问题 使用PagerAdapter的IllegalStateException

我有类似的问题，我有一个关于活动A的viewpager然后当用户点击viewpager中的项目时，它将转到具有viewpager的活动B.用户从活动B返回到活动A后，它将抛出异常，如下所示：

java.lang.IllegalStateException: The application's PagerAdapter changed the adapter's contents without calling PagerAdapter#notifyDataSetChanged! Expected adapter item count: 4, found: 0 Pager id: com.gbu.app.templateforbussiness:id/header_view_pager_list Pager class: class android.support.v4.view.ViewPager Problematic adapter: class com.gbu.app.templateforbussiness.adapter.DetailProductPagerAdapter

我认为问题是，viewpager的适配器始终为0的数据内容，因为适配器没有从Activity传递的数据。所以我试着像这个例子一样工作：

DetailProductActivity.class

public class DetailProductActivity extends FragmentActivity {
    private ViewPager product_detail_viewpager;
    private DetailProductPagerAdapter detail_product_adapter;
    private Intent product_detail_intent;
    public static List<Product> detail_product;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_detail_product);
        product_detail_viewpager = (ViewPager) findViewById(R.id.detail_product_viewpager);
        detail_product = HomeActivity.home_product;
    }

    @Override
    protected void onStart() {
        super.onStart();
        product_detail_intent = getIntent();
        startApp(product_detail_intent);
    }

    @Override
    protected void onStop() {
        super.onStop();
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
    }

    private void startApp(Intent data) {
        // TODO Auto-generated method stub
            // pass the Array, List of data to viewpager adapter like this
        detail_product_adapter = new DetailProductPagerAdapter(getSupportFragmentManager(), detail_product); 
        product_detail_viewpager.setAdapter(detail_product_adapter);
        product_detail_viewpager.setCurrentItem(data.getIntExtra("current_item", 0));
    }

}

和viewpager的适配器： DetailProductPagerAdapter.class

public class DetailProductPagerAdapter extends FragmentPagerAdapter {
    private ProductDetailFragment detail_product_fragment;
    private Bundle data;
    private List<Product> detail_product;

    // the data from Activity passed to this adapter        
    public DetailProductPagerAdapter(FragmentManager fm, List<Product> p) {
        super(fm);
        // TODO Auto-generated constructor stub
        detail_product = p;
    }

    // then passing the data again to your fragment class, like this example
    @Override
    public Fragment getItem(int arg0) {
        // TODO Auto-generated method stub
        detail_product_fragment = new ProductDetailFragment(detail_product);
        data = new Bundle();
        data.putInt("current_item", arg0);
        detail_product_fragment.setArguments(data);
        return detail_product_fragment;
    }

    @Override
    public int getCount() {
        // TODO Auto-generated method stub
        return detail_product.size();
    }

    @Override
    public int getItemPosition(Object object) {
        return POSITION_NONE;
    }   

}

和片段类： ProductDetailFragment.class

@SuppressLint("ValidFragment")
public class ProductDetailFragment extends Fragment {
    private RelativeLayout detail_item_header;
    private ImageView detail_item_imv;
    private TextView detail_item_tv_title;
    private WebView detail_item_web_content;
    private DisplayMetrics detail_metrics;
    private List<Product> detail_product;
    private int index_item;

    // the data from adapter pass it to this fragment
    public ProductDetailFragment(List<Product> p) {
        detail_product = p;
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        super.onCreateView(inflater, container, savedInstanceState);
        View view_detail = inflater.inflate(R.layout.item_product_detail_viewpager, container, false);
        detail_metrics = new DisplayMetrics();
        getActivity().getWindowManager().getDefaultDisplay().getMetrics(detail_metrics);
        savedInstanceState = getArguments();
        index_item = savedInstanceState.getInt("current_item");
        detail_item_header = (RelativeLayout) view_detail.findViewById(R.id.item_header_product_viewpager);
        detail_item_imv = (ImageView) detail_item_header.findViewById(R.id.item_imv_product_viewpager);
        detail_item_tv_title = (TextView) detail_item_header.findViewById(R.id.item_tv_title_product_viewpager);
        detail_item_web_content = (WebView) view_detail.findViewById(R.id.item_web_product_viewpager);
        startApp();
        return view_detail;
    }

    private void startApp() {
        // TODO Auto-generated method stub
        detail_item_header.getLayoutParams().height = (int) (detail_metrics.heightPixels * 0.38);
        if (detail_product.get(index_item).getStatus() == 0) {
            new loadImageProduct(detail_item_imv).execute(detail_product.get(index_item).getImage());
        }else {
            detail_item_imv.setImageBitmap(detail_product.get(index_item).getBmp());
        }
        detail_item_tv_title.setText(detail_product.get(index_item).getTitle());
        String web_content_product = "<!DOCTYPE html>"+
                                     "<html>"+
                                     "<body>"+
                                     "<p>Harga : "+detail_product.get(index_item).getPrice()+"</p><br>"+
                                     detail_product.get(index_item).getDetail()+"<br><br>"+
                                     detail_product.get(index_item).getDetail2()+
                                     "</body>"+
                                     "</html>";
        detail_item_web_content.loadDataWithBaseURL("https://www.google.com", web_content_product, "text/html", "UTF-8", null);
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
    }

    private class loadImageProduct extends AsyncTask<String, Integer, Bitmap> {
        private Bitmap b;
        private ImageView vimv;
        private GetImage get_image;

        public loadImageProduct(ImageView v) {
            vimv = v;
        }

        @Override
        protected void onPreExecute() {
            super.onPreExecute();
            b = null;
            get_image = new GetImage();
        }

        @Override
        protected Bitmap doInBackground(String...url) {
            try {
                b = get_image.loadImageFromServer(url[0]);
                if (b != null)
                    return b;
            } catch(OutOfMemoryError e) {

            }
            return b;
        }

        @Override
        protected void onPostExecute(Bitmap result) {
            super.onPostExecute(result);
            if (result != null) {
                detail_product.get(index_item).setBmp(result);
                detail_product.get(index_item).setStatus(1);
                vimv.setImageBitmap(result);
            }
        }
    }

}

现在，之前的Exception将不再显示，并且viewpager正常工作。这个方法尝试使viewpager像listview一样，因为listview将通过适配器传递数据，因此即使数据已经更改，适配器也不会丢失数据内容。我希望这个例子可以帮助你解决问题。干杯。

当我试图覆盖页面适配器的getCount（）时，它发生在我身上

在授权期间，我只显示一页。在授权结束后，我将页面数量更改为3.如果我不调用InvalidatePageAdapter（）一次，它就适合我

@Override
public int getCount() {

    if (mAuthorization_Status == AUTH_STATUS.AUTH_SUCCESS) {

        if (!isRefreshed) {
            isRefreshed = true;
            this.notifyDataSetChanged();
        }

        return NUM_PAGES;

    } else {

        return 1;
        //return NUM_PAGES;

    }

} // END: getCount