Android Camera2设置预览示例代码

当然，这里是一个简单的 Android Camera2 设置预览的示例代码：

首先，你需要在你的 AndroidManifest.xml 文件中添加相机权限：

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

然后，在你的活动或片段类中，你需要声明一些成员变量：

private CameraManager cameraManager;
private String cameraId;
private CameraDevice cameraDevice;
private CameraCaptureSession cameraCaptureSession;
private CaptureRequest.Builder captureRequestBuilder;
private ImageReader imageReader;
private SurfaceView surfaceView;

接下来，在你的 onCreate 方法中初始化这些变量：

surfaceView = findViewById(R.id.surfaceView);

cameraManager = (CameraManager) getSystemService(Context.CAMERA_SERVICE);
try {
    cameraId = cameraManager.getCameraIdList()[0];
} catch (CameraAccessException e) {
    e.printStackTrace();
}

然后，在 onResume 方法中打开相机并设置预览：

@Override
protected void onResume() {
    super.onResume();

    surfaceView.getHolder().addCallback(new SurfaceHolder.Callback() {
        @Override
        public void surfaceCreated(SurfaceHolder holder) {
            openCamera();
        }

        @Override
        public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
            // 不需要实现
        }

        @Override
        public void surfaceDestroyed(SurfaceHolder holder) {
            // 不需要实现
        }
    });
}

在 openCamera 方法中打开相机，并设置预览会话：

private void openCamera() {
    try {
        cameraManager.openCamera(cameraId, new CameraDevice.StateCallback() {
            @Override
            public void onOpened(@NonNull CameraDevice camera) {
                cameraDevice = camera;
                createCameraPreviewSession();
            }

            @Override
            public void onDisconnected(@NonNull CameraDevice camera) {
                cameraDevice.close();
                cameraDevice = null;
            }

            @Override
            public void onError(@NonNull CameraDevice camera, int error) {
                cameraDevice.close();
                cameraDevice = null;
            }
        }, null);
    } catch (CameraAccessException e) {
        e.printStackTrace();
    }
}

在 createCameraPreviewSession 方法中创建预览会话，并设置预览请求：

private void createCameraPreviewSession() {
    try {
        Surface surface = surfaceView.getHolder().getSurface();

        captureRequestBuilder = cameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW);
        captureRequestBuilder.addTarget(surface);

        cameraDevice.createCaptureSession(Arrays.asList(surface, imageReader.getSurface()), new CameraCaptureSession.StateCallback() {
            @Override
            public void onConfigured(@NonNull CameraCaptureSession session) {
                cameraCaptureSession = session;
                try {
                    cameraCaptureSession.setRepeatingRequest(captureRequestBuilder.build(), null, null);
                } catch (CameraAccessException e) {
                    e.printStackTrace();
                }
            }

            @Override
            public void onConfigureFailed(@NonNull CameraCaptureSession session) {
                // 处理配置失败的情况
            }
        }, null);
    } catch (CameraAccessException e) {
        e.printStackTrace();
    }
}

最后，在 onPause 方法中释放相机资源：

@Override
protected void onPause() {
    super.onPause();

    if (cameraCaptureSession != null) {
        cameraCaptureSession.close();
        cameraCaptureSession = null;
    }

    if (cameraDevice != null) {
        cameraDevice.close();
        cameraDevice = null;
    }
}

以上就是一个简单的 Android Camera2 设置预览的示例代码。希望对你有所帮助！如果还有其他问题，请随时提问。