android.support.v4.view
Class ViewCompat

java.lang.Object
  extended by android.support.v4.view.ViewCompat

public class ViewCompat
extends java.lang.Object

Helper for accessing features in View introduced after API level 4 in a backwards compatible fashion.


Field Summary
static int IMPORTANT_FOR_ACCESSIBILITY_AUTO
          Automatically determine whether a view is important for accessibility.
static int IMPORTANT_FOR_ACCESSIBILITY_NO
          The view is not important for accessibility.
static int IMPORTANT_FOR_ACCESSIBILITY_YES
          The view is important for accessibility.
static int OVER_SCROLL_ALWAYS
          Always allow a user to over-scroll this view, provided it is a view that can scroll.
static int OVER_SCROLL_IF_CONTENT_SCROLLS
          Allow a user to over-scroll this view only if the content is large enough to meaningfully scroll, provided it is a view that can scroll.
static int OVER_SCROLL_NEVER
          Never allow a user to over-scroll this view.
 
Constructor Summary
ViewCompat()
           
 
Method Summary
static boolean canScrollHorizontally(View v, int direction)
          Check if this view can be scrolled horizontally in a certain direction.
static boolean canScrollVertically(View v, int direction)
          Check if this view can be scrolled vertically in a certain direction.
static AccessibilityNodeProviderCompat getAccessibilityNodeProvider(View view)
          Gets the provider for managing a virtual view hierarchy rooted at this View and reported to android.accessibilityservice.AccessibilityServices that explore the window content.
static int getImportantForAccessibility(View view)
          Gets the mode for determining whether this View is important for accessibility which is if it fires accessibility events and if it is reported to accessibility services that query the screen.
static int getOverScrollMode(View v)
          Returns the over-scroll mode for this view.
static boolean hasTransientState(View view)
          Indicates whether the view is currently tracking transient state that the app should not need to concern itself with saving and restoring, but that the framework should take special note to preserve when possible.
static void onInitializeAccessibilityEvent(View v, AccessibilityEvent event)
          Initializes an AccessibilityEvent with information about this View which is the event source.
static void onInitializeAccessibilityNodeInfo(View v, AccessibilityNodeInfoCompat info)
          Initializes an android.view.accessibility.AccessibilityNodeInfo with information about this view.
static void onPopulateAccessibilityEvent(View v, AccessibilityEvent event)
          Called from View#dispatchPopulateAccessibilityEvent(AccessibilityEvent) giving a chance to this View to populate the accessibility event with its text content.
static void postInvalidateOnAnimation(View view)
          Cause an invalidate to happen on the next animation time step, typically the next display frame.
static void postInvalidateOnAnimation(View view, int left, int top, int right, int bottom)
          Cause an invalidate of the specified area to happen on the next animation time step, typically the next display frame.
static void postOnAnimation(View view, java.lang.Runnable action)
          Causes the Runnable to execute on the next animation time step.
static void postOnAnimationDelayed(View view, java.lang.Runnable action, long delayMillis)
          Causes the Runnable to execute on the next animation time step, after the specified amount of time elapses.
static void setAccessibilityDelegate(View v, AccessibilityDelegateCompat delegate)
          Sets a delegate for implementing accessibility support via compositon as opposed to inheritance.
static void setHasTransientState(View view, boolean hasTransientState)
          Set whether this view is currently tracking transient state that the framework should attempt to preserve when possible.
static void setImportantForAccessibility(View view, int mode)
          Sets how to determine whether this view is important for accessibility which is if it fires accessibility events and if it is reported to accessibility services that query the screen.
static void setOverScrollMode(View v, int overScrollMode)
          Set the over-scroll mode for this view.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

OVER_SCROLL_ALWAYS

public static final int OVER_SCROLL_ALWAYS
Always allow a user to over-scroll this view, provided it is a view that can scroll.

See Also:
Constant Field Values

OVER_SCROLL_IF_CONTENT_SCROLLS

public static final int OVER_SCROLL_IF_CONTENT_SCROLLS
Allow a user to over-scroll this view only if the content is large enough to meaningfully scroll, provided it is a view that can scroll.

See Also:
Constant Field Values

OVER_SCROLL_NEVER

public static final int OVER_SCROLL_NEVER
Never allow a user to over-scroll this view.

See Also:
Constant Field Values

IMPORTANT_FOR_ACCESSIBILITY_AUTO

public static final int IMPORTANT_FOR_ACCESSIBILITY_AUTO
Automatically determine whether a view is important for accessibility.

See Also:
Constant Field Values

IMPORTANT_FOR_ACCESSIBILITY_YES

public static final int IMPORTANT_FOR_ACCESSIBILITY_YES
The view is important for accessibility.

See Also:
Constant Field Values

IMPORTANT_FOR_ACCESSIBILITY_NO

public static final int IMPORTANT_FOR_ACCESSIBILITY_NO
The view is not important for accessibility.

