step1 获取一个相机实例

 /** A safe way to get an instance of the Camera object. */
    public static Camera getCameraInstance(int id) {
        Camera c = null;
        try {
            c = Camera.open(id); // attempt to get a Camera instance
        } catch (Exception e) {
            // Camera is not available (in use or does not exist)
        }
        return c; // returns null if camera is unavailable
    }

step2 检测设备是否存在相机

 /**
     * 检测设备是否存在相机
     */
    private boolean checkCameraHardware(Context c) {
        if (c.getPackageManager()
             .hasSystemFeature(PackageManager.FEATURE_CAMERA)) {
            return true;
        } else {
            return false;
        }
    }

step2 创建一个SurfacceView用于显示相机画面

public class SufaceCamera extends SurfaceView implements SurfaceHolder.Callback {
    android.hardware.Camera mCamera;
    private SurfaceHolder mSurfaceHolder;


    public SufaceCamera(Context context, android.hardware.Camera camera) {
        super(context);
        this.mCamera = camera;
        mSurfaceHolder = getHolder();
        mSurfaceHolder.addCallback(this);
        mSurfaceHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
    }


    @Override
    public void surfaceCreated(SurfaceHolder holder) {
        mSurfaceHolder = holder;
        try {
            mCamera.setDisplayOrientation(90);
            mCamera.setPreviewDisplay(holder);
            mCamera.startPreview();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }


    @Override
    public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {

    }


    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {
        if (mSurfaceHolder.getSurface() == null) {
            // preview surface does not exist
            return;
        }

        // stop preview before making changes
        try {
            mCamera.stopPreview();
        } catch (Exception e) {
            // ignore: tried to stop a non-existent preview
        }

        // set preview size and make any resize, rotate or
        // reformatting changes here

        // start preview with new settings
        try {
            mCamera.setPreviewDisplay(mSurfaceHolder);
            mCamera.startPreview();
        } catch (Exception e) {
        }
    }
}

step3 创建实例开启相机

 @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.cameralayout);
        ButterKnife.bind(this);
        if (checkCameraHardware(getApplication())) {
            cameraInstance = getCameraInstance(Camera.CameraInfo.CAMERA_FACING_FRONT);
            SufaceCamera sufaceCamera = new SufaceCamera(this, cameraInstance);
            submenuarrow.addView(sufaceCamera,0);
        }
    }