Java-叠加层仅在Android中的前2个GPS点之间绘制线条

概述我在Android中使用ItemizedOverlay遇到异常错误.我正在创建一个GPS跟踪设备,该设备可以绘制数据库中存储的航点之间的路线.当我通过Eclipse中的仿真器提供前两组经度和纬度点时,它会按照我的意愿绘制一条红线,但是如果我发送另一个GPS点,它将设置为动画点,但不会从该点绘制一条线最后一点.public class MyOverlay ex

我在Android中使用itemizedoverlay遇到异常错误.

我正在创建一个GPS跟踪设备,该设备可以绘制数据库中存储的航点之间的路线.

当我通过Eclipse中的仿真器提供前两组经度和纬度点时,它会按照我的意愿绘制一条红线,但是如果我发送另一个GPS点,它将设置为动画点,但不会从该点绘制一条线最后一点.

public class MyOverlay extends itemizedoverlay<OverlayItem> {   // private Projection projection;private Paint linePaint;private Vector<GeoPoint> points;public MyOverlay(Drawable defaultMarker) {    super(defaultMarker);    points = new Vector<GeoPoint>();    //set colour,stroke wIDth etc.    linePaint = new Paint();    linePaint.setARGB(255,255,0);    linePaint.setstrokeWIDth(3);    linePaint.setDither(true);    linePaint.setStyle(Style.FILL);    linePaint.setAntiAlias(true);    linePaint.setstrokeJoin(Paint.Join.ROUND);    linePaint.setstrokeCap(Paint.Cap.ROUND);}public voID addPoint(GeoPoint point) {    points.addElement(point);}public voID draw(Canvas canvas,MapVIEw vIEw,boolean shadow) {    int size = points.size();    Point lastPoint = new Point();    if(size == 0) return;    vIEw.getProjection().topixels(points.get(0),lastPoint);    Point point = new Point();    for(int i = 1; i<size; i++){       vIEw.getProjection().topixels(points.get(i),point);        canvas.drawline(lastPoint.x,lastPoint.y,point.x,point.y,linePaint);        lastPoint = point;    }}@OverrIDeprotected OverlayItem createItem(int arg0) {    // Todo auto-generated method stub    return null;}@OverrIDepublic int size() {    // Todo auto-generated method stub    return 0;}}

最佳答案在您的代码中,draw()方法仅被调用一次,因此永远不会被调用.填充方法将重新填充列表中每次出现的所有叠加点.因此,它将再次调用draw方法,它将为您绘制一条线.

package com.example.mymap;import java.util.ArrayList;import androID.graphics.Canvas;import androID.graphics.Paint;import androID.graphics.Point;import androID.graphics.drawable.Drawable;import com.Google.androID.maps.GeoPoint;import com.Google.androID.maps.itemizedoverlay;import com.Google.androID.maps.MapVIEw;import com.Google.androID.maps.OverlayItem;public class ItemOverLay extends itemizedoverlay<OverlayItem> {private ArrayList<OverlayItem> mOverlays = new ArrayList<OverlayItem>();GeoPoint prePoint=null,currentPoint=null;MapVIEw mapVIEw=null;Paint paint=new Paint();public ItemOverLay(GeoPoint prePoint,GeoPoint currentPoint,Drawable defaultMarker,MapVIEw mapvIEw) {    super(boundCenterBottom(defaultMarker));    this.currentPoint=currentPoint;    this.prePoint = prePoint;    mapVIEw=mapvIEw;    // Todo auto-generated constructor stub}public ItemOverLay(Drawable defaultMarker) {    super(defaultMarker);    // Todo auto-generated constructor stub}public voID addOverlay(OverlayItem item){    mOverlays.add(item);    populate();}@OverrIDeprotected OverlayItem createItem(int i) {     // Todo auto-generated method stub    return mOverlays.get(i);}    @OverrIDe    public voID draw(Canvas canvas,MapVIEw mapVIEw,boolean shadow) {        super.draw(canvas,mapVIEw,shadow);        Paint paint=new Paint();        Point screenCoords=new Point();        Point screenCoords1=new Point();        mapVIEw.getProjection().topixels(prePoint,screenCoords);        int x1=screenCoords.x;        int y1=screenCoords.y;        mapVIEw.getProjection().topixels(currentPoint,screenCoords1);        int x2=screenCoords1.x;        int y2=screenCoords1.y;        paint.setstrokeWIDth(1);        canvas.drawline(x1,y1,x2,y2,paint);    }        @OverrIDe    public int size() {        // Todo auto-generated method stub        return mOverlays.size();    }

} 总结

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