How can I create round volume control in android?

Question

I need to create round volume control, which should looks like this sample:

http://dmonzon.com/2011/04/16/free-tabletphone-user-interface-professional-set-v-7/

Are there any tutorials or ideas which way is better for things like this?

Answer 1

One easy way is to use a custom view:

• Create a custom view
• Draw the button in the custom view
• Use onTouchEvent
• In on MotionEvent.ACTION_MOVE call invalidate();
• In onDraw calulate the angle between your finger and the centre of the button using atan2() function
• Then use canvas.rotate to make the button follow the finger.

Some examples which may help: Simple custom view and how to set the initial data (e.g. volume): View Inflation and custom views

Rotate bitmap: Android: How to rotate a moving animated sprite based on the coordinates of its destination

onTouchEvent and invalidate: Make certain area of bitmap transparent on touch

How will the custom view comunicate back the volume? If your activity has a public static volume variable then the custom view can set a volume by calling MyActivity.volume = (100/360)*angle, or better your activity could have a public static method setVolume(volume){...} which then can perform some code when volume changed - Within the volume button custom view call MyActivity.setVolume(volume);