[otherguy]

You could set two buttons up to to change the state of the solenoid when they transition from not being pressed -- to being pressed.

The only problem I foresee with this is if you ever wanted to stop the thing from moving, you would need to set up a new command on another button which set both solenoid channels to their false state. (Added to the code example)

This can be thought of as a rising edge trigger. Something (whatever is in the if statement) will happen once when the button is pressed, and never again until the button is released and pressed again.

//These should be declared outside of the method which code
// is executing in.
Boolean currentButton1Value = false,
        prevButton1Value    = false,
        currentButton2Value = false,
        prevButton2Value    = false;




//The below code should be placed in whatever method is continually
//  executing code (e.g. teleop periodic)


//Check the current button values
currentButton1Value = joystick1.getRawButton(1);
currentButton2Value = joystick1.getRawButton(2);

//If the button was just transitioned from not pressed to pressed,
//  extend? completely.
if((currenButton1Value == true) && (prevButton1Value == false)) {
  //The only way to get in here is if button 1 is currently true,
  //  and used to be false.
  solenoid7.set(true);
  solenoid8.set(false);
}

//If the button was just transitioned from not pressed to pressed,
//  retract? completely.
//Using a simplified form for the boolean logic (does the same thing as above)
if(currenButton2Value && !prevButton2Value) {
  solenoid7.set(false);
  solenoid8.set(true);
}

//Keep a history of the button presses
prevButton1Value = currentButton1Value;
prevButton2Value = currentButton2Value;

if(joystick1.getRawButton(3)){
  solenoid7.set(false);
  solenoid8.set(false);
}

Note this code isn't tested, and I don't know what your application is, so I'm not sure if it fits the need well. Hope it helps.