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Using JavaScript and Tencent Maps to implement map rectangle drawing function

王林Original: 2023-11-21 17:59:15968browse

Using JavaScript and Tencent Maps to implement the map rectangle drawing function

Tencent Maps is one of the most widely used map applications in China, and it provides a wealth of APIs and tools , which can help developers implement various commonly used map functions. In this article, we will introduce how to use JavaScript and Tencent Map API to implement a simple map rectangle drawing function.

Step 1: Introduce Tencent Map API

First, to use Tencent Map API, we need to introduce the corresponding JavaScript file into the web page. We can add the following code snippet in the HTML file:

<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8">
    <title>地图矩形绘制</title>
    <script type="text/javascript" src="https://map.qq.com/api/js?v=2.exp&key=YOUR_KEY"></script>
  </head>
  <body>
    <div id="map" style="width:100%; height:100%;"></div>
  </body>
</html>

We need to replace https://map.qq.com/api/js with our own API key. For information on how to obtain and apply for API keys, please refer to [Tencent Map API official documentation](https://lbs.qq.com/webApi/javascriptV2/guide-getkey.html).

Step 2: Create a map object

After introducing the Tencent Map API, we need to create a map object in the JavaScript code. We can achieve this through the following code:

var map = new qq.maps.Map(document.getElementById("map"), {
    center: new qq.maps.LatLng(39.916527, 116.397128),
    zoom: 13
});

The above code creates a map object and binds it to the element with the ID "map" in the HTML page. The center of the initial map is the center of Beijing, and the zoom level is level 13.

Step 3: Create a rectangle

Next, we need to create a tool that can draw a rectangle. Tencent Maps API provides the qq.maps.Rectangle class, which can be used to draw rectangles. We can create a rectangular object and add it to the map through the following code:

var rectangle = new qq.maps.Rectangle({
    map: map,
    bounds: new qq.maps.LatLngBounds(
        new qq.maps.LatLng(39.922890, 116.394230),
        new qq.maps.LatLng(39.906240, 116.424124)
    ),
    strokeWeight: 3,
    fillColor: "#FF0000",
    fillOpacity: 0.35
});

The above code creates a rectangular object and sets the latitude and longitude boundaries of the rectangle through the bounds property,# The ##strokeWeight property sets the width of the rectangular border, the fillColor property sets the color of the rectangular area, and the fillOpacity property sets the transparency of the rectangular area.

Step 4: Implement dragging and resizing of the rectangle

After creating the rectangular object, we need to implement interactive functions, including dragging and resizing the rectangle.

var isDragging = false;
var isResizing = false;
var startX, startY;
var nw, sw, ne, se;

// 矩形拖拽事件
qq.maps.event.addListener(rectangle, "mousedown", function(e) {
    isDragging = true;
    startX = e.latLng.getLng();
    startY = e.latLng.getLat();
});

qq.maps.event.addListener(rectangle, "mousemove", function(e) {
    if (isDragging) {
        var dx = e.latLng.getLng() - startX;
        var dy = e.latLng.getLat() - startY;
        var bounds = rectangle.getBounds();
        var newBounds = new qq.maps.LatLngBounds(
            new qq.maps.LatLng(bounds.getSouthWest().getLat() + dy, bounds.getSouthWest().getLng() + dx),
            new qq.maps.LatLng(bounds.getNorthEast().getLat() + dy, bounds.getNorthEast().getLng() + dx)
        );
        rectangle.setBounds(newBounds);
        startX = e.latLng.getLng();
        startY = e.latLng.getLat();
    }
});

qq.maps.event.addListener(rectangle, "mouseup", function(e) {
    isDragging = false;
});

