Question

我有一个可由用户更新的列表，但在notifyDataSetChanged()上有一个错误，我正在做一个待办事项，当我在阵列适配器中添加notifyDataSetChanged()时，显示错误消息那

错误：ArrayAdapter中的notifyDataSetChanged（）是在无法访问的类或接口中定义的

无法访问“ android.widget.ArrayAdapter”中的“ notifyDataSetChanged（）”

note_editor 发生错误。以下是我的代码：

note_editor （另一项活动）

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

        EditText editText = (EditText) findViewById(R.id.editText);


        Intent intent = getIntent();
        noteId = intent.getIntExtra("noteId", -1);
        // note id variable transferred from main activity

        if (noteId != -1) { 

            editText.setText(MainActivity.notes.get(noteId));

        } else {

            MainActivity.notes.add("");
            noteId = MainActivity.notes.size() - 1; 
            MainActivity.arrayAdapter.notifyDataSetChanged();  //error happened here       
}

MainActivity

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

        CheckBox checkBox = (CheckBox) findViewById(R.id.checkBox);
        ListView listView = (ListView) findViewById(R.id.listView);
        FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);

        SharedPreferences sharedPreferences =
                getApplicationContext().getSharedPreferences
                        ("com.example.application1", Context.MODE_PRIVATE);


        HashSet<String> set = (HashSet<String>)
                sharedPreferences.getStringSet("notes", null);

        if (set == null) {

            notes.add("Example note");

        } else {

            notes = new ArrayList(set);

        }


        arrayAdapter = new CustomAdapter
                (this, R.layout.simplerow, notes);

        listView.setAdapter(arrayAdapter);

        fab.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
        Intent intent = new 
 Intent(getApplicationContext(),note_editor.class); 

                startActivity(intent);

            }
        });

        listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            public void onItemClick
            (AdapterView<?> adapterView, View view, int i, long l) {

                Intent intent = new Intent(getApplicationContext(),
                        note_editor.class);
                intent.putExtra("noteId", i);
                startActivity(intent);

            }

        });



listView.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() {

 public boolean onItemLongClick
   (AdapterView<?> adapterView, View view, int i, long l) {
          final int itemToDelete = i;
                 new AlertDialog.Builder(MainActivity.this)
                         .setIcon(android.R.drawable.ic_dialog_alert)
                         .setTitle("Are you sure?")
                         .setMessage("Do you want to delete this note?")
                         .setPositiveButton("Yes",
                                        new DialogInterface.OnClickListener() {

     public void onClick(DialogInterface dialogInterface, int i) {
        notes.remove(itemToDelete);

            arrayAdapter.notifyDataSetChanged();

SharedPreferences sharedPreferences =
getApplicationContext().getSharedPreferences("com.example.application1",Context.MODE_PRIVATE);

HashSet<String> set = new HashSet(MainActivity.notes);
sharedPreferences.edit().putStringSet("notes", set).apply();

                        }
                   }
              )

             .setNegativeButton("No", null)
             .show();


                        return true;
                    }


                });

    }

CustomAdapter

private class CustomAdapter extends ArrayAdapter<String> {
        Context context;
        ArrayList<String> notes = new ArrayList<>();
        int layoutResourceId;
        public CustomAdapter(Context context, int layoutResourceId,
                            ArrayList<String> objects) {
            super(context, layoutResourceId, objects);
            this.layoutResourceId = layoutResourceId;
            this.notes=objects;
            this.context=context;
        }
        @Override
        public View getView(int position, View convertView, ViewGroup parent) {

        CheckBox chBox = null;
        if (convertView == null) {
        LayoutInflater inflater = (LayoutInflater) context
                        .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
                convertView = inflater.inflate(R.layout.simplerow,
                        parent, false);
                chBox = (CheckBox) convertView.findViewById(R.id.checkBox);
                convertView.setTag(chBox);
                chBox.setOnClickListener(new View.OnClickListener() {

   @Override
   public void onClick(View v) {
   TextView tv = findViewById(R.id.rowTextView);
   tv.setPaintFlags(tv.getPaintFlags() | Paint.STRIKE_THRU_TEXT_FLAG);
                        arrayAdapter.notifyDataSetChanged();
                    }

                });
            }
            return convertView;
        }

    }

有什么主意吗？

Answer 1

只需要更改一行。只需如下更改arrayAdapter.notifyDataSetChanged（）即可。

class Ship{
public:
    int max_HP;
    int HP;
    int DMG;
};

class Fleet{
public:
    int amount_of_ships;
    Ship * ship = new Ship[amount_of_ships];


    Fleet(int fleet_size)
    {
        amount_of_ships=fleet_size;
    }
};

class Player{
public:
    string name;
    Fleet fleet{1}; //this line 
};

Answer 2

显示适配器对象不可访问的错误。

您实际上是在尝试更新已被破坏的活动。从MainActivity本身通知适配器。

Answer 3

在我看来，发生错误是因为您将CustomAdapter定义为 private 类，因此您不能在其外部访问其方法。

CustomAdapter应该定义为 public （如果所有内容都位于同一软件包中，则可以访问软件包）。

话虽如此，我也同意其他评论，指出这不是调用 notifyDataSetChanged 的正确方法（如果您对此仍有疑问，我建议为此提出一个不同的问题）。 / p>

NotifyDataSetChanged无法在arrayadapter中访问

3 个答案: