ViewConfiguration常量字段介绍

/**
 * 包含了方法和标准的常量用来设置UI的超时、大小和距离
 */
public class ViewConfiguration {
    // 设定水平滚动条的宽度和垂直滚动条的高度
    private static final int SCROLL_BAR_SIZE = 10;


    //定义滚动条逐渐消失的时间，单位是毫秒
    private static final int SCROLL_BAR_FADE_DURATION = 250;


    // 默认的滚动条多少秒之后消失，单位是毫秒
    private static final int SCROLL_BAR_DEFAULT_DELAY = 300;


    // 定义边缘地方褪色的长度
    private static final int FADING_EDGE_LENGTH = 12;


    //定义子控件按下状态的持续事件
    private static final int PRESSED_STATE_DURATION = 125;
    
    //定义一个按下状态转变成长按状态的转变时间
    private static final int LONG_PRESS_TIMEOUT = 500;
    
    //定义用户在按住适当按钮，弹出全局的对话框的持续时间
    private static final int GLOBAL_ACTIONS_KEY_TIMEOUT = 500;
    
    //定义一个touch事件中是点击事件还是一个滑动事件所需的时间，如果用户不在这个时间之内滑动，那么就认为是一个点击事件
    private static final int TAP_TIMEOUT = 115;
    
    /**
     * Defines the duration in milliseconds we will wait to see if a touch event 
     * is a jump tap. If the user does not complete the jump tap within this interval, it is
     * considered to be a tap. 
     */
    //定义一个touch事件时候是一个点击事件。如果用户在这个时间内没有完成这个点击，那么就认为是一个点击事件
    private static final int JUMP_TAP_TIMEOUT = 500;


    //定义双击事件的间隔时间
    private static final int DOUBLE_TAP_TIMEOUT = 300;
    
    //定义一个缩放控制反馈到用户界面的时间
    private static final int ZOOM_CONTROLS_TIMEOUT = 3000;


    /**
     * Inset in pixels to look for touchable content when the user touches the edge of the screen
     */
    private static final int EDGE_SLOP = 12;
    
    /**
     * Distance a touch can wander before we think the user is scrolling in pixels
     */
    private static final int TOUCH_SLOP = 16;
    
    /**
     * Distance a touch can wander before we think the user is attempting a paged scroll
     * (in dips)
     */
    private static final int PAGING_TOUCH_SLOP = TOUCH_SLOP * 2;
    
    /**
     * Distance between the first touch and second touch to still be considered a double tap
     */
    private static final int DOUBLE_TAP_SLOP = 100;
    
    /**
     * Distance a touch needs to be outside of a window's bounds for it to
     * count as outside for purposes of dismissing the window.
     */
    private static final int WINDOW_TOUCH_SLOP = 16;


   //用来初始化fling的最小速度，单位是每秒多少像素
    private static final int MINIMUM_FLING_VELOCITY = 50;
    
    //用来初始化fling的最大速度，单位是每秒多少像素
    private static final int MAXIMUM_FLING_VELOCITY = 4000;


    //视图绘图缓存的最大尺寸，以字节表示。在ARGB888格式下，这个尺寸应至少等于屏幕的大小
    @Deprecated
    private static final int MAXIMUM_DRAWING_CACHE_SIZE = 320 * 480 * 4; // HVGA screen, ARGB8888


    //flings和scrolls摩擦力度大小的系数
    private static float SCROLL_FRICTION = 0.015f;


    /**
     * Max distance to over scroll for edge effects
     */
    private static final int OVERSCROLL_DISTANCE = 0;


    /**
     * Max distance to over fling for edge effects
     */
    private static final int OVERFLING_DISTANCE = 4;

