java Android ListFragment数据未通过SimpleCursorAdapter/LoaderManager/notifyChange()更新
我有一个ListFragment,它显示了存储在数据库表中的所有购物清单的名称
问题是,当我向表中添加新的购物列表行时,UI上的ListFragment不会自动更新。(只有关闭并重新启动应用程序,才能看到更改。)
首先,这是我添加购物清单时在DbContentProvider
类中执行的代码:
`
// Insert the values into the table
id = db.insert(SHOPPING_LISTS_META_TABLE, null, values);
if (id > -1) {
// Construct and return the URI of the newly inserted row.
Uri insertedId = ContentUris.withAppendedId(CONTENT_URI_SHOPPING_LISTS_META, id);
// Notify any observers of the change in the data set.
Log.d(LOG_TAG, "................. notifyChange(\"" + insertedId + "\", null)");
getContext().getContentResolver().notifyChange(insertedId, null);
Log.d(LOG_TAG, "................. notifyChange() done");
return insertedId;
}
else {
return null;
}
`
。。。这是它的LogCat输出
10-28 12:29:41.133: D/SQLiteOpenHelper(19401): ................. notifyChange("content://org.example.myapp.DbContentProvider/shopping_lists_meta/12", null)
10-28 12:29:41.143: D/SQLiteOpenHelper(19401): ................. notifyChange() done
10-28 12:29:41.153: D/HomeActivity(19401): Shopping list, "My Test Shopping List" created: content://org.example.myapp.DbContentProvider/shopping_lists_meta/12
10-28 12:29:41.183: D/AbsListView(19401): unregisterIRListener() is called
10-28 12:29:41.193: E/ViewRootImpl(19401): sendUserActionEvent() mView == null
10-28 12:29:41.503: D/AbsListView(19401): unregisterIRListener() is called
在LogCat中,当我添加新的购物列表行时,我的ListFragment类根本没有输出。这是我的ListFragment类
`
公共类ShoppingListNamesListFragment扩展ListFragment实现LoaderManager。装载机回扣{
private final static String LOG_TAG = ShoppingListNamesListFragment.class.getSimpleName();
// This is the Adapter being used to display the list's data
public static SimpleCursorAdapter mAdapter;
// These are the Contacts rows that we will retrieve
static final String[] PROJECTION = {DbContentProvider.KEY_ID,
DbContentProvider.KEY_SHOPPING_LIST_NAME,
DbContentProvider.KEY_IS_SHOPPING_LIST_SELECTED};
// This is the select criteria
static final String SELECTION = null;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Log.d(LOG_TAG, "................. onCreate()");
}
@Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
Log.d(LOG_TAG, "................. onActivityCreated()");
// For the cursor adapter, specify which columns go into which views
String[] fromColumns = {DbContentProvider.KEY_SHOPPING_LIST_NAME};
int[] toViews = {安卓.R.id.text1}; // The TextView in simple_list_item_1
// Create an empty adapter we will use to display the loaded data.
// We pass null for the cursor, then update it in onLoadFinished()
mAdapter = new SimpleCursorAdapter(this.getActivity(),
安卓.R.layout.simple_list_item_1, null,
fromColumns, toViews, 0);
setListAdapter(mAdapter);
// Prepare the loader. Either re-connect with an existing one,
// or start a new one.
getLoaderManager().initLoader(0, null, this);
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
Log.d(LOG_TAG, "................. onCreateView()");
return super.onCreateView(inflater, container, savedInstanceState);
}
// Called when a new Loader needs to be created
@Override
public Loader<Cursor> onCreateLoader(int id, Bundle args) {
Log.d(LOG_TAG, "................. onCreateLoader()");
// Now create and return a CursorLoader that will take care of
// creating a Cursor for the data being displayed.
return new CursorLoader(getActivity(), DbContentProvider.CONTENT_URI_SHOPPING_LISTS_META,
PROJECTION, SELECTION, null, null);
}
// Called when a previously created loader has finished loading
@Override
public void onLoadFinished(Loader<Cursor> loader, Cursor data) {
Log.d(LOG_TAG, "................. onLoaderFinished()");
// Swap the new cursor in. (The framework will take care of closing the
// old cursor once we return.)
mAdapter.swapCursor(data);
}
// Called when a previously created loader is reset, making the data unavailable
@Override
public void onLoaderReset(Loader<Cursor> loader) {
Log.d(LOG_TAG, "................. onLoaderReset()");
// This is called when the last Cursor provided to onLoadFinished()
// above is about to be closed. We need to make sure we are no
// longer using it.
mAdapter.swapCursor(null);
}
@Override
public void onListItemClick(ListView l, View v, int position, long id) {
makeToast("shopping list clicked: " + position);
Log.d(LOG_TAG, "shopping list clicked: " + position);
}
private void makeToast(String msg) {
Toast.makeText(getActivity(), msg, Toast.LENGTH_SHORT).show();
}
}
注意——在我的DbContentProvider
课上,我有
public static final Uri CONTENT_URI_SHOPPING_LISTS_META = Uri.parse("content://org.example.myapp.DbContentProvider/shopping_lists_meta");
public static final String SHOPPING_LISTS_META_TABLE = "shopping_lists_meta";
我的代码基于this Android ListFragment / LoaderManager example。我发现,没有一个类似的问题能解决我的问题
我对安卓相当陌生,所以这可能是我犯的一个简单错误。但是,本质上,在我看来,当notifyChange()
在我的DbContentProvider
类中被调用时,我的ListFragment没有被通知(或者在这个区域有其他一些错误)。有人能帮忙吗
# 1 楼答案
在花了好几个小时做这件事之后,我创建了一个TestListActivity,它连接到了原生联系人内容提供商——所有这些都正常工作/更新,所以我知道问题可能出在我自己编写的内容提供商身上
我找到了答案。事实证明,我没有对我的内容提供者的
query()
方法返回的cursor
调用setNotificationUri(ContentResolver cr, Uri uri)
。(我敢肯定,这在我写的雷托·摩尔的书中从来没有提到过……):总之,现在一切都好了!:)