如何抽签标记在地图上 [英] How to draw lots of markers on a map

问题描述

我想用绘制标记在地图上。我遇到的问题是，当我尝试添加很多很多的话，我不能让它运行。
为了说明我的问题，比方说，我想提请由900个小方格（30×30）一个正方形。顺便说一句，我确实需要这些广场，不只是一个大广场
我试图标记添加到itemizedoverlay，再画吧。

I'm trying to draw on a map using markers. The problem I'm having is when I try to add lots of them, then I can't get it to run. To illustrate my problem, let's say I want to draw a square made of 900 smaller squares (30x30). By the way, I do need those squares, not just one big square I'm trying to add the markers to an itemizedoverlay, then drawing it.

在code如下。任何建议我怎么能做到这一点？
非常感谢你！

the code is below. Any suggestion how I could do that? Thank you very much!!

public class MainActivity extends MapActivity {
MapView mapView;
MapController mc;
GeoPoint p;
static Context context;

int k=1;    
List<Overlay> mapOverlays;
MyItemizedOverlay itemizedoverlay;  
int[] xx,yy;

/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);        
    context = getApplicationContext();        
    mapView = (MapView) findViewById(R.id.mapView);
    mapView.setBuiltInZoomControls(true);        

    mc = mapView.getController();
    String coordinates[] = {"36.186382", "-112.221909"};
    double lat = Double.parseDouble(coordinates[0]);
    double lng = Double.parseDouble(coordinates[1]);
    p = new GeoPoint(
                    (int) (lat * 1E6),
                    (int) (lng * 1E6));
    mc.animateTo(p);
    mc.setZoom(10);

    mapOverlays = mapView.getOverlays();
    Drawable squareM = this.getResources().getDrawable(R.drawable.square);
    itemizedoverlay = new MyItemizedOverlay(squareM);

    int n=0;
    xx = new int[30];
    yy = new int[30];
    while(n<30){
        xx[n]=n;
        yy[n]=n;
        n++;
    }

}

protected void drawNewMarker(GeoPoint p){
    OverlayItem overlayitem = new OverlayItem(p, "", "");
    itemizedoverlay.addOverlay(overlayitem);
    mapOverlays.add(itemizedoverlay);
    mapView.postInvalidate(); 
}

protected void drawNewMarkerD(){
    Point pointP = new Point(0,0);
    mapView.getProjection().toPixels(p, pointP);
    int xoff = 20*k;
    int yoff = 20*k;
    GeoPoint pp = mapView.getProjection().fromPixels(pointP.x + xoff, pointP.y + yoff);

    OverlayItem overlayitem = new OverlayItem(pp, "", "");
    Drawable iconM = this.getResources().getDrawable(R.drawable.icon);
    iconM.setBounds(0,0, 50, 50);
    overlayitem.setMarker(iconM);
    itemizedoverlay.addOverlay(overlayitem);
    mapOverlays.add(itemizedoverlay);
    k++;
    //mapView.postInvalidate(); 
}

@Override
protected boolean isRouteDisplayed() {

    return false;
}


protected void drawGrid(int xoff, int yoff){
    GeoPoint p = newGeoPointFromOffset(xoff, yoff);
    OverlayItem overlayitem = new OverlayItem(p, "", "");
    Drawable marker = this.getResources().getDrawable(R.drawable.grid);
    marker.setBounds(0,0, 15, 15);
    overlayitem.setMarker(marker);
    itemizedoverlay.addOverlay(overlayitem);
    mapOverlays.add(itemizedoverlay);
}

protected GeoPoint newGeoPointFromOffset(int xoff, int yoff){   
    Point screenPointP = new Point(0,0);      
    mapView.getProjection().toPixels(p, screenPointP);  
    int x = 15*xoff;
    int y = 15*yoff;    
    return mapView.getProjection().fromPixels(screenPointP.x + x, screenPointP.y + y);              
}

public boolean onKeyDown(int keyCode, KeyEvent event){
    MapController mc = mapView.getController();
    switch(keyCode){
    case KeyEvent.KEYCODE_3:
        mc.zoomIn();
        break;
    case KeyEvent.KEYCODE_1:
        mc.zoomOut();
        break;
    case KeyEvent.KEYCODE_0:
        drawNewMarker(p);
        break;
    case KeyEvent.KEYCODE_9:    
        for(int r=0;r<30;r++){
            for(int s=0;s<30;s++){
                 drawGrid(r,s);
            }
        }  
        mapView.postInvalidate();           
        break;
    }       
    return super.onKeyDown(keyCode, event);
}       

}

public class MyItemizedOverlay extends ItemizedOverlay{
private ArrayList<OverlayItem> mOverlays = new ArrayList<OverlayItem>();
private Context mContext;

public MyItemizedOverlay(Drawable defaultMarker) {
    super(boundCenterBottom(defaultMarker));
}

public MyItemizedOverlay(Drawable defaultMarker, Context context) {
      super(defaultMarker);
      mContext = context;
}

public void draw(android.graphics.Canvas canvas, MapView mapView,boolean shadow) {
        super.draw(canvas, mapView, false);
}

public void addOverlay(OverlayItem overlay) {
    mOverlays.add(overlay);
    populate();
}

@Override
protected OverlayItem createItem(int i) {
    return mOverlays.get(i);
}

}

推荐答案

有就是那MapView类可以处理重叠的项目数的限制。有这个限制是没有官方消息，但一些一阵子，你会看到缩放/平移过程中低迷的行为。

There is a limit to the number of overlay items that MapView can handle. There is no official word on what this limit is, but after some while, you will see sluggish behaviour during zoom/pan.

一些解决方案是：

• MapView类的惰性加载


• 加载只有尽可能多的标记，是可见的，这样做基于变焦水平和跨度。


• 10覆盖以99分比1与覆盖900点更快。

这篇关于如何抽签标记在地图上的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！