See Also:
Constant Field Values
Constructor Detail

ViewCompat

public ViewCompat()
Method Detail

canScrollHorizontally

public static boolean canScrollHorizontally(View v,
                                            int direction)
Check if this view can be scrolled horizontally in a certain direction.

Parameters:
v - The View against which to invoke the method.
direction - Negative to check scrolling left, positive to check scrolling right.
Returns:
true if this view can be scrolled in the specified direction, false otherwise.

canScrollVertically

public static boolean canScrollVertically(View v,
                                          int direction)
Check if this view can be scrolled vertically in a certain direction.

Parameters:
v - The View against which to invoke the method.
direction - Negative to check scrolling up, positive to check scrolling down.
Returns:
true if this view can be scrolled in the specified direction, false otherwise.

getOverScrollMode

public static int getOverScrollMode(View v)
Returns the over-scroll mode for this view. The result will be one of OVER_SCROLL_ALWAYS (default), OVER_SCROLL_IF_CONTENT_SCROLLS (allow over-scrolling only if the view content is larger than the container), or OVER_SCROLL_NEVER.

Parameters:
v - The View against which to invoke the method.
Returns:
This view's over-scroll mode.

setOverScrollMode

public static void setOverScrollMode(View v,
                                     int overScrollMode)
Set the over-scroll mode for this view. Valid over-scroll modes are OVER_SCROLL_ALWAYS (default), OVER_SCROLL_IF_CONTENT_SCROLLS (allow over-scrolling only if the view content is larger than the container), or OVER_SCROLL_NEVER. Setting the over-scroll mode of a view will have an effect only if the view is capable of scrolling.

Parameters:
v - The View against which to invoke the method.
overScrollMode - The new over-scroll mode for this view.

onPopulateAccessibilityEvent

public static void onPopulateAccessibilityEvent(View v,
                                                AccessibilityEvent event)
Called from View#dispatchPopulateAccessibilityEvent(AccessibilityEvent) giving a chance to this View to populate the accessibility event with its text content. While this method is free to modify event attributes other than text content, doing so should normally be performed in View#onInitializeAccessibilityEvent(AccessibilityEvent).

Example: Adding formatted date string to an accessibility event in addition to the text added by the super implementation:

 public void onPopulateAccessibilityEvent(AccessibilityEvent event) {
     super.onPopulateAccessibilityEvent(event);
     final int flags = DateUtils.FORMAT_SHOW_DATE | DateUtils.FORMAT_SHOW_WEEKDAY;
     String selectedDateUtterance = DateUtils.formatDateTime(mContext,
         mCurrentDate.getTimeInMillis(), flags);
     event.getText().add(selectedDateUtterance);
 }

If an android.view.View.AccessibilityDelegate has been specified via calling View#setAccessibilityDelegate(android.view.View.AccessibilityDelegate) its android.view.View.AccessibilityDelegate#onPopulateAccessibilityEvent(View, AccessibilityEvent) is responsible for handling this call.

Note: Always call the super implementation before adding information to the event, in case the default implementation has basic information to add.

Parameters:
v - The View against which to invoke the method.
event - The accessibility event which to populate.
See Also:
View#sendAccessibilityEvent(int), View#dispatchPopulateAccessibilityEvent(AccessibilityEvent)

onInitializeAccessibilityEvent

public static void onInitializeAccessibilityEvent(View v,
                                                  AccessibilityEvent event)
Initializes an AccessibilityEvent with information about this View which is the event source. In other words, the source of an accessibility event is the view whose state change triggered firing the event.

Example: Setting the password property of an event in addition to properties set by the super implementation:

 public void onInitializeAccessibilityEvent(AccessibilityEvent event) {
     super.onInitializeAccessibilityEvent(event);
     event.setPassword(true);
 }

If an android.view.View.AccessibilityDelegate has been specified via calling View#setAccessibilityDelegate(android.view.View.AccessibilityDelegate) its android.view.View.AccessibilityDelegate#onInitializeAccessibilityEvent(View, AccessibilityEvent) is responsible for handling this call.

Note: Always call the super implementation before adding information to the event, in case the default implementation has basic information to add.

Parameters:
v - The View against which to invoke the method.
event - The event to initialize.
See Also:
View#sendAccessibilityEvent(int), View#dispatchPopulateAccessibilityEvent(AccessibilityEvent)

onInitializeAccessibilityNodeInfo

public static void onInitializeAccessibilityNodeInfo(View v,
                                                     AccessibilityNodeInfoCompat info)
Initializes an android.view.accessibility.AccessibilityNodeInfo with information about this view. The base implementation sets:

Subclasses should override this method, call the super implementation, and set additional attributes.

If an android.view.View.AccessibilityDelegate has been specified via calling View#setAccessibilityDelegate(android.view.View.AccessibilityDelegate) its android.view.View.AccessibilityDelegate#onInitializeAccessibilityNodeInfo(View, android.view.accessibility.AccessibilityNodeInfo) is responsible for handling this call.

Parameters:
v - The View against which to invoke the method.
info - The instance to initialize.

setAccessibilityDelegate

public static void setAccessibilityDelegate(View v,
                                            AccessibilityDelegateCompat delegate)
Sets a delegate for implementing accessibility support via compositon as opposed to inheritance. The delegate's primary use is for implementing backwards compatible widgets. For more details see android.view.View.AccessibilityDelegate.

Parameters:
v - The View against which to invoke the method.
delegate - The delegate instance.
See Also:
android.view.View.AccessibilityDelegate

hasTransientState

public static boolean hasTransientState(View view)
Indicates whether the view is currently tracking transient state that the app should not need to concern itself with saving and restoring, but that the framework should take special note to preserve when possible.

Parameters:
view - View to check for transient state
Returns:
true if the view has transient state

setHasTransientState

public static void setHasTransientState(View view,
                                        boolean hasTransientState)
Set whether this view is currently tracking transient state that the framework should attempt to preserve when possible.

Parameters:
view - View tracking transient state
hasTransientState - true if this view has transient state

postInvalidateOnAnimation

public static void postInvalidateOnAnimation(View view)

Cause an invalidate to happen on the next animation time step, typically the next display frame.

This method can be invoked from outside of the UI thread only when this View is attached to a window.

Parameters:
view - View to invalidate

postInvalidateOnAnimation

public static void postInvalidateOnAnimation(View view,
                                             int left,
                                             int top,
                                             int right,
                                             int bottom)

Cause an invalidate of the specified area to happen on the next animation time step, typically the next display frame.

This method can be invoked from outside of the UI thread only when this View is attached to a window.

Parameters:
view - View to invalidate
left - The left coordinate of the rectangle to invalidate.
top - The top coordinate of the rectangle to invalidate.
right - The right coordinate of the rectangle to invalidate.
bottom - The bottom coordinate of the rectangle to invalidate.

postOnAnimation

public static void postOnAnimation(View view,
                                   java.lang.Runnable action)

Causes the Runnable to execute on the next animation time step. The runnable will be run on the user interface thread.

This method can be invoked from outside of the UI thread only when this View is attached to a window.

Parameters:
view - View to post this Runnable to
action - The Runnable that will be executed.

postOnAnimationDelayed

public static void postOnAnimationDelayed(View view,
                                          java.lang.Runnable action,
                                          long delayMillis)

Causes the Runnable to execute on the next animation time step, after the specified amount of time elapses. The runnable will be run on the user interface thread.

This method can be invoked from outside of the UI thread only when this View is attached to a window.

Parameters:
view - The view to post this Runnable to
action - The Runnable that will be executed.
delayMillis - The delay (in milliseconds) until the Runnable will be executed.

getImportantForAccessibility

public static int getImportantForAccessibility(View view)
Gets the mode for determining whether this View is important for accessibility which is if it fires accessibility events and if it is reported to accessibility services that query the screen.

Parameters:
view - The view whose property to get.
Returns:
The mode for determining whether a View is important for accessibility.
See Also:
IMPORTANT_FOR_ACCESSIBILITY_YES, IMPORTANT_FOR_ACCESSIBILITY_NO, IMPORTANT_FOR_ACCESSIBILITY_AUTO

setImportantForAccessibility

public static void setImportantForAccessibility(View view,
                                                int mode)
Sets how to determine whether this view is important for accessibility which is if it fires accessibility events and if it is reported to accessibility services that query the screen.

Parameters:
view - The view whose property to set.
mode - How to determine whether this view is important for accessibility.
See Also:
IMPORTANT_FOR_ACCESSIBILITY_YES, IMPORTANT_FOR_ACCESSIBILITY_NO, IMPORTANT_FOR_ACCESSIBILITY_AUTO

getAccessibilityNodeProvider

public static AccessibilityNodeProviderCompat getAccessibilityNodeProvider(View view)
Gets the provider for managing a virtual view hierarchy rooted at this View and reported to android.accessibilityservice.AccessibilityServices that explore the window content.

If this method returns an instance, this instance is responsible for managing AccessibilityNodeInfoCompats describing the virtual sub-tree rooted at this View including the one representing the View itself. Similarly the returned instance is responsible for performing accessibility actions on any virtual view or the root view itself.

If an AccessibilityDelegateCompat has been specified via calling #setAccessibilityDelegate(View, AccessibilityDelegateCompat) its {@link AccessibilityDelegateCompat#getAccessibilityNodeProvider(View)} is responsible for handling this call.

Parameters:
view - The view whose property to get.
Returns:
The provider.
See Also:
AccessibilityNodeProviderCompat