Android Camera系列（二）：TextureView+Camera

两岸猿声啼不住，轻舟已过万重山—李白

• 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

本章我们来讲解TextureView进行Camera预览，基于上一篇Android Camera系列（一）：SurfaceView+Camera的成果，我们已经对Camera进行了封装，CameraManager拿来直接使用就好

一.TextureView使用

优点：
支持复杂的视图变换‌：与SurfaceView不同，TextureView支持包括缩放、旋转在内的各种变换操作，这些操作在视图层次中进行，使得TextureView更加灵活和适应复杂的用户界面需求。
缺点：
性能不如SurfaceView：在低端设备或高GPU负荷情况下，可能会出现掉帧或卡顿现象，低性能可以给一个参考指标大概就是10年前的设备，或者是给欠发达国家提供的低性能的海外设备

TextureView作为Camera的预览视图与SurfaceView不同，TextureView要获取SurfaceTexture，并传递给Camera作为预览容器

CameraManager针对SurfaceTexture的预览接口

    /*** 使用TextureView预览Camera** @param surface*/@Overridepublic synchronized void startPreview(SurfaceTexture surface) {Logs.i(TAG, "startPreview...");if (isPreviewing) {return;}if (mCamera != null) {try {mCamera.setPreviewTexture(surface);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());}}}

1. 自定义CameraTextureView继承TextureView
2. 实现TextureView.SurfaceTextureListener接口，并在CameraTextureView初始化时设置回调
3. 实现自定义CameraCallback接口，监听Camera状态
4. 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TextureView** @author xiaozhi* @since 2024/8/22*/
public abstract class BaseTextureView extends TextureView implements TextureView.SurfaceTextureListener, CameraCallback, BaseCameraView {private static final String TAG = BaseTextureView.class.getSimpleName();private Context mContext;private SurfaceTexture mSurfaceTexture;private boolean isMirror;private boolean hasSurface; // 是否存在摄像头显示层private ICameraManager mCameraManager;private int mRatioWidth = 0;private int mRatioHeight = 0;private int mTextureWidth;private int mTextureHeight;public BaseTextureView(Context context) {super(context);init(context);}public BaseTextureView(Context context, AttributeSet attrs) {super(context, attrs);init(context);}public BaseTextureView(Context context, AttributeSet attrs, int defStyleAttr) {super(context, attrs, defStyleAttr);init(context);}private void init(Context context) {mContext = context;mCameraManager = createCameraManager(context);mCameraManager.setCameraCallback(this);setSurfaceTextureListener(this);}public abstract ICameraManager createCameraManager(Context context);/*** 获取摄像头工具类** @return*/public ICameraManager getCameraManager() {return mCameraManager;}/*** 是否镜像** @return*/public boolean isMirror() {return isMirror;}/*** 设置是否镜像** @param mirror*/public void setMirror(boolean mirror) {isMirror = mirror;requestLayout();}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, width * 4 / 3);} else {if (width < height * mRatioWidth / mRatioHeight) {setMeasuredDimension(width, width * mRatioHeight / mRatioWidth);} else {setMeasuredDimension(height * mRatioWidth / mRatioHeight, height);}}if (isMirror) {Matrix transform = new Matrix();transform.setScale(-1, 1, getMeasuredWidth() / 2, 0);setTransform(transform);} else {setTransform(null);}}/*** 获取SurfaceTexture** @return*/@Overridepublic SurfaceTexture getSurfaceTexture() {return mSurfaceTexture;}@Overridepublic void onSurfaceTextureAvailable(SurfaceTexture surfaceTexture, int width, int height) {Logs.i(TAG, "onSurfaceTextureAvailable.");mTextureWidth = width;mTextureHeight = height;mSurfaceTexture = surfaceTexture;hasSurface = true;openCamera();}@Overridepublic void onSurfaceTextureSizeChanged(SurfaceTexture surfaceTexture, int width, int height) {Logs.i(TAG, "onSurfaceTextureSizeChanged.");}@Overridepublic boolean onSurfaceTextureDestroyed(SurfaceTexture surfaceTexture) {Logs.v(TAG, "onSurfaceTextureDestroyed.");closeCamera();hasSurface = false;return true;}@Overridepublic void onSurfaceTextureUpdated(SurfaceTexture surfaceTexture) {}/*** 打开摄像头并预览*/@Overridepublic 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();}}/*** 停止预览并关闭摄像头*/@Overridepublic void onPause() {closeCamera();}@Overridepublic void onDestroy() {}/*** 初始化摄像头，较为关键的内容*/private void openCamera() {if (mSurfaceTexture == null) {Logs.e(TAG, "mSurfaceTexture is null.");return;}if (mCameraManager.isOpen()) {Logs.w(TAG, "Camera is opened！");return;}mCameraManager.openCamera();}private void closeCamera() {mCameraManager.releaseCamera();}@Overridepublic void onOpen() {mCameraManager.startPreview(mSurfaceTexture);}@Overridepublic void onOpenError(int error, String msg) {}@Overridepublic void onPreview(int previewWidth, int previewHeight) {if (mTextureWidth > mTextureHeight) {setAspectRatio(previewWidth, previewHeight);} else {setAspectRatio(previewHeight, previewWidth);}}@Overridepublic void onPreviewError(int error, String msg) {}@Overridepublic void onClose() {}
}

1.Camera操作时机

• 在onSurfaceTextureAvailable回调中打开Camera，在onSurfaceTextureDestroyed中关闭摄像头
• 一定要记得在onResume中也打开摄像头，onPause中关闭摄像头。

再次强调onResume和onPuase中一定也要对Camera进行打开关闭操作。SurfaceTexture的回调和SurfaceHolder不同，页面不显示时SurfaceHolder会destroy，而SurfaceTexture并不会回调onSurfaceTextureDestroyed。如果我们按Home键回到桌面打开系统相机，然后再次进入我们的应用你会发现预览黑屏，这就是没有正确在生命周期中关闭Camera导致。这也是很多别的开源项目正常用没问题，随便退出再进来总有Bug的源头。

2.TextureView计算大小

基本上和CameraSurfaceView一样，我们在onPreview回调中设置TextureView的大小和比例即可

二.最后

本文介绍了Camera+TextureView的基本操作及关键代码。本章内容不是很多，这得益于我们上一章定义好了CameraManager的功劳。下一章介绍GLSurfaceView同样也是用第一章的CameraManager，嘻嘻嘻。

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

每个包都可独立使用做到最低的耦合，方便白嫖

github地址：https://github.com/xiaozhi003/AndroidCamera，https://gitee.com/xiaozhi003/android-camera

参考：

1. https://github.com/afei-cn/CameraDemo
2. https://github.com/saki4510t/UVCCamera
3. https://github.com/google/grafika