Android ViewConfiguration.getScaledTouchSlop () 用法

在写下拉刷新的时候，遇到这个参数touchSlop= ViewConfiguration.get(context).getScaledTouchSlop()，它表示在被判定为滚动之前用户手指可以移动的最大值。然后特意查了一下ViewConfiguration滑动参数设置类：

/**      * 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，单位是像素px          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;                 }