java - 自定义适配器 ListView 错误

Question

我试图在 Listview 中列出一些用户详细信息，每行显示 4 个字符串。

字符串来自Firebase。

我总是得到一些错误。关于错误原因或任何其他解决方案的任何想法？

这是我的代码:

主要 Activity

public class SearchActivity extends AppCompatActivity {

    private ListView mListView;
    //public ArrayList<String> mUser = new ArrayList<>();
    private String userID;
    private String Lat;
    private String Lng;
    private Button mRefresh;
    private String Name;
    private String Birthday;
    private String Gender;
    private String Email;

    private FirebaseAuth mAuth = FirebaseAuth.getInstance();
    private FirebaseDatabase firebaseDatabase = FirebaseDatabase.getInstance();
    private DatabaseReference DatabaseReference = firebaseDatabase.getReference();

    //private DatabaseReference DatabaseReference = firebaseDatabase.getReference().child("Users/");
    //private DatabaseReference CoordenateReference = firebaseDatabase.getReference().child("Coordenate/");

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


        mListView = findViewById(R.id.listViewSearch);

        FirebaseUser user = mAuth.getCurrentUser();
        userID = user.getUid();
        mRefresh = findViewById(R.id.buttonRefresh);


        mRefresh.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {

                DatabaseReference.addValueEventListener(new ValueEventListener() {
                    @Override
                    public void onDataChange(DataSnapshot dataSnapshot) {
                        listClean();
                        FirebaseUser user = mAuth.getCurrentUser();
                        userID = user.getUid();
                        Lat = dataSnapshot.child("Users").child(userID).child("Coordenates/Rute/Lat").getValue(String.class);
                        Lng = dataSnapshot.child("Users").child(userID).child("Coordenates/Rute/Lng").getValue(String.class);
                        DataSnapshot dS = dataSnapshot.child("Coordenate").child(Lat).child(Lng);

                        for(DataSnapshot Ds : dS.getChildren()) {
                            Object key = Ds.getKey();
                            String StringKey = String.valueOf(key);
                            getname(StringKey);
                            //mUser.add(getName(StringKey));
                            //mUser.add(Name);
                        }

                    }

                    @Override
                    public void onCancelled(DatabaseError databaseError) {
                        Toast.makeText(SearchActivity.this,"Error 404",Toast.LENGTH_SHORT).show();

                    }
                });
            }
        });



    }
    private void getname(String ID){


        final String IDfinal = ID;
        Toast.makeText(SearchActivity.this,ID,Toast.LENGTH_SHORT).show();
        DatabaseReference.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {
                Name = dataSnapshot.child("Users").child(IDfinal).child("name").getValue(String.class);
                Email = dataSnapshot.child("Users").child(IDfinal).child("email").getValue(String.class);
                Gender = dataSnapshot.child("Users").child(IDfinal).child("gender").getValue(String.class);
                Birthday = dataSnapshot.child("Users").child(IDfinal).child("data_birth").getValue(String.class);

                list();


                Toast.makeText(SearchActivity.this,Name,Toast.LENGTH_SHORT).show();

            }

            @Override
            public void onCancelled(DatabaseError databaseError) {
                Toast.makeText(SearchActivity.this,"Error 404",Toast.LENGTH_SHORT).show();

            }
        });
    }

    private void list(){
        //final ArrayAdapter<String> arrayAdapter = new ArrayAdapter<>(this, android.R.layout.simple_list_item_1, mUser);
        //mListView.setAdapter(new customAdapter(this,new String[]{Name}));
        //mUser.add(Name);
        //arrayAdapter.notifyDataSetChanged();
        setContentView(R.layout.activity_search);
        List<UserInformation> userInformationsList = new ArrayList<>();
        UserInformation userInformation = new UserInformation(Name,Email,Gender,Birthday);
        userInformationsList.add(userInformation);
        customAdapter customAdapterIntent= new customAdapter((ValueEventListener) this,R.layout.userslist,userInformationsList);
        mListView.setAdapter(customAdapterIntent);
    }
}

这是用户列表.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
     xmlns:android="http://schemas.android.com/apk/res/android"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
     android:orientation="vertical">

    <TextView
        android:id="@+id/textNameList"
        android:textSize="25dp"
        android:textAlignment="textStart"
        android:text="Name"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:gravity="start"
        android:layout_margin="10dp"/>

    <TextView
        android:id="@+id/textEmailList"
        android:textSize="15dp"
        android:textAlignment="textStart"
        android:text="Age"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:gravity="start"
        android:layout_margin="10dp"/>

    <TextView
        android:id="@+id/textBirthdayList"
        android:textSize="15dp"
        android:textAlignment="textStart"
        android:text="Birthday"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:gravity="start"
        android:layout_margin="10dp"/>

    <TextView
        android:id="@+id/textGenderList"
        android:textSize="15dp"
        android:textAlignment="textStart"
        android:text="gender"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:gravity="start"
        android:layout_margin="10dp"/>

