我对Android开发相对较新，我创建了一个从数据库（MySQL）中获取数据的应用程序，并且（应该）显示在android中片段中加载的卡片上。我的所有java类都没有显示任何错误，但是当我启动应用程序时，卡不会在RecyclerView中膨胀。
以下是我试图无效的一些解决方案：
CardView not shown in RecyclerView，
Android MySQL Tutorial to Perform Basic CRUD Operation How to implement RecyclerView with CardView rows in a Fragment with TabLayout
任何帮助将不胜感激。 片段包含我正在使用的类：
public class bloodBanks extends Fragment {
private RecyclerView recylerView;
private MyAdapter adapter;
private List<MyData>data_List;
private OnFragmentInteractionListener mListener;
public bloodBanks() {
// Required empty public constructor
}
/**
* Use this factory method to create a new instance of
* this fragment using the provided parameters.
*
* @param param1 Parameter 1.
* @param param2 Parameter 2.
* @return A new instance of fragment bloodBanks.
*/
// TODO: Rename and change types and number of parameters
public static bloodBanks newInstance(String param1, String param2) {
bloodBanks fragment = new bloodBanks();
Bundle args = new Bundle();
fragment.setArguments(args);
return fragment;
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View v= inflater.inflate(R.layout.fragment_blood_banks, container, false);
//perform(v);
recylerView=(RecyclerView) v.findViewById(R.id.recyle);
recylerView.setHasFixedSize(true);
data_List = new ArrayList<>();
adapter=new MyAdapter(getActivity(),data_List);
recylerView.setAdapter(adapter);
LinearLayoutManager llm = new LinearLayoutManager(getActivity());
llm.setOrientation(LinearLayoutManager.VERTICAL);
recylerView.setLayoutManager(llm);
load_data_from_server(0);
return v;
}
private void load_data_from_server(final int id) {
AsyncTask<Integer,Void,Void> task = new AsyncTask<Integer, Void, Void>() {
@Override
protected Void doInBackground(Integer... params) {
OkHttpClient client= new OkHttpClient();
Request request = new Request.Builder()
.url("http://192.168.137.1:81/card.php?id="+id)
.build();
try {
Response response = client.newCall(request).execute();
JSONArray array = new JSONArray(response.body().string());
for (int i=0;i<array.length();i++){
JSONObject object=array.getJSONObject(i);
MyData data=new MyData(object.getInt("id"),object.getString("hospName"),object.getString("contact"));
data_List.add(data);
}
} catch(IOException e){
e.printStackTrace();
}catch (JSONException e){
System.out.println("No More Hospitals");
}
return null;
}
@Override
protected void onPostExecute(Void aVoid) {
adapter.notifyDataSetChanged();
}
};
task.execute(id);
}
// TODO: Rename method, update argument and hook method into UI event
public void onButtonPressed(Uri uri) {
if (mListener != null) {
mListener.onFragmentInteraction(uri);
}
}
@Override
public void onAttach(Context context) {
super.onAttach(context);
if (context instanceof OnFragmentInteractionListener) {
mListener = (OnFragmentInteractionListener) context;
} else {
throw new RuntimeException(context.toString()
+ " must implement OnFragmentInteractionListener");
}
}
@Override
public void onDetach() {
super.onDetach();
mListener = null;
}
/**
* This interface must be implemented by activities that contain this
* fragment to allow an interaction in this fragment to be communicated
* to the activity and potentially other fragments contained in that
* activity.
* <p>
* See the Android Training lesson <a href=
* "http://developer.android.com/training/basics/fragments/communicating.html"
* >Communicating with Other Fragments</a> for more information.