// 矩形大小调整事件
qq.maps.event.addListener(rectangle, "bounds_changed", function() {
    if (isResizing) {
        return;
    }
    nw = new qq.maps.Marker({
        icon: {
            path: "M -8,0 L -4,-12 L 8,-12 L 8,-16 L -16,-16 L -16,4 L -12,4 L -12,0 z",
            fillColor: "#FF0000",
            fillOpacity: 1,
            scale: 0.5,
            strokeColor: "#FFF",
            strokeWeight: 2
        },
        map: map,
        position: rectangle.getBounds().getNorthWest(),
        draggable: true,
        zIndex: 99999
    });
    sw = new qq.maps.Marker({
        icon: {
            path: "M -8,0 L -4,12 L 8,12 L 8,16 L -16,16 L -16,-4 L -12,-4 L -12,0 z",
            fillColor: "#FF0000",
            fillOpacity: 1,
            scale: 0.5,
            strokeColor: "#FFF",
            strokeWeight: 2
        },
        map: map,
        position: rectangle.getBounds().getSouthWest(),
        draggable: true,
        zIndex: 99999
    });
    ne = new qq.maps.Marker({
        icon: {
            path: "M -8,0 L -4,-12 L 8,-12 L 8,4 L -12,4 L -12,8 L -8,8 L -8,0 z",
            fillColor: "#FF0000",
            fillOpacity: 1,
            scale: 0.5,
            strokeColor: "#FFF",
            strokeWeight: 2
        },
        map: map,
        position: rectangle.getBounds().getNorthEast(),
        draggable: true,
        zIndex: 99999 
    });
    se = new qq.maps.Marker({
        icon: {
            path: "M -8,0 L -4,12 L 8,12 L 8,-4 L -12,-4 L -12,-8 L -8,-8 L -8,0 z",
            fillColor: "#FF0000",
            fillOpacity: 1,
            scale: 0.5,
            strokeColor: "#FFF",
            strokeWeight: 2
        },
        map: map,
        position: rectangle.getBounds().getSouthEast(),
        draggable: true,
        zIndex: 99999
    });

    // 区域大小调整事件
    qq.maps.event.addListener(nw, "drag", function() {
        isResizing = true;
        var bounds = rectangle.getBounds();
        var newBounds = new qq.maps.LatLngBounds(
            new qq.maps.LatLng(nw.getPosition().getLat(), nw.getPosition().getLng()),
            new qq.maps.LatLng(bounds.getSouthEast().getLat(), bounds.getSouthEast().getLng())
        );
        rectangle.setBounds(newBounds);
        isResizing = false;
    });
    
    qq.maps.event.addListener(sw, "drag", function() {
        isResizing = true;
        var bounds = rectangle.getBounds();
        var newBounds = new qq.maps.LatLngBounds(
            new qq.maps.LatLng(bounds.getNorthWest().getLat(), sw.getPosition().getLng()),
            new qq.maps.LatLng(sw.getPosition().getLat(), bounds.getNorthEast().getLng())
        );
        rectangle.setBounds(newBounds);
        isResizing = false;
    });
    
    qq.maps.event.addListener(ne, "drag", function() {
        isResizing = true;
        var bounds = rectangle.getBounds();
        var newBounds = new qq.maps.LatLngBounds(
            new qq.maps.LatLng(ne.getPosition().getLat(), bounds.getSouthWest().getLng()),
            new qq.maps.LatLng(bounds.getSouthEast().getLat(), ne.getPosition().getLng())
        );
        rectangle.setBounds(newBounds);
        isResizing = false;
    });
    
    qq.maps.event.addListener(se, "drag", function() {
        isResizing = true;
        var bounds = rectangle.getBounds();
        var newBounds = new qq.maps.LatLngBounds(
            new qq.maps.LatLng(bounds.getNorthWest().getLat(), bounds.getNorthWest().getLng()),
            new qq.maps.LatLng(se.getPosition().getLat(), se.getPosition().getLng())
        );
        rectangle.setBounds(newBounds);
        isResizing = false;
    });
});

In the above code, we implement the functions of dragging the rectangle and adjusting the size of the rectangle. Four arrows are created using the marker object, and the user can resize the rectangle by dragging these arrows. When dragging the arrow, we first create a new

qq.maps.LatLngBounds object, and then modify the latitude and longitude boundaries of the rectangle based on the position of the dragged arrow.

Conclusion

Through this article, we learned how to introduce Tencent Map API into HTML pages, create map objects and rectangle objects, and implement the interactive function of rectangles. This small example shows part of the usage of Tencent Map API, and also provides some basic JavaScript programming skills. The complete code can be viewed [here](https://codepen.io/halfoceans/pen/LYejvmG).

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