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POFragments and Notifications: Target different Activities from Notification; depending on screen configuration
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copied!<h2>Question:</h2> <p>How to decide what <code>Activity</code> a <code>Notification</code> should launch if the target might depend on the configuration (screen size, orientation etc); as is often the case when one uses <code>Fragment</code>s?</p> <hr> <h2>Details:</h2> <p>Let's consider the <a href="http://developer.android.com/training/multiscreen/index.html" rel="noreferrer">NewsReader sample</a> that demonstrates how to use <code>Fragment</code>s to produce an app that plays well with multiple screen sizes and orientations. This app is structured as follows:</p> <ul> <li>A <code>HeadlinesFragment</code>.</li> <li>An <code>ArticleFragment</code>.</li> <li>A "main" activity (<code>NewsReaderActivity</code>). In dual pane mode, this activity contains both the fragments. In single-pane mode, it only contains the <code>HeadlinesFragment</code>.</li> <li>An <code>ArticleActivity</code>. This activity is only used in single pane mode; and it contains the <code>ArticleFragment</code>.</li> </ul> <p>Now, suppose I were to enhance this app to add a background <code>Service</code> that listens for news updates and notifies the user via status bar notifications whenever there are new news items. A reasonable requirements listing might read like so:</p> <ol> <li>If there are multiple news updates, clicking on the notification should always take the user to the headlines list.</li> <li>If there's only one update, clicking on the notification should open up the brand new news article.</li> </ol> <p>Note that these requirements translate to different target activities depending on current configuration. In particular,</p> <ol> <li>Requirement (1) in either mode = <code>NewsReaderActivity</code>.</li> <li>Requirement (2) in dual-pane mode = <code>NewsReaderActivity</code>.</li> <li>Requirement (2) in single-pane mode = <code>ArticleActivity</code>.</li> </ol> <p>What would be an elegant way to achieve (2) and (3) above? I think one can safely rule out the possibility of the <code>Service</code> probing for the current configuration to decide what activity to target with the <code>PendingIntent</code>. </p> <p>One solution I thought of was to skip (2) and always do (3) - i.e., always launch <code>ArticleActivity</code> if there's only one news update. This snippet from ArticleActivity looked promising:</p> <pre><code>@Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); //... //... // If we are in two-pane layout mode, this activity is no longer necessary if (getResources().getBoolean(R.bool.has_two_panes)) { finish(); return; } //... //... } </code></pre> <p>This code ensures that if one is viewing the <code>ArticleActivity</code>, but switches to a configuration where it is no longer required (for example from portrait to landscape); then the activity simple closes. </p> <p>However, this won't work in our case since the intent will have the <code>FLAG_ACTIVITY_NEW_TASK</code> flag set; we would have created a new task, and there is no "previous" activity on the stack. So, calling <code>finish()</code> would just clear the entire stack.</p> <p>So, how does one decide what activity to launch from a notification, if the activity to launch depends on screen configuration?</p>

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