start time: 2016-1-19 21:30:41
in tomorrow night, I got two questions. one is callback. another is why conext need menus? I need some data. callback: a piece of code that gets called after a certain event has happend. like that

When something happens in my view I fire off an event that my activity is listening for:

// DECLARED IN (CUSTOM) VIEW

 private OnScoreSavedListener onScoreSavedListener; public interface OnScoreSavedListener { public void onScoreSaved(); } // ALLOWS YOU TO SET LISTENER && INVOKE THE OVERIDING METHOD  // FROM WITHIN ACTIVITY public void setOnScoreSavedListener(OnScoreSavedListener listener) { onScoreSavedListener = listener; }

// DECLARED IN ACTIVITY

 MyCustomView slider = (MyCustomView) view.findViewById(R.id.slider) slider.setOnScoreSavedListener(new OnScoreSavedListener() { @Override public void onScoreSaved() { Log.v("","EVENT FIRED"); } });

in simple way, what I understand is callback like a spy waiting for something happen then solve it.
let's check class window ,see how callback get work.
public abstract class

Window

extends Object

java.lang.Object
↳	android.view.Window

Class Overview

Abstract base class for a top-level window look and behavior policy. An instance of this class should be used as the top-level view added to the window manager. It provides standard UI policies such as a background, title area, default key processing, etc.

The only existing implementation of this abstract class is android.view.PhoneWindow, which you should instantiate when needing a Window.

Summary

Nested Classes
interface	Window.Callback	API from a Window back to its caller.

top-level window , window manger , standard UI policies ? great, it's looks like some keys.
nested class ? in java definition : A nested class is any class whose declaration occurs within the body of another class or interface. A top level class is a class that is not a nested class.
like that OnScoreSavedListenernested in class activity.
afer that , some thing show before us.

XML Attributes
Attribute Name	Related Method	Description
android:windowAllowEnterTransitionOverlap	setAllowEnterTransitionOverlap(boolean)	Flag indicating whether this Window's transition should overlap with the exiting transition of the calling Activity.
android:windowAllowReturnTransitionOverlap	setAllowReturnTransitionOverlap(boolean)	Flag indicating whether this Window's transition should overlap with the exiting transition of the called Activity when the called Activity finishes.
android:windowContentTransitionManager	setTransitionManager(TransitionManager)	Reference to a TransitionManager XML resource defining the desired transitions between different window content.
android:windowEnterTransition	setEnterTransition(Transition)	Reference to a Transition XML resource defining the desired Transition used to move Views into the initial Window's content Scene.
android:windowExitTransition	setExitTransition(Transition)	Reference to a Transition XML resource defining the desired Transition used to move Views out of the Window's content Scene when launching a new Activity.
android:windowReenterTransition	setReenterTransition(Transition)	Reference to a Transition XML resource defining the desired Transition used to move Views in to the scene when returning from a previously-started Activity.
android:windowReturnTransition	setReturnTransition(Transition)	Reference to a Transition XML resource defining the desired Transition used to move Views out of the scene when the Window is preparing to close.
android:windowSharedElementEnterTransition	setSharedElementEnterTransition(Transition)	Reference to a Transition XML resource defining the desired Transition used to move shared elements transferred into the Window's initial content Scene.
android:windowSharedElementExitTransition	setSharedElementExitTransition(Transition)	Reference to a Transition XML resource defining the desired Transition used when starting a new Activity to move shared elements prior to transferring to the called Activity.
android:windowSharedElementReenterTransition	setSharedElementReenterTransition(Transition)	Reference to a Transition XML resource defining the desired Transition used for shared elements transferred back to a calling Activity.
android:windowSharedElementReturnTransition	setSharedElementReturnTransition(Transition)	Reference to a Transition XML resource defining the desired Transition used to move shared elements transferred back to a calling Activity.
android:windowSharedElementsUseOverlay	setSharedElementsUseOverlay(boolean)	Indicates whether or not shared elements should use an overlay during transitions.
android:windowTransitionBackgroundFadeDuration	setTransitionBackgroundFadeDuration(long)	The duration, in milliseconds, of the window background fade duration when transitioning into or away from an Activity when called with an Activity Transition.

overlap transition move Views into the initial Window's content Scene move Views out of the Window's content Scene when launching a new Activity move shared elements starting a new Activity to move shared elements prior to transferring to the called Activity
what we all know about transition is like a procedure. all or not. so, move view or shared elements on window's context scene. that's key.

