Android入门教程 | Camera 相机（一） android音视频

概述 Android 使用 Android Camera API 完成音视频的采集、编码、封包成 mp4 输出。
基于android.hardware.Camera，创建一个横屏应用，实时预览摄像头图像，实现录像并输出MP4的功能。这里不使用Camera2。
申请权限

在 activity 中动态申请权限

private static final String[] VIDEO_PERMISSIONS = { Manifest.permission.CAMERA, Manifest.permission.RECORD_AUDIO, Manifest.permission.WRITE_EXTERNAL_STORAGE };

实现摄像头预览功能使用SurfaceView来预览。新建CameraPreview类继承自SurfaceView并实现SurfaceHolder.Callback； camera相关操作都放在这个View里。

surfaceCreated中获取Camera实例，启动预览；设置预览相关参数
surfaceDestroyed释放Camera

public class CameraPreview extends SurfaceView implements SurfaceHolder.Callback { private static final String TAG = "rustAppCameraPreview"; private SurfaceHolder mHolder; private Camera mCamera; public static final int MEDIA_TYPE_IMAGE = 1; public static final int MEDIA_TYPE_VIDEO = 2; private static int mOptVideoWidth = 1920; // 默认视频帧宽度 private static int mOptVideoHeight = 1080; private Uri outputMediaFileUri; private String outputMediaFileType; public CameraPreview(Context context) { super(context); mHolder = getHolder(); mHolder.addCallback(this); }private static Camera getCameraInstance() { Camera c = null; try { c = Camera.open(); } catch (Exception e) { Log.d(TAG, "camera is not available"); } return c; }@Override public void surfaceCreated(SurfaceHolder holder) { mCamera = getCameraInstance(); try { mCamera.setPreviewDisplay(holder); mCamera.startPreview(); getCameraOptimalVideoSize(); // 找到最合适的分辨率 } catch (IOException e) { Log.d(TAG, "Error setting camera preview: " + e.getMessage()); } }private void getCameraOptimalVideoSize() { try { Camera.Parameters parameters = mCamera.getParameters(); List mSupportedPreviewSizes = parameters.getSupportedPreviewSizes(); List mSupportedVideoSizes = parameters.getSupportedVideoSizes(); Camera.Size optimalSize = CameraHelper.getOptimalVideoSize(mSupportedVideoSizes, mSupportedPreviewSizes, getWidth(), getHeight()); mOptVideoWidth = optimalSize.width; mOptVideoHeight = optimalSize.height; Log.d(TAG, "prepareVideoRecorder: optimalSize:" + mOptVideoWidth + ", " + mOptVideoHeight); } catch (Exception e) { Log.e(TAG, "getCameraOptimalVideoSize: ", e); } }@Override public void surfaceDestroyed(SurfaceHolder holder) { mHolder.removeCallback(this); mCamera.setPreviewCallback(null); mCamera.stopPreview(); mCamera.release(); mCamera = null; }@Override public void surfaceChanged(SurfaceHolder holder, int format, int w, int h) { } }

在 Fragment 中显示摄像头预览
预置一个 FrameLayout，实例化一个 CameraPreview 添加进去

/** * 视频录制界面 * Created by Rust on 2018/5/17. */ public class VideoRecordFragment extends Fragment { private static final String TAG = "rustAppVideoFrag"; private Button mCaptureBtn; private CameraPreview mCameraPreview; public static VideoRecordFragment newInstance() { return new VideoRecordFragment(); }@Override public void onCreate(@Nullable Bundle savedInstanceState) { super.onCreate(savedInstanceState); Log.d(TAG, "frag onCreate"); }@Nullable @Override public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) { Log.d(TAG, "frag onCreateView"); return inflater.inflate(R.layout.frag_video_record, container, false); }@Override public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) { Log.d(TAG, "frag onViewCreated"); super.onViewCreated(view, savedInstanceState); mCaptureBtn = view.findViewById(R.id.capture_btn); //mCaptureBtn.setOnClickListener(mOnClickListener); // 录制键mCameraPreview = new CameraPreview(getContext()); FrameLayout preview = view.findViewById(R.id.camera_preview); preview.addView(mCameraPreview); } }

使用 MediaRecorder 录制给 MediaRecorder 指定参数后，调用 start() 开始录制，stop() 结束录制
录制开始前，获取 camera，mCamera.unlock() 解锁；录制完毕后，清除 MediaRecorder，mCamera.lock()

private MediaRecorder mMediaRecorder; public boolean startRecording() { if (prepareVideoRecorder()) { mMediaRecorder.start(); return true; } else { releaseMediaRecorder(); } return false; }public void stopRecording() { if (mMediaRecorder != null) { mMediaRecorder.stop(); } releaseMediaRecorder(); }public boolean isRecording() { return mMediaRecorder != null; }private boolean prepareVideoRecorder() { if (null == mCamera) { mCamera = getCameraInstance(); } mMediaRecorder = new MediaRecorder(); mCamera.unlock(); mMediaRecorder.setCamera(mCamera); mMediaRecorder.setAudioSource(MediaRecorder.AudioSource.DEFAULT); mMediaRecorder.setVideoSource(MediaRecorder.VideoSource.CAMERA); mMediaRecorder.setProfile(CamcorderProfile.get(CamcorderProfile.QUALITY_HIGH)); mMediaRecorder.setVideoSize(mOptVideoWidth, mOptVideoHeight); mMediaRecorder.setOutputFile(getOutputMediaFile(MEDIA_TYPE_VIDEO).toString()); mMediaRecorder.setPreviewDisplay(mHolder.getSurface()); try { mMediaRecorder.prepare(); } catch (IllegalStateException e) { Log.d(TAG, "IllegalStateException preparing MediaRecorder: " + e.getMessage()); releaseMediaRecorder(); return false; } catch (IOException e) { Log.d(TAG, "IOException preparing MediaRecorder: " + e.getMessage()); releaseMediaRecorder(); return false; } return true; }private void releaseMediaRecorder() { if (mMediaRecorder != null) { mMediaRecorder.reset(); mMediaRecorder.release(); mMediaRecorder = null; mCamera.lock(); } }private File getOutputMediaFile(int type) { File mediaStorageDir = new File(Environment.getExternalStoragePublicDirectory( Environment.DIRECTORY_PICTURES), TAG); if (!mediaStorageDir.exists()) { if (!mediaStorageDir.mkdirs()) { Log.d(TAG, "failed to create directory"); return null; } } String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss", Locale.CHINA).format(new Date()); File mediaFile; if (type == MEDIA_TYPE_IMAGE) { mediaFile = new File(mediaStorageDir.getPath() + File.separator + "IMG_" + timeStamp + ".jpg"); outputMediaFileType = "image/*"; } else if (type == MEDIA_TYPE_VIDEO) { mediaFile = new File(mediaStorageDir.getPath() + File.separator + "VID_" + timeStamp + ".mp4"); outputMediaFileType = "video/*"; } else { return null; } outputMediaFileUri = Uri.fromFile(mediaFile); return mediaFile; }

后台返回时预览黑屏的问题
CameraPreview 是我们在 Fragment 创建时实例化并添加进去的。应用退到后台后，CameraPreview 已经被销毁。应用回到前台时，我们应该在 onResume 方法中进行操作。恢复CameraPreview。
在 Fragment 中，判断销毁和重建预览的时机。

@Override public void onPause() { super.onPause(); Log.d(TAG, "onPause: 销毁预览"); mCameraPreview = null; }@Override public void onResume() { super.onResume(); Log.d(TAG, "onResume: 回到前台"); if (null == mCameraPreview) { initCameraPreview(); } }private void initCameraPreview() { mCameraPreview = new CameraPreview(getContext()); FrameLayout preview = mRoot.findViewById(R.id.camera_preview); preview.addView(mCameraPreview); }

【Android入门教程 | Camera 相机（一）】【Android音视频开发系列教程】