这是一个包含3个片段的应用程序（BottomNavigationView的每个选项一个）。在其中一个片段中，我有一个流程，该流程将从JSON文件在线获取数据并将其显示在Recycler视图中。但是我没有任何数据。 我上载了XML文件和logcat报告，以防万一您需要它
ItemOneFragment.java
public class ItemOneFragment extends Fragment {
private RecyclerView recyclerView;
private RecyclerView.Adapter adapter;
private List<ListItem> listItems;
private static final String URL_DATA = "https://www.simplifiedcoding.net/demos/marvel/";
public static ItemOneFragment newInstance() {
ItemOneFragment fragment = new ItemOneFragment();
return fragment;
}
@Override
public void onActivityCreated(@Nullable Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
recyclerView = (RecyclerView) getView().findViewById(R.id.list);
recyclerView.setHasFixedSize(true);
recyclerView.setLayoutManager(new LinearLayoutManager(this.getActivity()));
listItems = new ArrayList<>();
loadRecyclerViewData();
}
private void loadRecyclerViewData(){
final ProgressDialog progressDialog = new ProgressDialog((this.getActivity()));
progressDialog.setMessage("Loading Data.....");
progressDialog.show();
StringRequest stringRequest = new StringRequest(Request.Method.GET, URL_DATA,
new Response.Listener<String>() {
@Override
public void onResponse(String s) {
progressDialog.dismiss();
try {
JSONObject jsonObject = new JSONObject(s);
JSONArray array = jsonObject.getJSONArray(s);
for (int i = 0;i<array.length();i++){
JSONObject o = array.getJSONObject(i);
ListItem item = new ListItem(
o.getString("name"),
o.getString("team"),
o.getString("imageurl")
);
listItems.add(item);
Toast.makeText(getActivity().getApplicationContext(), (CharSequence) item,Toast.LENGTH_LONG).show();
}
adapter = new Adapter(listItems, getActivity().getApplicationContext());
} catch (JSONException e) {
e.printStackTrace();
}
}
},
new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
Toast.makeText(getActivity().getApplicationContext(),error.getMessage(),Toast.LENGTH_LONG).show();
}
});
RequestQueue requestQueue = Volley.newRequestQueue(this.getActivity());
requestQueue.add(stringRequest);
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
return inflater.inflate(R.layout.frag_one_home, container, false);
}
}
Adapter.java
public class Adapter extends RecyclerView.Adapter<Adapter.ViewHolder>{
private List<ListItem> listItems;
private Context context;
public Adapter(List<ListItem> listItems, Context context) {
this.listItems = listItems;
this.context = context;
}
@Override
public Adapter.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View v = LayoutInflater.from(parent.getContext())
.inflate(R.layout.card_txt,parent, false);
return new ViewHolder(v);
}
@Override
public void onBindViewHolder(Adapter.ViewHolder holder, int position) {
ListItem listItem = listItems.get(position);
holder.textViewTitle.setText(listItem.getTitle());
holder.textViewStatus.setText(listItem.getStatus());
}
@Override
public int getItemCount() {
return listItems.size();
}
public class ViewHolder extends RecyclerView.ViewHolder{
public TextView textViewTitle;
public TextView textViewStatus;
public ViewHolder(View itemView) {
super(itemView);
textViewTitle = (TextView) itemView.findViewById(R.id.place_title);
textViewStatus = (TextView) itemView.findViewById(R.id.place_description);
}
}
}
ListItem.java
public class ListItem {
private String title;
private String status;
private String imageURL;
public ListItem(String title, String status, String imageURL) {
this.title = title;
this.status = status;
this.imageURL = imageURL;
}
public String getTitle() {
return title;
}
public String getStatus() {
return status;
}
public String getImageURL() {
return imageURL;
}
}
card_txt.xml
<android.support.v7.widget.CardView
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
xmlns:android="http://schemas.android.com/apk/res/android"
style="@style/CardStyle.Home"
android:layout_width="match_parent"
android:layout_height="wrap_content"
>
<LinearLayout android:id="@+id/text_container"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical"
xmlns:android="http://schemas.android.com/apk/res/android">
<!--
<ImageView
android:id="@+id/cover_pic"
android:layout_width="fill_parent"
android:layout_height="155dp"
android:contentDescription="@string/todo"
android:adjustViewBounds="true"
android:scaleType="centerCrop"/>
-->
<TextView
android:id="@+id/place_title"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:textStyle="bold"
android:textSize="18sp"
/>
<TextView
android:id="@+id/place_description"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:textStyle="italic"
/>
</LinearLayout>
</android.support.v7.widget.CardView>
frag_one_home.xml
<LinearLayout android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical"
android:paddingTop="@dimen/view_spacing_small"
xmlns:android="http://schemas.android.com/apk/res/android">
<include layout="@layout/search_bar" />
<android.support.v7.widget.RecyclerView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="@+id/list"
/>
</LinearLayout>
LogCat = https://raw.githubusercontent.com/teeban10/sandbox/master/log.txt
答案 0 :(得分：0)
正如日志中指出的那样，由于您没有将this.state = {
orderDet: this.props.navigation.state.params.orderDet,
numOrder: null,
TotalSum: null,
};
fetchSum = async () => {
const response = await fetch("http://192.168.254.104:3308/OrderNo/ForSum/" + this.state.orderDet)
const json = await response.json()
this.setState({ TotalSum: json[0].TotalAmountOrdered })
}
fetchNumOrders = async () => {
const response = await fetch("http://192.168.254.104:3308/NumOrder/num/" + this.state.orderDet )
const json = await response.json()
this.setState({ numOrder: json[0].TotalItemsOrdered })
}
设置为Adapter，因此项目没有显示在RecyclerView中，因此它跳过了布局。
您可以这样设置
RecyclerView接下来，您的JSON数据是对象数组，因此您必须创建adapter = new Adapter(listItems, getActivity().getApplicationContext());
recyclerView.setAdapter(adapter);
而不是JSONArray
JSONObject最后，您尝试使用//JSONObject jsonObject = new JSONObject(s);
JSONArray array = new JSONArray(s);
，但没有在第二个参数中提供Toast，无法将String强制转换为ItemList或{{1 }}，只需删除该CharSequence即可解决。