Android Camera系列（一）：SurfaceView+Camera

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Android Camera系列（一）：SurfaceView+Camera
Android Camera系列（二）：TextureView+Camera
Android Camera系列（三）：GLSurfaceView+Camera

本系列主要讲述Android开发中Camera的相关操作、预览方式、视频录制等，项目结构代码耦合性低，旨在帮助大家能从中有所收获（方便copy :）），对于个人来说也是一个总结的好机会

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Camera_10">一. Camera操作

Android系统存在这么多年，google更新了不少API。光是对摄像头的操作目前就有3种API：

android.hardware.Camera：最早用来自定义Camera的API
android.hardware.camera2.*：Android5.0之后推荐使用的API，对Camera操作更灵活，功能更丰富
CameraX：对Camera2的封装，API更简单

由于Android版本众多，考虑兼容性，本文我们还是对android.hardware.Camera进行讲解，操作Camera具体需要哪些步骤呢？

设置Camera权限，Android6.0以上请动态申请
打开相机，Camera.open()
开始预览，startPreview
停止预览，stopPreview
关闭相机，release()

1. 打开相机

申请Camera权限，Android6.0以上记得在打开相机前进行动态申请

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"><uses-permission android:name="android.permission.CAMERA" /><uses-feature android:name="android.hardware.camera" />...
</manifest>

我们对Camera进行了简单的封装，无论是Camera还是Camera2我们预览视图都可以是SurfaceView、TextureView、GLSurfaceView，所以我们将Camera操作和预览视图进行分离，让预览View不在依赖具体的某种Camera实现

定义接口类ICameraManager:

/*** Camera和Camera2通用接口** @author xiaozhi* @since 2024/8/15*/
public interface ICameraManager {/*** 打开Camera*/void openCamera();/*** 关闭释放Camera*/void releaseCamera();/*** 开启预览** @param surfaceHolder*/void startPreview(SurfaceHolder surfaceHolder);/*** 开启预览** @param surfaceTexture*/void startPreview(SurfaceTexture surfaceTexture);/*** 停止预览*/void stopPreview();...
}

CameraManager实现ICameraManager，打开摄像头

    /*** 打开Camera*/@Overridepublic synchronized void openCamera() {Logs.i(TAG, "Camera open #" + mCameraId);if (mCamera == null) {if (mCameraId >= Camera.getNumberOfCameras()) {onOpenError(CAMERA_ERROR_NO_ID, "No camera.");return;}try {mCamera = Camera.open(mCameraId);Camera.getCameraInfo(mCameraId, mCameraInfo);mCamera.setErrorCallback(errorCallback);initCamera();onOpen();mOrientationEventListener.enable();} catch (Exception e) {onOpenError(CAMERA_ERROR_OPEN, e.getMessage());}}}

打开摄像头之后我们可以设置摄像头的一些基本参数，如预览尺寸，拍照尺寸等

    /*** 配置Camera参数*/private void initCamera() {if (mCamera != null) {mParameters = mCamera.getParameters();if (mDisplayOrientation == -1) {setCameraDisplayOrientation(mContext, mCameraId, mCamera);}// 设置预览方向mCamera.setDisplayOrientation(mDisplayOrientation);// 设置拍照方向mParameters.setRotation(mOrientation);// 如果摄像头不支持这些参数都会出错的，所以设置的时候一定要判断是否支持List<String> supportedFlashModes = mParameters.getSupportedFlashModes();if (supportedFlashModes != null && supportedFlashModes.contains(Parameters.FLASH_MODE_OFF)) {mParameters.setFlashMode(Parameters.FLASH_MODE_OFF); // 设置闪光模式}List<String> supportedFocusModes = mParameters.getSupportedFocusModes();if (supportedFocusModes != null && supportedFocusModes.contains(Parameters.FOCUS_MODE_AUTO)) {mParameters.setFocusMode(Parameters.FOCUS_MODE_AUTO); // 设置聚焦模式}mParameters.setPreviewFormat(ImageFormat.NV21); // 设置预览图片格式mParameters.setPictureFormat(ImageFormat.JPEG); // 设置拍照图片格式Camera.Size previewSize = getSuitableSize(mParameters.getSupportedPreviewSizes());mPreviewWidth = previewSize.width;mPreviewHeight = previewSize.height;mPreviewSize = new Size(mPreviewWidth, mPreviewHeight);mParameters.setPreviewSize(mPreviewWidth, mPreviewHeight);Logs.d(TAG, "previewWidth: " + mPreviewWidth + ", previewHeight: " + mPreviewHeight);Camera.Size pictureSize = mParameters.getPictureSize();mParameters.setPictureSize(pictureSize.width, pictureSize.height);Logs.d(TAG, "pictureWidth: " + pictureSize.width + ", pictureHeight: " + pictureSize.height);mCamera.setParameters(mParameters);isSupportZoom = mParameters.isSmoothZoomSupported();}}