Constants
int	DEFAULT_FEATURES	This constant was deprecated in API level 22. use`getDefaultFeatures(android.content.Context)`instead.
int	FEATURE_ACTION_BAR	Flag for enabling the Action Bar.
int	FEATURE_ACTION_BAR_OVERLAY	Flag for requesting an Action Bar that overlays window content.
int	FEATURE_ACTION_MODE_OVERLAY	Flag for specifying the behavior of action modes when an Action Bar is not present.
int	FEATURE_ACTIVITY_TRANSITIONS	Enables Activities to run Activity Transitions either through sending or receiving ActivityOptions bundle created with`makeSceneTransitionAnimation(android.app.Activity, android.util.Pair[])`or`makeSceneTransitionAnimation(android.app.Activity, View, String)`.
int	FEATURE_CONTENT_TRANSITIONS	Flag for requesting that window content changes should be animated using a TransitionManager.
int	FEATURE_CONTEXT_MENU	Flag for the context menu.
int	FEATURE_CUSTOM_TITLE	Flag for custom title.
int	FEATURE_INDETERMINATE_PROGRESS	Flag for indeterminate progress
int	FEATURE_LEFT_ICON	Flag for having an icon on the left side of the title bar
int	FEATURE_NO_TITLE	Flag for the "no title" feature, turning off the title at the top of the screen.
int	FEATURE_OPTIONS_PANEL	Flag for the "options panel" feature.
int	FEATURE_PROGRESS	Flag for the progress indicator feature
int	FEATURE_RIGHT_ICON	Flag for having an icon on the right side of the title bar
int	FEATURE_SWIPE_TO_DISMISS	Flag for requesting a decoration-free window that is dismissed by swiping from the left.
int	ID_ANDROID_CONTENT	The ID that the main layout in the XML layout file should have.
String	NAVIGATION_BAR_BACKGROUND_TRANSITION_NAME	The transitionName for the navigation bar background View when a custom background is used.
int	PROGRESS_END	Ending value for the (primary) progress
int	PROGRESS_INDETERMINATE_OFF	Flag for setting the progress bar's indeterminate mode off
int	PROGRESS_INDETERMINATE_ON	Flag for setting the progress bar's indeterminate mode on
int	PROGRESS_SECONDARY_END	Highest possible value for the secondary progress
int	PROGRESS_SECONDARY_START	Lowest possible value for the secondary progress
int	PROGRESS_START	Starting value for the (primary) progress
int	PROGRESS_VISIBILITY_OFF	Flag for setting the progress bar's visibility to GONE
int	PROGRESS_VISIBILITY_ON	Flag for setting the progress bar's visibility to VISIBLE
String	STATUS_BAR_BACKGROUND_TRANSITION_NAME	The transitionName for the status bar background View when a custom background is used.

Public Constructors
	Window( Context context)

OH!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! OMG!!!!????? Action Bar context menu custom title indeterminate progress an icon on the left/right side of the title bar main layout secondary progress? progress bar's VISIBLE/GONE
let me calm down. just calm down. what I found ? why context must have a menu. It's not more than menu, and Action Bar, title, progress. I think I figure out the second problem.
Look out, class window extends java.lang.Object. Object is basic. let's check its methds.

Public Methods
abstract void	addContentView( View view, ViewGroup.LayoutParams params) Variation on `setContentView(View, android.view.ViewGroup.LayoutParams)` to add an additional content view to the screen.
void	addFlags(int flags) Convenience function to set the flag bits as specified in flags, as per `setFlags(int, int)`.
void	clearFlags(int flags) Convenience function to clear the flag bits as specified in flags, as per `setFlags(int, int)`.
abstract void	closeAllPanels()
abstract void	closePanel(int featureId)
View	findViewById(int id) Finds a view that was identified by the id attribute from the XML that was processed in `onCreate(Bundle)`.
boolean	getAllowEnterTransitionOverlap() Returns how the transition set in `setEnterTransition(android.transition.Transition)` overlaps with the exit transition of the calling Activity.
boolean	getAllowReturnTransitionOverlap() Returns how the transition set in `setExitTransition(android.transition.Transition)` overlaps with the exit transition of the called Activity when reentering after if finishes.
final WindowManager.LayoutParams	getAttributes() Retrieve the current window attributes associated with this panel.
final Window.Callback	getCallback() Return the current Callback interface for this window.
final Window	getContainer() Return the container for this Window.
Scene	getContentScene() Retrieve the `Scene` representing this window's current content.
final Context	getContext() Return the Context this window policy is running in, for retrieving resources and other information.
abstract View	getCurrentFocus() Return the view in this Window that currently has focus, or null if there are none.
abstract View	getDecorView() Retrieve the top-level window decor view (containing the standard window frame/decorations and the client's content inside of that), which can be added as a window to the window manager.
static int	getDefaultFeatures( Context context) Return the feature bits set by default on a window.
Transition	getEnterTransition() Returns the transition used to move Views into the initial scene.
Transition	getExitTransition() Returns the Transition that will be used to move Views out of the scene when starting a new Activity.
abstract LayoutInflater	getLayoutInflater() Quick access to the `LayoutInflater` instance that this Window retrieved from its Context.
MediaController	getMediaController() Gets the `MediaController` that was previously set.
abstract int	getNavigationBarColor()
Transition	getReenterTransition() Returns the Transition that will be used to move Views in to the scene when returning from a previously-started Activity.
Transition	getReturnTransition() Returns he Transition that will be used to move Views out of the scene when the Window is preparing to close, for example after a call to `finishAfterTransition()`.
Transition	getSharedElementEnterTransition() Returns the Transition that will be used for shared elements transferred into the content Scene.
Transition	getSharedElementExitTransition() Returns the Transition to use for shared elements in the launching Window prior to transferring to the launched Activity's Window.
Transition	getSharedElementReenterTransition() Returns the Transition that will be used for shared elements reentering from a started Activity after it has returned the shared element to it start location.
Transition	getSharedElementReturnTransition() Returns the Transition that will be used for shared elements transferred back to a calling Activity.
boolean	getSharedElementsUseOverlay() Returns `true` when shared elements should use an Overlay during shared element transitions or `false`when they should animate as part of the normal View hierarchy.
abstract int	getStatusBarColor()
long	getTransitionBackgroundFadeDuration() Returns the duration, in milliseconds, of the window background fade when transitioning into or away from an Activity when called with an Activity Transition.
TransitionManager	getTransitionManager() Retrieve the `TransitionManager` responsible for for default transitions in this window.
abstract int	getVolumeControlStream()
WindowManager	getWindowManager() Return the window manager allowing this Window to display its own windows.
final TypedArray	getWindowStyle() Return the `Window` attributes from this window's theme.
final boolean	hasChildren()
boolean	hasFeature(int feature) Query for the availability of a certain feature.
void	injectInputEvent( InputEvent event) Inject an event to window locally.
abstract void	invalidatePanelMenu(int featureId)
final boolean	isActive()
abstract boolean	isFloating() Return whether this window is being displayed with a floating style (based on the `windowIsFloating`attribute in the style/theme).
abstract boolean	isShortcutKey(int keyCode, KeyEvent event) Is a keypress one of the defined shortcut keys for this window.
final void	makeActive()
abstract void	onConfigurationChanged( Configuration newConfig) Should be called when the configuration is changed.
abstract void	openPanel(int featureId, KeyEvent event)
abstract View	peekDecorView() Retrieve the current decor view, but only if it has already been created; otherwise returns null.
abstract boolean	performContextMenuIdentifierAction(int id, int flags)
abstract boolean	performPanelIdentifierAction(int featureId, int id, int flags)
abstract boolean	performPanelShortcut(int featureId, int keyCode, KeyEvent event, int flags)
boolean	requestFeature(int featureId) Enable extended screen features.
abstract void	restoreHierarchyState( Bundle savedInstanceState)
abstract Bundle	saveHierarchyState()
void	setAllowEnterTransitionOverlap(boolean allow) Controls how the transition set in `setEnterTransition(android.transition.Transition)` overlaps with the exit transition of the calling Activity.
void	setAllowReturnTransitionOverlap(boolean allow) Controls how the transition set in `setExitTransition(android.transition.Transition)` overlaps with the exit transition of the called Activity when reentering after if finishes.
void	setAttributes( WindowManager.LayoutParams a) Specify custom window attributes.
abstract void	setBackgroundDrawable( Drawable drawable) Change the background of this window to a custom Drawable.
void	setBackgroundDrawableResource(int resId) Change the background of this window to a Drawable resource.
void	setCallback( Window.Callback callback) Set the Callback interface for this window, used to intercept key events and other dynamic operations in the window.
abstract void	setChildDrawable(int featureId, Drawable drawable)
abstract void	setChildInt(int featureId, int value)
void	setClipToOutline(boolean clipToOutline) Sets whether window content should be clipped to the outline of the window background.
void	setContainer( Window container) Set the container for this window.
abstract void	setContentView(int layoutResID) Convenience for `setContentView(View, android.view.ViewGroup.LayoutParams)` to set the screen content from a layout resource.
abstract void	setContentView( View view) Convenience for `setContentView(View, android.view.ViewGroup.LayoutParams)` set the screen content to an explicit view.
abstract void	setContentView( View view, ViewGroup.LayoutParams params) Set the screen content to an explicit view.
void	setDimAmount(float amount) Set the amount of dim behind the window when using `FLAG_DIM_BEHIND`.
void	setElevation(float elevation) Sets the window elevation.
void	setEnterTransition( Transition transition) Sets the Transition that will be used to move Views into the initial scene.
void	setExitTransition( Transition transition) Sets the Transition that will be used to move Views out of the scene when starting a new Activity.
abstract void	setFeatureDrawable(int featureId, Drawable drawable) Set an explicit Drawable value for feature of this window.
abstract void	setFeatureDrawableAlpha(int featureId, int alpha) Set a custom alpha value for the given drawable feature, controlling how much the background is visible through it.
abstract void	setFeatureDrawableResource(int featureId, int resId) Set the value for a drawable feature of this window, from a resource identifier.
abstract void	setFeatureDrawableUri(int featureId, Uri uri) Set the value for a drawable feature of this window, from a URI.
abstract void	setFeatureInt(int featureId, int value) Set the integer value for a feature.
void	setFlags(int flags, int mask) Set the flags of the window, as per the `WindowManager.LayoutParams` flags.
void	setFormat(int format) Set the format of window, as per the PixelFormat types.
void	setGravity(int gravity) Set the gravity of the window, as per the Gravity constants.
void	setIcon(int resId) Set the primary icon for this window.
void	setLayout(int width, int height) Set the width and height layout parameters of the window.
void	setLocalFocus(boolean hasFocus, boolean inTouchMode) Set focus locally.
void	setLogo(int resId) Set the logo for this window.
void	setMediaController( MediaController controller) Sets a `MediaController` to send media keys and volume changes to.
abstract void	setNavigationBarColor(int color) Sets the color of the navigation bar to .
void	setReenterTransition( Transition transition) Sets the Transition that will be used to move Views in to the scene when returning from a previously-started Activity.
void	setReturnTransition( Transition transition) Sets the Transition that will be used to move Views out of the scene when the Window is preparing to close, for example after a call to `finishAfterTransition()`.
void	setSharedElementEnterTransition( Transition transition) Sets the Transition that will be used for shared elements transferred into the content Scene.
void	setSharedElementExitTransition( Transition transition) Sets the Transition that will be used for shared elements after starting a new Activity before the shared elements are transferred to the called Activity.
void	setSharedElementReenterTransition( Transition transition) Sets the Transition that will be used for shared elements reentering from a started Activity after it has returned the shared element to it start location.
void	setSharedElementReturnTransition( Transition transition) Sets the Transition that will be used for shared elements transferred back to a calling Activity.
void	setSharedElementsUseOverlay(boolean sharedElementsUseOverlay) Sets whether or not shared elements should use an Overlay during shared element transitions.
void	setSoftInputMode(int mode) Specify an explicit soft input mode to use for the window, as per `WindowManager.LayoutParams.softInputMode`.
abstract void	setStatusBarColor(int color) Sets the color of the status bar to `color`.
abstract void	setTitle( CharSequence title)
abstract void	setTitleColor(int textColor)
void	setTransitionBackgroundFadeDuration(long fadeDurationMillis) Sets the duration, in milliseconds, of the window background fade when transitioning into or away from an Activity when called with an Activity Transition.
void	setTransitionManager( TransitionManager tm) Set the `TransitionManager` to use for default transitions in this window.
void	setType(int type) Set the type of the window, as per the WindowManager.LayoutParams types.
void	setUiOptions(int uiOptions) Set extra options that will influence the UI for this window.
void	setUiOptions(int uiOptions, int mask) Set extra options that will influence the UI for this window.
abstract void	setVolumeControlStream(int streamType)
void	setWindowAnimations(int resId) Specify custom animations to use for the window, as per `WindowManager.LayoutParams.windowAnimations`.
void	setWindowManager( WindowManager wm, IBinder appToken, String appName) Set the window manager for use by this Window to, for example, display panels.
void	setWindowManager( WindowManager wm, IBinder appToken, String appName, boolean hardwareAccelerated) Set the window manager for use by this Window to, for example, display panels.
abstract boolean	superDispatchGenericMotionEvent( MotionEvent event) Used by custom windows, such as Dialog, to pass the generic motion event further down the view hierarchy.
abstract boolean	superDispatchKeyEvent( KeyEvent event) Used by custom windows, such as Dialog, to pass the key press event further down the view hierarchy.
abstract boolean	superDispatchKeyShortcutEvent( KeyEvent event) Used by custom windows, such as Dialog, to pass the key shortcut press event further down the view hierarchy.
abstract boolean	superDispatchTouchEvent( MotionEvent event) Used by custom windows, such as Dialog, to pass the touch screen event further down the view hierarchy.
abstract boolean	superDispatchTrackballEvent( MotionEvent event) Used by custom windows, such as Dialog, to pass the trackball event further down the view hierarchy.
abstract void	takeInputQueue( InputQueue.Callback callback) Take ownership of this window's InputQueue.
abstract void	takeKeyEvents(boolean get) Request that key events come to this activity.
abstract void	takeSurface( SurfaceHolder.Callback2 callback) Take ownership of this window's surface.
abstract void	togglePanel(int featureId, KeyEvent event)

Protected Methods
final int	getFeatures() Return the feature bits that are enabled.
final int	getForcedWindowFlags() Return the window flags that have been explicitly set by the client, so will not be modified by `getDecorView()`.
final int	getLocalFeatures() Return the feature bits that are being implemented by this Window.
final boolean	hasSoftInputMode() Has the app specified their own soft input mode?
abstract void	onActive()
void	setDefaultWindowFormat(int format) Set the default format of window, as per the PixelFormat types.

here I make a conclusion, amazing found.
add an additional content view to the screen findViewById(int id) Retrieve the current window attributesassociated with this panel container for this Window Return the Context this window policy is running in Return the view in this Window that currently has focus Returns the transitionused to move Views into the initial scene(do not know what's use to ) Quick access LayoutInflater instance Gets the MediaController Return the window managerallowing this Window to display Return the Window attributesfrom this window's theme isActive() Specify custom window attributes Change the backgroundof this window Set the Callback interface setContentView(int layoutResID) setElevation(float elevation) (>=android 6.0) setGravity(int gravity) superDispatchKeyEvent(KeyEvent event) superDispatchTouchEvent(MotionEvent event)
Window is wonderful ! I want to read its code. so I fix two problem. task is finish. here are another question. fist : class window is a basic. Activiy , Dialog and other panel base on it. I wan to know how window control OS resources. android is base on Linux. how her work? second : what is class contex ? like a container, a panel. I can feel it's like a browser which is loading javascript code or html code. Let's check tommorrow night.
I'm fish, I'm on. ----jack chen

day02- Upper- Window.Callback for android

Window

Class Overview

Summary

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