android - 如何将json数据加载到android中的 fragment 中

Question

我想在我的 Activity 中显示 3 个 fragments 并在任何 fragments 中从 json 加载数据!我想将每个 json 数据显示为一个 fragment ，但在我的应用程序中加载 3 个 fragments json 数据首先进入应用程序。
例如:当第一次进入应用程序时加载所有 fragment 数据，但我想在显示这个 fragment 时加载数据(滑动那个 fragment ).
fragment 1 代码:

public class free_fragment extends Fragment {

    private RecyclerView mRecyclerView;
    private free_recycler_adapter mAdapter;
    private RecyclerView.LayoutManager mLayoutManager;
    private List<DataModel> dataModels = new ArrayList<DataModel>();

    private Context context;

    @Override
    public View onCreateView(LayoutInflater inflater,
                             ViewGroup container, Bundle savedInstanceState) {

        View view = inflater.inflate(R.layout.fragment_free_layout, container, false);

        context = getContext();

        LoadData();

        ///----- RecyclerView -----
        mRecyclerView = (RecyclerView) view.findViewById(R.id.pdf_RecyclerView);
        mRecyclerView.setHasFixedSize(true);
        mRecyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));
        mAdapter = new free_recycler_adapter(context, dataModels);
        mRecyclerView.setAdapter(mAdapter);


        return view;
    }

    @Subscribe
    public void onEvent(MyEvent event) {
        List<DataModel> dataModels = event.getInfoModels();

        if (event.fragmentTag.equals("forfragment1")) {
            mAdapter.add(dataModels);
            mAdapter.notifyDataSetChanged();
        }
    }

    private void LoadData() {
        freeDataInfo dataInfo = new freeDataInfo();
        // here getMainDataInfo() should return the server response
        dataInfo.getFreeDataInfo(context);
    }

    @Override
    public void onResume() {
        super.onResume();
        EventBus.getDefault().register(this);
    }

    @Override
    public void onPause() {
        EventBus.getDefault().unregister(this);
        super.onPause();
    }
}

fragment 1 AsyncTask 代码:

public class freeDataInfo {
    private Context mContext;
    private String ServerAddress = freeServer_IP.getFreeIP();

    public void getFreeDataInfo(Context context) {
        mContext = context;
        new getInfo().execute(ServerAddress + "limit=10");
    }

    private class getInfo extends AsyncTask<String, Void, String> {
        EventBus bus = EventBus.getDefault();
        private String ou_response;
        private List<DataModel> infoModels = new ArrayList<>();
        private ProgressDialog dialog;

        @Override
        protected void onPreExecute() {
            //CustomProcessDialog.createAndShow(mContext);

            dialog = new ProgressDialog(mContext);
            this.dialog.setMessage("شکیبا باشید...");
            this.dialog.show();
        }

        @Override
        protected String doInBackground(String... params) {
            OkHttpClient client = new OkHttpClient();

            //String url = (String) params[0];
            Request request = new Request.Builder()
                    .url(ServerAddress + "limit=10")
                    .cacheControl(CacheControl.FORCE_NETWORK)
                    .build();

            Response response;
            try {
                response = client.newCall(request).execute();
                ou_response = response.body().string();
                response.body().close();
                if (ou_response != null) {
                    try {
                        JSONObject postObj = new JSONObject(ou_response);
                        JSONArray postsArray = postObj.optJSONArray("result");

                        for (int i = 0; i <= postsArray.length(); i++) {
                            JSONObject postObject = (JSONObject) postsArray.get(i);

                            int id = postObject.getInt("id");
                            Log.d("id", String.valueOf(id));
                            String title = postObject.getString("title");
                            String description = postObject.getString("description");
                            String image = postObject.getString("image");
                            String category = postObject.getString("categoryName");
                            String date = postObject.getString("publishDate");

                            Log.d("Data", "Post ID: " + id);
                            Log.d("Data", "Post title: " + title);
                            Log.d("Data", "Post image: " + image);
                            Log.d("Data", "---------------------------------");

                            //Use the title and id as per your requirement
                            infoModels.add(new DataModel(id, title, description, category, date, image));
                        }
                    } catch (JSONException e) {
                        e.printStackTrace();
                        Log.e("error", String.valueOf(e));
                    }
                }
            } catch (IOException e) {
                e.printStackTrace();
                Log.e("error2", String.valueOf(e));
            }
            return ou_response;
        }

        @Override
        protected void onPostExecute(String result) {
            //CustomProcessDialog.dissmis();