2.开始预览

    /*** 使用Surfaceview开启预览** @param holder*/@Overridepublic synchronized void startPreview(SurfaceHolder holder) {Logs.i(TAG, "startPreview...");if (isPreviewing) {return;}if (mCamera != null) {try {mCamera.setPreviewDisplay(holder);if (!mPreviewBufferCallbacks.isEmpty()) {mCamera.addCallbackBuffer(new byte[mPreviewWidth * mPreviewHeight * 3 / 2]);mCamera.setPreviewCallbackWithBuffer(mPreviewCallback);}mCamera.startPreview();onPreview(mPreviewWidth, mPreviewHeight);} catch (Exception e) {onPreviewError(CAMERA_ERROR_PREVIEW, e.getMessage());}}}

3. 停止预览

    /*** 关闭预览*/@Overridepublic synchronized void stopPreview() {Logs.v(TAG, "stopPreview.");if (isPreviewing && null != mCamera) {try {mCamera.setPreviewCallback(null);mCamera.stopPreview();mPreviewBufferCallbacks.clear();} catch (Exception e) {e.printStackTrace();}}isPreviewing = false;}

4. 关闭相机

    /*** 停止预览，释放Camera*/@Overridepublic synchronized void releaseCamera() {Logs.v(TAG, "releaseCamera.");if (null != mCamera) {stopPreview();try {mCamera.release();mCamera = null;mCameraBytes = null;mDisplayOrientation = -1;} catch (Exception e) {}onClose();}}

SurfaceView_218">二.SurfaceView使用

我们要预览Camera数据必须要使用一个视图承接，SurfaceView是最常用的，也是Camera最初的标配

SurfaceView的特点：在自己独立的线程中绘制，内部使用双缓冲机制，画面更流畅。相比于 TextureView，它内存占用低，绘制更及时，耗时也更低，但不支持动画和截图。

Camera预览需要将SurfaceHolder传递给Camera然后开启预览如何获取SurfaceHoler？

自定义Camera SurfaceView继承SurfaceView
实现SurfaceHolder.Callback接口，并在Camera SurfaceView初始化时设置回调
实现自定义CameraCallback接口，监听Camera状态
一定要实现onResume和onPause接口，并在对应的Activity生命周期中调用。这是所有使用Camera的bug的源头

