Android安卓 自定义mapbox地图比例尺
在给mapbox地图添加比例尺的时候，我没有找到mapbox自带的比例尺，所以就自己写了一个。和其他自定义比例尺原理其实都差不多。首先，加载mapbox地图，这个就不再详细叙述，照着mapbox官网的教程打下来就行了。
定义一个自定义View，MapScaleView,在这里计算每一级比例尺在屏幕上需要绘制的长度。计算比例尺的原理是获取屏幕中心的一点的每像素代表的实际距离，因为在同一纬度上每像素代表的实际距离是相同的。因此在纬度上 实际距离除以屏幕中心的每像素代表的距离就等于在屏幕上需要绘制的像素长度，然后使用画笔画线，长度等于算出的像素长度。
metersPerPixel = mapboxMap.getProjection().getMetersPerPixelAtLatitude(mapboxMap.getCameraPosition().target.getLatitude());这个就是在屏幕中心，在纬度上每像素代表的实际距离。
下面是自定义View
package com.geocompass.mapboxscale;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.util.AttributeSet;
import android.view.View;
import com.mapbox.mapboxsdk.maps.MapboxMap;
/**
* Created by admin on 2018/8/8.
*/
public class MapScaleView extends View {
private Paint mPaint;
private int scaleWidth;
private int scaleHeight;
private int scaleSpaceText;
private int textSize;
private String text;
private int marginStartX = 20;//距离x轴20px处开始绘制比例尺
private int verticalY = 5;//竖线相对横线向上或向下的距离
public MapScaleView(Context context) {
this(context, null);
}
public MapScaleView(Context context, AttributeSet attrs) {
super(context, attrs);
initView();
}
//这个构造方法是在第二个基础上再传入style的。
public MapScaleView(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
}
private void initView() {
mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
setBackgroundColor(getResources().getColor(R.color.transparent));
scaleWidth = 360;//比例尺宽度
scaleHeight = SystemHelper.dip2px(this.getContext(), 3);//比例尺高度
text = "10km";//比例尺文本
textSize = SystemHelper.sp2px(this.getContext(), 13);//比例尺字体
scaleSpaceText = scaleHeight;//比例尺文本与图形的间隔高度
mPaint.setColor(Color.BLACK);
mPaint.setAntiAlias(true);
mPaint.setStrokeWidth(2f);//设置画笔宽度
mPaint.setTextSize(textSize);
}
/**
* 从距离x轴20，y轴画布宽的2/3处开始画线
*/
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
//绘制直线
canvas.drawLine(marginStartX, 2 * getHeight() / 3 - verticalY, marginStartX, 2 * getHeight() / 3 + verticalY, mPaint);//绘制比例尺左边竖线
canvas.drawLine(marginStartX, 2 * getHeight() / 3, marginStartX + scaleWidth, 2 * getHeight() / 3, mPaint);//绘制比例尺可变横线
canvas.drawLine(marginStartX + scaleWidth, 2 * getHeight() / 3 - verticalY,
marginStartX + scaleWidth, 2 * getHeight() / 3 + verticalY, mPaint);//绘制比例尺右边竖线
canvas.drawText(text, marginStartX, textSize, mPaint);//绘制字体
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
int widthSize = MeasureSpec.getSize(widthMeasureSpec);
int widthMode = MeasureSpec.getMode(widthMeasureSpec);
int resultWidth;
if (widthMode == MeasureSpec.EXACTLY) {
resultWidth = widthSize;
} else {
resultWidth = scaleWidth;
if (widthMode == MeasureSpec.AT_MOST) {
resultWidth = Math.min(resultWidth, widthSize);
}
}
int heightSize = getHeightSize(heightMeasureSpec) + 20;
setMeasuredDimension(resultWidth, heightSize);
}
/**
* 测量ScaleView的高度
*/
private int getHeightSize(int heightMeasureSpec) {
int mode = MeasureSpec.getMode(heightMeasureSpec);
int height = 0;
switch (mode) {
case MeasureSpec.AT_MOST:
height = textSize + scaleSpaceText + scaleHeight;
break;
case MeasureSpec.EXACTLY: {
height = MeasureSpec.getSize(heightMeasureSpec);
break;
}
case MeasureSpec.UNSPECIFIED: {
height = Math.max(textSize + scaleSpaceText + scaleHeight, MeasureSpec.getSize(heightMeasureSpec));
break;
}
}
return height;
}
/**
* 根据缩放级别更新ScaleView的文字以及比例尺的长度
*/
double metersPerPixel = 0;
public void refreshScaleView(MapboxMap mapboxMap) {
if (mapboxMap == null) {
return;
}
metersPerPixel = mapboxMap.getProjection().getMetersPerPixelAtLatitude(mapboxMap.getCameraPosition().target.getLatitude());//获取在纬度上每像素代表的距离(米)
int curZoom = (int) Math.round(mapboxMap.getCameraPosition().zoom);
switch (curZoom) {
case 2:
text = "1000km";
scaleWidth = (int) (1000000 / metersPerPixel);
break;
case 3:
text = "500km";
scaleWidth = (int) (500000 / metersPerPixel);
break;
case 4:
text = "200km";
scaleWidth = (int) (200000 / metersPerPixel);
break;
case 5:
text = "100km";
scaleWidth = (int) (100000 / metersPerPixel);
break;
case 6:
text = "50km";
scaleWidth = (int) (50000 / metersPerPixel);
break;
case 7:
text = "20km";
scaleWidth = (int) (20000 / metersPerPixel);
break;
case 8:
text = "10km";
scaleWidth = (int) (10000 / metersPerPixel);
break;
case 9:
text = "5km";
scaleWidth = (int) (5000 / metersPerPixel);
break;
case 10:
text = "2km";
scaleWidth = (int) (2000 / metersPerPixel);
break;
case 11:
text = "1km";
scaleWidth = (int) (1000 / metersPerPixel);
break;
case 12:
text = "500m";
scaleWidth = (int) (500 / metersPerPixel);
break;
case 13:
text = "200m";
scaleWidth = (int) (200 / metersPerPixel);
break;
case 14:
text = "100m";
scaleWidth = (int) (100 / metersPerPixel);
break;
case 15:
text = "50m";
scaleWidth = (int) (50 / metersPerPixel);
break;
case 16:
text = "20m";
scaleWidth = (int) (20 / metersPerPixel);
break;
case 17:
text = "10m";
scaleWidth = (int) (10 / metersPerPixel);
break;
case 18:
text = "5m";
scaleWidth = (int) (5 / metersPerPixel);
break;
default:
break;
}
this.postInvalidate();
}
}
在MapActivity里面调用下面的代码就可以刷新比例尺。
/**
* 控制比例尺
* */
mMapboxMap.setOnCameraChangeListener(new MapboxMap.OnCameraChangeListener() {
@Override
public void onCameraChange(CameraPosition position) {
MapScaleView mapScaleView = findViewById(R.id.view_scale_map);
mapScaleView.refreshScaleView(mMapboxMap);
}
});
}源码链接：https://download.csdn.net/download/ymszzu/10594189