}

这是转载的比较早的版本，比如4.4.2就新增了一些常量

下面是源码字段

 /**     * Defines the width of the horizontal scrollbar and the height of the vertical scrollbar in     * dips     */    private static final int SCROLL_BAR_SIZE = 10;    /**     * Duration of the fade when scrollbars fade away in milliseconds     */    private static final int SCROLL_BAR_FADE_DURATION = 250;    /**     * Default delay before the scrollbars fade in milliseconds     */    private static final int SCROLL_BAR_DEFAULT_DELAY = 300;    /**     * Defines the length of the fading edges in dips     */    private static final int FADING_EDGE_LENGTH = 12;    /**     * Defines the duration in milliseconds of the pressed state in child     * components.     */    private static final int PRESSED_STATE_DURATION = 64;    /**     * Defines the default duration in milliseconds before a press turns into     * a long press     */    private static final int DEFAULT_LONG_PRESS_TIMEOUT = 500;    /**     * Defines the time between successive key repeats in milliseconds.     */    private static final int KEY_REPEAT_DELAY = 50;    /**     * Defines the duration in milliseconds a user needs to hold down the     * appropriate button to bring up the global actions dialog (power off,     * lock screen, etc).     */    private static final int GLOBAL_ACTIONS_KEY_TIMEOUT = 500;    /**     * Defines the duration in milliseconds we will wait to see if a touch event     * is a tap or a scroll. If the user does not move within this interval, it is     * considered to be a tap.     */    private static final int TAP_TIMEOUT = 180;    /**     * Defines the duration in milliseconds we will wait to see if a touch event     * is a jump tap. If the user does not complete the jump tap within this interval, it is     * considered to be a tap.     */    private static final int JUMP_TAP_TIMEOUT = 500;    /**     * Defines the duration in milliseconds between the first tap's up event and     * the second tap's down event for an interaction to be considered a     * double-tap.     */    private static final int DOUBLE_TAP_TIMEOUT = 300;    /**     * Defines the minimum duration in milliseconds between the first tap's up event and     * the second tap's down event for an interaction to be considered a     * double-tap.     */    private static final int DOUBLE_TAP_MIN_TIME = 40;    /**     * Defines the maximum duration in milliseconds between a touch pad     * touch and release for a given touch to be considered a tap (click) as     * opposed to a hover movement gesture.     */    private static final int HOVER_TAP_TIMEOUT = 150;    /**     * Defines the maximum distance in pixels that a touch pad touch can move     * before being released for it to be considered a tap (click) as opposed     * to a hover movement gesture.     */    private static final int HOVER_TAP_SLOP = 20;    /**     * Defines the duration in milliseconds we want to display zoom controls in response     * to a user panning within an application.     */    private static final int ZOOM_CONTROLS_TIMEOUT = 3000;    /**     * Inset in dips to look for touchable content when the user touches the edge of the screen     */    private static final int EDGE_SLOP = 12;    /**     * Distance a touch can wander before we think the user is scrolling in dips.     * Note that this value defined here is only used as a fallback by legacy/misbehaving     * applications that do not provide a Context for determining density/configuration-dependent     * values.     *     * To alter this value, see the configuration resource config_viewConfigurationTouchSlop     * in frameworks/base/core/res/res/values/config.xml or the appropriate device resource overlay.     * It may be appropriate to tweak this on a device-specific basis in an overlay based on     * the characteristics of the touch panel and firmware.     */    private static final int TOUCH_SLOP = 8;    /**     * Distance the first touch can wander before we stop considering this event a double tap     * (in dips)     */    private static final int DOUBLE_TAP_TOUCH_SLOP = TOUCH_SLOP;    /**     * Distance a touch can wander before we think the user is attempting a paged scroll     * (in dips)     *     * Note that this value defined here is only used as a fallback by legacy/misbehaving     * applications that do not provide a Context for determining density/configuration-dependent     * values.     *     * See the note above on {@link #TOUCH_SLOP} regarding the dimen resource     * config_viewConfigurationTouchSlop. ViewConfiguration will report a paging touch slop of     * config_viewConfigurationTouchSlop * 2 when provided with a Context.     */    private static final int PAGING_TOUCH_SLOP = TOUCH_SLOP * 2;    /**     * Distance in dips between the first touch and second touch to still be considered a double tap     */    private static final int DOUBLE_TAP_SLOP = 100;    /**     * Distance in dips a touch needs to be outside of a window's bounds for it to     * count as outside for purposes of dismissing the window.     */    private static final int WINDOW_TOUCH_SLOP = 16;    /**     * Minimum velocity to initiate a fling, as measured in dips per second     */    private static final int MINIMUM_FLING_VELOCITY = 50;    /**     * Maximum velocity to initiate a fling, as measured in dips per second     */    private static final int MAXIMUM_FLING_VELOCITY = 8000;    /**     * Delay before dispatching a recurring accessibility event in milliseconds.     * This delay guarantees that a recurring event will be send at most once     * during the {@link #SEND_RECURRING_ACCESSIBILITY_EVENTS_INTERVAL_MILLIS} time     * frame.     */    private static final long SEND_RECURRING_ACCESSIBILITY_EVENTS_INTERVAL_MILLIS = 100;    /**     * The maximum size of View's drawing cache, expressed in bytes. This size     * should be at least equal to the size of the screen in ARGB888 format.     */    @Deprecated    private static final int MAXIMUM_DRAWING_CACHE_SIZE = 480 * 800 * 4; // ARGB8888    /**     * The coefficient of friction applied to flings/scrolls.     */    private static final float SCROLL_FRICTION = 0.015f;    /**     * Max distance in dips to overscroll for edge effects     */    private static final int OVERSCROLL_DISTANCE = 0;    /**     * Max distance in dips to overfling for edge effects     */    private static final int OVERFLING_DISTANCE = 6;    private final int mEdgeSlop;    private final int mFadingEdgeLength;    private final int mMinimumFlingVelocity;    private final int mMaximumFlingVelocity;    private final int mScrollbarSize;    private final int mTouchSlop;    private final int mDoubleTapTouchSlop;    private final int mPagingTouchSlop;    private final int mDoubleTapSlop;    private final int mWindowTouchSlop;    private final int mMaximumDrawingCacheSize;    private final int mOverscrollDistance;    private final int mOverflingDistance;    private final boolean mFadingMarqueeEnabled;    private boolean sHasPermanentMenuKey;    private boolean sHasPermanentMenuKeySet;    static final SparseArray<ViewConfiguration> sConfigurations =            new SparseArray<ViewConfiguration>(2);