/*** 摄像头预览SurfaceView** @author xiaozhi* @since 2024/8/22*/
public class CameraSurfaceView extends SurfaceView implements SurfaceHolder.Callback, CameraCallback {private static final String TAG = CameraSurfaceView.class.getSimpleName();SurfaceHolder mSurfaceHolder;private Context mContext;private Handler mHandler;private boolean hasSurface; // 是否存在摄像头显示层private CameraManager mCameraManager;private int mRatioWidth = 0;private int mRatioHeight = 0;private int mSurfaceWidth;private int mSurfaceHeight;public CameraSurfaceView(Context context) {super(context);init(context);}public CameraSurfaceView(Context context, AttributeSet attrs) {super(context, attrs);init(context);}public CameraSurfaceView(Context context, AttributeSet attrs, int defStyleAttr) {super(context, attrs, defStyleAttr);init(context);}private void init(Context context) {mContext = context;mHandler = new Handler(context.getMainLooper());mSurfaceHolder = getHolder();mSurfaceHolder.setFormat(PixelFormat.TRANSPARENT);//translucent半透明 transparent透明mSurfaceHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);mSurfaceHolder.addCallback(this);mCameraManager = new CameraManager(context);mCameraManager.setCameraCallback(this);}public CameraManager getCameraManager() {return mCameraManager;}@Overridepublic void surfaceCreated(SurfaceHolder holder) {Logs.i(TAG, "surfaceCreated..." + hasSurface);if (!hasSurface && holder != null) {hasSurface = true;openCamera();}}@Overridepublic void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {Logs.i(TAG, "surfaceChanged [" + width + ", " + height + "]");mSurfaceWidth = width;mSurfaceHeight = height;}@Overridepublic void surfaceDestroyed(SurfaceHolder holder) {Logs.v(TAG, "surfaceDestroyed.");closeCamera();hasSurface = false;}public SurfaceHolder getSurfaceHolder() {return mSurfaceHolder;}public void onResume() {if (hasSurface) {// 当activity暂停，但是并未停止的时候，surface仍然存在，所以 surfaceCreated()// 并不会调用，需要在此处初始化摄像头openCamera();}}public void onPause() {closeCamera();}/*** 打开摄像头*/private void openCamera() {if (mSurfaceHolder == null) {Logs.e(TAG, "SurfaceHolder is null.");return;}if (mCameraManager.isOpen()) {Logs.w(TAG, "Camera is opened！");return;}mCameraManager.openCamera();}/*** 关闭摄像头*/private void closeCamera() {mCameraManager.releaseCamera();}private String getString(int resId) {return getResources().getString(resId);}private void setAspectRatio(int width, int height) {if (width < 0 || height < 0) {throw new IllegalArgumentException("Size cannot be negative.");}mRatioWidth = width;mRatioHeight = height;requestLayout();}@Overrideprotected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {super.onMeasure(widthMeasureSpec, heightMeasureSpec);int width = MeasureSpec.getSize(widthMeasureSpec);int height = MeasureSpec.getSize(heightMeasureSpec);if (0 == mRatioWidth || 0 == mRatioHeight) {setMeasuredDimension(width, height);} else {if (width < height * mRatioWidth / mRatioHeight) {setMeasuredDimension(width, width * mRatioHeight / mRatioWidth);} else {setMeasuredDimension(height * mRatioWidth / mRatioHeight, height);}}}@Overridepublic void onOpen() {mCameraManager.startPreview(getSurfaceHolder());}@Overridepublic void onOpenError(int error, String msg) {}@Overridepublic void onPreview(int previewWidth, int previewHeight) {if (mSurfaceWidth > mSurfaceHeight) {setAspectRatio(previewWidth, previewHeight);} else {setAspectRatio(previewHeight, previewWidth);}}@Overridepublic void onPreviewError(int error, String msg) {}@Overridepublic void onClose() {}
}

Camera_397">1.Camera操作时机

在surfaceCreated回调中打开Camera，在surfaceDestroyed中关闭摄像头
，这基本是所有Camera操作的常识，我们代码中也展示了同样的方式。
但这还不够完美，我们必须将Camera的操作和Activity的生命周期绑定，在onResume中也打开一次摄像头，在onPause中关闭一次摄像头，确保SurfaceHolder不可用以及Activity不在前台时正确关闭Camera

SurfaceView_401">2.SurfaceView大小计算时机

在操作摄像头之前我们并不知道预览的尺寸，只能设置一个我们想要的尺寸，最终预览尺寸只能等到openCamera之后，CameraCallback中提供了回调接口onPreview在此我们可以设置SurfaceView的大小比例来适配Camera预览尺寸，避免预览页面拉升或压缩。

三.最后

本文介绍了Camera+SurfaceView的基本操作及关键代码，但是你如果看github中代码会发现和文中出入很大。其原因在于文章我想用一种简单的方式让没有做过自定义Camera的人也能明白。而github中的项目我已经进行了多次重构、抽象。其中包括对Camera的抽象，定义ICameraManager接口。对预览的View的重构，定义BaseCameraView接口，以及预览视图的众多超类。

lib-camera库包结构如下：

包	说明
camera	camera相关操作功能包，包括Camera和Camera2。以及各种预览视图
encoder	MediaCdoec录制视频相关，包括对ByteBuffer和Surface的录制
gles	opengles操作相关
permission	权限相关
util	工具类