use Mending to exchange weapon from discard to hand, then it stock, not any option can choose.

I'm having the same issue. I cast Mending, chose to discard a Quarterstaff and was presented with a list of cards in my discard pile (Mace was highlighted). Can't do anything with the Mace.

 

I exited the game and then continued and now it's showing "Exchange 1 card in your hand with 1 discarded card." The Quarterstaff is offset under my discard pile and the only cards presented are what's currently in my hand (no list of cards to choose from).

 

This is on a Samsung Galaxy S4.

You have to drag that card to the right place.

Looking into this, thanks!

You have to drag that card to the right place.

 

I figure it's a dragging issue since I had trouble dragging Meri and Kyra into the party. Hopefully, I can do this on my tablet (knew I should've brought my tablet to work too).

I've mentioned this on two other different topics.  Any time you get to take something out of your Discard pile, you have to drag it to your hand to "Draw" or to your deck to "Recharge".  I suggested that buttons would be more intuitive.

We wanted to include buttons or a button like function for each situation where you can drag a card. So we'll be looking into the scenarios you suggested. Thanks!

I encountered this again recently. Definitely a dragging bug. HOWEVER, what appears to happen is that when you start to choose the card you are mending into (dragging from the discard pile), it seems like if you don't get it right on the first try, the card appears to disappear from the interface. This happened to me yesterday. I was able to complete the process by dragging the "invisible" card (which was on the right of the cards displayed from the discard) and brought it to my hand.

I used mending only once but I had some difficulty trying to drag the card out of the discard pile. It just couldn't move from the discard pile area. After a few tries, the card finally followed my finger's movement and I could drag it where I was supposed to.

I also had some troubles dragging Merisiel and Kyra into my party when first starting the adventure and sometimes I have to double try for the roll animation to start.

Definitely something about UI responsiveness.

I'm on iPad 3 with iOS 9.3.1

I encountered this again recently. Definitely a dragging bug. HOWEVER, what appears to happen is that when you start to choose the card you are mending into (dragging from the discard pile), it seems like if you don't get it right on the first try, the card appears to disappear from the interface. This happened to me yesterday. I was able to complete the process by dragging the "invisible" card (which was on the right of the cards displayed from the discard) and brought it to my hand.

This happened to me as well, Galaxy Tab A.

Lately I've been having a similar problem.  I just hold my finger on the card until I see it move slightly, and then drag it appropriately.