fix jump on first press

[davidbiller]

[antonKalinin]

Hey @davidbiller, many thanks for PR. I've checked new behaviour with changes you made. I looks like it fixes scrolling issue, but from other hand breaks vertical moving of picture. I now looking for solution to fix both problems (maybe some big changes needed).

[davidbiller]

So can you explain what do you mean? i can move the image in both directions...

[antonKalinin]

I cant move image up or down. If I swipe fast image view will close, but if vertical velocity is low, then image doesn't moving.

[danielgindi]

The real solution is to add this as the bottom of the constructor:

        this.state.imageTranslate = { x, y };
        this.state.imageScale = this.getInitialScale();