Question

我有一个利用我创建的Database类的Fragment。我有一个名为populateListView（）的方法，它使用CursorAdapter用数据填充ListView。我的问题是我不断收到语法错误，指出＆＃39; CursorAdapter是抽象的，无法实例化＆＃39;。在Activity中使用此代码时我没有遇到任何问题，但它不能在片段中工作。有人知道为什么吗？

以下是我片段中的代码：

    @Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {

    View view =  inflater.inflate(R.layout.fragment_contacts_fragments, container, false);

    inputName = (EditText)view.findViewById(R.id.inputName);
    inputNumber = (EditText)view.findViewById(R.id.inputNumber);
    inputEmail = (EditText)view.findViewById(R.id.inputEmail);
    saveButton = (Button)view.findViewById(R.id.saveButton);
    deleteAllButton = (Button)view.findViewById(R.id.deleteAllButton);
    openDB();
    populateListView();

    return view;
}

private void openDB(){
    myDB = new DBAdapter(getActivity());
    myDB.open();
}

public void populateListView(){
    View view = getView();
    Cursor cursor = myDB.getAllRows();
    String[] fromFieldNames = new String[] {DBAdapter.KEY_NAME,DBAdapter.KEY_NUMBER,DBAdapter.KEY_EMAIL};
    int[] toViewIDs = new int[] {R.id.customRowContactName,R.id.customRowContactNumber,R.id.customRowRowEmail};

    CursorAdapter cursorAdapter;
    //***SYNTAX ERROR WITH FOLLOWING LINE***
    cursorAdapter = new CursorAdapter(getActivity(),R.layout.contacts_custom_row,cursor,fromFieldNames,toViewIDs);

    myList = (ListView)view.findViewById(R.id.listView);
    myList.setAdapter(cursorAdapter);
}

Answer 1

CursorAdapter是一个抽象类，意味着它无法实例化。

在您的活动中，您可能正在使用SimpleCursorAdapter，因为您的构造函数参数符合其要求，或者您可能正在使用自己的CursorAdapter实现。

如果Fragment已经使用了Activity，则其中任何一个都可以在cursorAdapter = new SimpleCursorAdapter(getActivity(), R.layout.contacts_custom_row, cursor, fromFieldNames, toViewIDs);中使用。

EditText payable;
Button calculate;

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

    EditText salary = (EditText) findViewById(R.id.edit_salary);
    EditText allowance = (EditText) findViewById(R.id.edit_allowance);
    EditText incomeTax = (EditText) findViewById(R.id.IncTax_edit);
    EditText payable = (EditText) findViewById(R.id.payable_edit);
    EditText totalTax = (EditText) findViewById(R.id.deduction_edit);
    Button calculate = (Button) findViewById(R.id.calculate_button);

          if(salary.getText().toString().length()>0)
         {
         double realSalary=Double.parseDouble(salary.getText().toString());
         }
          if(allowance.getText().toString().length()>0)
         {
          double realAllowance = Double.parseDouble(allowance.getText().toString());

         }

片段中的自定义CursorAdapter

1 个答案: