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Diffstat (limited to 'docs/html/guide/components')
| -rw-r--r-- | docs/html/guide/components/recents.jd | 256 | ||||
| -rw-r--r-- | docs/html/guide/components/tasks-and-back-stack.jd | 152 |
2 files changed, 336 insertions, 72 deletions
diff --git a/docs/html/guide/components/recents.jd b/docs/html/guide/components/recents.jd new file mode 100644 index 0000000..b44c682 --- /dev/null +++ b/docs/html/guide/components/recents.jd @@ -0,0 +1,256 @@ +page.title=Overview Screen +page.tags="recents","overview" + +@jd:body + +<div id="qv-wrapper"> +<div id="qv"> + + <h2>In this document</h2> + <ol> + <li><a href="#adding">Adding Tasks to the Overview Screen</a> + <ol> + <li><a href="#flag-new-doc">Using the Intent flag to add a task</a></li> + <li><a href="#attr-doclaunch">Using the Activity attribute to add a task</a></li> + </ol> + </li> + <li><a href="#removing">Removing Tasks</a> + <ol> + <li><a href="#apptask-remove">Using the AppTask class to remove tasks</a></li> + <li><a href="#retain-finished">Retaining finished tasks</a></li> + </ol> + </li> + </ol> + + <h2>Key classes</h2> + <ol> + <li>{@link android.app.ActivityManager.AppTask}</li> + <li>{@link android.content.Intent}</li> + </ol> + + <h2>Sample code</h2> + <ol> + <li><a href="{@docRoot}samples/activitytasks/index.html">Document-centric Apps</a></li> + </ol> + +</div> +</div> + +<p>The overview screen (also referred to as the recents screen, recent task list, or recent apps) +is a system-level UI that lists recently accessed <a href="{@docRoot}guide/components/activities.html"> +activities</a> and <a href="{@docRoot}guide/components/tasks-and-back-stack.html">tasks</a>. The +user can navigate through the list and select a task to resume, or the user can remove a task from +the list by swiping it away. With the Android 5.0 release (API level 21), multiple instances of the +same activity containing different documents may appear as tasks in the overview screen. For example, +Google Drive may have a task for each of several Google documents. Each document appears as a +task in the overview screen.</p> + +<img src="{@docRoot}images/components/recents.png" alt="" width="284" /> +<p class="img-caption"><strong>Figure 1.</strong> The overview screen showing three Google Drive +documents, each represented as a separate task.</p> + +<p>Normally you should allow the system to define how your tasks and +activities are represented in the overview screen, and you don't need to modify this behavior. +However, your app can determine how and and when activities appear in the overview screen. The +{@link android.app.ActivityManager.AppTask} class lets you manage tasks, and the activity flags of +the {@link android.content.Intent} class let you specify when an activity is added or removed from +the overview screen. Also, the <code><a href="{@docRoot}guide/topics/manifest/activity-element.html"> +<activity></a></code> attributes let you set the behavior in the manifest.</p> + +<h2 id="adding">Adding Tasks to the Overview Screen</h2> + +<p>Using the flags of the {@link android.content.Intent} class to add a task affords greater control +over when and how a document gets opened or reopened in the overview screen. When you use the +<code><a href="{@docRoot}guide/topics/manifest/activity-element.html"><activity></a></code> +attributes you can choose between always opening the document in a new task or reusing an +existing task for the document.</p> + +<h3 id="flag-new-doc">Using the Intent flag to add a task</h3> + +<p>When you create a new document for your activity, you call the +{@link android.app.ActivityManager.AppTask#startActivity(android.content.Context, android.content.Intent, android.os.Bundle) startActivity()} +method of the {@link android.app.ActivityManager.AppTask} class, passing to it the intent that +launches the activity. To insert a logical break so that the system treats your activity as a new +task in the overview screen, pass the {@link android.content.Intent#FLAG_ACTIVITY_NEW_DOCUMENT} flag +in the {@link android.content.Intent#addFlags(int) addFlags()} method of the {@link android.content.Intent} +that launches the activity.</p> + +<p class="note"><strong>Note:</strong> The {@link android.content.Intent#FLAG_ACTIVITY_NEW_DOCUMENT} +flag replaces the {@link android.content.Intent#FLAG_ACTIVITY_CLEAR_WHEN_TASK_RESET} flag, +which is deprecated as of Android 5.0 (API level 21).</p> + +<p>If you set the {@link android.content.Intent#FLAG_ACTIVITY_MULTIPLE_TASK} flag when you create +the new document, the system always creates a new task with the target activity as the root. +This setting allows the same document to be opened in more than one task. The following code demonstrates +how the main activity does this:</p> + +<p class="code-caption"><a href="{@docRoot}samples/activitytasks/src/com/example/android/documentcentricrecents/DocumentCentricActivity.html"> +DocumentCentricActivity.java</a></p> +<pre> +public void createNewDocument(View view) { + final Intent newDocumentIntent = newDocumentIntent(); + if (useMultipleTasks) { + newDocumentIntent.addFlags(Intent.FLAG_ACTIVITY_MULTIPLE_TASK); + } + startActivity(newDocumentIntent); + } + + private Intent newDocumentIntent() { + boolean useMultipleTasks = mCheckbox.isChecked(); + final Intent newDocumentIntent = new Intent(this, NewDocumentActivity.class); + newDocumentIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_DOCUMENT); + newDocumentIntent.putExtra(KEY_EXTRA_NEW_DOCUMENT_COUNTER, incrementAndGet()); + return newDocumentIntent; + } + + private static int incrementAndGet() { + Log.d(TAG, "incrementAndGet(): " + mDocumentCounter); + return mDocumentCounter++; + } +} +</pre> + +<p class="note"><strong>Note:</strong> Activities launched with the {@code FLAG_ACTIVITY_NEW_DOCUMENT} +flag must have the {@code android:launchMode="standard"} attribute value (the default) set in the +manifest.</p> + +<p>When the main activity launches a new activity, the system searches through existing tasks for +one whose intent matches the intent component name and the Intent data for the activity. If the task +is not found, or the intent contained the {@link android.content.Intent#FLAG_ACTIVITY_MULTIPLE_TASK} +flag, a new task will be created with the activity as its root. If it finds one, it brings that task +to the front and passes the new intent to {@link android.app.Activity#onNewIntent onNewIntent()}. +The new activity gets the intent and creates a new document in the overview screen, as in the +following example:</p> + +<p class="code-caption"><a href="{@docRoot}samples/activitytasks/src/com/example/android/documentcentricrecents/NewDocumentActivity.html"> +NewDocumentActivity.java</a></p> +<pre> +@Override +protected void onCreate(Bundle savedInstanceState) { + super.onCreate(savedInstanceState); + setContentView(R.layout.activity_new_document); + mDocumentCount = getIntent() + .getIntExtra(DocumentCentricActivity.KEY_EXTRA_NEW_DOCUMENT_COUNTER, 0); + mDocumentCounterTextView = (TextView) findViewById( + R.id.hello_new_document_text_view); + setDocumentCounterText(R.string.hello_new_document_counter); +} + +@Override +protected void onNewIntent(Intent intent) { + super.onNewIntent(intent); + /* If FLAG_ACTIVITY_MULTIPLE_TASK has not been used, this activity + is reused to create a new document. + */ + setDocumentCounterText(R.string.reusing_document_counter); +} +</pre> + + +<h3 id="#attr-doclaunch">Using the activity attribute to add a task</h3> + +<p>An activity can also specify in its manifest that it always launches into a new task by using +the <code><a href="{@docRoot}guide/topics/manifest/activity-element.html"><activity></a></code> +attribute, <a href="{@docRoot}guide/topics/manifest/activity-element.html#dlmode"> +{@code android:documentLaunchMode}</a>. This attribute has four values which produce the following +effects when the user opens a document with the application:</p> + +<dl> + <dt>"{@code intoExisting}"</dt> + <dd>The activity reuses an existing task for the document. This is the same as setting the + {@link android.content.Intent#FLAG_ACTIVITY_NEW_DOCUMENT} flag <em>without</em> setting the + {@link android.content.Intent#FLAG_ACTIVITY_MULTIPLE_TASK} flag, as described in + <a href="#flag-new-doc">Using the Intent flag to add a task</a>, above.</dd> + + <dt>"{@code always}"</dt> + <dd>The activity creates a new task for the document, even if the document is already opened. Using + this value is the same as setting both the {@link android.content.Intent#FLAG_ACTIVITY_NEW_DOCUMENT} + and {@link android.content.Intent#FLAG_ACTIVITY_MULTIPLE_TASK} flags.</dd> + + <dt>"{@code none”}"</dt> + <dd>The activity does not create a new task for the document. The overview screen treats the + activity as it would by default: it displays a single task for the app, which + resumes from whatever activity the user last invoked.</dd> + + <dt>"{@code never}"</dt> + <dd>The activity does not create a new task for the document. Setting this value overrides the + behavior of the {@link android.content.Intent#FLAG_ACTIVITY_NEW_DOCUMENT} + and {@link android.content.Intent#FLAG_ACTIVITY_MULTIPLE_TASK} flags, if either of these are set + in the intent, and the overview screen displays a single task for the app, which resumes from + whatever activity the user last invoked.</dd> +</dl> + +<p class="note"><strong>Note:</strong> For values other than {@code none} and {@code never} the +activity must be defined with {@code launchMode="standard"}. If this attribute is not specified, +{@code documentLaunchMode="none"} is used.</p> + +<h2 id="removing">Removing Tasks</h2> + +<p>By default a document task is automatically removed from the overview screen when its activity +finishes. You can override this behavior with the {@link android.app.ActivityManager.AppTask} class, +with an {@link android.content.Intent} flag, or with an<code><a href="{@docRoot}guide/topics/manifest/activity-element.html"> +<activity></a></code> attribute.</p> + +<p>You can always exclude a task from the overview screen entirely by setting the +<code><a href="{@docRoot}guide/topics/manifest/activity-element.html"><activity></a></code> +attribute, <a href="{@docRoot}guide/topics/manifest/activity-element.html#exclude"> +{@code android:excludeFromRecents}</a> to {@code true}.</p> + +<p>You can set the maximum number of tasks that your app can include in the overview screen by setting +the <code><a href="{@docRoot}guide/topics/manifest/activity-element.html"><activity></a></code> +attribute <a href="{@docRoot}guide/topics/manifest/activity-element.html#maxrecents">{@code android:maxRecents} +</a> to an integer value. The default is 16. When the maximum number of tasks is reached, the least +recently used task is removed from the overview screen. The {@code android:maxRecents} maximum value +is 50 (25 on low memory devices); values less than 1 are not valid.</p> + +<h3 id="#apptask-remove">Using the AppTask class to remove tasks</h3> + +<p>In the activity that creates a new task in the overview screen, you can +specify when to remove the task and finish all activities associated with it by calling +the {@link android.app.ActivityManager.AppTask#finishAndRemoveTask() finishAndRemoveTask()} method.</p> + +<p class="code-caption"><a href="{@docRoot}samples/activitytasks/index.html"> +NewDocumentActivity.java</a></p> +<pre> +public void onRemoveFromRecents(View view) { + // The document is no longer needed; remove its task. + finishAndRemoveTask(); +} +</pre> + +<p class="note"><strong>Note:</strong> Using the +{@link android.app.ActivityManager.AppTask#finishAndRemoveTask() finishAndRemoveTask()} method +overrides the use of the {@link android.content.Intent#FLAG_ACTIVITY_RETAIN_IN_RECENTS} tag, +discussed below.</p> + +<h3 id="#retain-finished">Retaining finished tasks</h3> + +<p>If you want to retain a task in the overview screen, even if its activity has finished, pass +the {@link android.content.Intent#FLAG_ACTIVITY_RETAIN_IN_RECENTS} flag in the +{@link android.content.Intent#addFlags(int) addFlags()} method of the Intent that launches the activity.</p> + +<p class="code-caption"><a href="{@docRoot}samples/activitytasks/src/com/example/android/documentcentricrecents/DocumentCentricActivity.html"> +DocumentCentricActivity.java</a></p> +<pre> +private Intent newDocumentIntent() { + final Intent newDocumentIntent = new Intent(this, NewDocumentActivity.class); + newDocumentIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_DOCUMENT | + android.content.Intent.FLAG_ACTIVITY_RETAIN_IN_RECENTS); + newDocumentIntent.putExtra(KEY_EXTRA_NEW_DOCUMENT_COUNTER, incrementAndGet()); + return newDocumentIntent; +} +</pre> + +<p>To achieve the same effect, set the +<code><a href="{@docRoot}guide/topics/manifest/activity-element.html"><activity></a></code> +attribute <a href="{@docRoot}guide/topics/manifest/activity-element.html#autoremrecents"> +{@code android:autoRemoveFromRecents}</a> to {@code false}. The default value is {@code true} +for document activities, and {@code false} for regular activities. Using this attribute overrides +the {@link android.content.Intent#FLAG_ACTIVITY_RETAIN_IN_RECENTS} flag, discussed previously.</p> + + + + + + + diff --git a/docs/html/guide/components/tasks-and-back-stack.jd b/docs/html/guide/components/tasks-and-back-stack.jd index e054313..aaef10e 100644 --- a/docs/html/guide/components/tasks-and-back-stack.jd +++ b/docs/html/guide/components/tasks-and-back-stack.jd @@ -21,7 +21,8 @@ parent.link=activities.html <h2>Articles</h2> <ol> - <li><a href="http://android-developers.blogspot.com/2010/04/multitasking-android-way.html">Multitasking the Android Way</a></li> + <li><a href="http://android-developers.blogspot.com/2010/04/multitasking-android-way.html"> + Multitasking the Android Way</a></li> </ol> <h2>See also</h2> @@ -31,6 +32,7 @@ Navigation</a></li> <li><a href="{@docRoot}guide/topics/manifest/activity-element.html">{@code <activity>} manifest element</a></li> + <li><a href="{@docRoot}guide/components/recents.html">Overview Screen</a></li> </ol> </div> </div> @@ -39,12 +41,12 @@ element</a></li> <p>An application usually contains multiple <a href="{@docRoot}guide/components/activities.html">activities</a>. Each activity should be designed around a specific kind of action the user can perform and can start other -activities. For example, an email application might have one activity to show a list of new email. -When the user selects an email, a new activity opens to view that email.</p> +activities. For example, an email application might have one activity to show a list of new messages. +When the user selects a message, a new activity opens to view that message.</p> <p>An activity can even start activities that exist in other applications on the device. For -example, if your application wants to send an email, you can define an intent to perform a "send" -action and include some data, such as an email address and a message. An activity from another +example, if your application wants to send an email message, you can define an intent to perform a +"send" action and include some data, such as an email address and a message. An activity from another application that declares itself to handle this kind of intent then opens. In this case, the intent is to send an email, so an email application's "compose" activity starts (if multiple activities support the same intent, then the system lets the user select which one to use). When the email is @@ -53,8 +55,8 @@ though the activities may be from different applications, Android maintains this experience by keeping both activities in the same <em>task</em>.</p> <p>A task is a collection of activities that users interact with -when performing a certain job. The activities are arranged in a stack (the "back stack"), in the -order in which each activity is opened.</p> +when performing a certain job. The activities are arranged in a stack (the <em>back stack</em>), in +the order in which each activity is opened.</p> <!-- SAVE FOR WHEN THE FRAGMENT DOC IS ADDED <div class="sidebox-wrapper"> @@ -134,7 +136,8 @@ started Task A. Now, Task A comes to the foreground—all three activities in its stack are intact and the activity at the top of the stack resumes. At this point, the user can also switch back to Task B by going Home and selecting the application icon -that started that task (or by selecting the app's task from the <em>recent apps</em> screen). +that started that task (or by selecting the app's task from the +<a href="{@docRoot}guide/components/recents.html">overview screen</a>). This is an example of multitasking on Android.</p> <p class="note"><strong>Note:</strong> Multiple tasks can be held in the background at once. @@ -195,8 +198,8 @@ system memory. When this happens, information about the activity state is lost. system still knows that the activity has a place in the back stack, but when the activity is brought to the top of the stack the system must recreate it (rather than resume it). In order to -avoid losing the user's work, you should proactively retain it by implementing the {@link -android.app.Activity#onSaveInstanceState onSaveInstanceState()} callback +avoid losing the user's work, you should proactively retain it by implementing the +{@link android.app.Activity#onSaveInstanceState onSaveInstanceState()} callback methods in your activity.</p> <p>For more information about how to save your activity state, see the <a @@ -218,27 +221,26 @@ instance on top of the back stack); or, you want your back stack to be cleared o activities except for the root activity when the user leaves the task.</p> <p>You can do these things and more, with attributes in the -<a href="{@docRoot}guide/topics/manifest/activity-element.html">{@code -<activity>}</a> manifest element and with flags in the intent that you pass to {@link -android.app.Activity#startActivity startActivity()}.</p> +<a href="{@docRoot}guide/topics/manifest/activity-element.html">{@code <activity>}</a> +manifest element and with flags in the intent that you pass to +{@link android.app.Activity#startActivity startActivity()}.</p> -<p>In this regard, the principal <a -href="{@docRoot}guide/topics/manifest/activity-element.html">{@code <activity>}</a> -attributes you can use are:</p> +<p>In this regard, the principal <a href="{@docRoot}guide/topics/manifest/activity-element.html"> +{@code <activity>}</a> attributes you can use are:</p> <ul class="nolist"> - <li><a href="{@docRoot}guide/topics/manifest/activity-element.html#aff">{@code -taskAffinity}</a></li> - <li><a href="{@docRoot}guide/topics/manifest/activity-element.html#lmode">{@code -launchMode}</a></li> - <li><a href="{@docRoot}guide/topics/manifest/activity-element.html#reparent">{@code -allowTaskReparenting}</a></li> - <li><a href="{@docRoot}guide/topics/manifest/activity-element.html#clear">{@code -clearTaskOnLaunch}</a></li> - <li><a href="{@docRoot}guide/topics/manifest/activity-element.html#always">{@code -alwaysRetainTaskState}</a></li> - <li><a href="{@docRoot}guide/topics/manifest/activity-element.html#finish">{@code -finishOnTaskLaunch}</a></li> + <li><a href="{@docRoot}guide/topics/manifest/activity-element.html#aff"> + {@code taskAffinity}</a></li> + <li><a href="{@docRoot}guide/topics/manifest/activity-element.html#lmode"> + {@code launchMode}</a></li> + <li><a href="{@docRoot}guide/topics/manifest/activity-element.html#reparent"> + {@code allowTaskReparenting}</a></li> + <li><a href="{@docRoot}guide/topics/manifest/activity-element.html#clear"> + {@code clearTaskOnLaunch}</a></li> + <li><a href="{@docRoot}guide/topics/manifest/activity-element.html#always"> + {@code alwaysRetainTaskState}</a></li> + <li><a href="{@docRoot}guide/topics/manifest/activity-element.html#finish"> + {@code finishOnTaskLaunch}</a></li> </ul> <p>And the principal intent flags you can use are:</p> @@ -250,15 +252,18 @@ finishOnTaskLaunch}</a></li> </ul> <p>In the following sections, you'll see how you can use these manifest attributes and intent -flags to define how activities are associated with tasks and how the behave in the back stack.</p> +flags to define how activities are associated with tasks and how they behave in the back stack.</p> +<p>Also, discussed separately are the considerations for how tasks and activites may be represented +and managed in the overview screen. See <a href="{@docRoot}guide/components/recents.html">Overview Screen</a> +for more information. Normally you should allow the system to define how your task and +activities are represented in the overview screen, and you don't need to modify this behavior.</p> <p class="caution"><strong>Caution:</strong> Most applications should not interrupt the default behavior for activities and tasks. If you determine that it's necessary for your activity to modify the default behaviors, use caution and be sure to test the usability of the activity during launch and when navigating back to it from other activities and tasks with the <em>Back</em> button. -Be sure -to test for navigation behaviors that might conflict with the user's expected behavior.</p> +Be sure to test for navigation behaviors that might conflict with the user's expected behavior.</p> <h3 id="TaskLaunchModes">Defining launch modes</h3> @@ -389,7 +394,7 @@ default behavior are:</p> <dt>{@link android.content.Intent#FLAG_ACTIVITY_NEW_TASK}</dt> <dd>Start the activity in a new task. If a task is already running for the activity you are now starting, that task is brought to the foreground with its last state restored and the activity -receives the new intent in {@link android.app.Activity#onNewIntent onNewIntent()}. +receives the new intent in {@link android.app.Activity#onNewIntent onNewIntent()}. <p>This produces the same behavior as the {@code "singleTask"} <a href="{@docRoot}guide/topics/manifest/activity-element.html#lmode">{@code launchMode}</a> value, discussed in the previous section.</p></dd> @@ -408,11 +413,13 @@ through {@link android.app.Activity#onNewIntent onNewIntent()}). <p>There is no value for the <a href="{@docRoot}guide/topics/manifest/activity-element.html#lmode">{@code launchMode}</a> attribute that produces this behavior.</p> - <p>{@code FLAG_ACTIVITY_CLEAR_TOP} is most often used in conjunction with {@code -FLAG_ACTIVITY_NEW_TASK}. When used together, these flags are a way of locating an existing activity + <p>{@code FLAG_ACTIVITY_CLEAR_TOP} is most often used in conjunction with + {@code FLAG_ACTIVITY_NEW_TASK}. +When used together, these flags are a way of locating an existing activity in another task and putting it in a position where it can respond to the intent. </p> - <p class="note"><strong>Note:</strong> If the launch mode of the designated activity is {@code -"standard"}, it too is removed from the stack and a new instance is launched in its place to handle + <p class="note"><strong>Note:</strong> If the launch mode of the designated activity is + {@code "standard"}, +it too is removed from the stack and a new instance is launched in its place to handle the incoming intent. That's because a new instance is always created for a new intent when the launch mode is {@code "standard"}. </p> </dd> @@ -439,21 +446,23 @@ element.</p> <p>The <a href="{@docRoot}guide/topics/manifest/activity-element.html#aff">{@code taskAffinity}</a> attribute takes a string value, which must be unique from the default package name -declared in the <a href="{@docRoot}guide/topics/manifest/manifest-element.html">{@code -<manifest>}</a> element, because the system uses that name to identify the default task +declared in the <a href="{@docRoot}guide/topics/manifest/manifest-element.html"> +{@code <manifest>} +</a> element, because the system uses that name to identify the default task affinity for the application.</p> <p>The affinity comes into play in two circumstances:</p> <ul> - <li>When the intent that launches an activity contains the {@link -android.content.Intent#FLAG_ACTIVITY_NEW_TASK} flag. + <li>When the intent that launches an activity contains the + {@link android.content.Intent#FLAG_ACTIVITY_NEW_TASK} + flag. <p>A new activity is, by default, launched into the task of the activity that called {@link android.app.Activity#startActivity startActivity()}. It's pushed onto the same -back stack as the caller. However, if the intent passed to {@link -android.app.Activity#startActivity startActivity()} contains the {@link -android.content.Intent#FLAG_ACTIVITY_NEW_TASK} -flag, the system looks for a different task to house the new activity. Often, it's a new task. +back stack as the caller. However, if the intent passed to +{@link android.app.Activity#startActivity startActivity()} +contains the {@link android.content.Intent#FLAG_ACTIVITY_NEW_TASK} +flag, the system looks for a different task to house the new activity. Often, it's a new task. However, it doesn't have to be. If there's already an existing task with the same affinity as the new activity, the activity is launched into that task. If not, it begins a new task.</p> @@ -461,17 +470,17 @@ new activity, the activity is launched into that task. If not, it begins a new to leave it, there must be some way for the user to navigate back to the task. Some entities (such as the notification manager) always start activities in an external task, never as part of their own, so -they always put {@code FLAG_ACTIVITY_NEW_TASK} in the intents they pass to {@link -android.app.Activity#startActivity startActivity()}. If you have an activity that can be invoked by +they always put {@code FLAG_ACTIVITY_NEW_TASK} in the intents they pass to +{@link android.app.Activity#startActivity startActivity()}. +If you have an activity that can be invoked by an external entity that might use this flag, take care that the user has a independent way to get back to the task that's started, such as with a launcher icon (the root activity of the task has a {@link android.content.Intent#CATEGORY_LAUNCHER} intent filter; see the <a href="#Starting">Starting a task</a> section below).</p> </li> - <li>When an activity has its <a -href="{@docRoot}guide/topics/manifest/activity-element.html#reparent">{@code -allowTaskReparenting}</a> attribute set to {@code "true"}. + <li>When an activity has its <a href="{@docRoot}guide/topics/manifest/activity-element.html#reparent"> +{@code allowTaskReparenting}</a> attribute set to {@code "true"}. <p>In this case, the activity can move from the task it starts to the task it has an affinity for, when that task comes to the foreground.</p> <p>For example, suppose that an activity that reports weather conditions in selected cities is @@ -511,9 +520,9 @@ The task retains all activities in its stack even after a long period.</dd> href="{@docRoot}guide/topics/manifest/activity-element.html#clear">clearTaskOnLaunch</a></code></dt> <dd>If this attribute is set to {@code "true"} in the root activity of a task, the stack is cleared down to the root activity whenever the user leaves the task -and returns to it. In other words, it's the opposite of <a -href="{@docRoot}guide/topics/manifest/activity-element.html#always">{@code -alwaysRetainTaskState}</a>. The user always returns to the task in its +and returns to it. In other words, it's the opposite of +<a href="{@docRoot}guide/topics/manifest/activity-element.html#always"> +{@code alwaysRetainTaskState}</a>. The user always returns to the task in its initial state, even after a leaving the task for only a moment.</dd> <dt><code><a @@ -534,8 +543,9 @@ leaves and then returns to the task, it is no longer present.</dd> <h3 id="Starting">Starting a task</h3> <p>You can set up an activity as the entry point for a task by giving it an intent filter with -{@code "android.intent.action.MAIN"} as the specified action and {@code -"android.intent.category.LAUNCHER"} as the specified category. For example:</p> +{@code "android.intent.action.MAIN"} as the specified action and +{@code "android.intent.category.LAUNCHER"} +as the specified category. For example:</p> <pre> <activity ... > @@ -553,27 +563,25 @@ to return to the task that it creates any time after it has been launched. </p> <p>This second ability is important: Users must be able to leave a task and then come back to it -later using this activity launcher. For this reason, the two <a href="#LaunchModes">launch -modes</a> that mark activities as always initiating a task, {@code "singleTask"} and "{@code -"singleInstance"}, should be used only when the activity has an {@link -android.content.Intent#ACTION_MAIN} -and a {@link android.content.Intent#CATEGORY_LAUNCHER} -filter. Imagine, for example, what could happen if the filter is missing: An intent launches a -{@code "singleTask"} activity, initiating a new task, and the user spends some time working in -that task. The user then presses the <em>Home</em> button. The task is now sent to the background -and is -not visible. Now the user has no way to return to the task, because it is not represented in the -application launcher. -</p> +later using this activity launcher. For this reason, the two <a href="#LaunchModes">launch +modes</a> that mark activities as always initiating a task, {@code "singleTask"} and +{@code "singleInstance"}, should be used only when the activity has an +{@link android.content.Intent#ACTION_MAIN} +and a {@link android.content.Intent#CATEGORY_LAUNCHER} filter. Imagine, for example, what could +happen if the filter is missing: An intent launches a {@code "singleTask"} activity, initiating a +new task, and the user spends some time working in that task. The user then presses the <em>Home</em> +button. The task is now sent to the background and is not visible. Now the user has no way to return +to the task, because it is not represented in the application launcher.</p> <p>For those cases where you don't want the user to be able to return to an activity, set the - <code><a -href="{@docRoot}guide/topics/manifest/activity-element.html"><activity></a></code> element's -<a href="{@docRoot}guide/topics/manifest/activity-element.html#finish">{@code -finishOnTaskLaunch}</a> to {@code "true"} (see <a -href="#Clearing">Clearing the stack</a>).</p> - +<code><a href="{@docRoot}guide/topics/manifest/activity-element.html"><activity></a></code> +element's +<a href="{@docRoot}guide/topics/manifest/activity-element.html#finish">{@code finishOnTaskLaunch}</a> +to {@code "true"} (see <a href="#Clearing">Clearing the stack</a>).</p> +<p>Further information about how tasks and activites are represented and managed in +the overview screen is available in <a href="{@docRoot}guide/components/recents.html"> +Overview Screen</a>.</p> <!-- <h2>Beginner's Path</h2> |