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Added in API level 1

Summary: Nested Classes | Methods | Inherited Methods | [Expand All]

ViewTreeObserver

public final class ViewTreeObserver
extends Object

java.lang.Object
↳	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.

Summary

Nested classes
`interface`	`ViewTreeObserver.OnDrawListener` Interface definition for a callback to be invoked when the view tree is about to be drawn.
`interface`	`ViewTreeObserver.OnGlobalFocusChangeListener` Interface definition for a callback to be invoked when the focus state within the view tree changes.
`interface`	`ViewTreeObserver.OnGlobalLayoutListener` Interface definition for a callback to be invoked when the global layout state or the visibility of views within the view tree changes.
`interface`	`ViewTreeObserver.OnPreDrawListener` Interface definition for a callback to be invoked when the view tree is about to be drawn.
`interface`	`ViewTreeObserver.OnScrollChangedListener` Interface definition for a callback to be invoked when something in the view tree has been scrolled.
`interface`	`ViewTreeObserver.OnTouchModeChangeListener` Interface definition for a callback to be invoked when the touch mode changes.
`interface`	`ViewTreeObserver.OnWindowAttachListener` Interface definition for a callback to be invoked when the view hierarchy is attached to and detached from its window.
`interface`	`ViewTreeObserver.OnWindowFocusChangeListener` Interface definition for a callback to be invoked when the view hierarchy's window focus state changes.

Public methods
`void`	`addOnDrawListener(ViewTreeObserver.OnDrawListener listener)` Register a callback to be invoked when the view tree is about to be drawn.
`void`	`addOnGlobalFocusChangeListener(ViewTreeObserver.OnGlobalFocusChangeListener listener)` Register a callback to be invoked when the focus state within the view tree changes.
`void`	`addOnGlobalLayoutListener(ViewTreeObserver.OnGlobalLayoutListener listener)` Register a callback to be invoked when the global layout state or the visibility of views within the view tree changes
`void`	`addOnPreDrawListener(ViewTreeObserver.OnPreDrawListener listener)` Register a callback to be invoked when the view tree is about to be drawn
`void`	`addOnScrollChangedListener(ViewTreeObserver.OnScrollChangedListener listener)` Register a callback to be invoked when a view has been scrolled.
`void`	`addOnTouchModeChangeListener(ViewTreeObserver.OnTouchModeChangeListener listener)` Register a callback to be invoked when the invoked when the touch mode changes.
`void`	`addOnWindowAttachListener(ViewTreeObserver.OnWindowAttachListener listener)` Register a callback to be invoked when the view hierarchy is attached to a window.
`void`	`addOnWindowFocusChangeListener(ViewTreeObserver.OnWindowFocusChangeListener listener)` Register a callback to be invoked when the window focus state within the view tree changes.
`final void`	`dispatchOnDraw()` Notifies registered listeners that the drawing pass is about to start.
`final void`	`dispatchOnGlobalLayout()` Notifies registered listeners that a global layout happened.
`final boolean`	`dispatchOnPreDraw()` Notifies registered listeners that the drawing pass is about to start.
`boolean`	`isAlive()` Indicates whether this ViewTreeObserver is alive.
`void`	`removeGlobalOnLayoutListener(ViewTreeObserver.OnGlobalLayoutListener victim)` This method was deprecated in API level 16. Use #removeOnGlobalLayoutListener instead
`void`	`removeOnDrawListener(ViewTreeObserver.OnDrawListener victim)` Remove a previously installed pre-draw callback.
`void`	`removeOnGlobalFocusChangeListener(ViewTreeObserver.OnGlobalFocusChangeListener victim)` Remove a previously installed focus change callback.
`void`	`removeOnGlobalLayoutListener(ViewTreeObserver.OnGlobalLayoutListener victim)` Remove a previously installed global layout callback
`void`	`removeOnPreDrawListener(ViewTreeObserver.OnPreDrawListener victim)` Remove a previously installed pre-draw callback
`void`	`removeOnScrollChangedListener(ViewTreeObserver.OnScrollChangedListener victim)` Remove a previously installed scroll-changed callback
`void`	`removeOnTouchModeChangeListener(ViewTreeObserver.OnTouchModeChangeListener victim)` Remove a previously installed touch mode change callback
`void`	`removeOnWindowAttachListener(ViewTreeObserver.OnWindowAttachListener victim)` Remove a previously installed window attach callback.
`void`	`removeOnWindowFocusChangeListener(ViewTreeObserver.OnWindowFocusChangeListener victim)` Remove a previously installed window focus change callback.

