android - 从未在数据库上显式调用 Close

Question

我有一个来自 sqlite 数据库的 ListView 。我在几个不同的点调用 fillData() 来更新 ListView 。

private void fillData() {
    readDatabase.open();
    Cursor itemsCursor = readDatabase.fetchAllItems();


    startManagingCursor(itemsCursor);

    String[] from = new String[] { DatabaseHandler.KEY_ITEM,
            DatabaseHandler.KEY_UNITCOST, DatabaseHandler.KEY_QUANTITY,
            DatabaseHandler.KEY_TOTAL };

    int[] to = new int[] { R.id.itemtext, R.id.costtext, R.id.quantitytext,
            R.id.totaltext };

    SimpleCursorAdapter items = new SimpleCursorAdapter(this,
            R.layout.rowincart, itemsCursor, from, to);

    setListAdapter(items);
    }

此处添加了类的完整代码

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    this.setContentView(R.layout.cartactivity);
    readDatabase = new DatabaseHandler(this);
//  readDatabase.open();
    loadwidget();
    fillData();
    ListView lv = getListView();
    this.registerForContextMenu(lv);

}

private void loadwidget() {
    Bundle extras = getIntent().getExtras();
    cost = extras.getInt("Cost");
    quantity = extras.getInt("quantity");
    product = extras.getString("product");
    Log.i("Hello Testing", cost + " and " + quantity + "   " + product);

}

@SuppressWarnings("deprecation")
private void fillData() {
    readDatabase.open();
    itemsCursor = readDatabase.fetchAllItems();


    startManagingCursor(itemsCursor);

    String[] from = new String[] { DatabaseHandler.KEY_ITEM,
            DatabaseHandler.KEY_UNITCOST, DatabaseHandler.KEY_QUANTITY,
            DatabaseHandler.KEY_TOTAL };

    int[] to = new int[] { R.id.itemtext, R.id.costtext, R.id.quantitytext,
            R.id.totaltext };

    SimpleCursorAdapter items = new SimpleCursorAdapter(this,
            R.layout.rowincart, itemsCursor, from, to);

    setListAdapter(items);

    }


@Override
protected void onDestroy() {
    super.onDestroy();
    itemsCursor.close();
    readDatabase.close();
}

@Override
public void onCreateContextMenu(ContextMenu menu, View v,
        ContextMenuInfo menuInfo) {
    super.onCreateContextMenu(menu, v, menuInfo);

    menu.setHeaderTitle("SMARTAWAY");

    menu.add(0, DELETE_ID, 1, "Delete Item");

    menu.add(0, UPDATE_ID, 1, "Change Quantity");
}

public boolean onContextItemSelected(MenuItem item) {
    switch (item.getItemId()) {
    case DELETE_ID:
        AdapterContextMenuInfo info = (AdapterContextMenuInfo) item
                .getMenuInfo();
        readDatabase.deleteItem(info.id);
        fillData();
        return true;
    case UPDATE_ID:

        final AdapterContextMenuInfo info1 = (AdapterContextMenuInfo) item
                .getMenuInfo();
        final Dialog dialog = new Dialog(Cartactivity.this);
        dialog.setContentView(R.layout.dialog);
        final EditText edit0 = (EditText) dialog
                .findViewById(R.id.quantity);
        edit0.setText(String.valueOf(Quantity));
        Button ok = (Button) dialog.findViewById(R.id.ok);
        dialog.setTitle("          Add More Items          ");
        dialog.setCancelable(true);
        Button inc = (Button) dialog.findViewById(R.id.inc);
        inc.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                int c = Integer.parseInt(Quantity);
                c = c + 1;
                Quantity = String.valueOf(c);
                edit0.setText(Quantity);

            }
        });
        Button dec = (Button) dialog.findViewById(R.id.dec);
        dec.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                int c = Integer.parseInt(Quantity);
                c = c - 1;
                Quantity = String.valueOf(c);
                edit0.setText(Quantity);
            }
        });
        ok.setOnClickListener(new OnClickListener() {

            public void onClick(View v) {

                row1 = info1.id; 
                flag = 1;
                int b = Integer.parseInt(Quantity);
                int total = cost * b;
                _total = String.valueOf(total);
                _cost = String.valueOf(cost);
                _quantity = String.valueOf(b);
                _item = product;

                Log.i(row1+" id"+_total +" total"+ _cost +" cost"+ _quantity+" quant", "Hello updated database");

                readDatabase.updateItem(row1, _item, _cost, _quantity, _total);

                fillData();

                dialog.dismiss();

            }
        });
        Button cancel = (Button) dialog.findViewById(R.id.cancel);
        cancel.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
            dialog.dismiss();   
            }
        });
        dialog.show();

        return true;
    }

    return super.onContextItemSelected(item);
}

@Override
protected void onListItemClick(ListView l, View v, int position, long thisID) {
    super.onListItemClick(l, v, position, thisID);

    l.showContextMenuForChild(v);

    Cursor cursor = (Cursor) getListAdapter().getItem(position);
    Quantity = cursor.getString(cursor
            .getColumnIndex(DatabaseHandler.KEY_QUANTITY));
    /*Total = cursor.getString(cursor
            .getColumnIndex(DatabaseHandler.KEY_TOTAL));*/

}

这里一切都很顺利，但我在 Logcat 中发现了一些错误，即 close() 没有在数据库上显式调用，类似这样。该错误并没有阻止我在任何地方的工作，但问题看起来很奇怪。我想我必须关闭光标，但不确定。我已经关闭了销毁数据库，但不确定游标。请帮忙。

提到同样的问题here但没有得到实际的解决方案

提前致谢

Answer 1

每次使用后关闭您的光标，那么您的问题就会得到解决

itemsCursor.close()

由于您没有关闭它，因此当您关闭数据库时，不会释放游标的资源，您会收到该错误。

将光标设置为全局变量，然后在 onDestroy 上

@Override
protected void onDestroy() {
    super.onDestroy();
    itemsCursor.close();
    db.close();
}

当您现在添加 close 语句作为 filldata 方法的最后一个语句时，listview 的 Adapter > 没有获取任何数据，因为 cursor 已经释放，因此您在 listview 中没有获取任何数据。