一、Camera

1.1、结合SurfaceView实现预览

1.1.1、布局

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"xmlns:app="http://schemas.android.com/apk/res-auto"xmlns:tools="http://schemas.android.com/tools"android:layout_width="match_parent"android:layout_height="match_parent"android:orientation="vertical"tools:context=".CameraActivity"><SurfaceViewandroid:id="@+id/preview"android:layout_width="match_parent"android:layout_height="0dp"android:layout_weight="1"/>
</LinearLayout>

1.1.2、实现预览

mBinding.preview.getHolder().addCallback(new SurfaceHolder.Callback2() {@Overridepublic void surfaceRedrawNeeded(@NonNull SurfaceHolder holder) {mCamera = Camera.open();try {mCamera.setPreviewDisplay(holder);mCamera.startPreview();} catch (IOException e) {throw new RuntimeException(e);}}@Overridepublic void surfaceCreated(@NonNull SurfaceHolder holder) {}@Overridepublic void surfaceChanged(@NonNull SurfaceHolder holder, int format, int width, int height) {}@Overridepublic void surfaceDestroyed(@NonNull SurfaceHolder holder) {}});

• Camera.open()
  打开摄像头
• setPreviewDisplay
  设置预览展示的控件
• startPreview
  开始预览
  
  发现预览是横着的，需要使用setDisplayOrientation调整预览图像的方向
  

1.1.3、获取摄像头的原始数据

mBinding.preview.getHolder().addCallback(new SurfaceHolder.Callback2() {@Overridepublic void surfaceRedrawNeeded(@NonNull SurfaceHolder holder) {mCamera = Camera.open();try {mCamera.setPreviewDisplay(holder);mCamera.setDisplayOrientation(90);mCamera.setPreviewCallback(new PreviewCallBack());mCamera.startPreview();} catch (IOException e) {throw new RuntimeException(e);}}@Overridepublic void surfaceCreated(@NonNull SurfaceHolder holder) {}@Overridepublic void surfaceChanged(@NonNull SurfaceHolder holder, int format, int width, int height) {}@Overridepublic void surfaceDestroyed(@NonNull SurfaceHolder holder) {}});

private class PreviewCallBack implements Camera.PreviewCallback {@Overridepublic void onPreviewFrame(byte[] data, Camera camera) {try {bos.write(data);Camera.Size previewSize = camera.getParameters().getPreviewSize();Log.e(TAG, "onPreviewFrame:" + previewSize.width + "x" + previewSize.height);Log.e(TAG, "Image format:" + camera.getParameters().getPictureFormat());} catch (IOException e) {throw new RuntimeException(e);}}}

• setPreviewCallback
  设置预览数据的回调
• 2560*1440
  默认返回图像的分辨率
• Image format:256
  默认返回图像的数据格式是JPEG的
  

1.1.4、调整相机数据的分辨率和格式

Parameters

 private Camera.Size getBestPreviewSize(Camera.Parameters parameters, int desiredWidth, int desiredHeight) {List<Camera.Size> supportedSizes = parameters.getSupportedPreviewSizes();Camera.Size bestSize = null;int bestDiff = Integer.MAX_VALUE;for (Camera.Size size : supportedSizes) {int diff = Math.abs(size.width - desiredWidth) + Math.abs(size.height - desiredHeight);if (diff < bestDiff) {bestSize = size;bestDiff = diff;}}return bestSize;}

                    mCamera = Camera.open();try {mCamera.setPreviewDisplay(holder);Camera.Parameters parameters = mCamera.getParameters();// 设置预览尺寸int desiredWidth = 1280; // 设置所需的宽度int desiredHeight = 720; // 设置所需的高度Camera.Size bestSize = getBestPreviewSize(parameters, desiredWidth, desiredHeight);parameters.setPreviewSize(bestSize.width, bestSize.height);parameters.setFocusMode(Camera.Parameters.FOCUS_MODE_AUTO);//设置输出数据的格式为NV21parameters.setPictureFormat(ImageFormat.NV21);mCamera.setParameters(parameters);mCamera.setPreviewCallback(new PreviewCallBack());mCamera.setDisplayOrientation(90);mCamera.startPreview();} catch (IOException e) {throw new RuntimeException(e);}