Inherited methods

From class


  
    java.lang.Object

`Object`	`clone()` Creates and returns a copy of this object.
`boolean`	`equals(Object obj)` Indicates whether some other object is "equal to" this one.
`void`	`finalize()` Called by the garbage collector on an object when garbage collection determines that there are no more references to the object.
`final Class<?>`	`getClass()` Returns the runtime class of this `Object`.
`int`	`hashCode()` Returns a hash code value for the object.
`final void`	`notify()` Wakes up a single thread that is waiting on this object's monitor.
`final void`	`notifyAll()` Wakes up all threads that are waiting on this object's monitor.
`String`	`toString()` Returns a string representation of the object.
`final void`	`wait(long millis, int nanos)` Causes the current thread to wait until another thread invokes the `notify()` method or the `notifyAll()` method for this object, or some other thread interrupts the current thread, or a certain amount of real time has elapsed.
`final void`	`wait(long millis)` Causes the current thread to wait until either another thread invokes the `notify()` method or the `notifyAll()` method for this object, or a specified amount of time has elapsed.
`final void`	`wait()` Causes the current thread to wait until another thread invokes the `notify()` method or the `notifyAll()` method for this object.

Public methods

addOnDrawListener

Added in API level 16

void addOnDrawListener (ViewTreeObserver.OnDrawListener listener)

Note: this method cannot be invoked from onDraw().

Parameters
`listener`	`ViewTreeObserver.OnDrawListener`: The callback to add

Throws
`IllegalStateException`	If `isAlive()` returns false

addOnGlobalFocusChangeListener

Added in API level 1

void addOnGlobalFocusChangeListener (ViewTreeObserver.OnGlobalFocusChangeListener listener)

Parameters
`listener`	`ViewTreeObserver.OnGlobalFocusChangeListener`: The callback to add

Throws
`IllegalStateException`	If `isAlive()` returns false

addOnGlobalLayoutListener

Added in API level 1

void addOnGlobalLayoutListener (ViewTreeObserver.OnGlobalLayoutListener listener)

Parameters
`listener`	`ViewTreeObserver.OnGlobalLayoutListener`: The callback to add

Throws
`IllegalStateException`	If `isAlive()` returns false

addOnPreDrawListener

Added in API level 1

void addOnPreDrawListener (ViewTreeObserver.OnPreDrawListener listener)

Parameters
`listener`	`ViewTreeObserver.OnPreDrawListener`: The callback to add

Throws
`IllegalStateException`	If `isAlive()` returns false

addOnScrollChangedListener

Added in API level 3

void addOnScrollChangedListener (ViewTreeObserver.OnScrollChangedListener listener)

Parameters
`listener`	`ViewTreeObserver.OnScrollChangedListener`: The callback to add

Throws
`IllegalStateException`	If `isAlive()` returns false

addOnTouchModeChangeListener

Added in API level 1

void addOnTouchModeChangeListener (ViewTreeObserver.OnTouchModeChangeListener listener)

Parameters
`listener`	`ViewTreeObserver.OnTouchModeChangeListener`: The callback to add

Throws
`IllegalStateException`	If `isAlive()` returns false

addOnWindowAttachListener

Added in API level 18

void addOnWindowAttachListener (ViewTreeObserver.OnWindowAttachListener listener)

Parameters
`listener`	`ViewTreeObserver.OnWindowAttachListener`: The callback to add

Throws
`IllegalStateException`	If `isAlive()` returns false

addOnWindowFocusChangeListener

Added in API level 18

void addOnWindowFocusChangeListener (ViewTreeObserver.OnWindowFocusChangeListener listener)

Parameters
`listener`	`ViewTreeObserver.OnWindowFocusChangeListener`: The callback to add

Throws
`IllegalStateException`	If `isAlive()` returns false

dispatchOnDraw

Added in API level 16

void dispatchOnDraw ()

Notifies registered listeners that the drawing pass is about to start.

dispatchOnGlobalLayout

Added in API level 1

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.

dispatchOnPreDraw

Added in API level 1

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
`boolean`	True if the current draw should be canceled and resceduled, false otherwise.

isAlive

Added in API level 1

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
`boolean`	True if this object is alive and be used, false otherwise.

removeGlobalOnLayoutListener

Added in API level 1

void removeGlobalOnLayoutListener (ViewTreeObserver.OnGlobalLayoutListener victim)

This method was deprecated in API level 16.
Use #removeOnGlobalLayoutListener instead

Remove a previously installed global layout callback

Parameters
`victim`	`ViewTreeObserver.OnGlobalLayoutListener`: The callback to remove

Throws
`IllegalStateException`	If `isAlive()` returns false

See also:

addOnGlobalLayoutListener(OnGlobalLayoutListener)

removeOnDrawListener

Added in API level 16

void removeOnDrawListener (ViewTreeObserver.OnDrawListener victim)

Remove a previously installed pre-draw callback.

Note: this method cannot be invoked from onDraw().

Parameters
`victim`	`ViewTreeObserver.OnDrawListener`: The callback to remove

Throws
`IllegalStateException`	If `isAlive()` returns false

See also:

addOnDrawListener(OnDrawListener)

removeOnGlobalFocusChangeListener

Added in API level 1

void removeOnGlobalFocusChangeListener (ViewTreeObserver.OnGlobalFocusChangeListener victim)

Remove a previously installed focus change callback.

Parameters
`victim`	`ViewTreeObserver.OnGlobalFocusChangeListener`: The callback to remove

Throws
`IllegalStateException`	If `isAlive()` returns false

See also:

addOnGlobalFocusChangeListener(OnGlobalFocusChangeListener)

removeOnGlobalLayoutListener

Added in API level 16

void removeOnGlobalLayoutListener (ViewTreeObserver.OnGlobalLayoutListener victim)

Remove a previously installed global layout callback

Parameters
`victim`	`ViewTreeObserver.OnGlobalLayoutListener`: The callback to remove

Throws
`IllegalStateException`	If `isAlive()` returns false

See also:

addOnGlobalLayoutListener(OnGlobalLayoutListener)

removeOnPreDrawListener

Added in API level 1

void removeOnPreDrawListener (ViewTreeObserver.OnPreDrawListener victim)

Remove a previously installed pre-draw callback

Parameters
`victim`	`ViewTreeObserver.OnPreDrawListener`: The callback to remove

Throws
`IllegalStateException`	If `isAlive()` returns false

See also:

addOnPreDrawListener(OnPreDrawListener)

removeOnScrollChangedListener

Added in API level 3

void removeOnScrollChangedListener (ViewTreeObserver.OnScrollChangedListener victim)

Remove a previously installed scroll-changed callback

Parameters
`victim`	`ViewTreeObserver.OnScrollChangedListener`: The callback to remove

Throws
`IllegalStateException`	If `isAlive()` returns false

See also:

addOnScrollChangedListener(OnScrollChangedListener)

removeOnTouchModeChangeListener

Added in API level 1

void removeOnTouchModeChangeListener (ViewTreeObserver.OnTouchModeChangeListener victim)

Remove a previously installed touch mode change callback

Parameters
`victim`	`ViewTreeObserver.OnTouchModeChangeListener`: The callback to remove

Throws
`IllegalStateException`	If `isAlive()` returns false

See also:

addOnTouchModeChangeListener(OnTouchModeChangeListener)

removeOnWindowAttachListener

Added in API level 18

void removeOnWindowAttachListener (ViewTreeObserver.OnWindowAttachListener victim)

Remove a previously installed window attach callback.

Parameters
`victim`	`ViewTreeObserver.OnWindowAttachListener`: The callback to remove

Throws
`IllegalStateException`	If `isAlive()` returns false

See also:

addOnWindowAttachListener(android.view.ViewTreeObserver.OnWindowAttachListener)

removeOnWindowFocusChangeListener

Added in API level 18

void removeOnWindowFocusChangeListener (ViewTreeObserver.OnWindowFocusChangeListener victim)

Remove a previously installed window focus change callback.

Parameters
`victim`	`ViewTreeObserver.OnWindowFocusChangeListener`: The callback to remove

Throws
`IllegalStateException`	If `isAlive()` returns false

See also:

addOnWindowFocusChangeListener(android.view.ViewTreeObserver.OnWindowFocusChangeListener)

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Most visited

Recently visited

Results for

ViewTreeObserver

Summary

Nested classes

Public methods

Inherited methods

Public methods

addOnDrawListener

addOnGlobalFocusChangeListener

addOnGlobalLayoutListener

addOnPreDrawListener

addOnScrollChangedListener

addOnTouchModeChangeListener

addOnWindowAttachListener

addOnWindowFocusChangeListener

dispatchOnDraw

dispatchOnGlobalLayout

dispatchOnPreDraw

isAlive

removeGlobalOnLayoutListener

removeOnDrawListener

removeOnGlobalFocusChangeListener

removeOnGlobalLayoutListener

removeOnPreDrawListener

removeOnScrollChangedListener

removeOnTouchModeChangeListener

removeOnWindowAttachListener

removeOnWindowFocusChangeListener