问题:

I want to implement something similar to android seek bar.But not in a linear fashion,in an arc shape. is it possible to customize the seek bar in an arc shape?

回答1:

You can't make SeekBar to draw its thumb any other way than offset horizontally.

The code that actually draws thumb is in AbsSeekBar.onDraw, and there it's seen it's just horizontal offset. You may however make your own widget extending ProgressBar, which would draw thumb whatever way is needed (in arc). But you'll also need to make response to touches to translate it to linear range that ProgressBar expects.

回答2:

You can change the style of seekbar in your own themes, (have a look at android:style/Widget.SeekBar), but it could be hard to make it like a rainbow.
Try to read the source code of ProgressBar and write your own base on your requirements.

回答3:

I thought you might be able to achieve the effect with an XML drawable like the LevelList, though you would probably have to have lots of images to achieve the effect http://developer.android.com/guide/topics/resources/drawable-resource.html#LevelList