Question

我遇到FragmentPagerAdapter问题，我在viewpager中通过FragmentPagerAdapter设置了片段，我必须动态显示viewpager，我有listview数据，我需要在viewpager中显示，当我点击列表视图时，我必须在viewpager中加载准确的位置所以我只设置要在FragmentPagerAdapter中显示的项目的总大小，但问题是，当我通过mPager.setCurrentItem(listposition)选择viewpager位置时，它会显示viewpager的正确位置，但是数据加载在错误的地方，它在viewpager位置加载到下一个fragement，在FragmentPagerAdapter中进行一些跟踪后，我显示instantiateItem方法提前初始化一个片段，就像我设置了viewpager 2的currentitem（来自listview）然后instantiateItem方法初始化0到3个片段，我认为数据加载第3个片段的原因，我用FragmentStatePagerAdapter尝试了很多但是没有任何成功，请帮助我，提前谢谢。

主要活动类（Fragmnetactivity）：

 public class NewsDetail extends FragmentActivity implements OnClickListener {
    public static ViewPager mPager;
    private static int NUM_PAGES;
    private PagerAdapter mPagerAdapter;
    public static ArrayList<Integer> exist_detail = new ArrayList<Integer>();
    public static ArrayList<PageFragment> detailfragment = new ArrayList<PageFragment>();


    mPager = (ViewPager) findViewById(R.id.pager);
    mPagerAdapter = new ScreenSlidePagerAdapter(getSupportFragmentManager());
    mPager.setAdapter(mPagerAdapter);

    NUM_PAGES = topList.size();
    PageFragment fragment = new PageFragment();
    Bundle args = new Bundle();
    args.putInt("page", i);
    fragment.setArguments(args);
    detailfragment.add(fragment);

    mPager.setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {

        @Override
        public void onPageSelected(int arg0) {
                if (PageFragment.getInstance() != null) {
                    Log.d("LOG","PageFragment || "+ PageFragment.getInstance());
                    PageFragment.getInstance().startLoadingNews(
                            MusicList.topMusicList.get(arg0)._id);
                }
            return;
        }

        @Override
        public void onPageScrolled(int arg0, float arg1, int arg2) {}

        @Override
        public void onPageScrollStateChanged(int arg0) {}
    });
    mPagerAdapter.notifyDataSetChanged();

    mPager.setCurrentItem(listposition);// setcurrent item from here , it is selected from list. "listposition" indicate list position click



    private class ScreenSlidePagerAdapter extends FragmentPagerAdapter {

            private FragmentManager mFragmentManager;
            private FragmentTransaction mCurTransaction = null;
            private Fragment mCurrentPrimaryItem = null;
            private static final boolean DEBUG = false;

            public ScreenSlidePagerAdapter(FragmentManager fragmentManager) {
                super(fragmentManager);
                this.mFragmentManager = fragmentManager;
            }

            @Override
            public Fragment getItem(int position) {

                return detailfragment.get(position);
            }

            @Override
            public long getItemId(int position) {
                // TODO Auto-generated method stub
                return super.getItemId(position);
            }

            @Override
            public Object instantiateItem(ViewGroup container, int position) {

                Log.v("LOG", "On InstantiateItem " + position);// it indicate that this method initialize one fragment in advance.

                return super.instantiateItem(container, position);
            }

            public String makeFragmentName(int viewId, long index) {
                return "android:switcher:" + viewId + ":" + index;
            }

            @Override
            public void destroyItem(ViewGroup container, int position, Object object) {
                if (mCurTransaction == null) {
                    mCurTransaction = mFragmentManager.beginTransaction();
                }
                if (DEBUG)
                    Log.e("LOG", "Detaching item #" + position + ": f=" + object
                            + " v=" + ((Fragment) object).getView());
                mCurTransaction.detach((Fragment) object);
            }

            @Override
            public void restoreState(Parcelable state, ClassLoader loader) {
            }

            @Override
            public int getCount() {
                return NUM_PAGES;
            }
        }
        }

PageFragment

       public class PageFragment extends Fragment implements OnClickListener {

            @Override
            public void onCreate(Bundle savedInstanceState) {
                super.onCreate(savedInstanceState);
                mPageNumber = getArguments().getInt(ARG_PAGE);
                mDetailPageFragment = this;
            }

            @Override
            public View onCreateView(LayoutInflater inflater, ViewGroup container,
                    Bundle savedInstanceState) {
                // Inflate the layout containing a title and body text.
                rootView = (ViewGroup) inflater.inflate(R.layout.newsdetail, container,
                        false);
                //init();
                return rootView;
            }
            public void startLoadingNews(String _id) {

                if (NetworkUtil.cheackNetwork(mActivity)) {
                    executeTask(_id);
                } else {
                    showRetryCancelDialog();
                }
             }
            }

Answer 1

我可以在您发布的代码中看到两个问题：

仅在FragmentPagerAdapter.getItem中实例化您的片段。不要实例化它们并将它们保存到某个列表或数组中，让FragmentPagerAdapter为您执行此操作。在FragmentPagerAdapter.instantiateItem中，它检查Fragment是否已创建，如果是，则返回，如果没有，则会调用getItem来创建片段。
不要对您的片段使用Singleton方案，使用构造函数或.newInstance()静态助手创建新片段。

Android Viewpager.setCurrentitem（）和FragmentPagerAdapter instantiateItem（）片段初始化不匹配

1 个答案: