android - 如何将 Actionbar 项目与 Viewpager + Fragments 一起使用

Question

我试图弄清楚如何根据正在加载到我的 viewpager 中的 fragment 来实现 Actionbar 项目。我的代码在下面，我只是想找出使用​​ ABS + ViewPager + Fragments 的最佳实践。

主要 Activity

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];
}

fragment 1

 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");   
}

在我的 MainActivity 中，我尝试了以下方法，但无法获得正确的代码。

@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.

这是自动发生的。只需让 fragment 调用 setHasOptionsMenu(true)，然后执行 onCreateOptionsMenu() 和 onOptionsItemSelected()。 Fragment*PagerAdapter 将安排在页面更改后重新填充操作栏，从上一页中删除操作栏项目并从新当前页面引入操作栏项目。

Here is a sample project演示操作栏项目来来去去，因为只有奇数页(对于基于 1 的索引，用户看到的内容)有操作栏项目。