ImageFormat里面还定义的有YUV_420_888（yuv420）、YV12,那我们可以使用吗？


运行后，应用直接抛出异常了，我用的真机是VIVO x20的，android版本是8.1的，所以，不支持设置输出的摄像头数据为YUV_420_888的。

1.1.5、保存摄像头输出的nv21格式的数据

package com.aniljing.androidcamera;import android.content.Context;
import android.graphics.ImageFormat;
import android.hardware.Camera;
import android.os.Bundle;
import android.os.Environment;
import android.util.Log;
import android.view.SurfaceHolder;import com.aniljing.androidcamera.databinding.ActivityCameraBinding;import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.List;import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;public class CameraActivity extends AppCompatActivity {private final String TAG = CameraActivity.class.getSimpleName();private Context mContext;private ActivityCameraBinding mBinding;private Camera mCamera;private File mFile = new File(Environment.getExternalStorageDirectory(), "nv21.yuv");private BufferedOutputStream bos;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);mContext = this;mBinding = ActivityCameraBinding.inflate(getLayoutInflater());setContentView(mBinding.getRoot());try {if (mFile.exists()) {mFile.delete();}bos = new BufferedOutputStream(new FileOutputStream(mFile));} catch (FileNotFoundException e) {throw new RuntimeException(e);}mBinding.preview.getHolder().addCallback(new SurfaceHolder.Callback2() {@Overridepublic void surfaceRedrawNeeded(@NonNull SurfaceHolder holder) {mCamera = Camera.open();try {mCamera.setPreviewDisplay(holder);Camera.Parameters parameters = mCamera.getParameters();// 设置预览尺寸int desiredWidth = 1280; // 设置所需的宽度int desiredHeight = 720; // 设置所需的高度Camera.Size bestSize = getBestPreviewSize(parameters, desiredWidth, desiredHeight);parameters.setPreviewSize(bestSize.width, bestSize.height);parameters.setFocusMode(Camera.Parameters.FOCUS_MODE_AUTO);parameters.setPictureFormat(ImageFormat.NV21);mCamera.setParameters(parameters);mCamera.setPreviewCallback(new PreviewCallBack());mCamera.setDisplayOrientation(90);mCamera.startPreview();} catch (IOException e) {throw new RuntimeException(e);}}@Overridepublic void surfaceCreated(@NonNull SurfaceHolder holder) {}@Overridepublic void surfaceChanged(@NonNull SurfaceHolder holder, int format, int width, int height) {}@Overridepublic void surfaceDestroyed(@NonNull SurfaceHolder holder) {}});}private class PreviewCallBack implements Camera.PreviewCallback {@Overridepublic void onPreviewFrame(byte[] data, Camera camera) {try {bos.write(data);Camera.Size previewSize = camera.getParameters().getPreviewSize();Log.e(TAG, "onPreviewFrame:" + previewSize.width + "x" + previewSize.height);Log.e(TAG,"Image format:"+camera.getParameters().getPictureFormat());} catch (IOException e) {throw new RuntimeException(e);}}}@Overrideprotected void onDestroy() {super.onDestroy();mCamera.setPreviewCallback(null);mCamera.stopPreview();mCamera.release();mCamera = null;try {bos.flush();bos.close();bos = null;} catch (IOException e) {throw new RuntimeException(e);}}private Camera.Size getBestPreviewSize(Camera.Parameters parameters, int desiredWidth, int desiredHeight) {List<Camera.Size> supportedSizes = parameters.getSupportedPreviewSizes();Camera.Size bestSize = null;int bestDiff = Integer.MAX_VALUE;for (Camera.Size size : supportedSizes) {int diff = Math.abs(size.width - desiredWidth) + Math.abs(size.height - desiredHeight);if (diff < bestDiff) {bestSize = size;bestDiff = diff;}}return bestSize;}
}

• 保存为yuv格式的文件
  

• 使用YuvEye工具打开nv21.yuv文件
  
  
  

• 可以看出，虽然预览已经可以竖屏显示视频了，但是我们实际保存的数据却还是横屏的，所以就需要我们手动的调整

• 如果我们选择其他格式的，使用工具是否能够正常打开呢？
  
  
  我们会发现，柜子的颜色和使用正确的格式有很明显的差别的

• 如果我们输入错误的分辨率，又是什么效果呢？
  
  

1.1.6、数据旋转

java方式：

private void nv21_rotate_to_90(byte[] nv21_data, byte[] nv21_rotated, int width, int height) {int y_size = width * height;int buffser_size = y_size * 3 / 2;// Rotate the Y lumaint i = 0;int startPos = (height - 1) * width;for (int x = 0; x < width; x++) {int offset = startPos;for (int y = height - 1; y >= 0; y--) {nv21_rotated[i] = nv21_data[offset + x];i++;offset -= width;}}// Rotate the U and V color componentsi = buffser_size - 1;for (int x = width - 1; x > 0; x = x - 2) {int offset = y_size;for (int y = 0; y < height / 2; y++) {nv21_rotated[i] = nv21_data[offset + x];i--;nv21_rotated[i] = nv21_data[offset + (x - 1)];i--;offset += width;}}}

