类 java.util.ArrayList 具有泛型类型参数，请改用 GenericTypeIndicator

Posted 2023-03-08

【中文标题】类 java.util.ArrayList 具有泛型类型参数，请改用 GenericTypeIndicator

【英文标题】：Class java.util.ArrayList has generic type parameters, use GenericTypeIndicator instead

【发布时间】：2019-01-09 11:46:20

【问题描述】：

这是日志：

08-02 00:51:18.627 15840-15840/com.cosmichawk.classpro E/androidRuntime: 致命异常: main 进程：com.cosmichawk.classpro，PID：15840 com.google.firebase.database.DatabaseException：类 java.util.ArrayList 具有泛型类型参数，请使用 而是 GenericTypeIndicator 在 com.google.android.gms.internal.firebase_database.zzkt.zzb（未知 资源） 在 com.google.android.gms.internal.firebase_database.zzkt.zza（未知 资源） 在 com.google.android.gms.internal.firebase_database.zzkt.zzb（未知 资源） 在 com.google.android.gms.internal.firebase_database.zzku.zza（未知 资源） 在 com.google.android.gms.internal.firebase_database.zzkt.zzb（未知 资源） 在 com.google.android.gms.internal.firebase_database.zzkt.zza（未知 资源） 在 com.google.firebase.database.DataSnapshot.getValue（未知来源） 在 com.cosmichawk.classpro.MainActivity$6.onDataChange(MainActivity.java:205) 在 com.google.android.gms.internal.firebase_database.zzfc.zza（未知 资源） 在 com.google.android.gms.internal.firebase_database.zzgx.zzdr（未知 资源） 在 com.google.android.gms.internal.firebase_database.zzhd.run（未知 资源） 在 android.os.Handler.handleCallback(Handler.java:751) 在 android.os.Handler.dispatchMessage(Handler.java:95) 在 android.os.Looper.loop(Looper.java:154) 在 android.app.ActivityThread.main(ActivityThread.java:6186) 在 java.lang.reflect.Method.invoke（本机方法） 在 com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:889) 在 com.android.internal.os.ZygoteInit.main(ZygoteInit.java:779)

主要活动：

包 com.cosmichawk.classpro;

导入 android.content.Intent;进口 android.support.v7.app.AlertDialog；进口 android.support.v7.app.AppCompatActivity；导入android.os.Bundle； 导入 android.text.TextUtils；导入 android.view.LayoutInflater； 导入android.view.View；导入 android.widget.AdapterView；进口 android.widget.ArrayAdapter；导入android.widget.Button；进口 android.widget.EditText;导入 android.widget.ListView；进口 android.widget.Spinner;导入android.widget.Toast；

导入 com.google.firebase.database.DataSnapshot；进口 com.google.firebase.database.DatabaseError;进口 com.google.firebase.database.DatabaseReference；进口 com.google.firebase.database.FirebaseDatabase；进口 com.google.firebase.database.ValueEventListener;

导入 java.util.ArrayList;导入 java.util.List;

公共类 MainActivity 扩展 AppCompatActivity public static final String ARTIST_NAME = "com.cosmichawk.classpro.artistname"; public static final String ARTIST_ID = "com.cosmichawk.classpro.artistid";

EditText editTextName,editTextAmount, editTextNumber;
Button buttonAddArtist;
ArrayList array;
ListView listViewArtists;

//a list to store all the artist from firebase database
List<Artist> artists;

//our database reference object
DatabaseReference databaseArtists;

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

    //getting the reference of artists node
    databaseArtists = FirebaseDatabase.getInstance().getReference("artists");

    //getting views
    editTextName = (EditText) findViewById(R.id.editTextName);
    editTextAmount = (EditText) findViewById(R.id.editTextAmount);
    editTextNumber = (EditText) findViewById(R.id.editTextNumber);

    listViewArtists = (ListView) findViewById(R.id.listViewArtists);

    buttonAddArtist = (Button) findViewById(R.id.buttonAddArtist);

    //list to store artists
    artists = new ArrayList<>();


    //adding an onclicklistener to button
    buttonAddArtist.setOnClickListener(new View.OnClickListener() 
        @Override
        public void onClick(View view) 
            //calling the method addArtist()
            //the method is defined below
            //this method is actually performing the write operation
            addArtist();
        
    );

    //attaching listener to listview
    listViewArtists.setOnItemClickListener(new AdapterView.OnItemClickListener() 
        @Override
        public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) 
            //getting the selected artist
            Artist artist = artists.get(i);

            //creating an intent
            Intent intent = new Intent(getApplicationContext(), ArtistActivity.class);

            //putting artist name and id to intent
            intent.putExtra(ARTIST_ID, artist.getArtistId());
            intent.putExtra(ARTIST_NAME, artist.getArtistName());

            //starting the activity with intent
            startActivity(intent);
        
    );

    listViewArtists.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() 
        @Override
        public boolean onItemLongClick(AdapterView<?> adapterView, View view, int i, long l) 
            Artist artist = artists.get(i);
            showUpdateDeleteDialog(artist.getArtistId(), artist.getArtistName());
            return true;
        
    );




private void showUpdateDeleteDialog(final String artistId, String artistName) 

