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;
}
}
@Override
protected OverlayItem createItem(int arg0) {
// TODO Auto-generated method stub
return null;
}
@Override
public 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();
}
@Override
protected 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();
}
}
