1page.title=Loading Data in the Background
2page.tags=cursorloader
3
4trainingnavtop=true
5startpage=true
6
7@jd:body
8<div id="tb-wrapper">
9<div id="tb">
10
11<!-- Required platform, tools, add-ons, devices, knowledge, etc. -->
12<h2>Dependencies and prerequisites</h2>
13<ul>
14    <li>
15        Android 1.6 or later
16    </li>
17</ul>
18
19<!-- related docs (NOT javadocs) -->
20<h2>You should also read</h2>
21<ul>
22    <li>
23        <a href="{@docRoot}guide/components/loaders.html">Loaders</a>
24    </li>
25    <li>
26        <a href="{@docRoot}guide/topics/data/data-storage.html#db">Using Databases</a>
27    </li>
28    <li>
29<a href="{@docRoot}guide/topics/providers/content-provider-basics.html">Content Provider Basics</a>
30    </li>
31</ul>
32
33<h2>Try it out</h2>
34<div class="download-box">
35    <a href="{@docRoot}shareables/training/ThreadSample.zip" class="button">Download the sample</a>
36    <p class="filename">ThreadSample.zip</p>
37</div>
38
39</div>
40</div>
41<p>
42    Querying a {@link android.content.ContentProvider} for data you want to display takes time.
43    If you run the query directly from an {@link android.app.Activity}, it may get blocked and
44    cause the system to issue an "Application Not Responding" message. Even if it doesn't, users
45    will see an annoying delay in the UI. To avoid these problems, you should initiate a query on a
46    separate thread, wait for it to finish, and then display the results.
47</p>
48<p>
49    You can do this in a straightforward way by using an object that runs a query asynchronously in
50    the background and reconnects to your {@link android.app.Activity} when it's finished. This
51    object is a {@link android.support.v4.content.CursorLoader}. Besides doing the initial
52    background query, a {@link android.support.v4.content.CursorLoader} automatically re-runs the
53    query when data associated with the query changes.
54</p>
55<p>
56    This class describes how to use a {@link android.support.v4.content.CursorLoader} to run a
57    background query. Examples in this class use the <a
58    href="{@docRoot}tools/support-library/features.html#v4">v4 Support Library</a>
59    versions of classes, which support platforms starting with Android 1.6.
60</p>
61<h2>Lessons</h2>
62<dl>
63    <dt>
64        <strong><a href="setup-loader.html">Running a Query with a CursorLoader</a></strong>
65    </dt>
66    <dd>
67        Learn how to run a query in the background, using a
68        {@link android.support.v4.content.CursorLoader}.
69    </dd>
70    <dt>
71        <strong>
72        <a href="handle-results.html">Handling the Results</a>
73        </strong>
74    </dt>
75    <dd>
76        Learn how to handle the {@link android.database.Cursor} returned from the query, and how
77        to remove references to the current {@link android.database.Cursor} when the loader
78        framework re-sets the {@link android.support.v4.content.CursorLoader}.
79    </dd>
80</dl>
81