IT. Expert System.

Android Reference

ViewCompat

android.support.v4.view

Class ViewCompat

java.lang.Object
- android.support.v4.view.ViewCompat

```
public class ViewCompat
extends Object
```
Helper for accessing features in View introduced after API level 4 in a backwards compatible fashion.

Field Summary

Fields
Modifier and Type	Field and Description
`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`	`LAYER_TYPE_HARDWARE` Indicates that the view has a hardware layer.
`static int`	`LAYER_TYPE_NONE` Indicates that the view does not have a layer.
`static int`	`LAYER_TYPE_SOFTWARE` Indicates that the view has a software layer.
`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

Constructors
Constructor and Description

ViewCompat()

Constructors
Constructor and Description
`ViewCompat()`

Method Summary

Methods
Modifier and Type	Method and Description
`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 `AccessibilityService`s 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`	`getLabelFor(View view)` Gets the id of a view for which a given view serves as a label for accessibility purposes.
`static int`	`getLayerType(View view)` Indicates what type of layer is currently associated with this view.
`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 `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 boolean`	`performAccessibilityAction(View view, int action, Bundle arguments)` Performs the specified accessibility action on the view.
`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, Runnable action)` Causes the Runnable to execute on the next animation time step.
`static void`	`postOnAnimationDelayed(View view, 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`	`setLabelFor(View view, int labeledId)` Sets the id of a view for which a given view serves as a label for accessibility purposes.
`static void`	`setLayerType(View view, int layerType, Paint paint)` Specifies the type of layer backing this view.
`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
  - LAYER_TYPE_NONE
```
public static final int LAYER_TYPE_NONE
```
    Indicates that the view does not have a layer.
    
    See Also:
    Constant Field Values
  - LAYER_TYPE_SOFTWARE
```
public static final int LAYER_TYPE_SOFTWARE
```
    Indicates that the view has a software layer. A software layer is backed by a bitmap and causes the view to be rendered using Android's software rendering pipeline, even if hardware acceleration is enabled.
    
    Software layers have various usages:
    
    When the application is not using hardware acceleration, a software layer is useful to apply a specific color filter and/or blending mode and/or translucency to a view and all its children.
    
    When the application is using hardware acceleration, a software layer is useful to render drawing primitives not supported by the hardware accelerated pipeline. It can also be used to cache a complex view tree into a texture and reduce the complexity of drawing operations. For instance, when animating a complex view tree with a translation, a software layer can be used to render the view tree only once.
    
    Software layers should be avoided when the affected view tree updates often. Every update will require to re-render the software layer, which can potentially be slow (particularly when hardware acceleration is turned on since the layer will have to be uploaded into a hardware texture after every update.)
    
    See Also:
    Constant Field Values
  - LAYER_TYPE_HARDWARE
```
public static final int LAYER_TYPE_HARDWARE
```
    Indicates that the view has a hardware layer. A hardware layer is backed by a hardware specific texture (generally Frame Buffer Objects or FBO on OpenGL hardware) and causes the view to be rendered using Android's hardware rendering pipeline, but only if hardware acceleration is turned on for the view hierarchy. When hardware acceleration is turned off, hardware layers behave exactly as software layers.
    
    A hardware layer is useful to apply a specific color filter and/or blending mode and/or translucency to a view and all its children.
    
    A hardware layer can be used to cache a complex view tree into a texture and reduce the complexity of drawing operations. For instance, when animating a complex view tree with a translation, a hardware layer can be used to render the view tree only once.
    
    A hardware layer can also be used to increase the rendering quality when rotation transformations are applied on a view. It can also be used to prevent potential clipping issues when applying 3D transforms on a view.
    
    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 View.AccessibilityDelegate has been specified via calling View.setAccessibilityDelegate(android.view.View.AccessibilityDelegate) its 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 View.AccessibilityDelegate has been specified via calling View.setAccessibilityDelegate(android.view.View.AccessibilityDelegate) its 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 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 View.AccessibilityDelegate has been specified via calling View.setAccessibilityDelegate(android.view.View.AccessibilityDelegate) its 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 View.AccessibilityDelegate.
    
    Parameters:
    v - The View against which to invoke the method.
    delegate - The delegate instance.
    See Also:
    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,
                   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,
                          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
  - performAccessibilityAction
```
public static boolean performAccessibilityAction(View view,
                                 int action,
                                 Bundle arguments)
```
    Performs the specified accessibility action on the view. For possible accessibility actions look at AccessibilityNodeInfoCompat.
    If an AccessibilityDelegateCompat has been specified via calling setAccessibilityDelegate(View, AccessibilityDelegateCompat) its AccessibilityDelegateCompat.performAccessibilityAction(View, int, Bundle) is responsible for handling this call.
    
    Parameters:
    action - The action to perform.
    arguments - Optional action arguments.
    
    Returns:
    Whether the action was performed.
  - getAccessibilityNodeProvider
```
public static AccessibilityNodeProviderCompat getAccessibilityNodeProvider(View view)
```
    Gets the provider for managing a virtual view hierarchy rooted at this View and reported to 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
  - setLayerType
```
public static void setLayerType(View view,
                int layerType,
                Paint paint)
```
    Specifies the type of layer backing this view. The layer can be disabled, software or hardware.
    
    A layer is associated with an optional Paint instance that controls how the layer is composed on screen. The following properties of the paint are taken into account when composing the layer:
    If this view has an alpha value set to < 1.0 by calling setalpha(float), the alpha value of the layer's paint is replaced by this view's alpha value. calling setalpha(float) is therefore equivalent to setting a hardware layer on this view and providing a paint with the desired alpha value.
    
    Refer to the documentation of disabled, software and hardware for more information on when and how to use layers.
    Parameters:
    layerType - The ype of layer to use with this view, must be one of LAYER_TYPE_NONE, LAYER_TYPE_SOFTWARE or LAYER_TYPE_HARDWARE
    paint - The paint used to compose the layer. This argument is optional and can be null. It is ignored when the layer type is LAYER_TYPE_NONE
    view - View to set the layer type for
    layerType - The type of layer to use with this view, must be one of LAYER_TYPE_NONE, LAYER_TYPE_SOFTWARE or LAYER_TYPE_HARDWARE
    paint - The paint used to compose the layer. This argument is optional and can be null. It is ignored when the layer type is LAYER_TYPE_NONE
  - getLayerType
```
public static int getLayerType(View view)
```
    Indicates what type of layer is currently associated with this view. By default a view does not have a layer, and the layer type is LAYER_TYPE_NONE. Refer to the documentation of setLayerType(android.view.View, int, android.graphics.Paint) for more information on the different types of layers.
    
    Parameters:
    view - The view to fetch the layer type from
    
    Returns:
    LAYER_TYPE_NONE, LAYER_TYPE_SOFTWARE or LAYER_TYPE_HARDWARE
    See Also:
    setLayerType(android.view.View, int, android.graphics.Paint), LAYER_TYPE_NONE, LAYER_TYPE_SOFTWARE, LAYER_TYPE_HARDWARE
  - getLabelFor
```
public static int getLabelFor(View view)
```
    Gets the id of a view for which a given view serves as a label for accessibility purposes.
    
    Parameters:
    view - The view on which to invoke the corresponding method.
    
    Returns:
    The labeled view id.
  - setLabelFor
```
public static void setLabelFor(View view,
               int labeledId)
```
    Sets the id of a view for which a given view serves as a label for accessibility purposes.
    
    Parameters:
    view - The view on which to invoke the corresponding method.
    labeledId - The labeled view id.

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IT. Expert System.

Android Reference

ViewCompat

Class ViewCompat

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

OVER_SCROLL_ALWAYS

OVER_SCROLL_IF_CONTENT_SCROLLS

OVER_SCROLL_NEVER

IMPORTANT_FOR_ACCESSIBILITY_AUTO

IMPORTANT_FOR_ACCESSIBILITY_YES

IMPORTANT_FOR_ACCESSIBILITY_NO

LAYER_TYPE_NONE

LAYER_TYPE_SOFTWARE

LAYER_TYPE_HARDWARE

Constructor Detail

ViewCompat

Method Detail

canScrollHorizontally

canScrollVertically

getOverScrollMode

setOverScrollMode

onPopulateAccessibilityEvent

onInitializeAccessibilityEvent

onInitializeAccessibilityNodeInfo

setAccessibilityDelegate

hasTransientState

setHasTransientState

postInvalidateOnAnimation

postInvalidateOnAnimation

postOnAnimation

postOnAnimationDelayed

getImportantForAccessibility

setImportantForAccessibility

performAccessibilityAction

getAccessibilityNodeProvider

setLayerType

getLayerType

getLabelFor

setLabelFor

Android Reference

Java basics

Java Enterprise Edition (EE)

Java Standard Edition (SE)

SQL

HTML

PHP

CSS

Java Script

MYSQL

JQUERY

VBS

REGEX

C

C++

C#

Design patterns

RFC (standard status)

RFC (proposed standard status)

RFC (draft standard status)

RFC (informational status)

RFC (experimental status)

RFC (best current practice status)

RFC (historic status)

RFC (unknown status)

IT dictionary