title: How to combine tabs and action bar navigation in Android?
body: <p>I'm coming from the iOS world and need to port an app with the typical tabbar/navigation pattern to Android. The UI design is the client's decision, so I can't change it (I'd still like to hear from you if you think it's appropriate or not for Android).</p>
  
  <p>So the idea of the app is the following:
  3 Tabs are always shown on the bottom of the screen. Inside each tab there can be a hierarchy of screens, with the title and up-button showing in the action bar on the top.
  How do I implement this in Android? Am I correct in that the tabs need to be a fragment which need to be implemented in every single activity? How should the hardware back button behave? Say if I switch to a certain tab and then press the back button, should the tab change back or should it mirror the up-button's functionality?</p>
  
  <p>As you can see I'm struggling with all these basic concepts and I'm very thankful for any tip that can help me to implement this navigation structure.</p>
  
  <h2>Edit:</h2>
  
  <p>Thanks to the competent answer of CommonsWare and looking deeper into it, I realise that I really should push the client to use an UI that's more suitable for the platform. (Also, I know I should use an Android device for some time to get used to the concepts, but I can't change that for now. So I'm sorry for these newbie questions).</p>
  
  <p>The thing is, the app existed before as a web container app with an ugly jquery mobile UI with the above described UI elements. The idea is now to make the app navigation native with native animations, while keeping the content views in html/css/js inside webviews. So while it's possible to adapt each platform's UI principles, I cannot change the general structure of the app, which is: 3 different main entry points, and in each of them the content is navigated hierarchically. I've implemented that in iOS with a tabbar and navigation controllers which works great. The challenge is now to implement it in Android. To reassure that I'm on the right path and understood the points of CommonsWare correctly as well as to maybe receive more tips, I'm writing down what my thoughts on the steps involved:</p>
  
  <p>As CommonsWare suggested, I could replace the tab idea with action buttons in the action bar, which will work well as there are only 3 of it. So it's appropriate to use action buttons for navigation? There will be an additional button for switching the language (Yes I know, usually I should pick the current language of the system, but in this particular app language switching is important and the user will switch it several times while using the app). To separate the navigation action buttons from the language switcher, which works on the current content and is a bit less important, I put the language switcher under the so-called "action overflow" (the 3 dots on the upper right corner).</p>
  
  <p>Now there is an action bar button for each "tab", so far so good. But is there a way the user can tell on which "tab" he is? Or should I only show two action bar buttons at any given time, hiding the one he's currently "in"?</p>
  
  <p>Each of these action bar buttons starts a new activity (with it's own action bar, right?). Inside such activity, the user can navigate hierarchically and back using the up button or back button. He can also use the hardware back button to go back to the last "tab"; would this be appropriate?
  Every screen in the navigation hierarchy is a separate activity with a title and a webview.</p>
  
  <p>In the end, to make the whole app compatible back with gingerbread, I would use the actionbarsherlock library, right?</p>