package com.aniljing.androidcamera;import android.content.Context;
import android.graphics.ImageFormat;
import android.hardware.Camera;
import android.os.Bundle;
import android.os.Environment;
import android.util.Log;
import android.view.SurfaceHolder;import com.aniljing.androidcamera.databinding.ActivityCameraBinding;import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.List;import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;public class CameraActivity extends AppCompatActivity {private final String TAG = CameraActivity.class.getSimpleName();private Context mContext;private ActivityCameraBinding mBinding;private Camera mCamera;private File mFile = new File(Environment.getExternalStorageDirectory(), "nv21_rotated.yuv");private BufferedOutputStream bos;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);mContext = this;mBinding = ActivityCameraBinding.inflate(getLayoutInflater());setContentView(mBinding.getRoot());try {if (mFile.exists()) {mFile.delete();}bos = new BufferedOutputStream(new FileOutputStream(mFile));} catch (FileNotFoundException e) {throw new RuntimeException(e);}mBinding.preview.getHolder().addCallback(new SurfaceHolder.Callback2() {@Overridepublic void surfaceRedrawNeeded(@NonNull SurfaceHolder holder) {mCamera = Camera.open();try {mCamera.setPreviewDisplay(holder);Camera.Parameters parameters = mCamera.getParameters();// 设置预览尺寸int desiredWidth = 1280; // 设置所需的宽度int desiredHeight = 720; // 设置所需的高度Camera.Size bestSize = getBestPreviewSize(parameters, desiredWidth, desiredHeight);parameters.setPreviewSize(bestSize.width, bestSize.height);parameters.setFocusMode(Camera.Parameters.FOCUS_MODE_AUTO);parameters.setPictureFormat(ImageFormat.NV21);mCamera.setParameters(parameters);mCamera.setPreviewCallback(new PreviewCallBack());mCamera.setDisplayOrientation(90);mCamera.startPreview();} catch (IOException e) {throw new RuntimeException(e);}}@Overridepublic void surfaceCreated(@NonNull SurfaceHolder holder) {}@Overridepublic void surfaceChanged(@NonNull SurfaceHolder holder, int format, int width, int height) {}@Overridepublic void surfaceDestroyed(@NonNull SurfaceHolder holder) {}});}private class PreviewCallBack implements Camera.PreviewCallback {@Overridepublic void onPreviewFrame(byte[] data, Camera camera) {try {Camera.Size previewSize = camera.getParameters().getPreviewSize();byte[] nv21_rotated=new byte[data.length];nv21_rotate_to_90(data,nv21_rotated, previewSize.width, previewSize.height);bos.write(nv21_rotated);Log.e(TAG, "onPreviewFrame:" + previewSize.width + "x" + previewSize.height);Log.e(TAG,"Image format:"+camera.getParameters().getPictureFormat());} catch (IOException e) {throw new RuntimeException(e);}}}@Overrideprotected void onDestroy() {super.onDestroy();mCamera.setPreviewCallback(null);mCamera.stopPreview();mCamera.release();mCamera = null;try {bos.flush();bos.close();bos = null;} catch (IOException e) {throw new RuntimeException(e);}}private Camera.Size getBestPreviewSize(Camera.Parameters parameters, int desiredWidth, int desiredHeight) {List<Camera.Size> supportedSizes = parameters.getSupportedPreviewSizes();Camera.Size bestSize = null;int bestDiff = Integer.MAX_VALUE;for (Camera.Size size : supportedSizes) {int diff = Math.abs(size.width - desiredWidth) + Math.abs(size.height - desiredHeight);if (diff < bestDiff) {bestSize = size;bestDiff = diff;}}return bestSize;}private void nv21_rotate_to_90(byte[] nv21_data, byte[] nv21_rotated, int width, int height) {int y_size = width * height;int buffser_size = y_size * 3 / 2;// Rotate the Y lumaint i = 0;int startPos = (height - 1) * width;for (int x = 0; x < width; x++) {int offset = startPos;for (int y = height - 1; y >= 0; y--) {nv21_rotated[i] = nv21_data[offset + x];i++;offset -= width;}}// Rotate the U and V color componentsi = buffser_size - 1;for (int x = width - 1; x > 0; x = x - 2) {int offset = y_size;for (int y = 0; y < height / 2; y++) {nv21_rotated[i] = nv21_data[offset + x];i--;nv21_rotated[i] = nv21_data[offset + (x - 1)];i--;offset += width;}}}
}

• 因为我们对数据进行了顺时针旋转了90度，所以，旋转后的图像数据的宽高也会发生颠倒

libYuv库(使用ubuntu编译libyuv库可以参考http://t.csdnimg.cn/W24Pr)：

CMakeLists.txt

cmake_minimum_required(VERSION 3.22.1)project("androidcamera")#声明头文件路径
set(INCLUDE_DIR ${CMAKE_SOURCE_DIR}/../jniLibs/include)
#声明库文件路径
set(LIB_DIR ${CMAKE_SOURCE_DIR}/../jniLibs/lib)
#libYuv
set(YUV_LIB yuv)
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}  -L${LIB_DIR}/${ANDROID_ABI} -std=gnu++11")#设置头文件
include_directories(${INCLUDE_DIR})add_library(${CMAKE_PROJECT_NAME} SHAREDnative-lib.cppYuvUtil.cpp)target_link_libraries(${CMAKE_PROJECT_NAME}#链接yuv库${YUV_LIB}androidlog)

YuvUtil.h

//
// Created by company on 2024-01-25.
//#ifndef ANDROIDCAMERA_YUVUTIL_H
#define ANDROIDCAMERA_YUVUTIL_H
#include <jni.h>
#include <libyuv.h>void nv21ToI420(jbyte *src_nv21_data,jint width,jint height,jbyte* dst_i420_data);
/*** i420旋转* @param src_i420_data* @param width* @param height* @param dst_i420_data* @param degree*/
void rotateI420(jbyte*src_i420_data,jint width,jint height,jbyte*dst_i420_data,jint degree);#endif //ANDROIDCAMERA_YUVUTIL_H

