1.先设置camera的权限

 <uses-permission android:name="android.permission.CAMERA" />

2.布局

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"android:layout_width="match_parent"android:layout_height="match_parent"android:orientation="vertical"><TextureViewandroid:id="@+id/textureView"android:layout_width="match_parent"android:layout_height="0dp"android:layout_weight="1"/><Buttonandroid:id="@+id/btnSwitchCamera"android:layout_width="match_parent"android:layout_height="100dp"android:textSize="50dp"android:text="切换相机"/></LinearLayout>

3.主界面代码

package com.example.multiplecamerasimport android.Manifest
import android.content.pm.PackageManager
import android.graphics.SurfaceTexture
import android.hardware.camera2.*
import android.os.Build
import android.os.Bundle
import android.util.Log
import android.view.Surface
import android.view.TextureView
import android.view.TextureView.SurfaceTextureListener
import android.view.View
import androidx.annotation.NonNull
import androidx.annotation.RequiresApi
import androidx.appcompat.app.AppCompatActivity
import androidx.core.app.ActivityCompat
import com.hjq.permissions.OnPermission
import com.hjq.permissions.XXPermissionsclass MainActivity : AppCompatActivity() {private val TAG = MainActivity::class.java.simpleNameprivate var cameraManager: CameraManager? = nullprivate var cameraIds: Array<String>?=nullprivate var currentCameraIdIndex = 0private var cameraDevice: CameraDevice? = nullprivate var textureView: TextureView? = nullprivate var captureRequestBuilder: CaptureRequest.Builder? = nullprivate var cameraCaptureSession: CameraCaptureSession? = nullprivate var surfaceTexture: SurfaceTexture? = nulloverride fun onCreate(savedInstanceState: Bundle?) {super.onCreate(savedInstanceState)setContentView(R.layout.activity_main)XXPermissions.with(this).request(object : OnPermission {@RequiresApi(Build.VERSION_CODES.LOLLIPOP)override fun hasPermission(granted: List<String>, isAll: Boolean) {Log.e("TAG", "hasPermission=" + granted.size + "       " + isAll)initView()}override fun noPermission(denied: List<String>, quick: Boolean) {Log.e("TAG", "noPermission=" + denied.size + "       " + quick)}})}@RequiresApi(Build.VERSION_CODES.LOLLIPOP)fun initView(){cameraManager = getSystemService(CAMERA_SERVICE) as CameraManagertextureView = findViewById(R.id.textureView)// 设置 TextureView 的监听器，用于在 SurfaceTexture 准备好时打开相机textureView!!.surfaceTextureListener = surfaceTextureListener// 相机切换按钮的点击事件监听器findViewById<View>(R.id.btnSwitchCamera).setOnClickListener {Log.e("TAG", "switchCamera()=========")switchCamera()}}private val surfaceTextureListener: SurfaceTextureListener = object : SurfaceTextureListener {override fun onSurfaceTextureAvailable(surface: SurfaceTexture, width: Int, height: Int) {surfaceTexture = surfaceLog.e("TAG", "onSurfaceTextureAvailable")openCamera()}override fun onSurfaceTextureSizeChanged(surface: SurfaceTexture,width: Int,height: Int) {}override fun onSurfaceTextureDestroyed(surface: SurfaceTexture): Boolean {return false}override fun onSurfaceTextureUpdated(surface: SurfaceTexture) {}}@RequiresApi(Build.VERSION_CODES.LOLLIPOP)private fun openCamera() {Log.e("TAG", "openCamera============")try {cameraIds = cameraManager!!.cameraIdList} catch (e: Exception) {e.printStackTrace()}if (cameraIds != null && cameraIds!!.isNotEmpty()) {val cameraId = cameraIds!![currentCameraIdIndex]if (ActivityCompat.checkSelfPermission(this,Manifest.permission.CAMERA) != PackageManager.PERMISSION_GRANTED) {// TODO: Consider calling//    ActivityCompat#requestPermissions// here to request