            //Stop Progress
            if (dialog.isShowing()) {
                dialog.dismiss();
            }

            if (result != null) {
                bus.post(new MyEvent("forfragment1", infoModels));
            } else {
                Toast.makeText(mContext, "Empty", Toast.LENGTH_SHORT).show();
            }
        }
    }
}

fragment 2 代码:

public class paid_fragment extends Fragment {

    private RecyclerView mRecyclerView;
    private paid_recycler_adapter mAdapter;
    private RecyclerView.LayoutManager mLayoutManager;
    private List<DataModel> dataModels = new ArrayList<DataModel>();

    private Context context;

    @Override
    public View onCreateView(LayoutInflater inflater,
                             ViewGroup container, Bundle savedInstanceState) {

        View view = inflater.inflate(R.layout.fragment_paid_layout, container, false);

        context = getContext();

/*        if (!EventBus.getDefault().isRegistered(this)) {
            EventBus.getDefault().register(this);
        }*/

        LoadData();

        ///----- RecyclerView -----
        mRecyclerView = (RecyclerView) view.findViewById(R.id.voice_RecyclerView);
        mRecyclerView.setHasFixedSize(true);
        mRecyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));
        mAdapter = new paid_recycler_adapter(context, dataModels);
        mRecyclerView.setAdapter(mAdapter);

        return view;
    }

    @Subscribe
    public void onEvent(MyEvent event) {
        List<DataModel> dataModels = event.getInfoModels();
/*        if (dataModels.size() > 0) {
            dataModels.remove(dataModels.size() - 1);
            mAdapter.notifyItemRemoved(dataModels.size());
            //mAdapter.setLoaded();
        }*/
        if (event.fragmentTag.equals("forfragment2")) {
            mAdapter.add(dataModels);
            mAdapter.notifyDataSetChanged();
        }
    }

    private void LoadData() {
        paidDataInfo dataInfo = new paidDataInfo();
        // here getMainDataInfo() should return the server response
        dataInfo.getPaidDataInfo(context);
    }

    @Override
    public void onResume() {
        super.onResume();
        EventBus.getDefault().register(this);
    }

    @Override
    public void onPause() {
        EventBus.getDefault().unregister(this);
        super.onPause();
    }
}

Fragment 2 AsyncTask代码:

public class paidDataInfo {
    private Context mContext;
    private String ServerAddress = paidServer_IP.getPaidIP();

    public void getPaidDataInfo(Context context) {
        mContext = context;
        new getInfo().execute(ServerAddress + "limit=10");
    }

    private class getInfo extends AsyncTask<String, Void, String> {
        EventBus bus = EventBus.getDefault();
        private String ou_response;
        private List<DataModel> infoModels = new ArrayList<>();
        private ProgressDialog dialog;

        @Override
        protected void onPreExecute() {
            //CustomProcessDialog.createAndShow(mContext);
            //infoModels = new ArrayList<>();

            // Initiate Progress
            dialog = new ProgressDialog(mContext);
            this.dialog.setMessage("شکیبا باشید...");
            this.dialog.show();

            infoModels.clear();
        }

        @Override
        protected String doInBackground(String... params) {
            OkHttpClient client = new OkHttpClient();

            //String url = (String) params[0];
            Request request = new Request.Builder()
                    .url(ServerAddress + "limit=10")
                    .cacheControl(CacheControl.FORCE_NETWORK)
                    .build();

            Response response;
            try {
                response = client.newCall(request).execute();
                ou_response = response.body().string();
                response.body().close();
                if (ou_response != null) {
                    try {
                        JSONObject postObj = new JSONObject(ou_response);
                        JSONArray postsArray = postObj.optJSONArray("result");
                        infoModels = new ArrayList<>();

                        for (int i = 0; i <= postsArray.length(); i++) {
                            JSONObject postObject = (JSONObject) postsArray.get(i);

                            int id = postObject.getInt("id");
                            Log.d("id", String.valueOf(id));
                            String title = postObject.getString("title");
                            String description = postObject.getString("full_description");
                            String image = postObject.getString("image");
                            String category = postObject.getString("categoryName");
                            String date = postObject.getString("publishDate");

                            Log.d("Data", "Post ID: " + id);
                            Log.d("Data", "Post title: " + title);
                            Log.d("Data", "Post Desc: " + description);
                            Log.d("Data", "Post image: " + image);
                            Log.d("Data", "---------------------------------");

                            //Use the title and id as per your requirement
                            infoModels.add(new DataModel(id, title, description, category, date, image));
                        }
                    } catch (JSONException e) {
                        e.printStackTrace();
                        Log.e("error", String.valueOf(e));
                    }
                }
            } catch (IOException e) {
                e.printStackTrace();
                Log.e("error2", String.valueOf(e));
            }
            return ou_response;
        }

