我有一个BlogActivity有7个标签。我创建了一个BlogCategoryFragment，我想在用户滚动/切换标签时重复使用或回收。
例如，当用户切换到“新闻”选项卡时，BlogCategoryFragment将用于显示新闻项，当用户切换到另一个选项卡时，BlogCategoryFragment将获取不同的文章。
See the Tabs
在不同标签中提取的所有项目共享一个BlogModel模型
问题是：
1.第一个标签中的数据无法加载
2.其他选项卡可以加载数据，但单个项目会多次出现在recycleView中。
3.滚动一次会停止应用程序。
这是我的代码：
的 BlogActivity
public class BlogActivity extends AppCompatActivity {
ViewPager mViewPager;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_blog);
//viewpager initialization
BlogCategoryStatePagerAdapter blogCategoryStatePagerAdapter;
blogCategoryStatePagerAdapter = new BlogCategoryStatePagerAdapter(getSupportFragmentManager());
mViewPager = (ViewPager) findViewById(R.id.blog_container);
mViewPager.setOffscreenPageLimit(1);
mViewPager.setAdapter(blogCategoryStatePagerAdapter);
mViewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
@Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
}
@Override
public void onPageSelected(int position) {
mViewPager.getAdapter().notifyDataSetChanged();
}
@Override
public void onPageScrollStateChanged(int state) {
}
});
TabLayout tabLayout = (TabLayout) findViewById(R.id.blog_tabs);
tabLayout.setupWithViewPager(mViewPager);
//end viewpager
}
/**
* A {@link FragmentPagerAdapter} that returns a fragment corresponding to
* one of the sections/tabs/pages.
*/
public class BlogCategoryStatePagerAdapter extends FragmentPagerAdapter {
private int NUM_ITEMS = 7;
public BlogCategoryStatePagerAdapter(FragmentManager fm) {
super(fm);
}
@Override
public Fragment getItem(int position) {
switch (position) {
case 0:
return BlogCategoryFragment.addBlogCategory("1","yy");
//break;
case 1:
return BlogCategoryFragment.addBlogCategory("2","tt");
//break;
.........
case 6:
return BlogCategoryFragment.addBlogCategory("7","gg");
//break;
default:
return null;
}
//return fragment;
}
@Override
public int getItemPosition(Object object) {
return POSITION_NONE;
}
@Override
public int getCount() {
// Show 7 total pages.
return NUM_ITEMS;
}
@Override
public CharSequence getPageTitle(int position) {
switch (position) {
case 0:
return getString(R.string.title_general_category);
case 1:
return getString(R.string.title_county_category);
......
case 6:
return getString(R.string.title_lifestyle_category);
}
return null;
}
}
}
BlogCategoryFragment
public class BlogCategoryFragment extends Fragment {
boolean dataLoaded = false;
public static RecyclerView blogRecycleView;
public static BlogArticleAdapter blogArticleAdapter;
public static List<BlogModel> blogModelList = new ArrayList<>();
private SwipeRefreshLayout swipeRefreshLayout;
private BlogModel blogModel;
private Handler mHandler;
public BlogCategoryFragment() {
// Required empty public constructor
}
public static BlogCategoryFragment addBlogCategory(String categoryId, String categoryName) {
BlogCategoryFragment fragment = new BlogCategoryFragment();
CATEGORY_ID = categoryId;
CATEGORY_NAME = categoryName;
return fragment;
}
@Override
public void setUserVisibleHint(boolean isVisibleToUser) {
super.setUserVisibleHint(isVisibleToUser);
if (isVisibleToUser && !dataLoaded){
//loadBlogPosts;
loadDataDirect();
dataLoaded = true;
}
}
@Override
public void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View listView = inflater.inflate(R.layout.fragment_blog_category,container,false);
blogRecycleView = (RecyclerView) listView.findViewById(R.id.blogRecyclerView);
blogArticleAdapter = new BlogArticleAdapter(blogModelList, getActivity());
mHandler = new Handler(Looper.getMainLooper());
//set the layout manager
blogRecycleView.setLayoutManager(new LinearLayoutManager(getContext()));
blogRecycleView.setAdapter(blogArticleAdapter);
//blogRecycleView.stopScroll();
//setup swipe to refresh
swipeRefreshLayout = (SwipeRefreshLayout)listView.findViewById(R.id.refreshBlogLayout);
swipeRefreshLayout.setColorSchemeResources(R.color.colorPrimary,
android.R.color.holo_green_dark
,android.R.color.holo_orange_dark ,android.R.color.holo_blue_dark);
swipeRefreshLayout.setOnRefreshListener(new SwipeRefreshLayout.OnRefreshListener() {
@Override
public void onRefresh() {
//clear list
blogModelList.clear();
loadDataDirect();
//new LoadBlogPost(BlogCategoryFragment.this).execute(AppConstants.API_BLOG_URL);
//reload from the internet
}
});
swipeRefreshLayout.post(new Runnable() {
@Override
public void run() {
swipeRefreshLayout.setRefreshing(true);
if (new AppHelper(getActivity()).isNetworkAvailable()) {
//loadBlogPosts();
loadDataDirect();
blogModelList.clear();
//new LoadBlogPost(BlogCategoryFragment.this).execute(AppConstants.API_BLOG_URL);
} else {
Toast.makeText(getContext(), "Error internet connection", Toast.LENGTH_SHORT).show();
}
}
});
//end setup swipe to refresh
//loadBlogPosts();
loadDataDirect();
//new LoadBlogPost(BlogCategoryFragment.this).execute(AppConstants.API_BLOG_URL);
return listView;
}
private void loadDataDirect(){
// should be a singleton
OkHttpClient client = new OkHttpClient();
Request request = new Request.Builder()
.url(AppConstants.API_BLOG_URL)
.build();
client.newCall(request).enqueue(new Callback() {
@Override
public void onFailure(Call call, IOException e) {
}
@Override
public void onResponse(Call call, Response response) throws IOException {
try {
String responseData = response.body().string();
JSONObject jObject = new JSONObject(responseData);
JSONArray blogArticlesArray = jObject.getJSONArray("blog_article");
blogModelList.clear();
Log.d("BLOG", blogArticlesArray.toString());
//create an empty Blogmodel object
//loop though the data
for (int i = 0; i < blogArticlesArray.length(); i++) {
JSONObject blogItem = blogArticlesArray.getJSONObject(i);
blogModel = new BlogModel(
blogItem.getInt("id"),
blogItem.getString("article_title"),
blogItem.getString("images_url"),
blogItem.getString("created_at")
);
blogModelList.add(blogModel);
//update the BlogModel List
mHandler.post(new Runnable() {
@Override
public void run() {
blogArticleAdapter.notifyDataSetChanged();
}
});
}
//end loop
} catch (JSONException e) {
e.printStackTrace();
}
}
});
}
哪里可能是问题？