81 lines
2.8 KiB
Plaintext
81 lines
2.8 KiB
Plaintext
page.title=Loading Data in the Background
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page.tags=cursorloader
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trainingnavtop=true
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startpage=true
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@jd:body
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<div id="tb-wrapper">
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<div id="tb">
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<!-- Required platform, tools, add-ons, devices, knowledge, etc. -->
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<h2>Dependencies and prerequisites</h2>
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<ul>
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<li>
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Android 1.6 or later
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</li>
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</ul>
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<!-- related docs (NOT javadocs) -->
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<h2>You should also read</h2>
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<ul>
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<li>
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<a href="{@docRoot}guide/components/loaders.html">Loaders</a>
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</li>
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<li>
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<a href="{@docRoot}guide/topics/data/data-storage.html#db">Using Databases</a>
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</li>
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<li>
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<a href="{@docRoot}guide/topics/providers/content-provider-basics.html">Content Provider Basics</a>
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</li>
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</ul>
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<h2>Try it out</h2>
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<div class="download-box">
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<a href="{@docRoot}shareables/training/ThreadSample.zip" class="button">Download the sample</a>
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<p class="filename">ThreadSample.zip</p>
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</div>
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</div>
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</div>
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<p>
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Querying a {@link android.content.ContentProvider} for data you want to display takes time.
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If you run the query directly from an {@link android.app.Activity}, it may get blocked and
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cause the system to issue an "Application Not Responding" message. Even if it doesn't, users
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will see an annoying delay in the UI. To avoid these problems, you should initiate a query on a
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separate thread, wait for it to finish, and then display the results.
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</p>
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<p>
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You can do this in a straightforward way by using an object that runs a query asynchronously in
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the background and reconnects to your {@link android.app.Activity} when it's finished. This
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object is a {@link android.support.v4.content.CursorLoader}. Besides doing the initial
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background query, a {@link android.support.v4.content.CursorLoader} automatically re-runs the
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query when data associated with the query changes.
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</p>
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<p>
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This class describes how to use a {@link android.support.v4.content.CursorLoader} to run a
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background query. Examples in this class use the <a
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href="{@docRoot}tools/support-library/features.html#v4">v4 Support Library</a>
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versions of classes, which support platforms starting with Android 1.6.
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</p>
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<h2>Lessons</h2>
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<dl>
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<dt>
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<strong><a href="setup-loader.html">Running a Query with a CursorLoader</a></strong>
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</dt>
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<dd>
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Learn how to run a query in the background, using a
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{@link android.support.v4.content.CursorLoader}.
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</dd>
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<dt>
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<strong>
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<a href="handle-results.html">Handling the Results</a>
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</strong>
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</dt>
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<dd>
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Learn how to handle the {@link android.database.Cursor} returned from the query, and how
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to remove references to the current {@link android.database.Cursor} when the loader
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framework re-sets the {@link android.support.v4.content.CursorLoader}.
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</dd>
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</dl>
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