iOS in ScrollView a key back to the top

As long as there are some controls in iOS that have the function properties of ScrollView, when the interface is very long and slide to the bottom, the user wants a key back to the top.
We can set a button and set a click method for the button.

[Xxxtableview setcontentoffset:cgpointmake (0, 0) Animated:yes];

In the code, the first represents the x distance, the second represents the y distance, and basically if you just scroll up and down, you can achieve the effect by changing the second value of the Cgpointmake.