import android.hardware.Camera;
import android.media.CamcorderProfile;
import android.media.MediaRecorder;
import android.os.Bundle;
import android.os.CountDownTimer;
import android.os.Environment;
import android.util.Log;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

import java.io.File;
import java.io.IOException;

public class MainActivity extends Activity implements SurfaceHolder.Callback {

    private static final String LOG_TAG = MainActivity.class.getCanonicalName();
    Button myButton;
    MediaRecorder mediaRecorder;
    SurfaceHolder surfaceHolder;
    boolean recording;
    private TextView mTimer;
    private Camera mCamera;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        recording = false;
        mediaRecorder = new MediaRecorder();
        mCamera = Camera.open();
        initMediaRecorder();

        SurfaceView myVideoView = (SurfaceView) findViewById(R.id.videoview);
        surfaceHolder = myVideoView.getHolder();
        surfaceHolder.addCallback(this);

        myButton = (Button) findViewById(R.id.mybutton);
        myButton.setOnClickListener(myButtonOnClickListener);

        mTimer = (TextView) findViewById(R.id.timer);
    }

    private Button.OnClickListener myButtonOnClickListener
            = new Button.OnClickListener() {

        @Override
        public void onClick(final View arg0) {
            CountDownTimer countDownTimer = new CountDownTimer(90 * 1000, 1000) {
                @Override
                public void onTick(long millisUntilFinished) {
                    mTimer.setText(String.valueOf(millisUntilFinished / 1000));
                }

                @Override
                public void onFinish() {
                    onClick(arg0);
                }
            };

            if (recording) {
                // Stop recording and finish
                try {
                    mediaRecorder.stop();
                    mediaRecorder.reset();
                    mediaRecorder.release();
                    finish();
                } catch (Exception e) {
                    Log.e(LOG_TAG, "Failed to stop recorder", e);
                }

            } else {
                // Release the camera and start recording
                mCamera.release();
                countDownTimer.start();
                mediaRecorder.start();
                recording = true;
                myButton.setText("STOP");
            }
        }
    };


    @Override
    public void surfaceChanged(SurfaceHolder arg0, int arg1, int arg2, int arg3) {

    }

    @Override
    public void surfaceCreated(SurfaceHolder holder) {
        if (mCamera != null) {
            Camera.Parameters params = mCamera.getParameters();
            mCamera.setParameters(params);
            try {
                mCamera.setPreviewDisplay(holder);
            } catch (IOException e) {
                e.printStackTrace();
            }
            mCamera.startPreview();
        }
        prepareMediaRecorder();
    }

    @Override
    public void surfaceDestroyed(SurfaceHolder arg0) {

    }

    private void initMediaRecorder() {
        mediaRecorder.setAudioSource(MediaRecorder.AudioSource.DEFAULT);
        mediaRecorder.setVideoSource(MediaRecorder.VideoSource.DEFAULT);
        CamcorderProfile camcorderProfile_HQ = CamcorderProfile.get(CamcorderProfile.QUALITY_CIF);
        mediaRecorder.setProfile(camcorderProfile_HQ);
        File file = new File(getExternalFilesDir(Environment.DIRECTORY_MOVIES), "myvideo.mp4");
        if (file.exists()) {
            file.delete();
        }
        mediaRecorder.setOutputFile(file.getAbsolutePath());
        mediaRecorder.setMaxDuration(90000); // Set max duration 90 sec.
        mediaRecorder.setMaxFileSize(15000000); // Set max file size 15M
    }

    private void prepareMediaRecorder() {
        mediaRecorder.setPreviewDisplay(surfaceHolder.getSurface());

        try {
            mediaRecorder.prepare();
        } catch (IllegalStateException | IOException e) {
            Log.e(LOG_TAG, "Failed to prepare recorder", e);
        }
    }
}

来源：https://stackoverflow.com/questions/19176663/preview-display-in-android-media-recorder