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我想为我的学校制作Android应用程序。它应显示教师和菜单中的缺席，但该菜单不显示任何内容。它没有给出例外或我可以使用的任何东西。我使用JSON数据从网址获取数据。不幸的是，由于个人原因，我无法给你网址。Android RecyclerView不显示任何东西
不幸的是，它看起来是这样的。
我已经研究很多网页试图解决自己的问题，但它不是非常有益。我使用了两个RecyclerViews，两个适配器类和两个片段。在我实现了http请求和JSON解析器之前，它工作正常。有人可以帮助我吗？
MainActivity.java
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
FragAbsenz fragAbsenz = new FragAbsenz();
android.app.FragmentManager manager = getFragmentManager();
manager.beginTransaction().replace(R.id.contentLayout, fragAbsenz,
fragAbsenz.getTag()).commit();
setTitle("Lehrerabsenzen");
BottomNavigationView navigation = (BottomNavigationView)
findViewById(R.id.navigation);
navigation.setOnNavigationItemSelectedListener
(mOnNavigationItemSelectedListener);
MainActivity.context = getApplicationContext();
}
public static Context getAppContext() {
return MainActivity.context;
}
FragAbsenz.java: (I haven't implemented the http request and the JSON
parser on this one yet, but it only displays the first Item from 20 and
the others are gone.)
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View view = inflater.inflate(R.layout.fragment_frag_absenz,
container, false);
mRecycler = (RecyclerView) view.findViewById(R.id.rv_absenz);
mContacts = new ArrayList<>();
mContacts.add("Michi \n Zi");
mContacts.add("Michi Zi 2");
mContacts.add("Michi \n Zi 3");
for (int i = 4; i < 20; i++) {
mContacts.add("Michi Zi" + i);
}
mRecycler.setHasFixedSize(true);
mLayoutManager = new LinearLayoutManager(getActivity());
mAdapter = new Abse_MainAdapter(mContacts);
mRecycler.setLayoutManager(mLayoutManager);
mRecycler.setAdapter(mAdapter);
return view;
}
Abse_MainAdapter.java：
class Abse_MainAdapter extends
RecyclerView.Adapter<Abse_MainAdapter.ViewHolder> {
ArrayList<String> mContacts;
public Abse_MainAdapter(ArrayList<String> Contacts) {
mContacts = Contacts;
}
@Override
public Abse_MainAdapter.ViewHolder onCreateViewHolder(ViewGroup parent,
int viewType) {
View view =
LayoutInflater.from(parent.getContext()).inflate(R.layout.abse_row,
parent, false);
return new Abse_MainAdapter.ViewHolder(view);
}
@Override
public void onBindViewHolder(Abse_MainAdapter.ViewHolder holder, int
position) {
holder.mFullName.setText(mContacts.get(position));
}
@Override
public int getItemCount() {
return mContacts.size();
}
public class ViewHolder extends RecyclerView.ViewHolder {
public TextView mFullName;
public ViewHolder(View itemView) {
super(itemView);
mFullName = (TextView) itemView.findViewById(R.id.full_name);
}
}
FragMenu.java：
public class FragMenu extends Fragment {
ArrayList<String> mMenu;
RecyclerView mRv;
RecyclerView.LayoutManager mLm;
RecyclerView.Adapter mAd;
StringRequest stringRequest = null;
String result;
public FragMenu() {
// Required empty public constructor
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View view = inflater.inflate(R.layout.fragment_frag_menu,
container, false);
mRv = (RecyclerView) view.findViewById(R.id.rv_menu);
RequestQueue queue =
Volley.newRequestQueue(MainActivity.getAppContext());
String url = "Censored because of personal reasons";
stringRequest = new StringRequest(Request.Method.GET, url,
new Response.Listener<String>() {
@Override
public void onResponse(String response) {
result = response.substring(0);
try {
JSONObject JSONobj = new JSONObject(result);
String lastUpdate =
JSONobj.getString("lastUpdate");
result = lastUpdate;
JSONArray WMenu = JSONobj.getJSONArray("data");
mMenu = new ArrayList<>();
for (int i = 0; i < WMenu.length(); i++) {
String Str = "";
JSONObject TMenu = WMenu.getJSONObject(i);
Str = Str + TMenu.getString("time") + "|";
JSONArray Menu =
TMenu.getJSONArray("main");
String str = "";
for (int k = 0; k < Menu.length(); k++) {
str = str + Menu.getString(k) + "\n";
}
Str = Str + str + "|";
str = "";
JSONArray Hit = TMenu.getJSONArray("hit");
for (int k = 0; k < Menu.length(); k++) {
str = str + Hit.getString(k) + " \n";
}
Str = Str + str;
mMenu.add(Str);
}
mRv.setHasFixedSize(true);
mLm = new LinearLayoutManager(getActivity());
mAd = new Menu_MainAdapter(mMenu);
mRv.setLayoutManager(mLm);
mRv.setAdapter(mAd);
} catch (JSONException e) {
