I have an image that the user can drag to the right and it will spring back when the user releases it. I want to execute some code when a user drags it quickly and releases it. Now I have a very awkward requirement that the user can drag the image, then keep it still for any length of time (for example 5 seconds), then drag it quickly and release it. As long as the image is moving above a certain speed when it is released, it will execute the code. If it falls below the minimum speed, it executes some different code. So that means I can't calculate the length of time between the beginning of the gesture and the end and execute the code depending on the length of time. What can I do? I guess I somehow need to know the speed at which the image is moving in it's last 500 milliseconds before the gesture ends. However I've hit a brick wall figuring out how to do that. Any help would be greatly appreciated.
Can you please include an explanation and possible example code with your answer as that would be a great help.
If you get the start X,Y coordinates of when the image is dragged, and the X,Y coordinates for when the mouse is released, you can use pythagoras' theorm to calculate the distance between the two points: http://en.wikipedia.org/wiki/Pythagorean_theorem
Also, if you start a timer when the mouse is moved (and mouse button is down), and stop it in the mouseup event, you can calculate the speed using the time and distance (speed = distance / time)
edit following comments:
point delayedMousePos;
point previousMousePos;
bool secondDrag = false;
bool isStopped = false;
var timeFirstStopped;
var positionCount = 0;
array previousMousePositions[3];
// timer which monitors mouse position (set to an interval of say, 10ms)
function timerMonitorMousePos_Elapsed() {
point currentMousePos = getMousePos();
if (isStopped == false) {
if (positionCount >= 2) {
array_shift(previousMousePositions); // remove the first element of the array and move everything down to reindex numerical array to start counting from zero
positionCount = 2; // keep positionCount within array bounds
}
previousMousePositions[positionCount] = currentMousePos; // add the new position to the end of the 'stack'
positionCount++;
}
if (currentMousePos == previousMousePos) { // start check for stationary
isStopped = true;
if (timeFirstStopped == null) {
timeFirstStopped = NOW();
} else {
if (NOW() - timeFirstStopped >= 500) { // we have been stopped for at least 500ms (assumes time is counted in milliseconds)
secondDrag = true;
// previousMousePositions[0] = the mouse position 30ms before the mouse stopped
}
}
} else {
isStopped = false;
timeFirstStopped = null;
}
previousMousePos = currentMousePos;
}
I wouldn't use a timer. I would just save the starting date/time along with x,y position when the dragging starts.
When the dragging has ended, save the ending date/time and position. From those information, I can calculate the distance in pixel and duration in milliseconds.
After searching some more on the internet, I finally answered my own question.
I worked out what I needed to do:
My UIPanGestureRecognizer:
- (IBAction)handlePan3:(UIPanGestureRecognizer *)recognizer3
Get the velocity of the users finger moving across the screen:
CGPoint vel = [recognizer velocityInView:self.myView];
Then:
if (vel.x > /*value*/) {
// Your code
}
I was about to give up, but no! I got there in the end. Thanks for everyones help. I've upvoted one or two answers because they were helpful. bobnoble actually gave the suggestion to use velocityInView and I found this other stack overflow question which gave me the info I needed: iOS - Making sense of velocityInView on UIPanGesture
Related
I'm using a SpriteKit game engine within XCode while developing a game that bounces a ball and platforms come from the sky and the objective is to bounce on the platforms to get higher. I need to add a velocity to the ball when it falls down + comes in contact with a platform. I'm having trouble trying to detect the balls Y position. I had something like this in the update method but nothing happens... I'm open to suggestions.
//The value of the _number instance variable is the Y position of the ball.
if (_number++) {
NSLog(#"UP");
}
if (_number--) {
NSLog(#"DOWN");
}
You can see a node's position by using code like this:
if(myNode.position.y > 0)
NSLog(#"y is greater than 0");
If you want to check a node's current speed (vector) you can do it like this:
if(myNode.physicsBody.velocity.dy > 0)
NSLog(#"Moving up");
if(myNode.physicsBody.velocity.dy < 0)
NSLog(#"Moving down");
Remember that position and speed (vector) are not the same thing.
You need to read the SKPhysicsBody docs to understand about CGVector and other important issues.
Alright, this:
if (_number++) {
NSLog(#"UP");
}
if (_number--) {
NSLog(#"DOWN");
}
doesn't work to do anything. It shouldn't even run. I don't why it doesn't give an error.
number++; is a simplified form of
number = number + 1;
You can't place it in an if statement.
First make the variable #property int ypos in your header.
Then every update compare the current y to the ypos.
After comparing, save the current y to ypos.
Place this in your Update method.
if (ball.position.y > _ypos)
{
//going up
}
else if (ball.position.y < _ypos)
{
//going down
}
_ypos = ball.position.y;
P.S. I haven't had access to a computer so the formatting might suck from my phone
This is language-agnostic question, more about model of my game.
I have a snake game with elements, but I move the elements smoothly, they don't just move 1 block each time, but instead they move some amount of pixels every frame.
I have an update loop that calculates the positions of the element, but I am stuck on correct calculations.
I have heading for each element:
typedef NS_ENUM(int, kElementHeading)
{
kElementHeadingNorth = 1,
kElementHeadingSouth,
kElementHeadingEast,
kElementHeadingWest
};
I also have velocity (x, y) that determines in what direction snake is going. I have problem with snake movement, because my elements are in wrong positions. I managed to localize the thing for 2 elements, but my solution fails on more elements.
First solution I tried is to save point of rotation where the head changes direction. This worked, but due to different circumstances element can move different amount of pixels each turn. Often the element would skip the point. I tried increasing the zone where it should rotate, but it adds up error. I tried fixing this error, but element would still separate from snake (quite often).
On the second try I decided to keep the snake head in center of the screen and move the world around it. It worked good for 2 elements, as I just smoothly move the next element to desired position relatively to head. But this fails badly on more elements. If you make fast turns they start dancing and not following the path.
Third thing that I tried is leaving a path for other elements to follow. But that didn't work because I intend to keep my snake on center of the screen and technically it never moves to create a path.
I'm looking to replicate the movement pattern like in Nimble Quest (or any snake).
How should I implement snake elements moving to have no errors?
Here is my code for the first method, problem with it is that often the elements would fall off. The code is pretty self-explanatory. Rotation points are the places where to change direction.
CFTimeInterval delta = self.lastTime - currentTime;
CGPoint currentPosition = self.playerSnake.head.sprite.position;
CGPoint velocity = self.playerSnake.velocity;
self.playerSnake.head.sprite.position = CGPointMake(currentPosition.x + velocity.x * delta * CONSTANTSPEEDFACTOR , currentPosition.y + velocity.y * delta * CONSTANTSPEEDFACTOR);
for (SnakeElement *element in self.playerSnake.elements) {
CGPoint currentPositionE = element.sprite.position;
CGPoint velocityE = element.velocity;
element.sprite.position = CGPointMake(currentPositionE.x + velocityE.x * delta * CONSTANTSPEEDFACTOR , currentPositionE.y + velocityE.y * delta * CONSTANTSPEEDFACTOR);
}
BOOL markToDelete = NO;
NSDictionary *deleteDictionary;
for (NSDictionary *dict in self.playerSnake.rotationPoints) {
CGPoint positionCoordinate = CGPointFromString(dict[#"position"]);
CGPoint velocityNew = CGPointFromString(dict[#"velocity"]);
double newAngle = [dict[#"angle"] doubleValue];
for (SnakeElement *element in self.playerSnake.elements) {
int xDifference = element.sprite.position.x - positionCoordinate.x;
int yDifference = element.sprite.position.y - positionCoordinate.y;
if ((xDifference > -2 && xDifference < 2) && (yDifference > -2 && yDifference < 2) ) {
element.velocity = velocityNew;
element.sprite.position = CGPointMake(element.sprite.position.x + xDifference, element.sprite.position.y + yDifference);
SKAction *action = [SKAction rotateToAngle:newAngle duration:0.2 shortestUnitArc:YES];
[element.sprite runAction:action];
if ([element isEqual:[self.playerSnake.elements lastObject]]) {
markToDelete = YES;
deleteDictionary = dict;
}
}
}
}
[self.playerSnake.rotationPoints removeObject:deleteDictionary];
If I try increase the catch zone for the turning point, the elements tend to fall off more often then when it is 1 or 2 pixels wide. I'm not sure why this happens.
This is what I was suggesting you do in the comments in terms of handling your turning on points :
1.. calculate the distance that the element should move that frame based on speed and your elapsed time since last frame. (delta)
2.. calculate distance from element's current position to the turn point. This is the beforeDistance I spoke of in the comments
3.. calculate the distance the element should move towards the NEW target turning point AFTER the turn
afterDistance = distanceToMoveThisFrame - beforeDistance
4.. Calculate the new position for your element, starting at the current turning point towards the next target turning point of the element using afterDistance
If you follow this logic, you will NEVER overshoot or undershoot the turning point.
In my app I have the option for the user to pan upward to adjust a control, but it's a little slow when they pan up really quick, which I'd like to jump a lot more.
// If user is panning upwards or downwards, adjust WPM every 8 translations in either direction
if (translation.y<-8 || translation.y>8) {
// Reset translation so we can see when it exceeds 8 again
[recognizer setTranslation:CGPointMake(0, 0) inView:self.view];
// Figure out direction, if pan down, decrease by 5, if up, increase by 5
int sign = (translation.y > 0) ? -1 : 1;
WPM = #([WPM intValue] + (sign * 5));
if ([WPM intValue] >= 200 && [WPM intValue] <= 1500) {
self.WPMLabel.text = [WPM stringValue];
self.wordsPerMinute = WPM;
[[NSUserDefaults standardUserDefaults] setObject:WPM forKey:#"WPM"];
}
}
How would I go about changing this to account for faster acceleration?
Use the velocity property on the gesture recognizer.
https://developer.apple.com/library/ios/documentation/UIKit/Reference/UIPanGestureRecognizer_Class/Reference/Reference.html#//apple_ref/occ/instm/UIPanGestureRecognizer/velocityInView:
Speed involves time. So each time your code runs, you need to save in an instance variable what time it is on the event's timestamp. That way, the next time your code runs, you can compare both the translation change and the time elapsed to the previous change.
What I would do is experiment with saving three or four previous times and three or four previous locations in an array so that you can take a moving average and damp out speed variations.
I have a manometer, this needs to spin from a minimum value to a maximum. right now I have the manometer as a picture and the arrow as a movieclip. I've got it spinning at the right speed, but don't know how to stop it at the lowest/highest pressure.
It's suppose to work like this:
I have two movieclip/buttons; one for simulating more pressure, and one for less.
when the user presses the "more pressure" movieclip/button the pressure begins to rise and the arrow inside the manometer begin to turn.
At the same time as the pressure rises, another movieclip ("stamp") will push uppwards.
then another movieclip/button, "less pressure" simulates pressure drop; when pressed, the same point as the arrow stopped at when pressure rised, will start sinking towards minimum, and the stamp will go down again.
so, when the user presses "more pressure" pressure rises towards maximum, and as soon as the user stop pressing the button, the animation stops (both the stamp and the arrow). And if the user presses "lower pressure", the arrow starts sinking from where it stopped.
heres my code so far: pil1 = manometerarrow, the stamp = stamp, and "less pressure"/"more pressure" = Lpress / mpress
addEventListener (Event.ENTER_FRAME, rotate);
function rotate(event:Event):void
{
pil1.rotation = pil1.rotation+1;
}
ymutlu is on the right track. The mouse down event will only execute once when the mouse is depressed. To make the object rotate continuously while the mouse is depressed you need to increment or decrement the rotation of the object on each frame. I think the following should do the trick:
import flash.events.MouseEvent;
import flash.events.Event;
var rotate = 0;
Hpress.addEventListener(MouseEvent.MOUSE_DOWN, Hpressed);
Hpress.addEventListener(MouseEvent.MOUSE_UP, removeEnterFrame);
Lpress.addEventListener(MouseEvent.MOUSE_DOWN, Lpressed);
Lpress.addEventListener(MouseEvent.MOUSE_UP, removeEnterFrame);
function Hpressed(e:MouseEvent):void
{
rotate = 1;
addEnterFrame();
}
function Lpressed(e:MouseEvent):void
{
rotate = -1;
addEnterFrame();
}
function addEnterFrame():void
{
this.addEventListener(Event.ENTER_FRAME, update);
}
function removeEnterFrame(e:MouseEvent):void
{
this.removeEventListener(Event.ENTER_FRAME, update);
}
function update(e:Event):void
{
pil1.rotation += rotate;
}
hold to varaible that states if max button down or min button down, and check it in enterframe loop. Edited answer on your comment, hope you can sort it out.
addEventListener (Event.ENTER_FRAME, rotate);
function rotate(event:Event):void
{
if(isMaxDown) // true when max button down
pil1.rotation = Math.min(presMax,pil1.rotation+1); // presMax is max value that pressure can go
if(isMinDown) // true when min button down
pil1.rotation = Math.max(presMin,pil1.rotation-1);// presMin is min value that pressure can go
}
// isMaxDown and isMinDown are global values.
Hpress.addEventListener(MouseEvent.MOUSE_DOWN, Hpressed);
Lpress.addEventListener(MouseEvent.MOUSE_DOWN, Lpressed);
Hpress.addEventListener(MouseEvent.MOUSE_UP, H_up);
Lpress.addEventListener(MouseEvent.MOUSE_UP, L_up);
function H_up(e:MouseEvent):void {
isMaxDown=false;
}
function L_up(e:MouseEvent):void {
isMinDown=false;
}
function Hpressed(e:MouseEvent):void {
isMaxDown=true;
}
function Lpressed(e:MouseEvent):void {
isMinDown=true;
}
This code would help you but prob this is not a path to fallow to do somthing like that.
I'm currently trying to make a basic platformer with XNA and I'm wondering how to create a "jumping effect." I currently have basic keyboard input which allows for sideways movement, but I would like my sprite to slowly progress into a jump rather than instantly teleporting there (right now I have something like Rectangle.Y += 40 every time I jump, making the sprite instantly appear there). Does anyone have any insight?
I'm not totally across how to implement this in XNA/C#, but in Flash games I've made I just added a vertical velocity property. I'll try write everything as C# as I can..
Example; create the velocity property:
float verticalVelocity = 0;
Vertical velocity should be constantly reduced (by gravity). Set up a gravity property somewhere accessible from your player:
float Gravity = 2.5;
And in your update() method for the player, increment the verticalVelocity by Gravity. Also increment the Y position of your player by the verticalVelocity. This will simulate falling:
verticalVelocity += Gravity;
Position.Y += verticalVelocity; // this may be -= in XNA, not sure where the y axis beings
When you hit a surface, the velocity should be reset to 0.
And finally, to jump, simply subtract a given value from verticalVelocity:
public void Jump(float height)
{
// Only jump if standing on a surface.
if(verticalVelocity == 0)
verticalVelocity -= height;
}
You'll eventually want to add gravity and possibly other forces to your game, so I highly recommend you save yourself a lot of pain and implement some kind of basic force system. This can be done using Vector2s, as you can just add them to the speed of your character. Then just apply an instantaneous force to your character to push it up.
If you really don't want to use a physics engine, you can make a Vector2 with the high point of the jump for the Y and the characters X, and then use the Vector2.Lerp method to interpolate between the characters position and the end point of the jump.
This is generally a very bad system to use, and I highly recommend you either use an existing physics engine, or make your own simple one.
use a sinusoidcode should look something like this:
float ground = 0.0f;
float angle = 330.0f;
jump(){
if(ground == 0.0f)ground = Rectangle.Y;
if(Rectangle.Y <= ground)
{
Rectangle.Y+=Math.Sin(angle/(Math.Pi*180));
angle++;
}
}
You can accurately create a gravity effect if you modify the ySpeed dynamically, as opposed to just adding 40.
You want to declare a ySpeed
ySpeed = 0;
Then you want to use an acceleration variable
acceleration = 0.25;
Okay, now that we've done that, let's add gravity, provided that our player isn't touching the floor.
if(playerLocationY + playerHeight > floorLocationY)
{
gravity = false;
}
else
{
gravity = true;
}
if(gravity)
{
ySpeed += acceleration;
}
Now that we've got that down, we want to include something that allows us to jump.
if(KeyPressed == UP)
{
ySpeed -= acceleration;
}
This will move our player in the upward direction
We now want to make sure we actually move, so let's add one last line and we're done.
playerLocationY += ySpeed;
Congratulations, you made it.