Question

我在我的应用中实施了一个快餐栏，其中有一个撤销按钮来撤消删除。目前它的工作原理是，当用户删除项目时，我通过从数据库执行查询来保留项目的光标，然后从数据库中删除该项目，并通过notifyChange()更新列表。当用户点击小吃栏上的撤消按钮时，我从保存的光标中提取内容，创建一个新的ContentValue并将其插入数据库，再次调用notifyChange()来更新列表。
我不喜欢这种方法。数据库操作太多了有什么方法可以从ListView中删除/隐藏项目，只在小吃栏消失时删除项目？我尝试将可见性设置为GONE或INVISIBLE但是在ListView的中间留下了一个空白区域我正在使用CursorAdapter来填充ListView。每个列表项上都有一个3点菜单，显示删除选项这是我当前的CursorAdapter代码

public class ProductCursorAdapter extends CursorAdapter {

private static final String LOG_TAG = ProductCursorAdapter.class.getSimpleName();
protected ContentResolver contentResolver;

public ProductCursorAdapter(Context context, Cursor c, ContentResolver contentResolver) {
    super(context, c);
    this.contentResolver = contentResolver;
}

@Override
public View newView(Context context, Cursor cursor, ViewGroup parent) {
    return LayoutInflater.from(context).inflate(R.layout.list_item, parent, false);
}

@Override
public void bindView(final View view, final Context context, final Cursor cursor) {
    ImageView thumbnail = (ImageView) view.findViewById(R.id.thumbnail);
    TextView name = (TextView) view.findViewById(R.id.name);
    TextView quantity = (TextView) view.findViewById(R.id.quantity);
    TextView price = (TextView) view.findViewById(R.id.price);
    TextView supplier = (TextView) view.findViewById(R.id.supplier);

    final long id = cursor.getLong(cursor.getColumnIndexOrThrow(ProductEntry._ID));

    ImageView threeDotMenu = (ImageView) view.findViewById(R.id.three_dot_menu);
    threeDotMenu.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            PopupMenu popup = new PopupMenu(context, v);
            popup.getMenuInflater().inflate(R.menu.list_item_context_menu, popup.getMenu());
            popup.setOnMenuItemClickListener(new PopupMenu.OnMenuItemClickListener() {
                @Override
                public boolean onMenuItemClick(MenuItem item) {
                    switch (item.getItemId()) {
                        case R.id.context_delete_product:
                            //the uri of the product we're deleting
                            Uri currentProductUri = ContentUris.withAppendedId(ProductEntry.CONTENT_URI, id);
                            //What to extract from the database
                            String[] projection = {
                                    ProductEntry._ID,
                                    ProductEntry.COLUMN_NAME,
                                    ProductEntry.COLUMN_QUANTITY,
                                    ProductEntry.COLUMN_PRICE,
                                    ProductEntry.COLUMN_SUPPLIER,
                                    ProductEntry.COLUMN_IMAGE
                            };
                            //retrieve the product from the database before deleting in case
                            //we need to restore it later
                            Cursor cursor = contentResolver.query(currentProductUri,
                                    projection,
                                    null,
                                    null,
                                    null,
                                    null);
                            cursor.moveToFirst();
                            Snackbar snackbar = Snackbar.make(view.getRootView().findViewById(R.id.coordinator_layout), "Product Deleted", Snackbar.LENGTH_LONG);
                            snackbar.setAction("Undo", new MyUndoListener(cursor));
                            snackbar.show();
                            contentResolver.delete(currentProductUri, null, null);
                            return true;
                        default:
                            return false;
                    }
                }
            });
            popup.show();
        }
    });


    . . .


}

public class MyUndoListener implements View.OnClickListener {
    Cursor cursor = null;

    public MyUndoListener(Cursor cursor) {
        this.cursor = cursor;

    }

    @Override
    public void onClick(View v) {
        contentResolver.insert(ProductEntry.CONTENT_URI, extractFromCursor(cursor));
    }

    private ContentValues extractFromCursor(Cursor cursor) {

        int id = cursor.getInt(cursor.getColumnIndexOrThrow(ProductEntry._ID));

        String name = cursor.getString(cursor.getColumnIndexOrThrow(ProductEntry.COLUMN_NAME));

        int quantity = cursor.getInt(cursor.getColumnIndexOrThrow(ProductEntry.COLUMN_QUANTITY));

        int price = cursor.getInt(cursor.getColumnIndexOrThrow(ProductEntry.COLUMN_PRICE));

        String supplier = cursor.getString(cursor.getColumnIndexOrThrow(ProductEntry.COLUMN_SUPPLIER));

        byte[] image = cursor.getBlob(cursor.getColumnIndexOrThrow(ProductEntry.COLUMN_IMAGE));
        ContentValues value = new ContentValues();
        value.put(ProductEntry._ID, id);
        value.put(ProductEntry.COLUMN_NAME, name);
        value.put(ProductEntry.COLUMN_PRICE, price);
        value.put(ProductEntry.COLUMN_QUANTITY, quantity);
        value.put(ProductEntry.COLUMN_SUPPLIER, supplier);
        value.put(ProductEntry.COLUMN_IMAGE, image);
        cursor.close();
        return value;

    }

}

}

Answer 1

Nishan，For This制作数据库值的Arraylist，然后绑定listview。每当你想删除一个项目（不是从你的数据库中），然后制作没有该项目的arraylist的副本，并再次绑定列表视图。

因此，您的数据库保持不变，并且可以在撤消时再次使用它。那么你要删除哪个项目，在没有该项目的情况下从orignal arraylst绑定一个新的arraylist并使用它。

如何从ListView中删除项目而不将其从数据库中删除？

1 个答案: