iOS Question Rotating a circle on a circle path

tufanv · Aug 14, 2015

Hello,

I also need advice on another thing. Please see the pic below.

I need to rotate a circle picture or a circle around a circle track conitnously. ( you can think of world turning around the sun on a track ) . What is the best and easiest way to do it ?

TY

JanPRO · Aug 14, 2015

Hi,
for the best result you have to use for now (unfortunately) inline objective c code: http://nachbaur.com/blog/core-animation-part-4

narek adonts · Aug 14, 2015

You can draw a Circle and save all the coordiantes of the path and after use a timer to change the center of the circle

narek adonts · Aug 14, 2015

Attached small project demonstrating your issue.
I use my code module in the project to get and set the center of a view, but if you dont like it you can do the same with setting the left and top props.

strat · Aug 14, 2015

An imageview's moving along circle track is here:

B4X:

Sub Activity_Create(FirstTime As Boolean)
    angle=0
    radius=40%x
End Sub

This is main code: X and Y variables keep ImageView's circular coordinates.
You should edit to work in B4I, add variables, timer etc.

B4X:

Sub timer1_Tick
    angle=angle+1
    x=CosD(angle)*radius+50%x
    y=SinD(angle)*radius+50%y
    ImageView1.Left=x
    ImageView1.Top=y
End Sub

Edit : This is almost same as narek adonts sample. I didn't see it before post this.

tufanv · Aug 14, 2015

Thank you very much for your examples !

narek adonts · Aug 14, 2015

see attached project.
It use CAAnimation to be more smooth that the one with the timer.

Narek

tufanv · Aug 15, 2015

Yea i will tey it when i get home thanks !

tufanv · Aug 15, 2015

narek adonts said:
see attached project.
It use CAAnimation to be more smooth that the one with the timer.

Narek

Narek,

It is really smooth now ! Thank you Very much for your help .

tufanv · Aug 15, 2015

narek adonts said:
see attached project.
It use CAAnimation to be more smooth that the one with the timer.

Narek

I have made a small change on the code ( added a panel and initialized the circle on the new panel. btw i dont know why but i had to change the left and top values while adding the circle to panel to a minus otherwise there are 2 circles ,1 is staying at its posiion and other one is circling . you can try it by changing the : paneloyun.AddView(pnlCircle,-100,-50,20,20)to its actual positions on your code)

anyway, When i use a canvas to draw a circle exactly on the circle path with this code:

B4X:

dim cek as point
cek.X=CircleCenter.x
cek.Y=CircleCenter.y
  cv.DrawCircle(cek.X,cek.Y,150,Colors.Black,False,1)
     cv.Refresh

Now, the spinning circle has to spin just above the circle created with the canvas because their center is same and their radius is same but they are not. Am i doing stg wrong or ?

You can check the example.

TY

narek adonts · Aug 15, 2015

upload the project please

tufanv · Aug 15, 2015

sorry fogot it. Attached now

narek adonts · Aug 16, 2015

you should not initialize canvas in application_start event.

put cv.Initialize(paneloyun) in Page_resize event

tufanv · Aug 16, 2015

narek adonts said:
you should not initialize canvas in application_start event.

put cv.Initialize(paneloyun) in Page_resize event

Yes ! Thank you very much for all your help !

tufanv · Aug 17, 2015

narek adonts said:
you should not initialize canvas in application_start event.

put cv.Initialize(paneloyun) in Page_resize event

Dear Narek

I have one last question for you. I can't get the top,left values of the rotating circle with a timer. It always shows the top,left values of the initialized values. While it is moving i cant get the coordinates of current position via log(pnlcircle.top) for example. Is there any way i can get it ?

narek adonts · Aug 17, 2015

You can not. During any animation the views coordinates are the last coordinates and also you can not click, ... on the view.
You need to use a timer for that. I will upload my new class CADisplayLink which is also like a timer but it ticks on each screen Hz refresh. So you will be able to use it as I timer but you will have smooth animations

tufanv · Aug 17, 2015

narek adonts said:
You can not. During any animation the views coordinates are the last coordinates and also you can not click, ... on the view.
You need to use a timer for that. I will upload my new class CADisplayLink which is also like a timer but it ticks on each screen Hz refresh. So you will be able to use it as I timer but you will have smooth animations

Watiing for it Thank You !

narek adonts · Aug 17, 2015

At the moment you can use this function to retrieve the actual Rect of a view (event during animation).

B4X:

Sub GetCurrentRect (view As View) As Rect
Dim no As NativeObject=view
no =no.RunMethod("layer",Null).RunMethod("presentationLayer",Null).RunMethod("frame",Null)
Dim r As Rect=OBJC.CGRectToRect(no)
Return r
End Sub

You should also update the OBJC module (attached)

Narek

tufanv · Aug 17, 2015

Thank you, I have now updated the .bas an added the code to my project.
Now do i add under timer_tick getcurrentrect(x) . I tried pnlcircle,panelyoun but they did not work

narek adonts said:
At the moment you can use this function to retrieve the actual Rect of a view (event during animation).

B4X:

Sub GetCurrentRect (view As View) As Rect Dim no As NativeObject=view no =no.RunMethod("layer",Null).RunMethod("presentationLayer",Null).RunMethod("frame",Null) Dim r As Rect=OBJC.CGRectToRect(no) Return r End Sub

You should also update the OBJC module (attached)

Narek

narek adonts · Aug 17, 2015

Is there any error?

you should use this way.

B4X:

 getcurrentrect(pnlcircle).Left ' forexemple

' or

dim r as rect= getcurrentrect(pnlcircle)
log(r.Left)

iOS Question Rotating a circle on a circle path

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