YuvUtil.cpp

//
// Created by company on 2024-01-25.
//#include "YuvUtil.h"void nv21ToI420(jbyte *src_nv21_data, jint width, jint height, jbyte *dst_i420_data) {jint src_y_size = width * height;jint src_u_size = (width >> 1) * (height >> 1);jbyte *src_nv21_y_data = src_nv21_data;jbyte *src_nv21_vu_data = src_nv21_data + src_y_size;jbyte *dst_i420_y_data = dst_i420_data;jbyte *dst_i420_u_data = dst_i420_data + src_y_size;jbyte *dst_i420_v_data = dst_i420_data + src_y_size + src_u_size;libyuv::NV21ToI420((const uint8_t *) src_nv21_y_data, width,(const uint8_t *) src_nv21_vu_data, width,(uint8_t *) dst_i420_y_data, width,(uint8_t *) dst_i420_u_data, width >> 1,(uint8_t *) dst_i420_v_data, width >> 1,width, height);
}void rotateI420(jbyte *src_i420_data, jint width, jint height, jbyte *dst_i420_data, jint degree) {jint src_i420_y_size = width * height;jint src_i420_u_size = (width >> 1) * (height >> 1);jbyte *src_i420_y_data = src_i420_data;jbyte *src_i420_u_data = src_i420_data + src_i420_y_size;jbyte *src_i420_v_data = src_i420_data + src_i420_y_size + src_i420_u_size;jbyte *dst_i420_y_data = dst_i420_data;jbyte *dst_i420_u_data = dst_i420_data + src_i420_y_size;jbyte *dst_i420_v_data = dst_i420_data + src_i420_y_size + src_i420_u_size;if (degree == libyuv::kRotate90 || degree == libyuv::kRotate270) {//90或270的width和height在旋转后是相反的libyuv::I420Rotate((const uint8_t *) src_i420_y_data, width,(const uint8_t *) src_i420_u_data, width >> 1,(const uint8_t *) src_i420_v_data, width >> 1,(uint8_t *) dst_i420_y_data, height,(uint8_t *) dst_i420_u_data, height >> 1,(uint8_t *) dst_i420_v_data, height >> 1,width, height, (libyuv::RotationMode) degree);} else {libyuv::I420Rotate((const uint8_t *) src_i420_y_data, width,(const uint8_t *) src_i420_u_data, width >> 1,(const uint8_t *) src_i420_v_data, width >> 1,(uint8_t *) dst_i420_y_data, width,(uint8_t *) dst_i420_u_data, width >> 1,(uint8_t *) dst_i420_v_data, width >> 1,width, height, (libyuv::RotationMode) degree);}
}

native-lib.cpp

#include <jni.h>
#include <string>
#include "YuvUtil.h"extern "C"
JNIEXPORT void JNICALL
Java_com_aniljing_androidcamera_YuvUtil_nv21ToI420(JNIEnv *env, jobject thiz,jbyteArray src_nv21_array, jint width,jint height, jbyteArray dst_i420_array) {jbyte *src_nv21_data = env->GetByteArrayElements(src_nv21_array, JNI_FALSE);jbyte *dst_i420_data = env->GetByteArrayElements(dst_i420_array, JNI_FALSE);nv21ToI420(src_nv21_data, width, height, dst_i420_data);env->ReleaseByteArrayElements(src_nv21_array, src_nv21_data, 0);env->ReleaseByteArrayElements(dst_i420_array, dst_i420_data, 0);
}
extern "C"
JNIEXPORT void JNICALL
Java_com_aniljing_androidcamera_YuvUtil_i420Rotate(JNIEnv *env, jobject thiz,jbyteArray src_i420_array, jint width,jint height, jbyteArray dst_i420_array,jint degree) {jbyte *src_i420_data = env->GetByteArrayElements(src_i420_array, JNI_FALSE);jbyte *dst_i420_data = env->GetByteArrayElements(dst_i420_array, JNI_FALSE);rotateI420(src_i420_data, width, height, dst_i420_data, degree);env->ReleaseByteArrayElements(src_i420_array, src_i420_data, 0);env->ReleaseByteArrayElements(dst_i420_array, dst_i420_data, 0);
}

YuvUtil.java

package com.aniljing.androidcamera;public class YuvUtil {public native void nv21ToI420(byte[] src_nv21_data, int width, int height, byte[] dst_i420_data);public native void i420Rotate(byte[] src_i420_data, int width, int height, byte[] dst_i420_data, int degree);static {System.loadLibrary("androidcamera");}
}

• 格式选择 I420
• 分辨率设置为720*1280

二、Camera2

Camera2(android.hardware.camera2)是从 Android 5.0 L 版本开始引入的，并且废弃了旧的相机框架Camera1(android.hardware.Camera)。

相比于Camera1，Camera2架构上也发生了变化，API上的使用难度也增加了。Camera2将相机设备模拟成一个管道，它按顺序处理每一帧的请求并返回请求结果给客户端。

2.1、核心类

CameraManager

相机系统服务，用于管理和连接相机设备

CameraDevice

相机设备类，和Camera1中的Camera同级

CameraCharacteristics

主要用于获取相机信息，内部携带大量的相机信息，包含摄像头的正反(LENS_FACING)、AE模式、AF模式等，和Camera1中的Camera.Parameters类似