这是Userinformation.java

public class UserInformation {


    private static String Name;
    private static String Gender;
    private static String Email;
    private static String Birthday;

    public UserInformation(String Name,String Gender,String Email,String Birthday){
        this.Birthday=Birthday;
        this.Email=Email;
        this.Gender=Gender;
        this.Name=Name;
    }

    public static String getName(){return Name;}
    public static String getEmail(){return Email;}
    public static String getGender(){return Gender;}
    public static String getBirthday(){return Birthday;}

}

这是适配器

public class customAdapter extends ArrayAdapter<UserInformation> {




    public customAdapter(ValueEventListener context, int layoutResource, 
    List<UserInformation> userInformationsList) {
        super((Context) context, layoutResource, userInformationsList);

    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {

        View view = convertView;

        if (view == null) {
            LayoutInflater layoutInflater = LayoutInflater.from(getContext());
            view = layoutInflater.inflate(R.layout.userslist, null);
        }

        UserInformation userInformation = getItem(position);

        if (userInformation != null) {
            TextView Name = (TextView) view.findViewById(R.id.textNameList);
            //name.setText(name[position]);
            TextView email = (TextView) view.findViewById(R.id.textEmailList);
            //email.setText(Email[position]);
            TextView gender = (TextView) view.findViewById(R.id.textGenderList);
            //gender.setText(Gender[position]);
            TextView birthday = (TextView) view.findViewById(R.id.textBirthdayList);
            //birthday.setText(Birthday[position]);

            if (Name != null) {
                Name.setText(UserInformation.getName());
            }
            if (email != null) {
                email.setText(UserInformation.getEmail());
            }
            if (gender != null) {
                gender.setText(UserInformation.getGender());
            }
            if (birthday != null) {
                birthday.setText(UserInformation.getBirthday());
            }
        }

        return view;
    }
}

这是错误

E/AndroidRuntime: FATAL EXCEPTION: main
              Process: com.example.enrik.afrodita, PID: 2629
              java.lang.ClassCastException: 
com.example.enrik.afrodita.SearchActivity cannot be cast to 
com.google.firebase.database.ValueEventListener
                  at 
com.example.enrik.afrodita.SearchActivity.list(SearchActivity.java:130)
                  at 

com.example.enrik.afodita.SearchActivity.access$1100(SearchActivity.java:24)
                  at 

com.example.enrik.adita.Searchivity$2.onDataChange(SearchActivity.java:106)
                  at com.google.android.gms.internal.zzdtn.zza(Unknown Source)
                  at com.google.android.gms.internal.zzdvi.zzbur(Unknown Source)
                  at com.google.android.gms.internal.zzdvo.run(Unknown Source)
                  at android.os.Handler.handleCallback(Handler.java:751)
                  at android.os.Handler.dispatchMessage(Handler.java:95)
                  at android.os.Looper.loop(Looper.java:154)
                  at android.app.ActivityThread.main(ActivityThread.java:6119)
                  at java.lang.reflect.Method.invoke(Native Method)
                  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
                  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)

Answer 1

您需要传递 Context 而不是 ValueEventListener 因此将适配器更改为

public customAdapter(/*ValueEventListener*/ Context context, int layoutResource, 
List<UserInformation> userInformationsList) {
    super(context, layoutResource, userInformationsList);

}

同时删除类型转换

 customAdapter customAdapterIntent= new customAdapter(/*(ValueEventListener)*/ this,R.layout.userslist,userInformationsList);

当您调用 getContext() 时，layoutinflater 或适配器需要 context 来访问资源

并从 list 方法中删除 setContentView(R.layout.activity_search);，你做了两次，所以不需要

---

Thank so much, I did as you said and It works but it only list the last user's information

您需要获取所有用户并将它们添加到 list 中，因为当前您将最后一个用户的信息存储为字符串值并使用这些值创建单个用户对象的列表。

// outside onCreate
List<UserInformation> users = new ArrayList<>();


mRefresh.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View view) {

        DatabaseReference.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {
                listClean();
                FirebaseUser user = mAuth.getCurrentUser();
                userID = user.getUid();
                Lat = dataSnapshot.child("Users").child(userID).child("Coordenates/Rute/Lat").getValue(String.class);
                Lng = dataSnapshot.child("Users").child(userID).child("Coordenates/Rute/Lng").getValue(String.class);
                DataSnapshot dS = dataSnapshot.child("Coordenate").child(Lat).child(Lng);

                for(DataSnapshot Ds : dS.getChildren()) {
                    Object key = Ds.getKey();
                    String StringKey = String.valueOf(key);

                    // fetch the user Object based on key and add it to list
                    users.add(lidataSnapshot.child("Users").child(StringKey).getValue(UserInformation.class));
                }
                 // now display list with all user information 
                 customAdapter customAdapterIntent= new customAdapter(SearchActivity.this,
                                                                      R.layout.userslist,
                                                                      users);
                 mListView.setAdapter(customAdapterIntent);

            }

            @Override
            public void onCancelled(DatabaseError databaseError) {
                Toast.makeText(SearchActivity.this,"Error 404",Toast.LENGTH_SHORT).show();

            }
        });
    }
});