How to find out where the user has touched the screen?

Question

So I am making an android application where I have a set of circles. When the user touches a point in one of the circles I need to calculate a point according to where the user touched.
Somewhat similar to an archer's target.
how do I achieve this?

I have searched about touch interfaces but I haven't been able to figure out how i can do this

score 3 · Accepted Answer · answered Sep 18 '13 at 13:05

3

You should use TouchListener with following code to get to know that whether your touch event occur inside circle or not.

Formula

(x - center_x)^2 + (y - center_y)^2 < radius^2

code

int x = view.getX();  
int y = view.getY();  

if((xTouch - (x + radius)) * (xTouch - (x + radius)) + (yTouch - (y + radius)) * (yTouch - (y + radius)) <= (radius * radius)){
    ...
}

If this satisfies left side equation is less then right side one, your touch event is inside circle else outside circle.

answered Sep 18 '13 at 13:05

Chintan Rathod

25,864
13
83
93

Any ideas how i can get a fixed center for the app? I am planning to add those circles as the background of the app and then calculate accordingly.. or are there any other methods of doing this? – otaku Sep 18 '13 at 13:09
Yes, you can check my answer http://stackoverflow.com/questions/8974088/how-to-create-a-resizable-rectangle-with-user-touch-events-on-android/16359284#16359284. You can create custom circles on screens like that.. Just implement that code and you will get idea how to do that. – Chintan Rathod Sep 18 '13 at 13:14
@Chintan Rathod : I didn't get this answer. I did like this In side onTouch, float x=v.getX(); float y=v.getY(); Toast.makeText(getApplicationContext(), "X= "+x, Toast.LENGTH_SHORT).show(); Toast.makeText(getApplicationContext(), "Y= "+y, Toast.LENGTH_SHORT).show(); But No toast is coming for me... – Aneez Mar 24 '14 at 07:25
@Aneez its simple maths formula to find radios of a point. It will compare two circle whether they are intersect each other or not my friend. :) – Chintan Rathod Mar 24 '14 at 09:02

score 1 · Answer 2 · answered Sep 18 '13 at 12:27

1

Just set onTouchListener and make your logic with event.getX()/getY()

answered Sep 18 '13 at 12:27

Lebedevsd

950
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how do I get the location of then center of my circles from which i can calculate the distance of the touch? – otaku Sep 18 '13 at 12:32
1

some school maths you need to make – Lebedevsd Sep 18 '13 at 12:37

How to find out where the user has touched the screen?

2 Answers2