android-loadermanager | 易学教程

Using CursorLoader to query SQLite DB and populate AutoCompleteTextView

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问题 I have a SQLite database I would like to query. I want to target Android 2.2 through ICS. I came across this article on how to do this, but it uses deprecated code (does not query asynchronously, but on the UI thread). I've since read that I can use CursorLoader along with LoaderManager to do this task the preferred, best practices way (as to not bog down the UI thread). The problem is finding a concise example to explain to me how to do this. 1) Load the database, 2) query it, 3) use the

Accessing a Loader created in one fragment from another fragment

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I have an app with a fairly standard fragment layout. An expandable listview fragment on the left and a panel on the right that is used for different things depending on what the user chooses to do with the list on the left (displaying data, adding new data, etc). I'm using the LoaderManager (first time using loaders) with CommonWare's loaderex library as I have no need or desire to create a Content Provider for my database just so I can use a standard CursorLoader. This setup works great for displaying my list. The issue I am having is when I use the second fragment to add data to the

Why is Tablayout and Viewpager crashing with NullpointerException when I start a fragment with LoaderManager from TabFragment?

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I am following the tutorial of https://androidbelieve.com/navigation-drawer-with-swipe-tabs-using-design-support-library/ to implement sliding tablayout. It works perfect for empty fragments, However, I have 3 fragments with LoaderManagers and recyclerViews, each one loads different data. When the app loaded at the first time, if I click from the first fragment to the third fragment on the tabLayout without sliding or clicking to second one, it crashes. The data was not loading, as it implements LoaderManager, it started implementing from OnLoadFinished() method. I couldn't see onCreate().. or

IllegalStateException - Support LoaderManager with AutocompleteTextView

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One of the benefits I thought of using CursorLoaders and Loadermanagers was that you didn't need to manually manage the lifecycle of the cursor. So I used a loadermanager to bind an adapter to an AutoCompleteTextView using the support package. It works quite well except that it randomly throws an error saying "IllegalStateException - attempt to re-open an already closed object". Surely that's not supposed to happen if we're using the loader manager? Here's the code: package com.bhagwad.tennis; import android.appwidget.AppWidgetManager; import android.content.Intent; import android.database

Handle CursorLoader exceptions

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I have a Fragment implementing LoaderManager and using CursorLoader (nothing fancy). I want to catch exceptions thrown during the query but I don't see how!!! Any help? Thx. jsmith You would need to derive from CursorLoader to do it. Something like this: class MyCursorLoader extends CursorLoader { public MyCursorLoader(Context context) { super(context) } public CursorLoader(Context context, Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) { super(context, uri, projection, selection, selectionArgs, sortOrder); } @Override public Cursor loadInBackground()

Getting “Called doStart when already started” from LoaderManager. Why?

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My code has an Activity, that has a FragmentPagerAdapter that creates 'n' fragments as necessary. Activity has a loader, and each fragment has its own loader. All loaders have unique ID. (Activity's loader in fact determines the number of Pages in the adapter) I keep getting this warning here and there and can't put my finger on what's causing it. It doesn't seem to be critical, also looking at the LoaderManger's code throwing this warning, but still - warnings are usually signs for bugs.. Had originally used FragmentStatePagerAdapter and then moved to FragmentPagerAdapter, thinking that could

Android db loading chat for chat application

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问题 I'm creating a chat application and I need a little bit of guidance. I am using a sqlite database to store the chat as it comes in. I want my Activity, when it's open, to load the chat history from that particular chat and to continue to refresh as new chat is entered (my main question is how do I go about doing this). Should I use a CursorAdapter with an inital cursor of a query containing the chat for that conversation and set it as the adapter for the ListView? I have tried this, but the

Loaders and onLoaderReset Android

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问题 I implemented a Loader in my application for querying data from the database. I listen the changes that happen' by implementing LoaderCallbacks<Cursor> listener. The problem that I have is when using the onLoaderReset(Loader<Cursor> loader) method when my data change and I want to invalidate and free any data associated with the loader. In all the examples, in this method there is the following call: mAdapter.swapCursor(null); But the thing is I don't use the data from the cursor in adapter,

Will LoaderManager.restartLoader() always result in a call to onCreateLoader()?

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问题 LoaderManager has this method restartLoader(): public abstract Loader<D> restartLoader (int id, Bundle args, LoaderCallbacks<D> callback) Starts a new or restarts an existing Loader in this manager, registers the callbacks to it, and (if the activity/fragment is currently started) starts loading it. If a loader with the same id has previously been started it will automatically be destroyed when the new loader completes its work. The callback will be delivered before the old loader is

AsyncTaskLoader onLoadFinished with a pending task and config change

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问题 I'm trying to use an AsyncTaskLoader to load data in the background to populate a detail view in response to a list item being chosen. I've gotten it mostly working but I'm still having one issue. If I choose a second item in the list and then rotate the device before the load for the first selected item has completed , then the onLoadFinished() call is reporting to the activity being stopped rather than the new activity. This works fine when choosing just a single item and then rotating.