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。

1、申请权限

<!-- 需要录制音视频权限和写外部存储权限 -->
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.RECORD_AUDIO" />
<uses-permission android:name="android.permission.CAMERA" />
<uses-feature android:name="android.hardware.camera" />

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
};

2、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 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<Camera.Size> mSupportedPreviewSizes = parameters.getSupportedPreviewSizes();
List<Camera.Size> 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) {
}
}

3、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);
}

原创作者：CHSmile，原文链接：https://www.jianshu.com/p/b6386ba20d08

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