android.view
public
final
class
android.view.ViewTreeObserver
A view tree observer is used to register listeners that can be notified of global
changes in the view tree. Such global events include, but are not limited to,
layout of the whole tree, beginning of the drawing pass, touch mode change....
A ViewTreeObserver should never be instantiated by applications as it is provided
by the views hierarchy. Refer to getViewTreeObserver()
for more information.
Nested Classes
Summary
Public Methods
clone,
equals,
finalize,
getClass,
hashCode,
notify,
notifyAll,
toString,
wait,
wait,
wait
Details
Public Methods
Register a callback to be invoked when the focus state within the view tree changes.
Parameters
listener
| The callback to add |
Register a callback to be invoked when the global layout state or the visibility of views
within the view tree changes
Parameters
listener
| The callback to add |
Register a callback to be invoked when the view tree is about to be drawn
Parameters
listener
| The callback to add |
Register a callback to be invoked when the invoked when the touch mode changes.
Parameters
listener
| The callback to add |
public
final
void
dispatchOnGlobalLayout()
Notifies registered listeners that a global layout happened. This can be called
manually if you are forcing a layout on a View or a hierarchy of Views that are
not attached to a Window or in the GONE state.
public
final
boolean
dispatchOnPreDraw()
Notifies registered listeners that the drawing pass is about to start. If a
listener returns true, then the drawing pass is canceled and rescheduled. This can
be called manually if you are forcing the drawing on a View or a hierarchy of Views
that are not attached to a Window or in the GONE state.
Returns
- True if the current draw should be canceled and resceduled, false otherwise.
public
boolean
isAlive()
Indicates whether this ViewTreeObserver is alive. When an observer is not alive,
any call to a method (except this one) will throw an exception.
If an application keeps a long-lived reference to this ViewTreeObserver, it should
always check for the result of this method before calling any other method.
Returns
- True if this object is alive and be used, false otherwise.
Remove a previously installed global layout callback
Parameters
victim
| The callback to remove |
Remove a previously installed focus change callback.
Parameters
victim
| The callback to remove |
Remove a previously installed pre-draw callback
Parameters
victim
| The callback to remove |
Remove a previously installed touch mode change callback
Parameters
victim
| The callback to remove |