如何从cursoradapter列表视图中删除项目？

Question

我看过很多关于这个问题的帖子，但没有一个人引导我解决我的问题。我有一个listview使用自定义cursoradapter，每个项目都有一个复选框。此复选框未绑定到数据库，因为我的目的是将其用于删除。单击删除按钮后，应从视图和数据库中删除所有选中复选框的项目。我实现了以下逻辑，但事实证明方法<my listview instance>.getCheckedItemPositions()始终返回SparseBooleanArray空。谁能告诉我我做错了什么？我不确定这是否是最好的方法，所以欢迎任何其他解决方案或想法。

这是我的CursorAdapter

public class ExpenseCursorAdapter extends CursorAdapter {
private NumberFormat formatter = NumberFormat.getCurrencyInstance();
Context context;
private DatabaseHelper db;

public ExpenseCursorAdapter(Context context, Cursor c) {
    super(context, c);
}


@Override
public View newView(Context context, Cursor cursor, ViewGroup parent) {
    // when the view will be created for first time,
    // we need to tell the adapters, how each item will look
    LayoutInflater inflater = LayoutInflater.from(parent.getContext());
    View retView = inflater.inflate(R.layout.expense_single_row_item, parent, false); 

    return retView;
}

@Override
public void bindView(View view, Context context, Cursor cursor) {
    // here we are setting our data
    // that means, take the data from the cursor and put it in views

    TextView textViewParticipantId = (TextView) view.findViewById(R.id.tv_expense_participant);
    textViewParticipantId.setText(cursor.getString(cursor.getColumnIndex("name")));

    TextView textViewExpenseDescription = (TextView) view.findViewById(R.id.tv_expense_description);
    textViewExpenseDescription.setText(cursor.getString(cursor.getColumnIndex("description")));

    TextView textViewExpenseAmount = (TextView) view.findViewById(R.id.tv_expense_amount);
    textViewExpenseAmount.setText(formatter.format(Double.valueOf(cursor.getDouble(cursor.getColumnIndex("amount")))));



}

}

这是我的项目布局：

<?xml version="1.0" encoding="utf-8"?>
<TableLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:stretchColumns="1,2,3" >

<TableRow
    android:id="@+id/tableRow1"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:weightSum="10" >

    <CheckBox
        android:id="@+id/cb_expense_row"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_vertical"
        android:button="@drawable/selector_check"
        android:focusable="false"
        android:padding="2dip" 
        android:weightSum="1"/>

    <TextView
        android:id="@+id/tv_expense_participant"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:paddingBottom="5dp"
        android:weightSum="3" 
        android:gravity="left"/>

    <TextView
        android:id="@+id/tv_expense_description"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:paddingBottom="5dp"
        android:weightSum="3" 
        android:gravity="left"/>

    <TextView
        android:id="@+id/tv_expense_amount"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:paddingBottom="5dp"
        android:weightSum="3"
        android:gravity="left" />
</TableRow>

这是我在删除按钮上使用逻辑的活动--removeExpense（）：

private static final String TAG = ExpenseActivity.class.getSimpleName();
private ListView listView;
private ExpenseCursorAdapter customAdapter;
private DatabaseHelper databaseHelper;
private long eventId;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_expense);
    ActionBar actionBar = getSupportActionBar();
    actionBar.setDisplayHomeAsUpEnabled(true);


    eventId = getIntent().getLongExtra("tag_event_id", -1);

    databaseHelper = new DatabaseHelper(this);


    listView = (ListView) findViewById(R.id.expense_list_data);
    listView.setOnItemClickListener(new OnItemClickListener() {


        @Override
        public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
            Log.d(TAG, "clicked on item: " + position+" - ID: "+id);
        }
    });



    new Handler().post(new Runnable() {
        @Override
        public void run() {

            customAdapter = new ExpenseCursorAdapter(ExpenseActivity.this, databaseHelper.getAllExpensesByEventCursor(eventId));
            listView.setAdapter(customAdapter);

        }
    });

    listView.setChoiceMode(ListView.CHOICE_MODE_MULTIPLE);
 }
 ...
 private void removeExpenses() {
    Log.d(TAG, "Remove Expense button clicked on");

    DatabaseHelper db = new DatabaseHelper(this);

    SparseBooleanArray checkedItemPositions  = listView.getCheckedItemPositions();

    int itemCount = listView.getCount();        

    for (int i = itemCount - 1; i >=0; i--) {
        if (checkedItemPositions.valueAt(i)) {

            //db.deleteExpense(listView.getItemIdAtPosition(checkedItemPositions.keyAt(i)));
            db.deleteExpense(listView.getItemIdAtPosition(i));

        }

        customAdapter.notifyDataSetChanged();
    }

    checkedItemPositions.clear();

    listView.setAdapter(customAdapter);

    listView.clearChoices();

    if (db != null){
        db.close();
    }

}