java - 如何获取 FragmentPagerAdapter 中的当前位置？

Question

我有一个扩展 FragmentPagerAdapter 并利用 ICS 样式 actionBar 的适配器。此操作栏包含从当前选定页面获取输入的操作。

具体来说，我在操作栏中有一个屏幕截图图标，它获取当前页面的 url 并显示来自该 url 的任何屏幕截图。但是，我不知道如何检索当前选定的页面。

我怎样才能实现类似

的东西

    public int getActivePage() {
       return position;

我仍在研究 viewpager 的实现，所以我的代码仍然严重依赖于示例，所以请忽略这些乱七八糟的东西 :P

下面标记了问题区域。

public class ListFragmentViewPagerActivity extends FragmentActivity {
ArrayList<String> URLS;
ArrayList<String> TITLES;
BroadcastReceiver receiver;
String threadTitle = null;
public static String threadUrl = null;
String type = null;
String threadAuthor = null;
String ident = null;
boolean isFav = false;
String author = null;

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.thread_view);

    Bundle extras = getIntent().getExtras();
    threadTitle = extras.getString("title");
    threadUrl = extras.getString("url");
    type = extras.getString("type");
    ident = extras.getString("ident");
    author = extras.getString("author");
    try {
        URLS = extras.getStringArrayList("urls");
        TITLES = extras.getStringArrayList("titles");
    } catch (Exception e) {
        URLS = null;
    }        

    final FDBAdapter db = new FDBAdapter(this);
    db.open();
    Cursor c = db.getAllFavs();
    if (c.getCount()>0) {
        if (c.getString(2).equals(threadTitle)) {
            isFav = true;
        }
            try {
                while (c.moveToNext()) {
                    Log.d("FAVS", c.getString(2));
                    if (c.getString(2).equals(threadTitle)) {
                        isFav = true;
                    }
                }
            } catch (Exception ep) {
                ep.printStackTrace();
            }
    }
    c.close();
    db.close();

    ViewPager pager = (ViewPager) findViewById(android.R.id.list);
    pager.setAdapter(new ExamplePagerAdapter(getSupportFragmentManager()));
    TitlePageIndicator indicator = (TitlePageIndicator)findViewById( R.id.indicator );
    indicator.setViewPager(pager);

    receiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            String action = intent.getAction();
            if (DownloadManager.ACTION_DOWNLOAD_COMPLETE.equals(action)) {
                long downloadId = intent.getLongExtra(
                        DownloadManager.EXTRA_DOWNLOAD_ID, 0);

                String ns = Context.NOTIFICATION_SERVICE;
                NotificationManager mNotificationManager = (NotificationManager) context.getSystemService(ns);

                int icon = R.drawable.ic_launcher;        // icon from resources
                CharSequence tickerText = "Download ready!";              // ticker-text
                long when = System.currentTimeMillis();         // notification time
                CharSequence contentTitle = "OMG";  // expanded message title
                CharSequence contentText = "Your download is finished!";      // expanded message text

                Intent notificationIntent = new Intent(context, ExampleListFragment.class);

                PendingIntent contentIntent = PendingIntent.getActivity(context, 0, notificationIntent, 0);

                Notification notification = new Notification(icon, tickerText, when);
                notification.setLatestEventInfo(context, contentTitle, contentText, contentIntent);
                notification.defaults |= Notification.DEFAULT_VIBRATE;
                notification.flags |= Notification.FLAG_AUTO_CANCEL;
                final int HELLO_ID = 1;

                mNotificationManager.notify(HELLO_ID, notification);
            }
        }
};

registerReceiver(receiver, new IntentFilter(
        DownloadManager.ACTION_DOWNLOAD_COMPLETE));

}

public class ExamplePagerAdapter extends FragmentPagerAdapter implements TitleProvider{

    public ExamplePagerAdapter(FragmentManager fm) {
        super(fm);
    }

    @Override
    public int getCount() {
        return URLS.size();
    }

    @Override
    public Fragment getItem(int position) {
        Fragment fragment = new ExampleListFragment();

        // set arguments here, if required
        Bundle args = new Bundle();
        args.putString("url", URLS.get(position));
        fragment.setArguments(args);

        return fragment;
    }

    @Override
    public String getTitle(int pos) {
        return TITLES.get(pos);
    }

}

public boolean onCreateOptionsMenu(Menu menu) {
    MenuInflater menuinflate = new MenuInflater(this);
    menuinflate.inflate(R.menu.thread_menu, menu);
    if (type.equals("xda")) {
        menu.removeItem(R.id.ss_view);
    }
    if (isFav) {
        menu.getItem(2).setIcon(R.drawable.fav_ab);
    }
    return true;        
}   

@Override
public boolean onOptionsItemSelected(MenuItem item) {

    switch (item.getItemId()) {
        case android.R.id.home:
            Intent intent = new Intent(this, MainActivity.class);
            intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
            startActivity(intent);
        break;
        case R.id.ss_view:
            Intent ssi = new Intent(this, SSActivity.class);
            ssi.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
            Bundle b = new Bundle();

//I need to get the position of the currently active page here so that I can retrieve the //corresponding values for the title and url.
                b.putString("title", threadTitle);
                b.putString("url", threadUrl);
                ssi.putExtras(b);
                startActivity(ssi);
            break;
            case R.id.restart:
            break;
            case R.id.fav_ab:
                threadUrl = new String(threadUrl.replaceAll("http://", ""));
                FDBAdapter fdb = new FDBAdapter(this);
                fdb.open();             
                if (isFav) {
                    Cursor c = fdb.getAllUrls();
                      while (c.moveToNext()) {
                          String id = c.getString(c.getColumnIndex("_id"));
                          int rowId = Integer.parseInt(id);
                          if(c.getString(c.getColumnIndex("url")).equals(threadUrl)) {
                              if (fdb.deleteUrl(rowId)) {
                                  Log.d("THREAD", "SUCCESS");
                              } else {
                                  Log.d("THREAD", "FAILED");
                              }
                          }
                    }
                    c.close();
                    item.setIcon(R.drawable.fav_ab_off);
                    isFav = false;
                } else {
                    fdb.insertFav(threadUrl, threadTitle, ident, type, author, "thread");
                    item.setIcon(R.drawable.fav_ab);
                    isFav = true;
                }
                fdb.close();
            default:
                return super.onOptionsItemSelected(item);
        }
        return false;
    }

    @Override
    public void onStop() {
        super.onStop();
        unregisterReceiver(receiver);       
    }

    @Override
    public void onStart() {
        super.onStart();
        registerReceiver(receiver, new IntentFilter(
                DownloadManager.ACTION_DOWNLOAD_COMPLETE));
    }

}

这是我所说的当前选定页面的意思。

Answer 1

我相信您正在寻找的是 onPageChangedListener()。此方法属于 TitlePageIndicator。像...

indicator.setOnPageChangedListener(new OnPageChangedListener() {
// Implement unimplemented methods...
});