Question

I am trying to implement Tab Navigation, but I want to make sure people that have older versions of Android can still use my application.

The app in mind ATM is fairly simple, I just want to be able to understand how to implement the layout and then I’ll add the missing bits.

Anyhow, I have a Container Activity that extends Fragment Activity (to ensure compatibility), and this Activity creates a TabView using an ActionBar (I believe my problem resides here). The app will try to create three tabs and add them to the ActionBar, and I want to make sure the user can scroll back and forth using lateral navigation.

Here is TabListener I am trying to implement:

public static class TabListener<T extends Fragment> implements ActionBar.TabListener {

    private Fragment mFragment;
    private final Activity mActivity;
    private final String mTag;
    private final Class<T> mClass;

    public TabListener(Activity activity, String tag, Class<T> clz) {
        mActivity = activity;
        mTag = tag;
        mClass = clz;
    }

    public void onTabSelected(Tab tab, FragmentTransaction ft) {
        if (mFragment == null) {
            mFragment = Fragment.instantiate(mActivity, mClass.getName());
            ft.add(android.R.id.content, mFragment, mTag);
        } else {
            ft.attach(mFragment);
        }
    }

    public void onTabUnselected(Tab tab, FragmentTransaction ft) {
        if (mFragment != null) {
            ft.detach(mFragment);
        }
    }

    public void onTabReselected(Tab tab, FragmentTransaction ft) {
    }
}

Here are my imports, because I wanted to make sure I was using the support library:

import android.app.ActionBar;
import android.app.ActionBar.Tab;
import android.app.Activity;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentTransaction;
import android.support.v4.view.ViewPager;
import android.view.Menu;

However, Eclipse is giving me issues with the TabListener methods. It is telling me the following: “The type LayoutContainer.TabListener must implement the inherited abstract method ActionBar.TabListener.onTabSelected(ActionBar.Tab, FragmentTransaction)”

When I select Add unimplemented methods Eclipse basically adds the OnTabSelected OnTabReselected and OnTabUnselected methods, but this time, passing the non-support version of the Fragment (android..app.Fragment) as a parameter.

Any ideas on how to make another implementation of lateral navigation through the support library to ensure compatibility?

Answer 1

actionBar = getActionBar();
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);

actionBar.setDisplayShowHomeEnabled(false);
actionBar.setDisplayShowTitleEnabled(false);

tabA = actionBar.newTab().setText("");
tabB = actionBar.newTab().setText("");

Fragment fragmentA = new AFragmentTab();
Fragment fragmentB = new BFragmentTab();

tabA.setTabListener(new MyTabsListener(fragmentA));
tabB.setTabListener(new MyTabsListener(fragmentB));

actionBar.addTab(tabA);
actionBar.addTab(tabB);

The tab listener is as follows:

protected class MyTabsListener implements ActionBar.TabListener{
    private Fragment fragment;

    public MyTabsListener(Fragment fragment){
        this.fragment = fragment;
    }
    public void onTabSelected(Tab tab, FragmentTransaction ft){
        ft.add(R.id.layout2, fragment, null);
    }
    public void onTabReselected(Tab tab, FragmentTransaction ft) {
    }
    public void onTabUnselected(Tab tab, FragmentTransaction ft) {
        ft.remove(fragment);
    }
}

and then you make a class for each tab:

public class BFragmentTab extends Fragment {

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
    {
        return inflater.inflate(R.layout.login, container, false);
    }
}

But keep in mind that the action bar isn’t supported for android versions below 3.0 . If you want to use it in older versions I suggest you use actionBarSherlock Library.