如何将Actionbar项与Viewpager + Fragments一起使用

Question

Im trying to figure out how to implement Actionbar items based on the Fragment that is being loaded inside my viewpager. My code is below and im just trying to figure out the best practice for working with ABS + ViewPager + Fragments.

MainActivity

public class MainActivity extends SherlockFragmentActivity {
private ViewPager mPager;
private TitlePageIndicator mIndicator;
private MainPagerAdapter mAdapter;
private List<Fragment> mFragments;

private static final String FRAGMENT1 = Fragment1.class.getName();
private static final String FRAGMENT2 = Fragment2.class.getName();
private static final String FRAGMENT3 = SupportFragment.class.getName();

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.a_main);

    // add fragments
    mFragments = new ArrayList<Fragment>();
    mFragments.add(Fragment.instantiate(this, FRAGMENT1));
    mFragments.add(Fragment.instantiate(this, FRAGMENT2));
    mFragments.add(Fragment.instantiate(this, FRAGMENT3));

    // adapter
    mAdapter = new MainPagerAdapter(getSupportFragmentManager(), mFragments);

    // pager
    mPager = (ViewPager) findViewById(R.id.view_pager);
    mPager.setAdapter(mAdapter);

    // indicator
    mIndicator = (TitlePageIndicator) findViewById(R.id.title_indicator);
    mIndicator.setViewPager(mPager);
}
  ...

MainPagerAdapter

public class MainPagerAdapter extends FragmentPagerAdapter {
private List<Fragment> mFragments;
private String[] titles = new String[] {"System", "Community", "Support"};
private int mCount = titles.length;

public MainPagerAdapter(FragmentManager fm, List<Fragment> f) {
    super(fm);
    mFragments = f;
}

@Override
public Fragment getItem(int position) {
    return mFragments.get(position);
}

@Override
public int getCount() {
    return mCount;
}
@Override
public CharSequence getPageTitle(int position) {
    return titles[position];
}

Fragment1

 public class Fragment1 extends SherlockFragment {
WebView web;
static ProgressBar progressBar;

@Override
public View onCreateView(LayoutInflater inf, ViewGroup grp, Bundle icicle) {
    View v = inf.inflate(R.layout.activity_main, grp, false);
    web = (WebView) v.findViewById(R.id.webView);
    progressBar = (ProgressBar) v.findViewById(R.id.progressBar1);
    return v;
}
@Override
public void onActivityCreated(Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);
    web.setWebViewClient(new SpecialWebView(progressBar));
    web.setWebChromeClient(new SpecialWebChromeClient(progressBar));
    // Progress Bar - End

    WebSettings websettings = web.getSettings();
    websettings.setBuiltInZoomControls(false);
    web.setBackgroundColor(Color.parseColor("#f2f2f2"));
    websettings.setUseWideViewPort(true);
    websettings.setJavaScriptEnabled(true);
    websettings.setAllowFileAccess(true);
    websettings.setDomStorageEnabled(true);
    websettings.setLoadWithOverviewMode(true);
    websettings.setSavePassword(true);
    web.loadUrl("http://www.google.com");   
}

Inside my MainActivity i've tried the following and cant get the code right.

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    MenuInflater Inflater = getSupportMenuInflater();
    Inflater.inflate(R.menu.menu, menu);
    return true;

}
@Override
public boolean onOptionsItemSelected(MenuItem Item) {
    final int current = ((ViewPager) mFragments).getCurrentItem();
    String currentId = current == 0 ? FRAGMENT1: (current == 1 ? FRAGMENT2: FRAGMENT3);
    //WebView web = (WebView) findViewById(currentId);
    switch (Item.getItemId()) {
    case R.id.menu_back:
    //  web.goBack();
        return true;
    case R.id.menu_forward:
        //web.goForward();
        return true;
    case R.id.menu_refresh:
        //web.reload();
        return true;
    }
    return super.onOptionsItemSelected(Item);
}

Answer 1

Im trying to figure out how to implement Actionbar items based on the Fragment that is being loaded inside my viewpager.

That happens automatically. Just have the fragments call setHasOptionsMenu(true) , then implement onCreateOptionsMenu() and onOptionsItemSelected() . The Fragment*PagerAdapter will arrange to repopulate the action bar after a page change, to remove action bar items from the previous page and introduce action bar items from the newly-current page.

Here is a sample project demonstrating having action bar items come and go, as only odd-numbered pages (for 1-based indexes, what the user sees) have action bar items.