    AlertDialog.Builder dialogBuilder = new AlertDialog.Builder(this);
    LayoutInflater inflater = getLayoutInflater();
    final View dialogView = inflater.inflate(R.layout.update_dialog, null);
    dialogBuilder.setView(dialogView);

    final EditText editTextName = (EditText) dialogView.findViewById(R.id.editTextName);
    final EditText editTextAmount = (EditText) dialogView.findViewById(R.id.editTextAmount);
    final EditText editTextNumber = (EditText) dialogView.findViewById(R.id.editTextNumber);
    final Button buttonUpdate = (Button) dialogView.findViewById(R.id.buttonUpdateArtist);
    final Button buttonDelete = (Button) dialogView.findViewById(R.id.buttonDeleteArtist);

    dialogBuilder.setTitle(artistName);
    final AlertDialog b = dialogBuilder.create();
    b.show();


    buttonUpdate.setOnClickListener(new View.OnClickListener() 
        @Override
        public void onClick(View view) 
            String name = editTextName.getText().toString().trim();
            String amount = editTextAmount.getText().toString().trim();
            String number = editTextNumber.getText().toString().trim();
            int fb = Integer.parseInt(amount);
            int rl = Integer.parseInt(number);
            int m = fb / rl;
            ArrayList array=new ArrayList();





            if (!TextUtils.isEmpty(name)) 

                for(int l=0; l<rl; l++)
                    array.add(l,m);
                
                Toast.makeText(getBaseContext(), array+"", Toast.LENGTH_SHORT).show();
                updateArtist(artistId, name, amount, number, array);
                b.dismiss();
            

        
    );



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

            deleteArtist(artistId);
            b.dismiss();
        
    );


private boolean updateArtist(String id, String name, String amount, String number, ArrayList array) 
    //getting the specified artist reference
    DatabaseReference dR = FirebaseDatabase.getInstance().getReference("artists").child(id);

    //updating artist
    Artist artist = new Artist(id, name, amount, number, array);
    dR.setValue(artist);
    Toast.makeText(getApplicationContext(), "Artist Updated", Toast.LENGTH_LONG).show();
    return true;


private boolean deleteArtist(String id) 
    //getting the specified artist reference
    DatabaseReference dR = FirebaseDatabase.getInstance().getReference("artists").child(id);

    //removing artist
    dR.removeValue();

    //getting the tracks reference for the specified artist
    DatabaseReference drTracks = FirebaseDatabase.getInstance().getReference("tracks").child(id);

    //removing all tracks
    drTracks.removeValue();
    Toast.makeText(getApplicationContext(), "Artist Deleted", Toast.LENGTH_LONG).show();

    return true;


@Override
protected void onStart() 
    super.onStart();
    //attaching value event listener
    databaseArtists.addValueEventListener(new ValueEventListener() 
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) 

            //clearing the previous artist list
            artists.clear();

            //iterating through all the nodes
            for (DataSnapshot postSnapshot : dataSnapshot.getChildren()) 
                //getting artist


                Artist artist = postSnapshot.getValue(Artist.class);
                //adding artist to the list
                artists.add(artist);
            

            //creating adapter
            ArtistList artistAdapter = new ArtistList(MainActivity.this, artists);
            //attaching adapter to the listview
            listViewArtists.setAdapter(artistAdapter);
        

        @Override
        public void onCancelled(DatabaseError databaseError) 

        
    );



/*
 * This method is saving a new artist to the
 * Firebase Realtime Database
 * */
private void addArtist() 
    //getting the values to save
    String name = editTextName.getText().toString().trim();
    String amount = editTextAmount.getText().toString().trim();
    String number = editTextNumber.getText().toString().trim();
    int fb = Integer.parseInt(amount);
    int rl = Integer.parseInt(number);
    int m = fb / rl;

    ArrayList array = new ArrayList();

    for(int l=0; l<rl; l++)
        array.add(l,m);
    

    Toast.makeText(getBaseContext(), array+"", Toast.LENGTH_SHORT).show();
    //checking if the value is provided
    if (!TextUtils.isEmpty(name)) 

        //getting a unique id using push().getKey() method
        //it will create a unique id and we will use it as the Primary Key for our Artist
        String id = databaseArtists.push().getKey();

        //creating an Artist Object
        Artist artist = new Artist(id, name, amount, number, array);

        //Saving the Artist
        databaseArtists.child(id).setValue(artist);

        //setting edittext to blank again
        editTextName.setText("");
        editTextAmount.setText("");
        editTextNumber.setText("");


        //displaying a success toast
        Toast.makeText(this, "Artist added", Toast.LENGTH_LONG).show();
     else 
        //if the value is not given displaying a toast
        Toast.makeText(this, "Please enter a name", Toast.LENGTH_LONG).show();
    
 

此外，Artist.java 配备了它的空构造函数

包 com.cosmichawk.classpro;

导入 com.google.firebase.database.IgnoreExtraProperties；

导入 java.sql.Array;导入 java.util.ArrayList;

@IgnoreExtraProperties 公共类艺术家 私人字符串艺术家ID； 私人字符串艺术家姓名； 私人字符串艺术家数量； 私人字符串艺术家编号； 私有 ArrayList 艺术家数组；

public Artist()
    //this constructor is required


public Artist(String artistId, String artistName, String artistAmount, String artistNumber, ArrayList artistArray) 
    this.artistId = artistId;
    this.artistName = artistName;
    this.artistAmount = artistAmount;
    this.artistNumber = artistNumber;
    this.artistArray = artistArray;




public String getArtistId() 
    return artistId;


public String getArtistName() 
    return artistName;


public String getArtistAmount() 
    return artistAmount;


public String getArtistNumber()  return artistNumber; 

public ArrayList getArtistArray()  return artistArray;  

这是我的数据库的样子：-

enter image description here

【问题讨论】：

如果您将我的答案标记为已接受的答案，我将不胜感激。谢谢

请添加您的数据库结构。

添加数据库结构

【参考方案1】：

你需要指定类型

artists = new ArrayList<Artist>();

更简洁的方法是在声明空间中初始化艺术家

所以不是

List<Artist> artists;

你可以这样做

List<Artist> artists = new ArrayList<>();

【讨论】：

这一次显示了数组，但应用力关闭时出现完全相同的错误