CaptureRequest

相机捕获图像的设置请求，包含传感器，镜头，闪光灯等

CaptureRequest.Builder

CaptureRequest的构造器，使用Builder模式，设置更加方便

CameraCaptureSession

请求抓取相机图像帧的会话，会话的建立主要会建立起一个通道。一个CameraDevice一次只能开启一个CameraCaptureSession。源端是相机，另一端是 Target，Target可以是Preview，也可以是ImageReader。

ImageReader

用于从相机打开的通道中读取需要的格式的原始图像数据，可以设置多个ImageReader。

2.2、使用流程

2.2.1、获取CameraManager

CameraManager cameraManager = (CameraManager) mContext.getSystemService(Context.CAMERA_SERVICE);

2.2.2、获取相机信息,并打开相机

try {String[] cameraIds = cameraManager.getCameraIdList();for (int i = 0; i < cameraIds.length; i++) {//描述相机设备的属性类CameraCharacteristics characteristics = cameraManager.getCameraCharacteristics(cameraIds[i]);Range<Integer>[] allFpsRanges = characteristics.get(CameraCharacteristics.CONTROL_AE_AVAILABLE_TARGET_FPS_RANGES);fpsRanges = allFpsRanges[allFpsRanges.length - 1];//获取是前置还是后置摄像头Integer facing = characteristics.get(CameraCharacteristics.LENS_FACING);//使用后置摄像头if (facing != null && facing == CameraCharacteristics.LENS_FACING_BACK) {StreamConfigurationMap map = characteristics.get(CameraCharacteristics.SCALER_STREAM_CONFIGURATION_MAP);//寻找一个 最合适的尺寸     ---》 一模一样mPreviewSize = getBestSupportedSize(new ArrayList<Size>(Arrays.asList(map.getOutputSizes(SurfaceTexture.class))));if (map != null) {mCameraId = cameraIds[i];}orientation = characteristics.get(CameraCharacteristics.SENSOR_ORIENTATION);//maxImages 此时需要2路，一路渲染到屏幕，一路用于网络传输mImageReader = ImageReader.newInstance(mPreviewSize.getWidth(), mPreviewSize.getHeight(),ImageFormat.YUV_420_888, 2);mImageReader.setOnImageAvailableListener(mOnImageAvailableListener, mCameraHandler);cameraManager.openCamera(mCameraId, mCameraDeviceStateCallback, mCameraHandler);}}} catch (CameraAccessException r) {Log.e(TAG, "openCamera:" + r);Log.e(TAG, "openCamera getMessage:" + r.getMessage());Log.e(TAG, "openCamera getLocalizedMessage:" + r.getLocalizedMessage());}

• ImageReader
  ImageReader是获取图像数据的重要途径，通过它可以获取到不同格式的图像数据，例如JPEG、YUV、RAW等。通过ImageReader.newInstance(int width, int height, int format, int maxImages)创建ImageReader对象，有4个参数：

  • width：图像数据的宽度
  • height：图像数据的高度
  • format：图像数据的格式，例如ImageFormat.JPEG，ImageFormat.YUV_420_888等
  • maxImages：最大Image个数，Image对象池的大小，指定了能从ImageReader获取Image对象的最大值，过多获取缓冲区可能导致OOM，所以最好按照最少的需要去设置这个值

  ImageReader其他相关的方法和回调：

  • ImageReader.OnImageAvailableListener：有新图像数据的回调
  • acquireLatestImage()：从ImageReader的队列里面，获取最新的Image，删除旧的，如果没有可用的Image，返回null
  • acquireNextImage()：获取下一个最新的可用Image，没有则返回null
  • close()：释放与此ImageReader关联的所有资源
  • getSurface()：获取为当前ImageReader生成Image的Surface

• 打开相机设备
  cameraManager.openCamera(@NonNull String cameraId,@NonNull final CameraDevice.StateCallback callback, @Nullable Handler handler)的三个参数:

  • cameraId：摄像头的唯一标识
  • callback：设备连接状态变化的回调
  • handler：回调执行的Handler对象，传入null则使用当前的主线程Handler

2.2.3、创建CaptureRequest

private final CameraDevice.StateCallback mCameraDeviceStateCallback = new CameraDevice.StateCallback() {@Overridepublic void onOpened(CameraDevice camera) {try {mCameraDevice = camera;SurfaceTexture surfaceTexture = mTextureView.getSurfaceTexture();surfaceTexture.setDefaultBufferSize(1280, 720);//Surface负责渲染Surface previewSurface = new Surface(surfaceTexture);//创建请求mPreviewBuilder = mCameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW);mPreviewBuilder.set(CaptureRequest.CONTROL_AE_TARGET_FPS_RANGE, fpsRanges);mPreviewBuilder.set(CaptureRequest.CONTROL_AF_MODE, CaptureRequest.CONTROL_AF_MODE_CONTINUOUS_PICTURE);mPreviewBuilder.addTarget(previewSurface);mPreviewBuilder.addTarget(mImageReader.getSurface());//创建会话mCameraDevice.createCaptureSession(Arrays.asList(previewSurface, mImageReader.getSurface()), mCaptureSessionStateCallBack, mCameraHandler);} catch (CameraAccessException e) {e.printStackTrace();Log.e(TAG, "onOpened:" + e.getMessage());Log.e(TAG, "onOpened:" + e.getLocalizedMessage());Log.e(TAG, "onOpened:" + e);}}@Overridepublic void onDisconnected(CameraDevice camera) {Log.e(TAG, "onDisconnected");camera.close();mCameraDevice = null;}@Overridepublic void onError(CameraDevice camera, int error) {Log.e(TAG, "onError:" + error);camera.close();mCameraDevice = null;}};