e.printStackTrace();
}
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
//mText.setText("That didn't work!");
}
});
queue.add(stringRequest);
return view;
}
Menu_MainAdapter.java:
class Menu_MainAdapter extends
RecyclerView.Adapter<Menu_MainAdapter.ViewHolder> {
ArrayList<String> mMenu;
public Menu_MainAdapter(ArrayList<String> Menu) {
mMenu = Menu;
}
@Override
public Menu_MainAdapter.ViewHolder onCreateViewHolder(ViewGroup parent,
int viewType) {
View view =
LayoutInflater.from(parent.getContext()).inflate(R.layout.menu_row,
parent, false);
return new ViewHolder(view);
}
@Override
public void onBindViewHolder(Menu_MainAdapter.ViewHolder holder, int
position) {
String date = ((mMenu.get(position)).split("|"))[0];
String Menu = ((mMenu.get(position)).split("|"))[1];
String Hit = ((mMenu.get(position)).split("|"))[2];
holder.tDate.setText(date);
holder.tDate.setText(Menu);
holder.tDate.setText(Hit);
}
@Override
public int getItemCount() {
return mMenu.size();
}
public class ViewHolder extends RecyclerView.ViewHolder {
public TextView tDate;
public TextView tMenu;
public TextView tHit;
public ViewHolder(View itemView) {
super(itemView);
tDate = (TextView) itemView.findViewById(R.id.tDate);
tMenu = (TextView) itemView.findViewById(R.id.menu);
tHit = (TextView) itemView.findViewById(R.id.hit);
}
}
activity_main.xml中：
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/container"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context="systems.exygen.examp.MainActivity">
<FrameLayout
android:id="@+id/contentLayout"
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="1">
</FrameLayout>
<android.support.design.widget.BottomNavigationView
android:id="@+id/navigation"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_gravity="bottom"
android:background="?android:attr/windowBackground"
app:menu="@menu/navigation" />
</LinearLayout>
fragment_frag_absenz.xml：
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="systems.exygen.examp.FragAbsenz">
<!-- TODO: Update blank fragment layout -->
<android.support.v7.widget.RecyclerView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="@+id/rv_absenz">
</android.support.v7.widget.RecyclerView>
</LinearLayout>
abse_row.xml：
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="match_parent"
android:layout_height="match_parent">
<android.support.v7.widget.CardView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_margin="12dp">
<TextView
android:id="@+id/full_name"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:textSize="32sp"
android:padding="12dp"
/>
</android.support.v7.widget.CardView>
</LinearLayout>
fragment_frag_menu.xml：
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="systems.exygen.examp.FragMenu">
<!-- TODO: Update blank fragment layout -->
<android.support.v7.widget.RecyclerView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="@+id/rv_menu">
</android.support.v7.widget.RecyclerView>
</FrameLayout>
menu_row.xml：
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="wrap_content">
<android.support.v7.widget.CardView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_margin="12dp"
>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical">
<TextView
android:id="@+id/tDate"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Time"
android:layout_margin="12dp"
android:textSize="24dp" />
<TextView
android:id="@+id/textView5"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Tages-Menü"
android:layout_margin="12dp"
android:textSize="24dp"
android:textStyle="bold"/>
<TextView
android:id="@+id/menu"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Tages-Menü"
android:layout_margin="12dp"
android:textSize="16dp"/>
<TextView
android:id="@+id/textView3"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Tages-Hit"
android:layout_margin="12dp"
android:textSize="24dp"
android:textStyle="bold"/>
<TextView
android:id="@+id/hit"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Tages-Hit"
android:layout_margin="12dp"
android:textSize="16dp"
/>
</LinearLayout>
</android.support.v7.widget.CardView>
</LinearLayout>
请阅读[如何创建最小，完整和可验证示例]（https://stackoverflow.com/help/mcve） –