Package icyllis.modernui.view

Class OneShotPreDrawListener

java.lang.Object

icyllis.modernui.view.OneShotPreDrawListener

All Implemented Interfaces:

View.OnAttachStateChangeListener, ViewTreeObserver.OnPreDrawListener

public final class OneShotPreDrawListener
extends Object
implements ViewTreeObserver.OnPreDrawListener, View.OnAttachStateChangeListener

An OnPreDrawListener that will remove itself after one OnPreDraw call. Typical usage is:

     OneShotPreDrawListener.add(view, () -> view.doSomething())
 

The onPreDraw always returns true.

The listener will also remove itself from the ViewTreeObserver when the view is detached from the view hierarchy. In that case, the Runnable will never be executed.

Method Summary

Modifier and Type	Method	Description
static OneShotPreDrawListener	add(View view, Runnable runnable)	Creates a OneShotPreDrawListener and adds it to view's ViewTreeObserver.
boolean	onPreDraw()	Callback method to be invoked when the view tree is about to be drawn.
void	onViewAttachedToWindow(View v)	Called when the view is attached to a window.
void	onViewDetachedFromWindow(View v)	Called when the view is detached from a window.
void	removeListener()	Removes the listener from the ViewTreeObserver.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Details

add

@NonNull
public static OneShotPreDrawListener add(@NonNull
 View view,
 @NonNull
 Runnable runnable)

Creates a OneShotPreDrawListener and adds it to view's ViewTreeObserver.

Parameters:

view - The view whose ViewTreeObserver the OnPreDrawListener should listen.

runnable - The Runnable to execute in the OnPreDraw (once)

Returns:

The added OneShotPreDrawListener. It can be removed prior to the onPreDraw by calling removeListener().

onPreDraw

public boolean onPreDraw()

Description copied from interface: ViewTreeObserver.OnPreDrawListener

Callback method to be invoked when the view tree is about to be drawn. At this point, all views in the tree have been measured and given a frame. Clients can use this to adjust their scroll bounds or even to request a new layout before drawing occurs.

Specified by:

onPreDraw in interface ViewTreeObserver.OnPreDrawListener

Returns:

Return true to proceed with the current drawing pass, or false to cancel.

See Also:

• View.onMeasure(int, int)
• View.onLayout(boolean, int, int, int, int)
• View.onDraw(icyllis.modernui.graphics.Canvas)

removeListener

public void removeListener()

Removes the listener from the ViewTreeObserver. This is useful to call if the callback should be removed prior to onPreDraw().

onViewAttachedToWindow

public void onViewAttachedToWindow(@NonNull
 View v)

Description copied from interface: View.OnAttachStateChangeListener

Called when the view is attached to a window.

Specified by:

onViewAttachedToWindow in interface View.OnAttachStateChangeListener

Parameters:

v - The view that was attached

onViewDetachedFromWindow

public void onViewDetachedFromWindow(@NonNull
 View v)

Description copied from interface: View.OnAttachStateChangeListener

Called when the view is detached from a window.

Specified by:

onViewDetachedFromWindow in interface View.OnAttachStateChangeListener

Parameters:

v - The view that was detached