the missing permissions, and then overriding//   public void onRequestPermissionsResult(int requestCode, String[] permissions,//                                          int[] grantResults)// to handle the case where the user grants the permission. See the documentation// for ActivityCompat#requestPermissions for more details.return}Log.e("TAG", "openCamera============$cameraId")cameraManager!!.openCamera(cameraId, cameraCallback, null)}}private val cameraCallback: CameraDevice.StateCallback = @RequiresApi(Build.VERSION_CODES.LOLLIPOP)object : CameraDevice.StateCallback() {@RequiresApi(Build.VERSION_CODES.O)override fun onOpened(@NonNull camera: CameraDevice) {cameraDevice = cameraLog.e("TAG", "onOpened============$cameraDevice")startPreview()}override fun onDisconnected(@NonNull camera: CameraDevice) {cameraDevice!!.close()}override fun onError(@NonNull camera: CameraDevice, error: Int) {cameraDevice!!.close()}}@RequiresApi(Build.VERSION_CODES.O)private fun startPreview() {if (cameraDevice == null) {return}Log.e("TAG", "startPreview=====1=======$cameraDevice")try {val surface = Surface(surfaceTexture)// 创建 CaptureRequest.Builder，并设置 Surface 作为目标captureRequestBuilder = cameraDevice!!.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW)captureRequestBuilder!!.addTarget(surface)Log.e("TAG", "startPreview===2=========${cameraDevice!!.id}")// 创建相机捕获会话cameraDevice!!.createCaptureSession(listOf(surface),captureSessionCallback,null)} catch (e: Exception) {Log.e("TAG", "e============${e.message}")}}private val captureSessionCallback: CameraCaptureSession.StateCallback =@RequiresApi(Build.VERSION_CODES.LOLLIPOP)object : CameraCaptureSession.StateCallback() {override fun onConfigured(@NonNull session: CameraCaptureSession) {cameraCaptureSession = session// 设置重复预览请求try {cameraCaptureSession!!.setRepeatingRequest(captureRequestBuilder!!.build(),null,null)} catch (e: CameraAccessException) {e.printStackTrace()}}override fun onConfigureFailed(@NonNull session: CameraCaptureSession) {Log.e(TAG, "Failed to configure camera capture session")}}private fun switchCamera() {if (cameraIds != null && cameraIds!!.size > 1) {cameraDevice!!.close()currentCameraIdIndex = (currentCameraIdIndex + 1) % cameraIds!!.sizeval cameraId = cameraIds!![currentCameraIdIndex]try {if (ActivityCompat.checkSelfPermission(this,Manifest.permission.CAMERA) != PackageManager.PERMISSION_GRANTED) {// TODO: Consider calling//    ActivityCompat#requestPermissions// here to request the missing permissions, and then overriding//   public void onRequestPermissionsResult(int requestCode, String[] permissions,//                                          int[] grantResults)// to handle the case where the user grants the permission. See the documentation// for ActivityCompat#requestPermissions for more details.return}cameraManager!!.openCamera(cameraId, cameraCallback, null)} catch (e: CameraAccessException) {e.printStackTrace()}}}@RequiresApi(Build.VERSION_CODES.LOLLIPOP)override fun onPause() {super.onPause()cameraDevice?.close()}override fun onResume() {super.onResume()if (cameraDevice == null && surfaceTexture != null) {openCamera()}}}

---

XXPermissions.with(this).request(object : OnPermission {@RequiresApi(Build.VERSION_CODES.LOLLIPOP)override fun hasPermission(granted: List<String>, isAll: Boolean) {Log.e("TAG", "hasPermission=" + granted.size + "       " + isAll)}override fun noPermission(denied: List<String>, quick: Boolean) {Log.e("TAG", "noPermission=" + denied.size + "       " + quick)}})

这部分代码是用来授权AndroidManifest.xml里面权限的第三方sdk代码

效果: