Run-time spawned objects don't have physics attached to them.

Getting Started Newbie Questions
#21

@Aidin:
Here’s how you do it correctly - you need to return the gameUI.dragBody, instead of just calling it.
[lua]local function localDrag( event )
event.target.isTouched = true;
– foodObject:addEventListener(“touch”, foodOnTouch);
– gameUI.dragBody( event, {} )
– gameUI.dragBody(event, {maxForce = 100, frequency = 2} ) – slow, elastic dragging
– gameUI.dragBody(event, {maxForce = 100, frequency = 2, center = true } ) – slow, elastic dragging
return gameUI.dragBody(event, {maxForce = 20000, frequency = 10, dampingRatio = 0.2, center = true }) --very tight

end[/lua]

And then add your listener.

Let me know if this works.

Caleb [import]uid: 147322 topic_id: 34449 reply_id: 137610[/import]

#22

@Caleb wrote:

Here’s how you do it correctly - you need to return the gameUI.dragBody, instead of just calling it.

Hey Caleb, curious, what’s the difference between returning the gameUI.dragBody and just adding "return true"at the end of the function.

Both seem to produce the same results in the simulator from what I can tell.

Nail [import]uid: 106779 topic_id: 34449 reply_id: 137628[/import]

#23

Here’s some behind-the-screen info as to what’s happening:

When you touch something with something else behind it, it’s creating two joints - one for the top object and one for the bottom object. Then, when you move your touch, it’s only registering one object to be moved. So it’s adjusting the top joint, but not adjusting the bottom joint. Then, when you touch the bottom object, it’s already got a joint, so it creates another, and now you have two. When you move the touch, the two joints fight for control, and it goes between them like a slingshot without any launch power.

This also happens if you have a touch listener that does not return true at the end and you release the touch on top of something that does have return true at the end - it doesn’t register an “ended” phase. That’s why I told you to add “return true”.

So that’s some background information so that you can know what exactly is happening. [import]uid: 147322 topic_id: 34449 reply_id: 137201[/import]

#24

I’m really not completely sure - I think they have the same effect, but the “return gameUI.dragBody” only takes one line of code, instead of an extra line. I really think it’s just your preference, however I’m not sure.

It would be nice to have one of the staff’s opinion on this. [import]uid: 147322 topic_id: 34449 reply_id: 137662[/import]

#25

@xnailbender: Why would I need to differentiate them? Whenever any of them is called, it will be called by reference and I’ll have pointer to the actual object.

@Caleb: I didn’t totally understand your first paragraph but I think you are right. So what do you think I can do to solve this? [import]uid: 206803 topic_id: 34449 reply_id: 137438[/import]

#26

Aidin wrote:

@xnailbender: Why would I need to differentiate them? Whenever any of them is called, it will be called by reference and I’ll have pointer to the actual object.

Newb here, so understand I’m not an expert on anything. Just trying to help and hope I’m not creating confusion. As I stated, I haven’t used the physics drag module before either.

I’m not really sure what your “pointer” actually is. I probably just don’t see the obvious.

From my “newbish” viewpoint, it seems to me your only “pointer” is “foodObject”.

I just don’t see how 1 “foodObject” is differentiated from another “foodObject”,

I can see how “foodObject[1]” is differentiated from “foodObject[2]” as the index values are different.

It seems to me the event.target is “foodObject”, unless the event.target can somehow differentiate 1 similar object from another, really not sure how that works if it does.

It seems to me, foodObject.x = event.target.x will move both similar foodObject’s at the same time when 1 of them is dragged, causing unexpected behavior.

I can see how foodObject[1].x = event.target.x will move only foodObject[1].x when dragged and foodObject[2] will be unaffected.

I’m thinking this is why both of your foodObjects are moving simultaneously when dragged, but not really sure because every similar object I spawn has an index reference.

If your get your issue resolved, I’d like to know what the solution was if you’d post it here.

Hope this helps,

Nail

[import]uid: 106779 topic_id: 34449 reply_id: 137506[/import]

#27

@Nail/xnailbender:

If it was what you described, then if you drag any object, any (and perhaps all) other object would move with it or cause the bug I described in the very first post. But it’s not. As I tried to explain earlier, you do not need to ID objects because you do not access them with code, so you would not know which is which.

The way you find which object is under touch is via touch event. Because each object is registered with touch event, then if you touch any of them, the only one that is affected by touch event will be called. So no need for an ID.

I believe problem is perhaps the gameUI’s drag code. As far as I understood, when you drag an object with dragUI’s drag code, it temporarily makes a joint and uses that [somehow] to make that joint follow your finger around. And I believe it’s in this process of making a temporary joint that the bug occurs.

Somehow when there is another object under the designated/touched object, the under object gets stuck to the background.

I can be totally wrong about this as I’m new to Corona and have very little understanding of it and other areas such as gameUI.

Thanks. [import]uid: 206803 topic_id: 34449 reply_id: 137542[/import]

#28

The gameUI code is not wrong. It’s worked many times for me before.

I’ll describe it again, see if you understand now:
To dragBody something from gameUI, it creates a joint attached to 1) the touch point and 2) the object. When you move your mouse (or finger), the joint is updated to connect 1) your touch point and 2) the object. So the object is pulled towards your click (or touch). When you touch something with something else underneath it, for some reason the touch registers to the bottom object, too. So now we have two joints, one attached from your touch point to object 1 (in the front) and one attached from your touch point to object 2 (in the back). When you move your touch, it does not pick up the bottom object as being touched (that should have been what it did from the start). So it only updates the top object’s joint. And an extra joint is still attached to the previous object - going towards the original touch point. So when you move your touch, object 1 moves and object 2 doesn’t. Then, when you try to move object 2, it’s already got a joint attached to it. So both joints fight with each other and you get what you thought was “stuck to the background”.

So in the end, I don’t believe gameUI is wrong - I think it’s something in your code. Can you post the part where you add the dragBody listener to the foods? [import]uid: 147322 topic_id: 34449 reply_id: 137546[/import]

#29

Thanks Caleb,
I don’t do anything fancy here, I just register my foodObject with a localDrag function to control and experiment with different types of dragBody configs, so essentially localDrag is just one line of code:

[lua]local function localDrag( event )
– foodObject:addEventListener(“touch”, foodOnTouch);
– gameUI.dragBody( event, {} )
– gameUI.dragBody(event, {maxForce = 100, frequency = 2} ) – slow, elastic dragging
– gameUI.dragBody(event, {maxForce = 100, frequency = 2, center = true } ) – slow, elastic dragging
gameUI.dragBody(event, {maxForce = 20000, frequency = 10, dampingRatio = 0.2, center = true }) --very tight

– isTouched is a flag to indicate that player previously touched this food object and if later on this
– object hits with a monster, then that collision is valid. So this prevents foods to get eaten by
– monsters when they move freely and accidentally collide with a monster.
– (We can toggle this to false after some time, if we want)
event.target.isTouched = true;
end[/lua]

And in the creation of a foodObject, somewhere in the end I do this:
[lua] foodObject:setReferencePoint(display.CenterReferencePoint); --we need to revert reference point to center physic will move it by center.
foodObject:addEventListener(“touch”, localDrag);[/lua]

Hope that helps. [import]uid: 206803 topic_id: 34449 reply_id: 137547[/import]

#30

@Aidin wrote:

The way you find which object is under touch is via touch event

Got it, I see how it is working now, at least for now anyways as long as their is an event to handle the object.

I’d still spawn into a table as it’s so versatile, but realize it’s not part of your issue now.

Like Caleb says, “return true” and stop the touch propagation (I think that’s the term anyways).

The drag code works, it’s pretty cool, I’ve never played with it.

I’ve also never passed a “touch” event through an event listener before, I didn’t even know that could be done.

Hope this helps,

Nail

[import]uid: 106779 topic_id: 34449 reply_id: 137576[/import]

#31

Thanks Caleb, that did it. [import]uid: 206803 topic_id: 34449 reply_id: 138141[/import]

#32

@Aidin:
Here’s how you do it correctly - you need to return the gameUI.dragBody, instead of just calling it.
[lua]local function localDrag( event )
event.target.isTouched = true;
– foodObject:addEventListener(“touch”, foodOnTouch);
– gameUI.dragBody( event, {} )
– gameUI.dragBody(event, {maxForce = 100, frequency = 2} ) – slow, elastic dragging
– gameUI.dragBody(event, {maxForce = 100, frequency = 2, center = true } ) – slow, elastic dragging
return gameUI.dragBody(event, {maxForce = 20000, frequency = 10, dampingRatio = 0.2, center = true }) --very tight

end[/lua]

And then add your listener.

Let me know if this works.

Caleb [import]uid: 147322 topic_id: 34449 reply_id: 137610[/import]

#33

@Caleb wrote:

Here’s how you do it correctly - you need to return the gameUI.dragBody, instead of just calling it.

Hey Caleb, curious, what’s the difference between returning the gameUI.dragBody and just adding "return true"at the end of the function.

Both seem to produce the same results in the simulator from what I can tell.

Nail [import]uid: 106779 topic_id: 34449 reply_id: 137628[/import]

#34

I’m really not completely sure - I think they have the same effect, but the “return gameUI.dragBody” only takes one line of code, instead of an extra line. I really think it’s just your preference, however I’m not sure.

It would be nice to have one of the staff’s opinion on this. [import]uid: 147322 topic_id: 34449 reply_id: 137662[/import]

#35

Thanks Caleb, that did it. [import]uid: 206803 topic_id: 34449 reply_id: 138141[/import]