Android has no preview photo function

Recently got a demand, take a picture in the background and save it

public void onTakePhotoClicked() {
   final SurfaceView preview = new SurfaceView(this);
   SurfaceHolder holder = preview.getHolder();
   // deprecated setting, but required on Android versions prior to 3.0
holder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
 holder.addCallback(new SurfaceHolder.Callback() {
     @Override
     //The preview must happen at or after this point or takePicture fails
     public void surfaceCreated(SurfaceHolder holder) {
       Log.d(TAG, "Surface created");
        camera = null;
       try {
         camera = Camera.open(Camera.CameraInfo.CAMERA_FACING_BACK);
         Log.d(TAG, "Opened camera");
         try {
           camera.setPreviewDisplay(holder);
         } catch (IOException e) {
           throw new RuntimeException(e);
         }
         camera.startPreview();
         Log.d(TAG, "Started preview");
      // Delayed photographing 
         ThreadUtils.postOnUiThreadDelayed(new Runnable() {
           @Override
           public void run() {
             Log.e("zgj"," Start taking pictures ");
             camera.takePicture(null, null, CameraService.this);
           }
         },5000);
       } catch (Exception e) {
         if (camera != null)
           camera.release();
         throw new RuntimeException(e);
       }
     }
     @Override
     public void surfaceDestroyed(SurfaceHolder holder) {}
     @Override
     public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {}
   });
   WindowManager wm = (WindowManager)getSystemService(Context.WINDOW_SERVICE);
   WindowManager.LayoutParams params = new WindowManager.LayoutParams(
       1, 1, //Must be at least 1x1
       WindowManager.LayoutParams.TYPE_SYSTEM_OVERLAY,
       0,
       //Don't know if this is a safe default
       PixelFormat.UNKNOWN);
   //Don't set the preview visibility to GONE or INVISIBLE
   wm.addView(preview, params);
 }
 @Override
 public void onPictureTaken(byte[] bytes, Camera camera) {
   Log.e("zgj", " End of photo shoot ");
   File pictureDir = Environment.getExternalStorageDirectory();
   if (pictureDir == null) {
     Log.d("zgj",
         "Error creating media file, check storage permissions!");
     return;
   }
   try {
     String pictureName = "ssss.png";
     File file = new File(pictureDir + "/pic/");
     if (!file.exists()) {
       file.mkdir();
     }
     file = new File(pictureDir + "/pic/" + pictureName);
     FileOutputStream fos = new FileOutputStream(file);
     fos.write(bytes);
     fos.close();
   } catch (FileNotFoundException e) {
     Log.d("zgj", "File not found: " + e.getMessage());
   } catch (IOException e) {
     Log.d("zgj", "Error accessing file: " + e.getMessage());
   }
 }

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