Simpler Click and Drag Rotation in Flash AS2

Although this is more lines of code, the code is easier to follow.

The last example used trigonometry to calculate the angle of rotation and gave a realistic simulation of dragging an object in a circle. This is much more basic, and sets the rotation of the object based on a horizontal drag only.

The Script

/* sets the starting point for the maths that follows */
var objectnewdeg = 0;
var objectdeg = 0;
var mindeg = 0;
var maxdeg = 300;
/* this function rotates the object live as the user drags */
rotateobject = function () {
/* this checks whether the user is rotating within the max and min rotation factors defined in the variables above, it only allows rotation if it is within the set limits, otherwise the object won't move */
if (objectnewdeg>=mindeg && objectnewdeg<=maxdeg) {
curpoint = _xmouse;
objectnewdeg = objectdeg+(curpoint-objectstartdeg);
_root.object_mc._rotation = objectnewdeg;
}
}; 
/* This starts the object rotation function and sets the starting point of the user's click - all rotation is then based on the difference between where the user first clicks and where they drag to */
_root.object_mc.onPress = function() {
objectstartdeg = _xmouse;
objectrotInterval = setInterval(rotateobject, 10);
}; 
/* This stops the rotation as soon as the user let's go. It also checks that the user has not been able to drag further than the min or max limits before the code could correct them, and if they have, adjusts the rotation to fit within the limit boundaries */
_root.object_mc.onRelease = function() {
clearInterval(objectrotInterval);
if (objectnewdegmaxdeg) {
_root.object_mc._rotation=maxdeg;
objectnewdeg = maxdeg;
}
objectdeg = objectnewdeg;
};
/* This is the same as the function above, but executes if the user has drifted off the object when they stop dragging */
_root.object_mc.onReleaseOutside = function() {
clearInterval(objectrotInterval);
if (objectnewdegmaxdeg) {
_root.object_mc._rotation=maxdeg;
objectnewdeg = maxdeg;
}
objectdeg = objectnewdeg;
};


While this code may have more lines, it's much simpler to follow. In addition it also allows you to set a maximum and minimum rotation factor, so you can set how far you want the user to be allowed to rotate the object in either direction.

To use it, simply paste it into frame 1, and create and MovieClip on the stage with the instance name 'object_mc'.

Try It



Making it Useful

Let's say you wanted to use this to make a user input for a program. The user rotates the object (say a dial or a volume knob) and you want to use the numerical value of the object's rotation for something. Nothing could be simpler.

If you want the numerical value only once the user has stopped dragging then base your program on the variable objectdeg.

If you want the numerical value to constantly update as the user drags, then base your program on the variable objectnewdeg.