圆环状的按钮，类似于ipod下面的实体键，IOS编程学习源码，很好的参考资料。-A circular button, similar to the iPod entity keys below, learning IOS programming source code, a good reference.

在iOS设备为输入键盘NumPad的状态时，实现对数字键的自定义，在空白的地方加上确定键。- In iOS device as an input keyboard NumPad the state, to achieve self-definition of the number keys, plus a blank place the OK button.

riglol hacked to generate keys for the Rigol MSO1000Z series scope