android之camera2预览

前面研究过了camera1，但是新的android sdk支持camera2，所以必须也要掌握camera2.

先参考资料：

https://blog.csdn.net/afei__/article/details/92102775

https://blog.csdn.net/tong5956/article/details/82688886

https://www.cnblogs.com/lonelyxmas/p/9175768.html

https://blog.csdn.net/afei__/article/details/86326991

几个概念：

SurfaceView：图像显示的地方

SurfaceHolder：连接图像显示地方与外部的通道，相当于接口

CameraManager：摄像机的管理类

CameraDevice：具体相机的操作类

调用流程：

1、获取摄像机管理类：mCameraManager = (CameraManager) getSystemService(Context.CAMERA_SERVICE);

2、打开某个具体的摄像机：mCameraManager.openCamera(cameraId, stateCallback, null);

3、在打开成功的回调里面，创建预览请求：mCameraDevice.createCaptureSession

4、在创建预览请求的回调里面，设置预览模式：mCameraCaptureSession.setRepeatingRequest

大概分为以上4个步骤

实现代码如下：

package com.example.grammartest;import androidx.annotation.NonNull;
import androidx.annotation.RequiresApi;
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.app.ActivityCompat;
import androidx.core.content.ContextCompat;import android.Manifest;
import android.content.Context;
import android.content.pm.PackageManager;
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.os.Build;
import android.os.Bundle;
import android.util.Log;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.view.View;
import android.widget.Button;import java.io.IOException;
import java.util.Arrays;
import android.widget.Toast;public class Camera2Activity extends AppCompatActivity {String tag = "Camera2Activity";private static final String[] REQUIRED_PERMISSIONS = {Manifest.permission.CAMERA};private static final int REQUEST_PERMISSIONS_CODE = 1;private CameraManager mCameraManager;//摄像头管理器CameraDevice mCameraDevice;String FRONTId, BACKId;private SurfaceHolder mSurfaceHolder;private CameraCaptureSession mCameraCaptureSession;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_camera2);InitView();InitCameraInfo();}void InitView() {Button ViewBt = findViewById(R.id.Camera2PlayBt);Button ViewCloseBt = findViewById(R.id.Camera2CloseBt);SurfaceView surfaceView = findViewById(R.id.Camera2surfaceViewId);mSurfaceHolder = surfaceView.getHolder();ViewBt.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View v) {Log.i(tag,"setOnClickListener");OpenCamera(BACKId);}});ViewCloseBt.setOnClickListener(new View.OnClickListener(){@Overridepublic void onClick(View v) {CloseCamera();}});}void InitCameraInfo() {if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {mCameraManager = (CameraManager) getSystemService(Context.CAMERA_SERVICE);String[] cameraList = new String[0];try {cameraList = mCameraManager.getCameraIdList();} catch (CameraAccessException e) {e.printStackTrace();}for (String item : cameraList) {Log.i(tag, "Camera2Activity:" + item);String FrontItem = CameraCharacteristics.LENS_FACING_FRONT + "";String BackItem = CameraCharacteristics.LENS_FACING_BACK + "";if (item.equals(FrontItem)) {FRONTId = item;} else if (item.equals(BackItem)) {BACKId = item;}}}}void OpenCamera(String cameraId) {if (false == isRequiredPermissionsGranted()) {Log.i(tag, "isRequiredPermissionsGranted false");if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {requestPermissions(REQUIRED_PERMISSIONS, REQUEST_PERMISSIONS_CODE);}return;}try {if (ActivityCompat.checkSelfPermission(this, Manifest.permission.CAMERA) != PackageManager.PERMISSION_GRANTED) {return;}mCameraManager.openCamera(cameraId, stateCallback, null);} catch (CameraAccessException e) {e.printStackTrace();}}void  CloseCamera(){if (null != mCameraDevice){mCameraDevice.close();mCameraDevice = null;}}private void takePreview() {try {// 创建CameraCaptureSession，该对象负责管理处理预览请求和拍照请求mCameraDevice.createCaptureSession(Arrays.asList(mSurfaceHolder.getSurface()), new CameraCaptureSession.StateCallback() // ③{@Overridepublic void onConfigured(CameraCaptureSession cameraCaptureSession) {if (null == mCameraDevice) return;// 当摄像头已经准备好时，开始显示预览mCameraCaptureSession = cameraCaptureSession;try {// 创建预览需要的CaptureRequest.Builderfinal CaptureRequest.Builder previewRequestBuilder = mCameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW);// 将SurfaceView的surface作为CaptureRequest.Builder的目标previewRequestBuilder.addTarget(mSurfaceHolder.getSurface());// 自动对焦previewRequestBuilder.set(CaptureRequest.CONTROL_AF_MODE, CaptureRequest.CONTROL_AF_MODE_CONTINUOUS_PICTURE);// 打开闪光灯previewRequestBuilder.set(CaptureRequest.CONTROL_AE_MODE, CaptureRequest.CONTROL_AE_MODE_ON_AUTO_FLASH);// 显示预览CaptureRequest previewRequest = previewRequestBuilder.build();mCameraCaptureSession.setRepeatingRequest(previewRequest, null, null);} catch (CameraAccessException e) {e.printStackTrace();}}@Overridepublic void onConfigureFailed(CameraCaptureSession cameraCaptureSession) {Toast.makeText(Camera2Activity.this, "配置失败", Toast.LENGTH_SHORT).show();}}, null);} catch (CameraAccessException e) {e.printStackTrace();}}private final CameraDevice.StateCallback stateCallback = new CameraDevice.StateCallback() {@Overridepublic void onOpened(CameraDevice camera) {mCameraDevice = camera;Log.i(tag, "CameraDevice onOpened");takePreview();}@Overridepublic void onDisconnected(@NonNull CameraDevice camera) {Log.i(tag, "CameraDevice Disconnected");}@Overridepublic void onError(@NonNull CameraDevice camera, int error) {Log.e(tag, "CameraDevice Error");}};private boolean isRequiredPermissionsGranted() {for (String permission : REQUIRED_PERMISSIONS) {if (ContextCompat.checkSelfPermission(this, permission) == PackageManager.PERMISSION_DENIED) {return false;}}return true;}
}

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