在CameraDevice.StateCallback的onOpened回调中执行：这段的代码核心方法是mCameraDevice.createCaptureSession()创建Capture会话，它接受了三个参数：

• outputs：用于接受图像数据的surface集合，这里传入的是一个preview的surface
• callback：用于监听 Session 状态的CameraCaptureSession.StateCallback对象
• handler：用于执行CameraCaptureSession.StateCallback的Handler对象，传入null则使用当前的主线程Handler

通过CameraDevice.createCaptureRequest()创建CaptureRequest.Builder对象，传入一个templateType参数，templateType用于指定使用何种模板创建CaptureRequest.Builder对象，templateType的取值：

• TEMPLATE_PREVIEW：预览模式
• TEMPLATE_STILL_CAPTURE：拍照模式
• TEMPLATE_RECORD：视频录制模式
• TEMPLATE_VIDEO_SNAPSHOT：视频截图模式
• TEMPLATE_MANUAL：手动配置参数模式

2.2.4、预览

   private final CameraCaptureSession.StateCallback mCaptureSessionStateCallBack = new CameraCaptureSession.StateCallback() {@Overridepublic void onConfigured(CameraCaptureSession session) {try {mCaptureSession = session;CaptureRequest request = mPreviewBuilder.build();// Finally, we start displaying the camera preview.session.setRepeatingRequest(request, null, mCameraHandler);} catch (CameraAccessException e) {e.printStackTrace();}}@Overridepublic void onConfigureFailed(CameraCaptureSession session) {Log.e(TAG, "onConfigureFailed:");}};

在CameraCaptureSession.StateCallback回调中，Camera2通过连续重复的Capture实现预览功能，每次Capture会把预览画面显示到对应的Surface上。连续重复的Capture操作通过mCaptureSession.setRepeatingRequest(mPreviewRequest,mCaptureCallback, mBackgroundHandler)实现，该方法有三个参数：

• request：CaptureRequest对象
• listener：监听Capture 状态的回调
• handler：用于执行CameraCaptureSession.CaptureCallback的Handler对象，传入null则使用当前的主线程Handler

