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一、获取CameraManager实例

   CameraManager manager = (CameraManager) getSystemService(Context.CAMERA_SERVICE);

二、获取可用的相机列表

   String[] cameraIds = manager.getCameraIdList();

三、选择一个相机并打开它

   String cameraId = cameraIds[0];manager.openCamera(cameraId, new CameraDevice.StateCallback() {@Overridepublic void onOpened(CameraDevice camera) {// 相机已经打开，可以进行后续操作}@Overridepublic void onDisconnected(CameraDevice camera) {// 相机断开连接，需要释放资源camera.close();}@Overridepublic void onError(CameraDevice camera, int error) {// 相机打开出错，需要释放资源camera.close();}}, null);

四、创建一个CaptureRequest.Builder对象

   CaptureRequest.Builder builder = camera.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW);

五、设置CaptureRequest.Builder对象的参数

   builder.set(CaptureRequest.CONTROL_MODE, CameraMetadata.CONTROL_MODE_AUTO);

六、创建一个CaptureSession对象

   camera.createCaptureSession(Arrays.asList(surface), new CameraCaptureSession.StateCallback() {@Overridepublic void onConfigured(CameraCaptureSession session) {// CaptureSession已经创建，可以进行后续操作}@Overridepublic void onConfigureFailed(CameraCaptureSession session) {// CaptureSession创建失败，需要释放资源camera.close();}}, null);

七、开始预览

   session.setRepeatingRequest(builder.build(), null, null);

代码示例

• xml布局

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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"tools:context=".MainActivity"><TextureViewandroid:id="@+id/texture_view"android:layout_width="match_parent"android:layout_height="match_parent" /></RelativeLayout>

• 处理

public class MainActivity extends AppCompatActivity implements  TextureView.SurfaceTextureListener{private String[] cameraIds;private  String cameraId;private CameraManager cameraManager;//从系统服务中获取相机管理器private TextureView textureView;private CameraDevice mCameraDevice;private CameraCaptureSession cameraCaptureSession;private CaptureRequest.Builder captureRequestBuilder = null;private static final int ACTION_REQUEST_PERMISSIONS = 0x001;/*** 所需的所有权限信息*/private static final String[] NEEDED_PERMISSIONS = new String[]{Manifest.permission.CAMERA,//相机};@SuppressLint({"MissingPermission", "MissingInflatedId"})@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);//权限检查if (!checkPermissions(NEEDED_PERMISSIONS)) {ActivityCompat.requestPermissions(this, NEEDED_PERMISSIONS,ACTION_REQUEST_PERMISSIONS);}textureView=findViewById(R.id.texture_view);textureView.setSurfaceTextureListener(this);//设置布局}/*** 权限检查* @param neededPermissions 需要的权限* @return 是否全部被允许*/protected boolean checkPermissions(String[] neededPermissions) {if (neededPermissions == null || neededPermissions.length == 0) {return true;}boolean allGranted = true;for (String neededPermission : neededPermissions) {allGranted &= ContextCompat.checkSelfPermission(this, neededPermission) == PackageManager.PERMISSION_GRANTED;}return allGranted;}@Overridepublic void onSurfaceTextureAvailable(@NonNull SurfaceTexture surfaceTexture, int i, int i1) {//布局初始化完成,打开相机openCamera2();}@SuppressLint("MissingPermission")private void openCamera2(){//一、获取cameraManagercameraManager = (CameraManager) getSystemService(Context.CAMERA_SERVICE);try {cameraIds = cameraManager.getCameraIdList();//获取摄像机id的集合cameraId = cameraIds[0];cameraManager.openCamera(cameraId,callback,null);} catch (Exception e) {throw new RuntimeException(e);}}CameraDevice.StateCallback callback=new CameraDevice.StateCallback() {@Overridepublic void onOpened(@NonNull CameraDevice cameraDevice) {mCameraDevice = cameraDevice;createCameraPreviewSession();}@Overridepublic void onDisconnected(@NonNull CameraDevice cameraDevice) {}@Overridepublic void onError(@NonNull CameraDevice cameraDevice, int i) {}};private void createCameraPreviewSession() {try {SurfaceTexture surfaceTexture = textureView.getSurfaceTexture();
//            surfaceTexture.setDefaultBufferSize(textureView.getWidth(), textureView.getHeight());surfaceTexture.setDefaultBufferSize(640, 480);
//            surfaceTexture.setDefaultBufferSize(480,640 );Surface previewSurface = new Surface(surfaceTexture);captureRequestBuilder = mCameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW);captureRequestBuilder.addTarget(previewSurface);mCameraDevice.createCaptureSession(Arrays.asList(previewSurface), new CameraCaptureSession.StateCallback() {@Overridepublic void onConfigured(CameraCaptureSession session) {cameraCaptureSession = session;try {cameraCaptureSession.setRepeatingRequest(captureRequestBuilder.build(), null, null);} catch (CameraAccessException e) {e.printStackTrace();}}@Overridepublic void onConfigureFailed(CameraCaptureSession session) {Toast.makeText(MainActivity.this, "Failed to create camera capture session", Toast.LENGTH_SHORT).show();}}, null);} catch (CameraAccessException e) {e.printStackTrace();}}@Overridepublic void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {super.onRequestPermissionsResult(requestCode, permissions, grantResults);switch (requestCode) {case ACTION_REQUEST_PERMISSIONS: {// 如果请求被取消，结果数组将为空if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {// 授权成功，执行相关操作} else {// 授权失败，禁用相关功能或显示提示信息}return;}// 处理其他权限请求}}@Overridepublic void onSurfaceTextureSizeChanged(@NonNull SurfaceTexture surfaceTexture, int i, int i1) {}@Overridepublic boolean onSurfaceTextureDestroyed(@NonNull SurfaceTexture surfaceTexture) {return false;}@Overridepublic void onSurfaceTextureUpdated(@NonNull SurfaceTexture surfaceTexture) {}@Overrideprotected void onResume() {super.onResume();}}