| java.lang.Object | ||||
| ↳ | android.view.View | |||
| ↳ | android.view.ViewGroup | |||
| ↳ | android.widget.FrameLayout | |||
| ↳ | android.widget.ScrollView | |||
Layout container for a view hierarchy that can be scrolled by the user,
allowing it to be larger than the physical display. A ScrollView
is a FrameLayout, meaning you should place one child in it
containing the entire contents to scroll; this child may itself be a layout
manager with a complex hierarchy of objects. A child that is often used
is a LinearLayout in a vertical orientation, presenting a vertical
array of top-level items that the user can scroll through.
You should never use a ScrollView with a ListView, because
ListView takes care of its own vertical scrolling. Most importantly, doing this
defeats all of the important optimizations in ListView for dealing with
large lists, since it effectively forces the ListView to display its entire
list of items to fill up the infinite container supplied by ScrollView.
The TextView class also
takes care of its own scrolling, so does not require a ScrollView, but
using the two together is possible to achieve the effect of a text view
within a larger container.
ScrollView only supports vertical scrolling. For horizontal scrolling,
use HorizontalScrollView.
| XML Attributes | |||||||||||
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| android:fillViewport | setFillViewport(boolean) | Defines whether the scrollview should stretch its content to fill the viewport. | |||||||||
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Inherited XML Attributes | |||||||||||
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 From class
android.widget.FrameLayout
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From class
android.view.ViewGroup
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From class
android.view.View
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Inherited Constants | |||||||||||
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From class
android.view.ViewGroup
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From class
android.view.View
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Inherited Fields | |||||||||||
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From class
android.view.View
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| Public Constructors | |||||||||||
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| Public Methods | |||||||||||
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Adds a child view. | |||||||||||
Adds a child view.
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Adds a child view with the specified layout parameters.
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Adds a child view with the specified layout parameters.
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Handle scrolling in response to an up or down arrow click.
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Called by a parent to request that a child update its values for mScrollX
and mScrollY if necessary.
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Dispatch a key event to the next view on the focus path.
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Manually render this view (and all of its children) to the given Canvas.
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You can call this function yourself to have the scroll view perform
scrolling from a key event, just as if the event had been dispatched to
it by the view hierarchy.
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Fling the scroll view
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Handles scrolling in response to a "home/end" shortcut press. | |||||||||||
Indicates whether this ScrollView's content is stretched to fill the viewport.
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Implement this method to handle generic motion events.
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Initializes an
AccessibilityEvent with information about
this View which is the event source. | |||||||||||
Initializes an
AccessibilityNodeInfo with information about this view. | |||||||||||
Implement this method to intercept all touch screen motion events.
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Implement this method to handle touch screen motion events.
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Handles scrolling in response to a "page up/down" shortcut press. | |||||||||||
Performs the specified accessibility action on the view.
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Called when a child of this parent wants focus
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Called when a child of this group wants a particular rectangle to be
positioned onto the screen.
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Called when a child does not want this parent and its ancestors to
intercept touch events with
onInterceptTouchEvent(MotionEvent).
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Call this when something has changed which has invalidated the
layout of this view.
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Set the scrolled position of your view.
This version also clamps the scrolling to the bounds of our child. | |||||||||||
Indicates this ScrollView whether it should stretch its content height to fill
the viewport or not.
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Set the over-scroll mode for this view.
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Set whether arrow scrolling will animate its transition.
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Return true if the pressed state should be delayed for children or descendants of this
ViewGroup.
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Like
scrollBy(int, int), but scroll smoothly instead of immediately. | |||||||||||
Like
scrollTo(int, int), but scroll smoothly instead of immediately. | |||||||||||
| Protected Methods | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
Compute the amount to scroll in the Y direction in order to get
a rectangle completely on the screen (or, if taller than the screen,
at least the first screen size chunk of it).
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Compute the vertical offset of the vertical scrollbar's thumb within the horizontal range. | |||||||||||
The scroll range of a scroll view is the overall height of all of its children. | |||||||||||
Returns the strength, or intensity, of the bottom faded edge.
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Returns the strength, or intensity, of the top faded edge.
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Ask one of the children of this view to measure itself, taking into
account both the MeasureSpec requirements for this view and its padding.
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Ask one of the children of this view to measure itself, taking into
account both the MeasureSpec requirements for this view and its padding
and margins.
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This is called when the view is detached from a window.
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Called from layout when this view should
assign a size and position to each of its children.
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Measure the view and its content to determine the measured width and the measured height. | |||||||||||
Called by
overScrollBy(int, int, int, int, int, int, int, int, boolean) to
respond to the results of an over-scroll operation. | |||||||||||
When looking for focus in children of a scroll view, need to be a little
more careful not to give focus to something that is scrolled off screen.
| |||||||||||
Hook allowing a view to re-apply a representation of its internal state that had previously
been generated by
onSaveInstanceState(). | |||||||||||
Hook allowing a view to generate a representation of its internal state
that can later be used to create a new instance with that same state.
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This is called during layout when the size of this view has changed.
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[Expand]
Inherited Methods | |||||||||||
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From class
android.widget.FrameLayout
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From class
android.view.ViewGroup
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From class
android.view.View
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From class
java.lang.Object
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From interface
android.graphics.drawable.Drawable.Callback
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From interface
android.view.KeyEvent.Callback
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From interface
android.view.ViewManager
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From interface
android.view.ViewParent
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From interface
android.view.accessibility.AccessibilityEventSource
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Defines whether the scrollview should stretch its content to fill the viewport.
Must be a boolean value, either "true" or "false".
This may also be a reference to a resource (in the form
"@[package:]type:name") or
theme attribute (in the form
"?[package:][type:]name")
containing a value of this type.
This corresponds to the global attribute
resource symbol fillViewport.
Adds a child view. If no layout parameters are already set on the child, the default parameters for this ViewGroup are set on the child.
Note: do not invoke this method from
draw(android.graphics.Canvas), onDraw(android.graphics.Canvas),
dispatchDraw(android.graphics.Canvas) or any related method.
| child | the child view to add |
|---|
Adds a child view. If no layout parameters are already set on the child, the default parameters for this ViewGroup are set on the child.
Note: do not invoke this method from
draw(android.graphics.Canvas), onDraw(android.graphics.Canvas),
dispatchDraw(android.graphics.Canvas) or any related method.
| child | the child view to add |
|---|---|
| index | the position at which to add the child |
Adds a child view with the specified layout parameters.
Note: do not invoke this method from
draw(android.graphics.Canvas), onDraw(android.graphics.Canvas),
dispatchDraw(android.graphics.Canvas) or any related method.
| child | the child view to add |
|---|---|
| index | the position at which to add the child |
| params | the layout parameters to set on the child |
Adds a child view with the specified layout parameters.
Note: do not invoke this method from
draw(android.graphics.Canvas), onDraw(android.graphics.Canvas),
dispatchDraw(android.graphics.Canvas) or any related method.
| child | the child view to add |
|---|---|
| params | the layout parameters to set on the child |
Handle scrolling in response to an up or down arrow click.
| direction | The direction corresponding to the arrow key that was pressed |
|---|
Called by a parent to request that a child update its values for mScrollX
and mScrollY if necessary. This will typically be done if the child is
animating a scroll using a Scroller
object.
Dispatch a key event to the next view on the focus path. This path runs from the top of the view tree down to the currently focused view. If this view has focus, it will dispatch to itself. Otherwise it will dispatch the next node down the focus path. This method also fires any key listeners.
| event | The key event to be dispatched. |
|---|
Manually render this view (and all of its children) to the given Canvas.
The view must have already done a full layout before this function is
called. When implementing a view, implement
onDraw(android.graphics.Canvas) instead of overriding this method.
If you do need to override this method, call the superclass version.
| canvas | The Canvas to which the View is rendered. |
|---|
You can call this function yourself to have the scroll view perform scrolling from a key event, just as if the event had been dispatched to it by the view hierarchy.
| event | The key event to execute. |
|---|
Fling the scroll view
| velocityY | The initial velocity in the Y direction. Positive numbers mean that the finger/cursor is moving down the screen, which means we want to scroll towards the top. |
|---|
Handles scrolling in response to a "home/end" shortcut press. This method will scroll the view to the top or bottom and give the focus to the topmost/bottommost component in the new visible area. If no component is a good candidate for focus, this scrollview reclaims the focus.
| direction | the scroll direction: FOCUS_UP
to go the top of the view or
FOCUS_DOWN to go the bottom |
|---|
Indicates whether this ScrollView's content is stretched to fill the viewport.
Implement this method to handle generic motion events.
Generic motion events describe joystick movements, mouse hovers, track pad
touches, scroll wheel movements and other input events. The
source of the motion event specifies
the class of input that was received. Implementations of this method
must examine the bits in the source before processing the event.
The following code example shows how this is done.
Generic motion events with source class SOURCE_CLASS_POINTER
are delivered to the view under the pointer. All other generic motion events are
delivered to the focused view.
public boolean onGenericMotionEvent(MotionEvent event) {
if (event.isFromSource(InputDevice.SOURCE_CLASS_JOYSTICK)) {
if (event.getAction() == MotionEvent.ACTION_MOVE) {
// process the joystick movement...
return true;
}
}
if (event.isFromSource(InputDevice.SOURCE_CLASS_POINTER)) {
switch (event.getAction()) {
case MotionEvent.ACTION_HOVER_MOVE:
// process the mouse hover movement...
return true;
case MotionEvent.ACTION_SCROLL:
// process the scroll wheel movement...
return true;
}
}
return super.onGenericMotionEvent(event);
}| event | The generic motion event being processed. |
|---|
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
setAccessibilityDelegate(AccessibilityDelegate) its
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.
| event | The event to initialize. |
|---|
Initializes an AccessibilityNodeInfo with information about this view.
The base implementation sets:
setParent(View),setBoundsInParent(Rect),setBoundsInScreen(Rect),setPackageName(CharSequence),setClassName(CharSequence),setContentDescription(CharSequence),setEnabled(boolean),setClickable(boolean),setFocusable(boolean),setFocused(boolean),setLongClickable(boolean),setSelected(boolean),Subclasses should override this method, call the super implementation, and set additional attributes.
If an View.AccessibilityDelegate has been specified via calling
setAccessibilityDelegate(AccessibilityDelegate) its
onInitializeAccessibilityNodeInfo(View, AccessibilityNodeInfo)
is responsible for handling this call.
| info | The instance to initialize. |
|---|
Implement this method to intercept all touch screen motion events. This allows you to watch events as they are dispatched to your children, and take ownership of the current gesture at any point.
Using this function takes some care, as it has a fairly complicated
interaction with View.onTouchEvent(MotionEvent), and using it requires implementing
that method as well as this one in the correct way. Events will be
received in the following order:
ACTION_CANCEL, and all further
events will be delivered to your onTouchEvent() method and no longer
appear here.
| ev | The motion event being dispatched down the hierarchy. |
|---|
Implement this method to handle touch screen motion events.
If this method is used to detect click actions, it is recommended that
the actions be performed by implementing and calling
performClick(). This will ensure consistent system behavior,
including:
ACTION_CLICK when
accessibility features are enabled
| ev | The motion event. |
|---|
Handles scrolling in response to a "page up/down" shortcut press. This method will scroll the view by one page up or down and give the focus to the topmost/bottommost component in the new visible area. If no component is a good candidate for focus, this scrollview reclaims the focus.
| direction | the scroll direction: FOCUS_UP
to go one page up or
FOCUS_DOWN to go one page down |
|---|
Performs the specified accessibility action on the view. For
possible accessibility actions look at AccessibilityNodeInfo.
If an View.AccessibilityDelegate has been specified via calling
setAccessibilityDelegate(AccessibilityDelegate) its
performAccessibilityAction(View, int, Bundle)
is responsible for handling this call.
| action | The action to perform. |
|---|---|
| arguments | Optional action arguments. |
Called when a child of this parent wants focus
| child | The child of this ViewParent that wants focus. This view will contain the focused view. It is not necessarily the view that actually has focus. |
|---|---|
| focused | The view that is a descendant of child that actually has focus |
Called when a child of this group wants a particular rectangle to be
positioned onto the screen. ViewGroups overriding this can trust
that:
ViewGroups overriding this should uphold the contract:
| child | The direct child making the request. |
|---|---|
| rectangle | The rectangle in the child's coordinates the child wishes to be on the screen. |
| immediate | True to forbid animated or delayed scrolling, false otherwise |
Called when a child does not want this parent and its ancestors to
intercept touch events with
onInterceptTouchEvent(MotionEvent).
This parent should pass this call onto its parents. This parent must obey this request for the duration of the touch (that is, only clear the flag after this parent has received an up or a cancel.
| disallowIntercept | True if the child does not want the parent to intercept touch events. |
|---|
Call this when something has changed which has invalidated the
layout of this view. This will schedule a layout pass of the view
tree. This should not be called while the view hierarchy is currently in a layout
pass (isInLayout(). If layout is happening, the request may be honored at the
end of the current layout pass (and then layout will run again) or after the current
frame is drawn and the next layout occurs.
Subclasses which override this method should call the superclass method to handle possible request-during-layout errors correctly.
Set the scrolled position of your view. This will cause a call to
onScrollChanged(int, int, int, int) and the view will be
invalidated.
This version also clamps the scrolling to the bounds of our child.
| x | the x position to scroll to |
|---|---|
| y | the y position to scroll to |
Indicates this ScrollView whether it should stretch its content height to fill the viewport or not.
| fillViewport | True to stretch the content's height to the viewport's boundaries, false otherwise. |
|---|
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.
| mode | The new over-scroll mode for this view. |
|---|
Set whether arrow scrolling will animate its transition.
| smoothScrollingEnabled | whether arrow scrolling will animate its transition |
|---|
Return true if the pressed state should be delayed for children or descendants of this ViewGroup. Generally, this should be done for containers that can scroll, such as a List. This prevents the pressed state from appearing when the user is actually trying to scroll the content. The default implementation returns true for compatibility reasons. Subclasses that do not scroll should generally override this method and return false.
Like scrollBy(int, int), but scroll smoothly instead of immediately.
| dx | the number of pixels to scroll by on the X axis |
|---|---|
| dy | the number of pixels to scroll by on the Y axis |
Like scrollTo(int, int), but scroll smoothly instead of immediately.
| x | the position where to scroll on the X axis |
|---|---|
| y | the position where to scroll on the Y axis |
Compute the amount to scroll in the Y direction in order to get a rectangle completely on the screen (or, if taller than the screen, at least the first screen size chunk of it).
| rect | The rect. |
|---|
Compute the vertical offset of the vertical scrollbar's thumb within the horizontal range. This value is used to compute the position of the thumb within the scrollbar's track.
The range is expressed in arbitrary units that must be the same as the
units used by computeVerticalScrollRange() and
computeVerticalScrollExtent().
The default offset is the scroll offset of this view.
The scroll range of a scroll view is the overall height of all of its children.
The default range is the drawing height of this view.
Returns the strength, or intensity, of the bottom faded edge. The strength is a value between 0.0 (no fade) and 1.0 (full fade). The default implementation returns 0.0 or 1.0 but no value in between. Subclasses should override this method to provide a smoother fade transition when scrolling occurs.
Returns the strength, or intensity, of the top faded edge. The strength is a value between 0.0 (no fade) and 1.0 (full fade). The default implementation returns 0.0 or 1.0 but no value in between. Subclasses should override this method to provide a smoother fade transition when scrolling occurs.
