本文介绍了从列表片段中删除项目无法正常工作的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
我正在做一个基本的 android 应用程序来了解 sqlite.该应用程序只有一个列表片段，其中列出了一些产品和价格，例如:
Im doing a basic android app to learn about sqlite. The app just have a listfragment that list some products and the price like:
Pencil 1
Pen 1.20
...
并且可以单击列表中的项目将其删除.我使用游标加载器，因此数据库操作在后台完成.但我遇到了一个问题:
And its possible to click in a item of the list to delete it. Im using cursorloader so the db operations are done in background. But Im getting a issue:
- 当用户单击某个项目时，该项目不会从列表中删除，但如果我关闭并再次打开该应用，列表中的所有项目都已删除.
你知道问题出在哪里吗?为什么在项目中点击后通过删除点击的项目没有更新片段列表，为什么所有项目都被删除?
Do you know where is the issue? Why the fragmentlist is not updated by removing the clicked item after click in the item and why all items are being removed?
//列出产品和各自的价格
public class ProductsFragment extends ListFragment implements OnClickListener, LoaderManager.LoaderCallbacks<Cursor> {
private static final String[] PROJECTION=new String[] {
Provider.Products._ID, Provider.Products.TITLE,
Provider.Products.PRICE };
private CursorAdapter cursorAdapter;
public void onViewCreated(View view, Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
Cursor cursor = getActivity().getContentResolver().query(Provider.Products.CONTENT_URI, DBHelper.ALL_COLUMNS,
null,null,null,null);
String[] from = {DBHelper.TITLE, DBHelper.PRICE};
int[] to = {R.id.title, R.id.price};
cursorAdapter = new SimpleCursorAdapter(getActivity(), R.layout.item, null, from, to, 0);
setListAdapter(cursorAdapter);
getLoaderManager().initLoader(0, null, this);
}
//删除产品
@Override
public void onListItemClick(ListView l, View v, int pos, long id) {
super.onListItemClick(l, v, pos, id);
getActivity().getContentResolver().delete(Provider.Products.CONTENT_URI,String.valueOf(id), null);
Toast.makeText(getActivity(), "Item " + id + " clicked", Toast.LENGTH_SHORT).show();
}
//游标加载器方法
@Override
public Loader<Cursor> onCreateLoader(int i, Bundle bundle) {
return new CursorLoader(getActivity().getApplicationContext(), Provider.Products.CONTENT_URI, null, null, null, null);
}
@Override
public void onLoadFinished(Loader<Cursor> loader, Cursor cursor) {
cursorAdapter.swapCursor(cursor);
}
public void onLoaderReset(Loader<Cursor> loader) {
cursorAdapter.swapCursor(null);
}
//Provider 类删除方法:
@Override
public int delete(Uri url, String where, String[] whereArgs) {
return database.delete(DBHelper.TABLE_PRODUCTS, where, whereArgs);
}
同样的问题:
@Override
public int delete(Uri url, String where, String[] whereArgs) {
int count=db.getWritableDatabase().delete(TABLE, where, whereArgs);
getContext().getContentResolver().notifyChange(url, null);
return(count);
}
item.xml:
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="horizontal"
android:layout_width="match_parent"
android:layout_height="match_parent"
>
<TextView
android:id="@+id/title"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
/>
<TextView
android:id="@+id/price"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentRight="true"
/>
</RelativeLayout>
完整的产品片段:
public class ConstantsFragment extends ListFragment implements OnClickListener, LoaderManager.LoaderCallbacks<Cursor> {
private CursorAdapter cursorAdapter;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setHasOptionsMenu(true);
}
public void onViewCreated(View view, Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
Cursor cursor = getActivity().getContentResolver().query(Provider.Constants.CONTENT_URI, DatabaseHelper.ALL_COLUMNS,
null,null,null,null);
String[] from = {DatabaseHelper.TITLE, DatabaseHelper.VALUE};
int[] to = {R.id.title, R.id.value};
cursorAdapter = new SimpleCursorAdapter(getActivity(), R.layout.row, null, from, to, 0);
setListAdapter(cursorAdapter);
getLoaderManager().initLoader(0, null, this);
}
@Override
public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
inflater.inflate(R.menu.actions, menu);
super.onCreateOptionsMenu(menu, inflater);
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
if (item.getItemId()==R.id.add) {
add();
return(true);
}
return(super.onOptionsItemSelected(item));
}
@Override
public void onClick(DialogInterface dialog, int which) {
ContentValues values=new ContentValues();
AlertDialog dlg=(AlertDialog)dialog;
EditText title=(EditText)dlg.findViewById(R.id.title);
EditText value=(EditText)dlg.findViewById(R.id.value);
values.put(DatabaseHelper.TITLE, title.getText().toString());
values.put(DatabaseHelper.VALUE, value.getText().toString());
getActivity().getContentResolver().insert(Provider.Constants.CONTENT_URI, values);
getLoaderManager().restartLoader(0, null, this);
}
@Override
public void onListItemClick(ListView l, View v, int pos, long id) {
super.onListItemClick(l, v, pos, id);
getLoaderManager().restartLoader(0, null, this);
getActivity().getContentResolver().delete(Provider.Constants.CONTENT_URI,String.valueOf(id), null);
Toast.makeText(getActivity(), "Item id " + id + "clicked", Toast.LENGTH_SHORT).show();
}
private void add() {
LayoutInflater inflater=getActivity().getLayoutInflater();
View addView=inflater.inflate(R.layout.add_edit, null);
AlertDialog.Builder builder=new AlertDialog.Builder(getActivity());
builder.setTitle(R.string.add_title).setView(addView)
.setPositiveButton(R.string.ok, this)
.setNegativeButton(R.string.cancel, null).show();
}
@Override
public Loader<Cursor> onCreateLoader(int i, Bundle bundle) {
return new CursorLoader(getActivity().getApplicationContext(), Provider.Constants.CONTENT_URI, null, null, null, null);
}
public void insertNote(String title, Double value){
ContentValues values = new ContentValues();
values.put(DatabaseHelper.TITLE, title);
values.put(DatabaseHelper.VALUE, value);
Uri noteUri = getActivity().getContentResolver().insert(Provider.Constants.CONTENT_URI, values);
Log.d("MainActivity", "Inserted" + noteUri.getLastPathSegment());
}
@Override
public void onLoadFinished(Loader<Cursor> loader, Cursor cursor) {
cursorAdapter.swapCursor(cursor);
}
@Override
public void onLoaderReset(Loader<Cursor> loader) {
cursorAdapter.swapCursor(null);
}
}
推荐答案
in on click after item delete call to notifyDatasetChanged()
in on click after item deleted call to notifyDatasetChanged()
这篇关于从列表片段中删除项目无法正常工作的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！