最近几年来，地理信息系统无论是在理论上还是应用上都处在一个飞速发展的阶段。 GIS被应用于多个领域的建模和决策支持，如城市管理、区划、环境整治等等，地理信息成为信息时代重要的组成部分之一； “数字地球”概念的提出，更进一步推动了作为其技术支撑的GIS的发展。 与此同时，一些学者致力于相关的理论研究，如空间感知、空间数据误差、空间关系的形式化等等。 这恰好说明了地理信息系统作为应用技术和学科的两个方面，并且这两个方面构成了相互促进的发展过程。
Drag and drop is part of the HTML5 standard.
Drag the RUNOOB.COM icon into the rectangle. Drag and drop is a common feature that grabs an object and then drags it to another location. In HTML5, drag and drop is part of the standard, and any element can be dragged and dropped. Internet Explorer 9, Firefox, Opera, Chrome, and Safari support dragging. Note: Safari 5.1.2 does not support dragging. The following example is a simple drag and drop example: drag RUNOOB.COM Picture to rectangular box: First, to make the element draggable, set the Then, specify what happens when the element is dragged. In the above example, the ondragstart property calls a function, drag (event), which specifies the data being dragged. By default, data / elements cannot be placed in other elements. If we need to set allow placement, we must block the default handling of the element. This is done by calling the ondragover event’s Occurs when the dragged data is placed In the above example Code interpretation: Call Pass through The data being dragged is the id (“drag1”) of the dragged element. Append the dragged element to the placement element 11.36.1. Drag and drop ¶
11.36.2. Browser support ¶
11.36.3. HTML5 drag and drop instance ¶
Example ¶
<p> It may seem a little complicated, but we can look at different parts of the drag-and-drop event separately. </p>
11.36.4. Set the element to be draggable ¶
draggable property is set to true : <img draggable="true">
11.36.5. Drag what-
ondragstart and setData() ¶ dataTransfer.setData() method to set the data type and value of the data being dragged function drag(ev) { ev.dataTransfer.setData("Text",ev.target.id); }
Text It’s a DOMString represents the type of drag data to add to the drag object. The value is the id (“drag1”) of the draggable element. 11.36.6. Where to put it-
ondragover ¶ ondragover event specifies where to place the dragged data. event.preventDefault() methods: *event*.preventDefault()
11.36.7. Make placement-ondrop ¶
drop Events. ondrop property calls a function drop(event) : function drop(ev) { ev.preventDefault(); var data=ev.dataTransfer.getData("Text"); ev.target.appendChild(document.getElementById(data)); }
preventDefault() to avoid the browser’s default handling of data (the default behavior of the drop event is to open as a link) dataTransfer.getData("Text") method to get the data being dragged. The method will return in the setData() any data set to the same type in the.