Ask one of the children of this view to measure itself, taking into account both the MeasureSpec requirements for this view and its padding. The heavy lifting is done in getChildMeasureSpec.
| child | The child to measure |
|---|---|
| parentWidthMeasureSpec | The width requirements for this view |
| parentHeightMeasureSpec | The height requirements for this view |
Ask one of the children of this view to measure itself, taking into account both the MeasureSpec requirements for this view and its padding and margins. The child must have MarginLayoutParams The heavy lifting is done in getChildMeasureSpec.
| child | The child to measure |
|---|---|
| parentWidthMeasureSpec | The width requirements for this view |
| widthUsed | Extra space that has been used up by the parent horizontally (possibly by other children of the parent) |
| parentHeightMeasureSpec | The height requirements for this view |
| heightUsed | Extra space that has been used up by the parent vertically (possibly by other children of the parent) |
This is called when the view is detached from a window. At this point it no longer has a surface for drawing.
Called from layout when this view should assign a size and position to each of its children. Derived classes with children should override this method and call layout on each of their children.
| changed | This is a new size or position for this view |
|---|---|
| l | Left position, relative to parent |
| t | Top position, relative to parent |
| r | Right position, relative to parent |
| b | Bottom position, relative to parent |
Measure the view and its content to determine the measured width and the
measured height. This method is invoked by measure(int, int) and
should be overriden by subclasses to provide accurate and efficient
measurement of their contents.
CONTRACT: When overriding this method, you
must call setMeasuredDimension(int, int) to store the
measured width and height of this view. Failure to do so will trigger an
IllegalStateException, thrown by
measure(int, int). Calling the superclass'
onMeasure(int, int) is a valid use.
The base class implementation of measure defaults to the background size,
unless a larger size is allowed by the MeasureSpec. Subclasses should
override onMeasure(int, int) to provide better measurements of
their content.
If this method is overridden, it is the subclass's responsibility to make
sure the measured height and width are at least the view's minimum height
and width (getSuggestedMinimumHeight() and
getSuggestedMinimumWidth()).
| widthMeasureSpec | horizontal space requirements as imposed by the parent.
The requirements are encoded with
View.MeasureSpec. |
|---|---|
| heightMeasureSpec | vertical space requirements as imposed by the parent.
The requirements are encoded with
View.MeasureSpec. |
Called by overScrollBy(int, int, int, int, int, int, int, int, boolean) to
respond to the results of an over-scroll operation.
| scrollX | New X scroll value in pixels |
|---|---|
| scrollY | New Y scroll value in pixels |
| clampedX | True if scrollX was clamped to an over-scroll boundary |
| clampedY | True if scrollY was clamped to an over-scroll boundary |
When looking for focus in children of a scroll view, need to be a little
more careful not to give focus to something that is scrolled off screen.
This is more expensive than the default ViewGroup
implementation, otherwise this behavior might have been made the default.
| direction | One of FOCUS_UP, FOCUS_DOWN, FOCUS_LEFT, and FOCUS_RIGHT |
|---|---|
| previouslyFocusedRect | The rectangle (in this View's coordinate system) to give a finer grained hint about where focus is coming from. May be null if there is no hint. |
Hook allowing a view to re-apply a representation of its internal state that had previously
been generated by onSaveInstanceState(). This function will never be called with a
null state.
| state | The frozen state that had previously been returned by
onSaveInstanceState(). |
|---|
Hook allowing a view to generate a representation of its internal state that can later be used to create a new instance with that same state. This state should only contain information that is not persistent or can not be reconstructed later. For example, you will never store your current position on screen because that will be computed again when a new instance of the view is placed in its view hierarchy.
Some examples of things you may store here: the current cursor position in a text view (but usually not the text itself since that is stored in a content provider or other persistent storage), the currently selected item in a list view.
This is called during layout when the size of this view has changed. If you were just added to the view hierarchy, you're called with the old values of 0.
| w | Current width of this view. |
|---|---|
| h | Current height of this view. |
| oldw | Old width of this view. |
| oldh | Old height of this view. |