What is the method to write code in Java to draw polygons on the map through Baidu Map API?

What is the method to write code in Java to draw polygons on the map through Baidu Map API?

Map is widely used in various scenarios in modern society, such as navigation, geographic information system, etc. As one of the largest online map service providers in China, Baidu Maps' API provides developers with rich functions and convenient interfaces, allowing developers to flexibly use map functions in their own applications. This article will introduce how to use Java to write code to draw polygons on the map through Baidu Map API.

First of all, to use Baidu Map API, you need to apply for a developer key (ak). After applying for ak, we can use Java to write code to realize the function of drawing polygons on the map.

The following is a sample code to implement the function of drawing polygons on the map:

import com.baidu.mapapi.SDKInitializer;
import com.baidu.mapapi.map.BaiduMap;
import com.baidu.mapapi.map.MapView;
import com.baidu.mapapi.map.OverlayOptions;
import com.baidu.mapapi.map.Polygon;
import com.baidu.mapapi.map.PolygonOptions;
import com.baidu.mapapi.model.LatLng;
import com.baidu.mapapi.overlayutil.OverlayManager;

import java.util.ArrayList;
import java.util.List;

public class MainActivity extends AppCompatActivity {

    MapView mMapView;
    BaiduMap mBaiduMap;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        // 初始化百度地图SDK
        SDKInitializer.initialize(getApplicationContext());

        setContentView(R.layout.activity_main);

        // 初始化地图控件
        mMapView = findViewById(R.id.map_view);
        mBaiduMap = mMapView.getMap();

        // 创建多边形的坐标点列表
        List<LatLng> points = new ArrayList<>();
        points.add(new LatLng(39.906901, 116.397972));
        points.add(new LatLng(39.867026, 116.422738));
        points.add(new LatLng(39.889168, 116.462823));
        points.add(new LatLng(39.913135, 116.446974));

        // 绘制多边形
        OverlayOptions polygonOptions = new PolygonOptions()
                .points(points)
                .fillColor(0xABCDEF)
                .stroke(new Stroke(5, 0xAA000000));
        Polygon polygon = (Polygon) mBaiduMap.addOverlay(polygonOptions);

        // 设置地图中心点为多边形的中心点
        mBaiduMap.setMapStatus(MapStatusUpdateFactory.newLatLng(polygon.getPoints().get(0)));
    }

    @Override
    protected void onResume() {
        super.onResume();
        mMapView.onResume();
    }

    @Override
    protected void onPause() {
        super.onPause();
        mMapView.onPause();
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        mMapView.onDestroy();
    }
}

In the above sample code, we use the BaiduMap class and PolygonOptions class to implement polygon drawing. First, we need to create a map control MapView and obtain the map object BaiduMap. We then create a coordinate point list that specifies the coordinates of each vertex of the polygon. Next, we use the points method of PolygonOptions to pass in the list of coordinate points, and set the fill color and border style of the polygon through the fillColor and stroke methods. Finally, we call the addOverlay method of mBaiduMap to draw the polygon onto the map and set the map center point as the center point of the polygon.

It should be noted that in the above sample code, the relevant permissions and configuration information of Baidu Map need to be added to the AndroidManifest.xml file in order to correctly use the Baidu Map API.

Summary: Through the above code, we can realize the function of drawing polygons on the map. Using the BaiduMap and PolygonOptions classes provided by Baidu Map API, we can easily specify the coordinate point list of the polygon and set the fill color and border style. By calling the addOverlay method, polygons can be drawn on the map to meet the requirement of drawing polygons on the map.

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