android - カスタムカメラの新しいキャプチャ画像は古い画像を上書きします

Question

写真を撮って電話の内部ストレージのフォルダーに保存するカスタムカメラを作成しました。しかし、新しい写真を撮るたびに、古い写真が上書きされます。

主な活動

public class MainActivity extends AppCompatActivity {
Camera camera;
Button capture, gallery;
FrameLayout frameLayout;
ShowCamera showCamera;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    frameLayout = findViewById(R.id.frameLayout);
    capture = findViewById(R.id.button);
    gallery = findViewById(R.id.button2);

    camera = Camera.open();
    showCamera = new ShowCamera(this,camera);
    frameLayout.addView(showCamera);

    Handler handler = new Handler();
    handler.postDelayed(new Runnable() {
        @Override
        public void run() {
            captureImage(showCamera);
        }
    },4000);
}

Camera.PictureCallback mPictureCallback = new Camera.PictureCallback() {
    @Override
    public void onPictureTaken(byte[] data, Camera camera) {

        File picture_file = getOutputMediaFile();
            if(picture_file==null) {
                return;
            }
            try {
             FileOutputStream fos = new FileOutputStream(picture_file);
                fos.write(data);
                fos.close();
                camera.startPreview();
            }  catch (IOException e) {
                e.printStackTrace();
            }
        }

         };


private File getOutputMediaFile() {
    String state = Environment.getExternalStorageState();
    if(!state.equals(Environment.MEDIA_MOUNTED)) {
        return null;
    }
    else {
        File folder_gui = new File (Environment.getExternalStorageDirectory() + File.separator+"GUI");
        if(!folder_gui.exists()) {
            folder_gui.mkdirs();
        }
        File outputFile = new File(folder_gui,"temp.jpg");
        return outputFile;
    }
}

public void captureImage(View v) {
    if(camera!=null) {
        camera.takePicture(null,null,mPictureCallback);
    }
}
}

ショーカメラ

public class ShowCamera extends SurfaceView implements SurfaceHolder.Callback{

Camera camera;
SurfaceHolder holder;

public ShowCamera(Context context, Camera camera) {
    super(context);
    this.camera = camera;
    holder = getHolder();
    holder.addCallback(this);

}

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

}

@Override
public void surfaceDestroyed(SurfaceHolder holder) {
    camera.stopPreview();
    camera.release();
}

@Override
public void surfaceCreated(SurfaceHolder holder) {
    Camera.Parameters params = camera.getParameters();
    //change the orientation of the camera

    List<Camera.Size> sizes = params.getSupportedPictureSizes();
    Camera.Size mSize = null;
    for(Camera.Size size : sizes) {
        mSize = size;
    }

    if(this.getResources().getConfiguration().orientation!= Configuration.ORIENTATION_LANDSCAPE) {
        params.set("orientation","portrait");
        camera.setDisplayOrientation(90);
        params.setRotation(90);
    }
    else {
        params.set("orientation","landscape");
        camera.setDisplayOrientation(0);
        params.setRotation(0);
    }
    params.setPictureSize(mSize.width,mSize.height);

    camera.setParameters(params);
    try {
        camera.setPreviewDisplay(holder);
        camera.startPreview();
    } catch (IOException e) {
        e.printStackTrace();
    }

}
}

新しい写真がスナップされたときに、既存の写真を上書きするのではなく、その写真をフォルダーに追加したい。どうすればいいですか？