Summary:
The default itemPositioning is `automatic` (referred to `auto` in this pull request) - you can check its behaviour in the docs attached.
Sometimes that value has to be modified to have more predictable appearance as described in #4136.
Closes https://github.com/facebook/react-native/pull/7217
Differential Revision: D3220958
Pulled By: mkonicek
fbshipit-source-id: d4bf648b16e71825cd31c06d6b6396479767d19f
Summary:
Hi,
This PR Solves this issue #3083.
This PR solves the problem of default color on TabBar being always grey. Which looks great if the barTintColor is unchanged. However if we set the barTintColor to something else (like blue in example) text and icons become quite unreadable.
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Commit (c206417) - Enable setting color of unselected tabs
Solves this issue with a prop (unselectedTintColor) on TabBarIOS to which you just pass a color like you can for barTintColor and tintColor.
This leaves us with a result that is on second picture. Notice the color of text on tabs.

Or change it to yellow for demonstrating purposes

If you don't want to use this mechanism then for now it is still possible to declare the property as a BOOL instead and use the old mechanism (this approach is now deprecated however, and may eventually be removed altogether).
Summary:
To be on par with NavigatorIOS, I added the translucent property to TabBarIOS.
Usage:
```
<TabBarIOS
translucent={false} // default is true
/>
```
Closes https://github.com/facebook/react-native/pull/1937
Github Author: Jean Regisser <jean.regisser@gmail.com>
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