This issue has been posted, but it was considered resolved with update 1.6.2, well that's not the case for me. When I enter into my inventory (creative or survival) I can't left click to pick up an item. I have to hold the left click to move a single item, can't move stacks, can't shift click, and can't divide among placements with right click. I love this game, and just want to be able to play it again.
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duplicates
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Sounds to me like you have touchscreen mode enabled.