Spritekit如何根据触摸和按住的位置运行SKAction

Question

So I'm trying to implement a method into a game where if a player has their finger touching the screen at lets say 50 on the y axis or lower, an SKAction will run to move the character sprite down, and if their finger is touching above the 50, another action will run moving the sprite up. I don't know how you have it recognize a touch and hold though. Help please.

Answer 1

You will need to capture the touch event of the user in order to pull this off. I suggest checking out the excellent tutorial provided by RayWenderlich at: Animating Textures and Moving Them With Touch Events

If you don't have time for that this is what your code might look like:

First the knowledge that you will need is that the two most generic touch events are the: -(void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event and the: -(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event

Basically the touches began method is called when the user places their finger on the screen whereas the touches ended method will be triggered when the user takes their finger off the screen.

For this example I will use touchesEnded, but feel free to change it if you want, its as easy as switching the "Ended" with "Began".

All of the code I am about to show you will take place within the scenes implementation file:

If you just want the sprite to move up when above a certain point and down when below a certain point use the following:

-(void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{
    //capture the location of the touch
    CGPoint location = [[touches anyObject] locationInNode:self];

    //used to hold the location to travel
    CGPoint moveLocation;

    //check if the Y location is less than 50
    if(location.y < 50)
    {
        //the the location to the bottom of the screen
         moveLocation = CGPointMake(sprite.position.x, 0);
    }
    //and then if its more than 50
    else
    {
        //set the locaiton to the top of the screen
        moveLocation = CGPointMake(sprite.position.x, self.frame.size.height);
    }

    //move the sprite

    //Check if their already moving
    if(sprite actionForKey:@"moving")
    {
        //If they are stop them so they can move in the new direction
        [sprite removeActionForKey:@"moving"];
    }
    SKAction *moveAction = [SKAction moveTo:location duration:5.0f];

    //remember to give the action a key so that we can check for it during the above if statement
    [sprite runAction:moveAction withKey:@"moving"];
}

And there you have it. The only flaw is that it will always take 5 seconds to reach the location regardless of your distance from it, read on if you would like hints on how to correct that, or if you would like to see how to make the sprite travel to any touched location on the screen.

-(void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{
    //capture the location of the touch
    CGPoint location = [[touches anyObject] locationInNode:self];

    //move the sprite

    //Check if their already moving
    if(sprite actionForKey:@"moving")
    {
        //If they are stop them so they can move in the new direction
        [sprite removeActionForKey:@"moving"];
    }
    SKAction *moveAction = [SKAction moveTo:location duration:5.0f];

    //remember to give the action a key so that we can check for it during the above if statement
    [sprite runAction:moveAction withKey:@"moving"];
}

That code will make it so that for 5 seconds the sprite will move to the location touched on the screen. Just remember to replace the instances of "sprite" with the name of your SKSpriteNode variable. For more complex movement try the following:

-(void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{
    //capture the location of the touch
    CGPoint location = [[touches anyObject] locationInNode:self];
    //set the velocity of the subject
    float velocity = self.frame.size.width/3.0;
    //The above will ensure that it will take the sprite 3 seconds to travel the distance of the screen

    //Determine the difference between the point touched and the sprites position
    CGPoint moveDifference = CGPointMake(location.x - sprite.position.x, location.y - sprite.position.y);

    //Use pythagorean theorem to figure out the actual length to move
    float distanceToMove = sqrtf(moveDifference.x * moveDifference.x + moveDifference.y*moveDifference.y);

    //Use the distance to travel and the velocity to determine how long the sprite should move for
    float moveDuration = distanceToMove / velocity;

    //and finally move the sprite
    if(sprite actionForKey:@"moving")
    {
        [sprite removeActionForKey:@"moving"];
    }
    SKAction *moveAction = [SKAction moveTo:location duration:moveDuration];

    [sprite runAction:moveAction withKey:@"moving"];
}

That will set a velocity for the sprite, determine the length of the travel, and how long it will take to get to the new location.

If you want to involve textures I highly suggest reading the link I provided.

Upon request I would be glad to offer examples using forces to control movement speed as well.

I hope that helps, let me know if there are any problems I wasn't in a position where I could run the code but I am sure that it is fine.