获取ViewPager特定位置的Fragment

ViewPagerUtils.java

import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentStatePagerAdapter;
import android.support.v4.view.ViewPager;

/**
 * Created by Chaojun Wang on 5/6/14.
 */
public class ViewPagerUtils {
  private ViewPagerUtils() {}

  /**
   * Find fragment in certain position of viewpager.
   * 
   * @param fragmentManager
   * @param viewPager
   * @param position
   * @return The Fragment if found or null otherwise.
   */
  public static Fragment findFragment(FragmentManager fragmentManager, ViewPager viewPager,
      int position) {
    return fragmentManager.findFragmentByTag(makeFragmentName(viewPager.getId(), position));
  }

  private static String makeFragmentName(long viewPagerId, int position) {
    return "android:switcher:" + viewPagerId + ":" + position;
  }

  /**
   * Find fragment in certain position of viewpager.
   * 
   * @param adapter {@link android.support.v4.app.FragmentStatePagerAdapter} of this ViewPager
   * @param viewPager
   * @param position
   * @return The Fragment if found or null otherwise.
   */
  public static Object findFragment(FragmentStatePagerAdapter adapter, ViewPager viewPager,
      int position) {
    return adapter.instantiateItem(viewPager, position);
  }
}

可以定义一个BaseFragmentPagerAdapter extends FragmentPagerAdapter
子FragmentPagerAdapter Override getTag方法
BaseFragmentPagerAdapter Override instantiateItem方法，mCurTransaction.add(container.getId(), fragment, getTag(position));

这样子FragmentPagerAdapter可以这样拿Fragment
public Fragment findFragment(FragmentManager fm, String tag) {
return fm.findFragmentByTag(tag);
}