停止预览使用mCaptureSession.stopRepeating()方法。

2.3、完整实现代码

package com.aniljing.androidcamera;import android.annotation.SuppressLint;
import android.app.Activity;
import android.content.Context;
import android.graphics.ImageFormat;
import android.graphics.Point;
import android.graphics.Rect;
import android.graphics.SurfaceTexture;
import android.hardware.camera2.CameraAccessException;
import android.hardware.camera2.CameraCaptureSession;
import android.hardware.camera2.CameraCharacteristics;
import android.hardware.camera2.CameraDevice;
import android.hardware.camera2.CameraManager;
import android.hardware.camera2.CaptureRequest;
import android.hardware.camera2.params.StreamConfigurationMap;
import android.media.Image;
import android.media.ImageReader;
import android.os.Handler;
import android.os.HandlerThread;
import android.util.Log;
import android.util.Range;
import android.util.Size;
import android.view.Surface;
import android.view.TextureView;import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;/*** @ClassName Camera2ProviderPreviewWithYUV* Camera2 两路预览：* 1、使用TextureView预览，直接输出。* 2、使用ImageReader获取数据，输出格式为ImageFormat.YUV_420_888，java端转化为NV21*/
public class Camera2WithYUV {private static final String TAG = Camera2WithYUV.class.getSimpleName();private Activity mContext;private String mCameraId;private HandlerThread handlerThread;private Handler mCameraHandler;private CameraDevice mCameraDevice;private TextureView mTextureView;private CaptureRequest.Builder mPreviewBuilder;private CameraCaptureSession mCaptureSession;private ImageReader mImageReader;private Size mPreviewSize;private final Point previewViewSize;private Range<Integer> fpsRanges;private byte[] i420;private YUVDataCallBack mYUVDataCallBack;private int orientation;private YuvUtil mYuvUtil;public Camera2WithYUV(Activity mContext) {this.mContext = mContext;handlerThread = new HandlerThread("camera");handlerThread.start();mCameraHandler = new Handler(handlerThread.getLooper());previewViewSize = new Point();previewViewSize.x = 640;previewViewSize.y = 480;mYuvUtil=new YuvUtil();}public void initTexture(TextureView textureView) {Log.e(TAG, "initTexture:" + textureView);mTextureView = textureView;mTextureView.setSurfaceTextureListener(new TextureView.SurfaceTextureListener() {@Overridepublic void onSurfaceTextureAvailable(SurfaceTexture surface, int width, int height) {openCamera();}@Overridepublic void onSurfaceTextureSizeChanged(SurfaceTexture surface, int width, int height) {}@Overridepublic boolean onSurfaceTextureDestroyed(SurfaceTexture surface) {return true;}@Overridepublic void onSurfaceTextureUpdated(SurfaceTexture surface) {}});}@SuppressLint("MissingPermission")private void openCamera() {CameraManager cameraManager = (CameraManager) mContext.getSystemService(Context.CAMERA_SERVICE);try {String[] cameraIds = cameraManager.getCameraIdList();for (int i = 0; i < cameraIds.length; i++) {//描述相机设备的属性类CameraCharacteristics characteristics = cameraManager.getCameraCharacteristics(cameraIds[i]);Range<Integer>[] allFpsRanges = characteristics.get(CameraCharacteristics.CONTROL_AE_AVAILABLE_TARGET_FPS_RANGES);fpsRanges = allFpsRanges[allFpsRanges.length - 1];//获取是前置还是后置摄像头Integer facing = characteristics.get(CameraCharacteristics.LENS_FACING);//使用后置摄像头if (facing != null && facing == CameraCharacteristics.LENS_FACING_BACK) {StreamConfigurationMap map = characteristics.get(CameraCharacteristics.SCALER_STREAM_CONFIGURATION_MAP);//寻找一个 最合适的尺寸     ---》 一模一样mPreviewSize = getBestSupportedSize(new ArrayList<Size>(Arrays.asList(map.getOutputSizes(SurfaceTexture.class))));if (map != null) {mCameraId = cameraIds[i];}orientation = characteristics.get(CameraCharacteristics.SENSOR_ORIENTATION);//maxImages 此时需要2路，一路渲染到屏幕，一路用于网络传输mImageReader = ImageReader.newInstance(mPreviewSize.getWidth(), mPreviewSize.getHeight(),ImageFormat.YUV_420_888, 2);mImageReader.setOnImageAvailableListener(mOnImageAvailableListener, mCameraHandler);cameraManager.openCamera(mCameraId, mCameraDeviceStateCallback, mCameraHandler);}}} catch (CameraAccessException r) {Log.e(TAG, "openCamera:" + r);Log.e(TAG, "openCamera getMessage:" + r.getMessage());Log.e(TAG, "openCamera getLocalizedMessage:" + r.getLocalizedMessage());}}private final CameraDevice.StateCallback mCameraDeviceStateCallback = new CameraDevice.StateCallback() {@Overridepublic void onOpened(CameraDevice camera) {try {mCameraDevice = camera;SurfaceTexture surfaceTexture = mTextureView.getSurfaceTexture();surfaceTexture.setDefaultBufferSize(1280, 720);//Surface负责渲染Surface previewSurface = new Surface(surfaceTexture);//创建请求mPreviewBuilder = mCameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW);mPreviewBuilder.set(CaptureRequest.CONTROL_AE_TARGET_FPS_RANGE, fpsRanges);mPreviewBuilder.set(CaptureRequest.CONTROL_AF_MODE, CaptureRequest.CONTROL_AF_MODE_CONTINUOUS_PICTURE);mPreviewBuilder.addTarget(previewSurface);mPreviewBuilder.addTarget(mImageReader.getSurface());//创建会话mCameraDevice.createCaptureSession(Arrays.asList(previewSurface, mImageReader.getSurface()), mCaptureSessionStateCallBack, mCameraHandler);} catch (CameraAccessException e) {e.printStackTrace();Log.e(TAG, "onOpened:" + e.getMessage());Log.e(TAG, "onOpened:" + e.getLocalizedMessage());Log.e(TAG, "onOpened:" + e);}}@Overridepublic void onDisconnected(CameraDevice camera) {Log.e(TAG, "onDisconnected");camera.close();mCameraDevice = null;}@Overridepublic void onError(CameraDevice