Qt开发的功能软键盘，实现了数字输入，小数点输入，小数点判断，负号输出功能，退格功能，清楚功能，输出功能，通过信号将textedit中的值传给主界面-Qt development function soft keyboard, realization of the digital input, the decimal point input, the decimal point to determine the negative signal output function, a backspa