        @Override
        protected void onPostExecute(String result) {
            //Stop Progress
            if (dialog.isShowing()) {
                dialog.dismiss();
            }
            //CustomProcessDialog.dissmis();
            if (result != null) {
                bus.post(new MyEvent("forfragment2", infoModels));
            } else {
                Toast.makeText(mContext, "Empty", Toast.LENGTH_SHORT).show();
            }
        }
    }
}

MainActivity 代码:

public class Main_Page extends AppCompatActivity {

    private CollapsingToolbarLayout mCollapsingToolbarLayout;
    private Toolbar toolbar;
    private TabLayout tabLayout;
    private ViewPager viewPager;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main__page);

        mCollapsingToolbarLayout = (CollapsingToolbarLayout) findViewById(R.id.collapsing_toolbar_layout);
        //mCollapsingToolbarLayout.setTitle(getResources().getString(R.string.app_name));

        toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        //getSupportActionBar().setDisplayHomeAsUpEnabled(true);

        viewPager = (ViewPager) findViewById(R.id.viewpager);
        setupViewPager(viewPager);

        tabLayout = (TabLayout) findViewById(R.id.tabs);
        tabLayout.setupWithViewPager(viewPager);
        setupTabIcons();
    }

    /**
     * Adding custom view to tab
     */
    private void setupTabIcons() {

        TextView tabOne = (TextView) LayoutInflater.from(this).inflate(R.layout.custom_tab, null);
        tabOne.setText(R.string.free_fragment_title);
        tabOne.setCompoundDrawablesWithIntrinsicBounds(0, R.drawable.ic_download_image, 0, 0);
        tabLayout.getTabAt(0).setCustomView(tabOne);

        TextView tabTwo = (TextView) LayoutInflater.from(this).inflate(R.layout.custom_tab, null);
        tabTwo.setText(R.string.paid_fragment_title);
        tabTwo.setCompoundDrawablesWithIntrinsicBounds(0, R.drawable.ic_paid_download_image, 0, 0);
        tabLayout.getTabAt(1).setCustomView(tabTwo);

        TextView tabThree = (TextView) LayoutInflater.from(this).inflate(R.layout.custom_tab, null);
        tabThree.setText(R.string.pdf_fragment_title);
        tabThree.setCompoundDrawablesWithIntrinsicBounds(0, R.drawable.ic_pdf_icon, 0, 0);
        tabLayout.getTabAt(2).setCustomView(tabThree);
    }

    /**
     * Adding fragments to ViewPager
     * @param viewPager
     */
    private void setupViewPager(ViewPager viewPager) {
        ViewPagerAdapter adapter = new ViewPagerAdapter(getSupportFragmentManager());
        adapter.addFrag(new free_fragment(), "رایگان ها");
        adapter.addFrag(new paid_fragment(), "پرداختی ها");
        adapter.addFrag(new pdf_fragment(), "مقالات");
        viewPager.setAdapter(adapter);
    }

    class ViewPagerAdapter extends FragmentPagerAdapter {
        private final List<Fragment> mFragmentList = new ArrayList<>();
        private final List<String> mFragmentTitleList = new ArrayList<>();

        public ViewPagerAdapter(FragmentManager manager) {
            super(manager);
        }

        @Override
        public Fragment getItem(int position) {
            return mFragmentList.get(position);
        }

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

        public void addFrag(Fragment fragment, String title) {
            mFragmentList.add(fragment);
            mFragmentTitleList.add(title);
        }

        @Override
        public CharSequence getPageTitle(int position) {
            return mFragmentTitleList.get(position);
        }
    }

我该如何解决这个问题并加载 fragment 数据只显示该 fragment ？谢谢大家<3

Answer 1

当 fragment 对用户可见时，会调用一个回调方法。您可以在此方法中触发 loadData()。有一个 bool 值告诉你数据是否已经被获取。请引用以下代码行:

在您的 fragment 代码中添加以下方法。

@Override 
 public void setUserVisibleHint(boolean isVisibleToUser) { 
    mIsVisibleToUser = isVisibleToUser; 
    if (isVisibleToUser && !isDataFetched && getContext() != null) { 
    context = getContext(); 
    LoadData(); //Remove this call from onCreateView 
    }  
}

在 onEvent 方法中进行以下更改。

@Subscribe
public void onEvent(MyEvent event) {
    List<DataModel> dataModels = event.getInfoModels();

    if (event.fragmentTag.equals("forfragment1")) {
        mAdapter.add(dataModels);
        isDataFetched = true;
        mAdapter.notifyDataSetChanged();
    }
}

在 fragment 代码中添加实例变量。

private boolean isDataFetched;
private boolean mIsVisibleToUser;

最后修改OnCreateView()

   if(mIsVisibleToUser)
       LoadData();

Make sure you do these changes for both the fragments.