基于vue.js 2.x的虚拟滚动条的示例代码(4)

8、滚动内容

滚动内容的原理无非就是改变 scrollPanel 的 scrollTop/scrollLeft 来达到控制内容上下左右移动的目的。

scrollVBar: function(pos, time) {
    // >0 scroll to down <0 scroll to up
     
    var top = this.vScrollBar.state.top; 
    var scrollPanelHeight = getComputed(this.scrollPanel.el, 'height').replace('px', "");
    var scrollPanelScrollHeight = this.scrollPanel.el.scrollHeight;
    var scrollPanelScrollTop = this.scrollPanel.el.scrollTop;
    var height = this.vScrollBar.state.height;
    var innerdeltaY = this.vScrollBar.innerDeltaY;
    var deltaY = this.vScrollBar.ops.deltaY;
    if (!((pos < 0 && top <= 0) || (scrollPanelHeight <= top + height && pos > 0) || (Math.abs(scrollPanelScrollHeight - scrollPanelHeight) < this.accuracy))) {
      var Top = top + pos * innerdeltaY * time;
      var ScrollTop = scrollPanelScrollTop + pos * deltaY * time;
      if (pos < 0) {
        // scroll ip
        this.vScrollBar.state.top = Math.max(0, Top);
        this.scrollPanel.el.scrollTop = Math.max(0, ScrollTop);
      } else if (pos > 0) {
        // scroll down
        this.vScrollBar.state.top = Math.min(scrollPanelHeight - height, Top);
        this.scrollPanel.el.scrollTop = Math.min(scrollPanelScrollHeight - scrollPanelHeight, ScrollTop);
      }
    }
    // 这些是传递给父组件的监听滚动的函数的。
    var content = {};
    var bar = {};
    var process = "";
    content.residual = (scrollPanelScrollHeight - scrollPanelScrollTop - scrollPanelHeight);
    content.scrolled = scrollPanelScrollTop;
    bar.scrolled = this.vScrollBar.state.top;
    bar.residual = (scrollPanelHeight - this.vScrollBar.state.top - this.vScrollBar.state.height);
    bar.height = this.vScrollBar.state.height;
    process = bar.scrolled/(scrollPanelHeight - bar.height);
    bar.name = "vBar";
    content.name = "content";
    this.$emit('vscroll', bar, content, process);
  },

9、销毁注册的事件。

刚才我们已经把注册事件放到listeners数组里面了,我们可以在beforedestroy钩子里将他们进行销毁。

// remove the registryed event.
  this.listeners.forEach(function(item) {
    item.dom.removeEventListener(item.event, item.type);
  });

运行截图

PC端运行截图如下图所示:

注册监听事件以后如下图所示:

在手机上运行截图:

可以看出,跟原生滚动条表现效果一致。