*/
public interface OnFragmentInteractionListener {
// TODO: Update argument type and name
void onFragmentInteraction(Uri uri);
}
}
我的适配器类：
public class MyAdapter extends RecyclerView.Adapter<MyAdapter.ViewHolder>{
private Context context;
private List<MyData> my_data;
public MyAdapter(Context context, List<MyData> my_data) {
this.context = context;
this.my_data = my_data;
}
@Override
public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View itemView = LayoutInflater.from(parent.getContext()).inflate(R.layout.cards,parent,false);
return new ViewHolder(itemView);
}
@Override
public void onBindViewHolder(ViewHolder holder, int position) {
holder.hospName.setText(my_data.get(position).getHospName());
holder.contact.setText(my_data.get(position).getContact());
}
@Override
public int getItemCount() {
return my_data.size();
}
public static class ViewHolder extends RecyclerView.ViewHolder {
public TextView hospName;
public TextView contact;
public ViewHolder(View itemView){
super(itemView);
hospName=(TextView) itemView.findViewById(R.id.hosp);
contact=(TextView) itemView.findViewById(R.id.contact);
}
}
}
数据定义：
public class MyData {
private int id;
private String hospName,contact;
public MyData(int id, String hospName, String contact) {
this.id = id;
this.hospName = hospName;
this.contact = contact;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getHospName() {
return hospName;
}
public void setHospName(String hospName) {
this.hospName = hospName;
}
public String getContact() {
return contact;
}
public void setContact(String contact) {
this.contact = contact;
}
}
Cards.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"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent">
<android.support.v7.widget.CardView
android:id="@+id/cdBanks"
android:layout_width="329dp"
android:layout_height="137dp"
android:layout_marginBottom="8dp"
android:layout_marginEnd="8dp"
android:layout_marginRight="8dp"
android:layout_marginStart="8dp"
android:layout_marginTop="8dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_bias="0.022"
android:layout_marginLeft="8dp"
app:layout_constraintLeft_toLeftOf="parent">
<RelativeLayout
android:layout_width="337dp"
android:layout_height="wrap_content">
<ImageView
android:id="@+id/hospPhoto"
android:layout_width="148dp"
android:layout_height="wrap_content"
android:src="@drawable/contacts_icon" />
<TextView
android:id="@+id/hosp"
android:layout_width="195dp"
android:layout_height="wrap_content"
android:layout_toRightOf="@+id/hospPhoto"
android:textSize="26sp"
tools:layout_editor_absoluteX="256dp"
tools:layout_editor_absoluteY="16dp" />
<TextView
android:id="@+id/contact"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_below="@+id/hosp"
android:layout_toRightOf="@+id/hospPhoto" />
<TextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_below="@+id/contact"
android:layout_toRightOf="@+id/hospPhoto"
android:text="Blood Units: " />
</RelativeLayout>
</android.support.v7.widget.CardView>
</LinearLayout>
fragment_blood_banks.xml
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:card_view="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
card_view:context="layout.bloodBanks">
<android.support.v7.widget.RecyclerView
android:id="@+id/recyle"
android:layout_width="match_parent"
android:layout_height="wrap_content"
card_view:cardUSeCompatPadding="true"
card_view:cardElevation="5dp"
card_view:cardCornerRadius="5dp"
android:scrollbars="vertical"
android:layout_marginRight="6dp"
android:layout_marginLeft="6dp"
android:layout_marginTop="6dp"
/>
</android.support.constraint.ConstraintLayout>
答案 0 :(得分：0)
在适配器的xml中将整个布局放在CardView ....
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical">
<android.support.v7.widget.CardView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginRight="10dp"
android:layout_marginBottom="5dp"
android:layout_marginLeft="10dp"
android:layout_marginTop="10dp"
xmlns:card_view="http://schemas.android.com/apk/res-auto"
android:background="@color/color"
android:id="@+id/cv1"
card_view:cardElevation="3.5dp"
card_view:cardBackgroundColor="#fff"
card_view:cardCornerRadius="3dp"
android:foreground="?android:attr/selectableItemBackground"
xmlns:android="http://schemas.android.com/apk/res/android">
<put your whole layout here....>
</android.support.v7.widget.CardView>
</LinearLayout>