page.title=<activity> @jd:body

syntax:

<activity android:allowTaskReparenting=["true" | "false"]
          android:alwaysRetainTaskState=["true" | "false"]
          android:clearTaskOnLaunch=["true" | "false"]
          android:configChanges=["mcc", "mnc", "locale",
                                 "touchscreen", "keyboard", "keyboardHidden",
                                 "navigation", "orientation", "screenLayout",
                                 "fontScale", "uiMode"]
          android:enabled=["true" | "false"]
          android:excludeFromRecents=["true" | "false"]
          android:exported=["true" | "false"]
          android:finishOnTaskLaunch=["true" | "false"]
          android:icon="drawable resource"
          android:label="string resource"
          android:launchMode=["multiple" | "singleTop" |
                              "singleTask" | "singleInstance"]
          android:multiprocess=["true" | "false"]
          android:name="string"
          android:noHistory=["true" | "false"]  
          android:permission="string"
          android:process="string"
          android:screenOrientation=["unspecified" | "user" | "behind" |
                                     "landscape" | "portrait" |
                                     "sensor" | "nosensor"]
          android:stateNotNeeded=["true" | "false"]
          android:taskAffinity="string"
          android:theme="resource or theme"
          android:windowSoftInputMode=["stateUnspecified",
                                       "stateUnchanged", "stateHidden",
                                       "stateAlwaysHidden", "stateVisible",
                                       "stateAlwaysVisible", "adjustUnspecified",
                                       "adjustResize", "adjustPan"] >   
    . . .
</activity>

contained in:

<application>

can contain:

<intent-filter>
<meta-data>

description:

Declares an activity (an {@link android.app.Activity} subclass) that implements part of the application's visual user interface. All activities must be represented by {@code <activity>} elements in the manifest file. Any that are not declared there will not be seen by the system and will never be run.

attributes:

{@code android:allowTaskReparenting}

Whether or not the activity can move from the task that started it to the task it has an affinity for when that task is next brought to the front — "{@code true}" if it can move, and "{@code false}" if it must remain with the task where it started.

If this attribute is not set, the value set by the corresponding allowTaskReparenting attribute of the <application> element applies to the activity. The default value is "{@code false}".

Normally when an activity is started, it's associated with the task of the activity that started it and it stays there for its entire lifetime. You can use this attribute to force it to be re-parented to the task it has an affinity for when its current task is no longer displayed. Typically, it's used to cause the activities of an application to move to the main task associated with that application.

For example, if an e-mail message contains a link to a web page, clicking the link brings up an activity that can display the page. That activity is defined by the browser application, but is launched as part of the e-mail task. If it's reparented to the browser task, it will be shown when the browser next comes to the front, and will be absent when the e-mail task again comes forward.

The affinity of an activity is defined by the taskAffinity attribute. The affinity of a task is determined by reading the affinity of its root activity. Therefore, by definition, a root activity is always in a task with the same affinity. Since activities with "{@code singleTask}" or "{@code singleInstance}" launch modes can only be at the root of a task, re-parenting is limited to the "{@code standard}" and "{@code singleTop}" modes. (See also the launchMode attribute.)

{@code android:alwaysRetainTaskState}

Whether or not the state of the task that the activity is in will always be maintained by the system — "{@code true}" if it will be, and "{@code false}" if the system is allowed to reset the task to its initial state in certain situations. The default value is "{@code false}". This attribute is meaningful only for the root activity of a task; it's ignored for all other activities.

Normally, the system clears a task (removes all activities from the stack above the root activity) in certain situations when the user re-selects that task from the home screen. Typically, this is done if the user hasn't visited the task for a certain amount of time, such as 30 minutes.

However, when this attribute is "{@code true}", users will always return to the task in its last state, regardless of how they get there. This is useful, for example, in an application like the web browser where there is a lot of state (such as multiple open tabs) that users would not like to lose.

{@code android:clearTaskOnLaunch}

Whether or not all activities will be removed from the task, except for the root activity, whenever it is re-launched from the home screen — "{@code true}" if the task is always stripped down to its root activity, and "{@code false}" if not. The default value is "{@code false}". This attribute is meaningful only for activities that start a new task (the root activity); it's ignored for all other activities in the task.

When the value is "{@code true}", every time users start the task again, they are brought to its root activity, regardless of what they were last doing in the task and regardless of whether they used BACK or HOME to last leave it. When the value is "{@code false}", the task may be cleared of activities in some situations (see the alwaysRetainTaskState attribute), but not always.

Suppose, for example, that someone launches activity P from the home screen, and from there goes to activity Q. The user next presses HOME, and then returns to activity P. Normally, the user would see activity Q, since that is what they were last doing in P's task. However, if P set this flag to "{@code true}", all of the activities on top of it (Q in this case) were removed when the user pressed HOME and the task went to the background. So the user sees only P when returning to the task.

If this attribute and allowTaskReparenting are both "{@code true}", any activities that can be re-parented are moved to the task they share an affinity with; the remaining activities are then dropped, as described above.

{@code android:configChanges}

Lists configuration changes that the activity will handle itself. When a configuration change occurs at runtime, the activity is shut down and restarted by default, but declaring a configuration with this attribute will prevent the activity from being restarted. Instead, the activity remains running and its

{@link android.app.Activity#onConfigurationChanged
onConfigurationChanged()}

method is called.

Note: Using this attribute should be avoided and used only as a last-resort. Please read Handling Runtime Changes for more information about how to properly handle a restart due to a configuration change.

Any or all of the following strings are valid values for this attribute. Multiple values are separated by '{@code |}' — for example, "{@code locale|navigation|orientation}".

Value	Description
"{@code mcc}"	The IMSI mobile country code (MCC) has changed — a SIM has been detected and updated the MCC.
"{@code mnc}"	The IMSI mobile network code (MNC) has changed — a SIM has been detected and updated the MNC.
"{@code locale}"	The locale has changed — the user has selected a new language that text should be displayed in.
"{@code touchscreen}"	The touchscreen has changed. (This should never normally happen.)
"{@code keyboard}"	The keyboard type has changed — for example, the user has plugged in an external keyboard.
"{@code keyboardHidden}"	The keyboard accessibility has changed — for example, the user has revealed the hardware keyboard.
"{@code navigation}"	The navigation type (trackball/dpad) has changed. (This should never normally happen.)
"{@code orientation}"	The screen orientation has changed — the user has rotated the device.
"{@code screenLayout}"	The screen layout has changed — this might be caused by a different display being activated.
"{@code fontScale}"	The font scaling factor has changed — the user has selected a new global font size.
"{@code uiMode}"	The user interface mode has changed — this can be caused when the user places the device into a desk/car dock or when the the night mode changes. See {@link android.app.UiModeManager}. Introduced in API Level 8.

All of these configuration changes can impact the resource values seen by the application. Therefore, when {@link android.app.Activity#onConfigurationChanged onConfigurationChanged()} is called, it will generally be necessary to again retrieve all resources (including view layouts, drawables, and so on) to correctly handle the change.

{@code android:enabled}

Whether or not the activity can be instantiated by the system — "{@code true}" if it can be, and "{@code false}" if not. The default value is "{@code true}".

The <application> element has its own enabled attribute that applies to all application components, including activities. The <application> and {@code <activity>} attributes must both be "{@code true}" (as they both are by default) for the system to be able to instantiate the activity. If either is "{@code false}", it cannot be instantiated.

{@code android:excludeFromRecents}

Whether or not the activity should be excluded from the list of recently launched activities that can be displayed to users — "{@code true}" if it should be excluded, and "{@code false}" if it should be included. The default value is "{@code false}".

{@code android:exported}

Whether or not the activity can be launched by components of other applications — "{@code true}" if it can be, and "{@code false}" if not. If "{@code false}", the activity can be launched only by components of the same application or applications with the same user ID.

The default value depends on whether the activity contains intent filters. The absence of any filters means that the activity can be invoked only by specifying its exact class name. This implies that the activity is intended only for application-internal use (since others would not know the class name). So in this case, the default value is "{@code false}". On the other hand, the presence of at least one filter implies that the activity is intended for external use, so the default value is "{@code true}".

This attribute is not the only way to limit an activity's exposure to other applications. You can also use a permission to limit the external entities that can invoke the activity (see the permission attribute).

{@code android:finishOnTaskLaunch}

Whether or not an existing instance of the activity should be shut down (finished) whenever the user again launches its task (chooses the task on the home screen) — "{@code true}" if it should be shut down, and "{@code false}" if not. The default value is "{@code false}".

If this attribute and allowTaskReparenting are both "{@code true}", this attribute trumps the other. The affinity of the activity is ignored. The activity is not re-parented, but destroyed.

{@code android:icon}

An icon representing the activity. The icon is displayed to users when a representation of the activity is required on-screen. For example, icons for activities that initiate tasks are displayed in the launcher window. The icon is often accompanied by a label (see the {@code label} attribute).

This attribute must be set as a reference to a drawable resource containing the image definition. If it is not set, the icon specified for the application as a whole is used instead (see the <application> element's icon attribute).

The activity's icon — whether set here or by the <application> element — is also the default icon for all the activity's intent filters (see the <intent-filter> element's icon attribute).

{@code android:label}

A user-readable label for the activity. The label is displayed on-screen when the activity must be represented to the user. It's often displayed along with the activity icon.

If this attribute is not set, the label set for the application as a whole is used instead (see the <application> element's label attribute).

The activity's label — whether set here or by the <application> element — is also the default label for all the activity's intent filters (see the <intent-filter> element's label attribute).

The label should be set as a reference to a string resource, so that it can be localized like other strings in the user interface. However, as a convenience while you're developing the application, it can also be set as a raw string.

{@code android:launchMode}

An instruction on how the activity should be launched. There are four modes that work in conjunction with activity flags ({@code FLAG_ACTIVITY_*} constants) in {@link android.content.Intent} objects to determine what should happen when the activity is called upon to handle an intent. They are:

"{@code standard}"
"{@code singleTop}"
"{@code singleTask}"
"{@code singleInstance}"

The default mode is "{@code standard}".

As shown in the table below, the modes fall into two main groups, with "{@code standard}" and "{@code singleTop}" activities on one side, and "{@code singleTask}" and "{@code singleInstance}" activities on the other. An activity with the "{@code standard}" or "{@code singleTop}" launch mode can be instantiated multiple times. The instances can belong to any task and can be located anywhere in the activity stack. Typically, they're launched into the task that called {@link android.content.Context#startActivity startActivity()} (unless the Intent object contains a {@link android.content.Intent#FLAG_ACTIVITY_NEW_TASK} instruction, in which case a different task is chosen — see the taskAffinity attribute).

In contrast, "singleTask" and "singleInstance" activities can only begin a task. They are always at the root of the activity stack. Moreover, the device can hold only one instance of the activity at a time — only one such task.

The "{@code standard}" and "{@code singleTop}" modes differ from each other in just one respect: Every time there's a new intent for a "{@code standard}" activity, a new instance of the class is created to respond to that intent. Each instance handles a single intent. Similarly, a new instance of a "{@code singleTop}" activity may also be created to handle a new intent. However, if the target task already has an existing instance of the activity at the top of its stack, that instance will receive the new intent (in an {@link android.app.Activity#onNewIntent onNewIntent()} call); a new instance is not created. In other circumstances — for example, if an existing instance of the "{@code singleTop}" activity is in the target task, but not at the top of the stack, or if it's at the top of a stack, but not in the target task — a new instance would be created and pushed on the stack.

The "{@code singleTask}" and "{@code singleInstance}" modes also differ from each other in only one respect: A "{@code singleTask}" activity allows other activities to be part of its task. It's always at the root of its task, but other activities (necessarily "{@code standard}" and "{@code singleTop}" activities) can be launched into that task. A "{@code singleInstance}" activity, on the other hand, permits no other activities to be part of its task. It's the only activity in the task. If it starts another activity, that activity is assigned to a different task — as if {@code FLAG_ACTIVITY_NEW_TASK} was in the intent.

Use Cases	Launch Mode	Multiple Instances?	Comments
Normal launches for most activities	"`standard`"	Yes	Default. The system always creates a new instance of the activity in the target task and routes the intent to it.
Normal launches for most activities	"`singleTop`"	Conditionally	If an instance of the activity already exists at the top of the target task, the system routes the intent to that instance through a call to its {@link android.app.Activity#onNewIntent onNewIntent()} method, rather than creating a new instance of the activity.
Specialized launches (not recommended for general use)	"`singleTask`"	No	The system creates the activity at the root of a new task and routes the intent to it. However, if an instance of the activity already exists, the system routes the intent to existing instance through a call to its {@link android.app.Activity#onNewIntent onNewIntent()} method, rather than creating a new one.
Specialized launches (not recommended for general use)	"`singleInstance`"	No	Same as "`singleTask"`, except that the system doesn't launch any other activities into the task holding the instance. The activity is always the single and only member of its task.

As shown in the table above, standard is the default mode and is appropriate for most types of activities. SingleTop is also a common and useful launch mode for many types of activities. The other modes — singleTask and singleInstance — are not appropriate for most applications, since they result in an interaction model that is likely to be unfamiliar to users and is very different from most other applications.

Regardless of the launch mode that you choose, make sure to test the usability of the activity during launch and when navigating back to it from other activities and tasks using the BACK key.

For more information on launch modes and their interaction with Intent flags, see the Activities and Tasks section of the Application Fundamentals document.

{@code android:multiprocess}

Whether an instance of the activity can be launched into the process of the component that started it — "{@code true}" if it can be, and "{@code false}" if not. The default value is "{@code false}".

Normally, a new instance of an activity is launched into the process of the application that defined it, so all instances of the activity run in the same process. However, if this flag is set to "{@code true}", instances of the activity can run in multiple processes, allowing the system to create instances wherever they are used (provided permissions allow it), something that is almost never necessary or desirable.

{@code android:name}

The name of the class that implements the activity, a subclass of {@link android.app.Activity}. The attribute value should be a fully qualified class name (such as, "{@code com.example.project.ExtracurricularActivity}"). However, as a shorthand, if the first character of the name is a period (for example, "{@code .ExtracurricularActivity}"), it is appended to the package name specified in the <manifest> element.

There is no default. The name must be specified.

{@code android:noHistory}

Whether or not the activity should be removed from the activity stack and finished (its {@link android.app.Activity#finish finish()} method called) when the user navigates away from it and it's no longer visible on screen — "{@code true}" if it should be finished, and "{@code false}" if not. The default value is "{@code false}".

A value of "{@code true}" means that the activity will not leave a historical trace. It will not remain in the activity stack for the task, so the user will not be able to return to it.

This attribute was introduced in API Level 3.

{@code android:permission}

The name of a permission that clients must have to launch the activity or otherwise get it to respond to an intent. If a caller of {@link android.content.Context#startActivity startActivity()} or {@link android.app.Activity#startActivityForResult startActivityForResult()} has not been granted the specified permission, its intent will not be delivered to the activity.

If this attribute is not set, the permission set by the <application> element's permission attribute applies to the activity. If neither attribute is set, the activity is not protected by a permission.

For more information on permissions, see the Permissions section in the introduction and another document, Security and Permissions.

{@code android:process}

The name of the process in which the activity should run. Normally, all components of an application run in the default process created for the application. It has the same name as the application package. The <application> element's process attribute can set a different default for all components. But each component can override the default, allowing you to spread your application across multiple processes.

If the name assigned to this attribute begins with a colon (':'), a new process, private to the application, is created when it's needed and the activity runs in that process. If the process name begins with a lowercase character, the activity will run in a global process of that name, provided that it has permission to do so. This allows components in different applications to share a process, reducing resource usage.

{@code android:screenOrientation}

The orientation of the activity's display on the device. The value can be any one of the following strings:

"{@code unspecified}"	The default value. The system chooses the orientation. The policy it uses, and therefore the choices made in specific contexts, may differ from device to device.
"{@code landscape}"	Landscape orientation (the display is wider than it is tall).
"{@code portrait}"	Portrait orientation (the display is taller than it is wide).
"{@code user}"	The user's current preferred orientation.
"{@code behind}"	The same orientation as the activity that's immediately beneath it in the activity stack.
"{@code sensor}"	The orientation determined by a physical orientation sensor. The orientation of the display depends on how the user is holding the device; it changes when the user rotates the device.
"{@code nosensor}"	An orientation determined without reference to a physical orientation sensor. The sensor is ignored, so the display will not rotate based on how the user moves the device. Except for this distinction, the system chooses the orientation using the same policy as for the "{@code unspecified}" setting.

{@code android:stateNotNeeded}

Whether or not the activity can be killed and successfully restarted without having saved its state — "{@code true}" if it can be restarted without reference to its previous state, and "{@code false}" if its previous state is required. The default value is "{@code false}".

Normally, before an activity is temporarily shut down to save resources, its {@link android.app.Activity#onSaveInstanceState onSaveInstanceState()} method is called. This method stores the current state of the activity in a {@link android.os.Bundle} object, which is then passed to {@link android.app.Activity#onCreate onCreate()} when the activity is restarted. If this attribute is set to "{@code true}", {@code onSaveInstanceState()} may not be called and {@code onCreate()} will be passed {@code null} instead of the Bundle — just as it was when the activity started for the first time.

A "{@code true}" setting ensures that the activity can be restarted in the absence of retained state. For example, the activity that displays the home screen uses this setting to make sure that it does not get removed if it crashes for some reason.

{@code android:taskAffinity}

The task that the activity has an affinity for. Activities with the same affinity conceptually belong to the same task (to the same "application" from the user's perspective). The affinity of a task is determined by the affinity of its root activity.

The affinity determines two things — the task that the activity is re-parented to (see the allowTaskReparenting attribute) and the task that will house the activity when it is launched with the {@link android.content.Intent#FLAG_ACTIVITY_NEW_TASK} flag.

By default, all activities in an application have the same affinity. You can set this attribute to group them differently, and even place activities defined in different applications within the same task. To specify that the activity does not have an affinity for any task, set it to an empty string.

If this attribute is not set, the activity inherits the affinity set for the application (see the <application> element's taskAffinity attribute). The name of the default affinity for an application is the package name set by the <manifest> element.

{@code android:theme}

A reference to a style resource defining an overall theme for the activity. This automatically sets the activity's context to use this theme (see {@link android.content.Context#setTheme setTheme()}, and may also cause "starting" animations prior to the activity being launched (to better match what the activity actually looks like).

If this attribute is not set, the activity inherits the theme set for the application as a whole — see the <application> element's theme attribute. If that attribute is also not set, the default system theme is used.

{@code android:windowSoftInputMode}

How the main window of the activity interacts with the window containing the on-screen soft keyboard. The setting for this attribute affects two things:

The state of the soft keyboard — whether it is hidden or visible — when the activity becomes the focus of user attention.
The adjustment made to the activity's main window — whether it is resized smaller to make room for the soft keyboard or whether its contents pan to make the current focus visible when part of the window is covered by the soft keyboard.

The setting must be one of the values listed in the following table, or a combination of one "{@code state...}" value plus one "{@code adjust...}" value. Setting multiple values in either group — multiple "{@code state...}" values, for example &mdash has undefined results. Individual values are separated by a vertical bar ({@code |}). For example:

<activity android:windowSoftInputMode="stateVisible|adjustResize" . . . >

Values set here (other than "{@code stateUnspecified}" and "{@code adjustUnspecified}") override values set in the theme.

Value	Description
"{@code stateUnspecified}"	The state of the soft keyboard (whether it is hidden or visible) is not specified. The system will choose an appropriate state or rely on the setting in the theme. This is the default setting for the behavior of the soft keyboard.
"{@code stateUnchanged}"	The soft keyboard is kept in whatever state it was last in, whether visible or hidden, when the activity comes to the fore.
"{@code stateHidden}"	The soft keyboard is hidden when the user chooses the activity — that is, when the user affirmatively navigates forward to the activity, rather than backs into it because of leaving another activity.
"{@code stateAlwaysHidden}"	The soft keyboard is always hidden when the activity's main window has input focus.
"{@code stateVisible}"	The soft keyboard is visible when that's normally appropriate (when the user is navigating forward to the activity's main window).
"{@code stateAlwaysVisible}"	The soft keyboard is made visible when the user chooses the activity — that is, when the user affirmatively navigates forward to the activity, rather than backs into it because of leaving another activity.
"{@code adjustUnspecified}"	It is unspecified whether the activity's main window resizes to make room for the soft keyboard, or whether the contents of the window pan to make the currentfocus visible on-screen. The system will automatically select one of these modes depending on whether the content of the window has any layout views that can scroll their contents. If there is such a view, the window will be resized, on the assumption that scrolling can make all of the window's contents visible within a smaller area. This is the default setting for the behavior of the main window.
"{@code adjustResize}"	The activity's main window is always resized to make room for the soft keyboard on screen.
"{@code adjustPan}"	The activity's main window is not resized to make room for the soft keyboard. Rather, the contents of the window are automatically panned so that the current focus is never obscured by the keyboard and users can always see what they are typing. This is generally less desirable than resizing, because the user may need to close the soft keyboard to get at and interact with obscured parts of the window.

This attribute was introduced in API Level 3.

introduced in:

API Level 1 for all attributes except for noHistory and windowSoftInputMode, which were added in API Level 3.

see also:

<application>
<activity-alias>