camera, int error) {Log.e(TAG, "onError:" + error);camera.close();mCameraDevice = null;}};private final ImageReader.OnImageAvailableListener mOnImageAvailableListener = new ImageReader.OnImageAvailableListener() {@SuppressLint("LongLogTag")@Overridepublic void onImageAvailable(ImageReader reader) {Image image = reader.acquireNextImage();// Y:U:V == 4:2:2if (mYUVDataCallBack != null && image.getFormat() == ImageFormat.YUV_420_888) {Rect crop = image.getCropRect();int format = image.getFormat();int width = crop.width();int height = crop.height();if (i420 == null) {i420 = new byte[width * height * ImageFormat.getBitsPerPixel(format) / 8];}i420 = getI420(image);if (mYUVDataCallBack != null) {mYUVDataCallBack.yuvData(i420, width, height, orientation);}}image.close();}};private final CameraCaptureSession.StateCallback mCaptureSessionStateCallBack = new CameraCaptureSession.StateCallback() {@Overridepublic void onConfigured(CameraCaptureSession session) {try {mCaptureSession = session;CaptureRequest request = mPreviewBuilder.build();// Finally, we start displaying the camera preview.session.setRepeatingRequest(request, null, mCameraHandler);} catch (CameraAccessException e) {e.printStackTrace();}}@Overridepublic void onConfigureFailed(CameraCaptureSession session) {Log.e(TAG, "onConfigureFailed:");}};public void releaseCamera() {Log.e(TAG, "releaseCamera");if (mCaptureSession != null) {mCaptureSession.close();mCaptureSession = null;}if (mCameraDevice != null) {mCameraDevice.close();mCameraDevice = null;}if (mPreviewBuilder != null) {mPreviewBuilder = null;}if (mImageReader != null) {mImageReader.setOnImageAvailableListener(null, null);mImageReader.close();mImageReader = null;}if (handlerThread != null && !handlerThread.isInterrupted()) {handlerThread.quit();handlerThread.interrupt();handlerThread = null;}if (mCameraHandler != null) {mCameraHandler = null;}}public interface YUVDataCallBack {void yuvData(byte[] data, int width, int height, int orientation);}public void setYUVDataCallBack(YUVDataCallBack YUVDataCallBack) {mYUVDataCallBack = YUVDataCallBack;}private Size getBestSupportedSize(List<Size> sizes) {Point maxPreviewSize = new Point(640, 480);Point minPreviewSize = new Point(480, 320);Size defaultSize = sizes.get(0);Size[] tempSizes = sizes.toArray(new Size[0]);Arrays.sort(tempSizes, (o1, o2) -> {if (o1.getWidth() > o2.getWidth()) {return -1;} else if (o1.getWidth() == o2.getWidth()) {return o1.getHeight() > o2.getHeight() ? -1 : 1;} else {return 1;}});sizes = new ArrayList<>(Arrays.asList(tempSizes));for (int i = sizes.size() - 1; i >= 0; i--) {if (maxPreviewSize != null) {if (sizes.get(i).getWidth() > maxPreviewSize.x || sizes.get(i).getHeight() > maxPreviewSize.y) {sizes.remove(i);continue;}}if (minPreviewSize != null) {if (sizes.get(i).getWidth() < minPreviewSize.x || sizes.get(i).getHeight() < minPreviewSize.y) {sizes.remove(i);}}}if (sizes.size() == 0) {return defaultSize;}Size bestSize = sizes.get(0);float previewViewRatio;if (previewViewSize != null) {previewViewRatio = (float) previewViewSize.x / (float) previewViewSize.y;} else {previewViewRatio = (float) bestSize.getWidth() / (float) bestSize.getHeight();}if (previewViewRatio > 1) {previewViewRatio = 1 / previewViewRatio;}for (Size s : sizes) {if (Math.abs((s.getHeight() / (float) s.getWidth()) - previewViewRatio) < Math.abs(bestSize.getHeight() / (float) bestSize.getWidth() - previewViewRatio)) {bestSize = s;}}return bestSize;}private byte[] getI420(Image image) {try {int w = image.getWidth(), h = image.getHeight();// size是宽乘高的1.5倍 可以通过ImageFormat.getBitsPerPixel(ImageFormat.YUV_420_888)得到int i420Size = w * h * 3 / 2;Image.Plane[] planes = image.getPlanes();//remaining0 = rowStride*(h-1)+w => 27632= 192*143+176 Y分量byte数组的sizeint remaining0 = planes[0].getBuffer().remaining();int remaining1 = planes[1].getBuffer().remaining();//remaining2 = rowStride*(h/2-1)+w-1 =>  13807=  192*71+176-1 V分量byte数组的sizeint remaining2 = planes[2].getBuffer().remaining();//获取pixelStride，可能跟width相等，可能不相等int pixelStride = planes[2].getPixelStride();int rowOffest = planes[2].getRowStride();byte[] nv21 = new byte[i420Size];//分别准备三个数组接收YUV分量。byte[] yRawSrcBytes = new byte[remaining0];byte[] uRawSrcBytes = new byte[remaining1];byte[] vRawSrcBytes = new byte[remaining2];planes[0].getBuffer().get(yRawSrcBytes);planes[1].getBuffer().get(uRawSrcBytes);planes[2].getBuffer().get(vRawSrcBytes);if (pixelStride == image.getWidth()) {//两者相等，说明每个YUV块紧密相连，可以直接拷贝System.arraycopy(yRawSrcBytes, 0, nv21, 0, rowOffest * h);System.arraycopy(vRawSrcBytes, 0, nv21, rowOffest * h, rowOffest * h / 2 - 1);} else {//根据每个分量的size先生成byte数组byte[] ySrcBytes = new byte[w * h];byte[] uSrcBytes = new byte[w * h / 2 - 1];byte[] vSrcBytes = new byte[w * h / 2 - 1];for (int row = 0; row < h; row++) {//源数组每隔 rowOffest 个bytes 拷贝 w 个bytes到目标数组System.arraycopy(yRawSrcBytes, rowOffest * row, ySrcBytes, w * row, w);//y执行两次，uv执行一次if (row % 2 == 0) {//最后一行需要减一if (row == h - 2) {System.arraycopy(vRawSrcBytes, rowOffest * row / 2, vSrcBytes, w * row / 2, w - 1);} else {System.arraycopy(vRawSrcBytes, rowOffest * row / 2, vSrcBytes, w * row / 2, w);}}}//yuv拷贝到一个数组里面System.arraycopy(ySrcBytes, 0, nv21, 0, w * h);System.arraycopy(vSrcBytes, 0, nv21, w * h, w * h / 2 - 1);byte[] i420 = new byte[nv21.length];mYuvUtil.nv21ToI420(nv21, w, h, i420);return i420;}} catch (Exception e) {e.printStackTrace();}return null;}
}

源码