滑轮控件的研究五、ViewConfiguration的简单介绍(转)

/** 
 * 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;  
  
}