Android地图覆盖问题

Question

有没有什么办法可以实现缩放监听器，只要缩放级别发生变化就可以触发事件。到目前为止，我已经使用onUserinteraction方法手动检查变化的缩放级别。 另一件事是我想要动态地添加/删除叠加层。到目前为止，我所做的是在onUserinteraction方法中，我调用一个函数，它使用mapOverlays.add（）函数动态地添加叠加层，并且实际上添加会动态发生。但不知何故，mapOverlays.remove（）函数不删除覆盖

 //Function for adding first set of markers 
    public void setOverlay() 
{ 
    worldLength = World.length; 
    mapOverlays = mapView.getOverlays(); 
    drawable0 = this.getResources().getDrawable(R.drawable.marker); 
    itemizedOverlay0 = new MyItemizedOverlay(drawable0); 
    for (int i = 0; i < worldLength; i++) 
    { 
     itemizedOverlay0.addOverlay(World[i]); 
    } 
    mapOverlays.add(itemizedOverlay0); 
    mapView.postInvalidate(); 
} 
    //Function for adding second set of markers 
    public void setOverlay1() 
    { 
     mapView.setStreetView(true); 
     usaLength = USA.length; 
     mexicoLength = Mexico.length; 
       mapOverlays = mapView.getOverlays(); 
     drawable1 = this.getResources().getDrawable(R.drawable.marker); 
     itemizedOverlay1 = new MyItemizedOverlay(drawable1); 
     itemizedOverlay2 = new MyItemizedOverlay(drawable1); 


     for (int i = 0; i < usaLength; i++) { 
      itemizedOverlay1.addOverlay(USA[i]); 
     } 
     for (int i = 0; i < mexicoLength; i++) { 
      itemizedOverlay2.addOverlay(Mexico[i]); 
     } 

     mapOverlays.add(itemizedOverlay1); 
     mapOverlays.add(itemizedOverlay2); 


    mapView.postInvalidate(); 

} 

    public void onUserInteraction() { 
    super.onUserInteraction(); 
    if(mapView.getZoomLevel()>3) 
    { 
     mapOverlays.remove(itemizedOverlay0); 
     setOverlay1(); 
       //the above happens 
    } 
    else if(mapView.getZoomLevel()<=3 && mapOverlays.size()>5) 
    { 
     mapOverlays.remove(itemizedOverlay1); 
     mapOverlays.remove(itemizedOverlay2); 
       //the above doesn't 
     setOverlay(); 
    } 
    else if(mapView.getZoomLevel()<=3) 
    { 

    } 
} 

Answer 1

为了实现您的自定义缩放处理程序并添加侦听器，您需要创建MapView的子类。首先，我们来创建OnZoomListener的界面。请注意，你可以改变接口，以满足您的需要，下面只是一个框架代码与

public interface OnZoomListener { 
    /*** 
    * /** 
    * Called when there is a zoom changes 
    * @param mapView Reference to the current map view 
    * @param currentZoom The current zoom, set to -1 initially 
    * @param newZoom The new zoom level 
    */ 
    public void onZoomChanged(MapView mapView, int currentZoom, int newZoom); 
} 

现在开始，你需要一个子类，它会调用这个OnZoomListener每当变焦的变化。以下是一个框架代码这是this SO Answer

public class MyMapView extends MapView { 
    int oldZoomLevel=-1; 
    OnZoomListener onZoomListener; 

    public MyMapView(Context context, AttributeSet attrs, int defStyle) { 
     super(context, attrs, defStyle); 
    } 

    public MyMapView(Context context, AttributeSet attrs) { 
     super(context, attrs); 
    } 

    public MyMapView(Context context, String apiKey) { 
     super(context, apiKey); 
    } 

    public void setOnZoomListener(OnZoomListener onZoomListener) { 
     this.onZoomListener = onZoomListener; 
    } 

    @Override 
    public void dispatchDraw(Canvas canvas) { 
     super.dispatchDraw(canvas); 
     int newZoom = this.getZoomLevel(); 

     if (newZoom != oldZoomLevel) { 
      // dispatch the listeners 
      if(oldZoomLevel != -1 && onZoomListener != null) { 
       onZoomListener.onZoomChanged(this, oldZoomLevel, newZoom); 
      } 

      // update the new zoom level 
      oldZoomLevel = getZoomLevel(); 
     } 
    } 
} 

的扩展现在，你可以在你的布局中使用MyMapView而不是标准的MapView的。注意：代码包com.so4729255是我仅用于测试的。

    <com.so4729255.MyMapView 
       android:id="@+id/mapview" 
       android:layout_width="fill_parent" 
       android:layout_height="fill_parent" 
       android:enabled="true" 
       android:apiKey="YOUR API KEY" 
       android:clickable="true" 
     /> 

最后在您的代码中添加OnZoomListener。下面的代码只显示吐司的用法说明，你可以做任何你需要做的还有

MyMapView mapView = (MyMapView)this.findViewById(R.id.mapview); 
     mapView.setOnZoomListener(new OnZoomListener() { 
      public void onZoomChanged(MapView mapView, int currentZoom, 
        int newZoom) { 
       // implement your handler here 
       Toast t = Toast.makeText(WebViewMain.this, "Zoom has changed from " + currentZoom + " to " + 
         newZoom, 500); 
       t.show(); 
      } 
     }); 

关于你的第二个问题，每个人都回答，称MapView.invalidate()应重绘地图与新的状态它会强制查看重绘每the API documentation

Answer 2

好，你必须使用刷新

mapview.invalidate() 

postInvalidate职位UI线程上的无效请求的地图，而 呼叫无效（）立即无效查看

Answer 3

当缩放级别改变时，地图重绘，所以我只是把这种类型的func在我的覆盖的绘制方法，如下所示：

e@Override 
public void draw(Canvas canvas, MapView mapv, boolean shadow) 
{  
    int zoom = mapv.getZoomLevel(); 

    switch(zoom) 
    { 
     case 19: 
      setMarkersForZoomLevel19(); 
      break; 
     case 18: 
      setMarkersForZoomLevel18(); 
      break; 
     case 17: 
      setMarkersForZoomLevel17(); 
      break; 
     case 16: 
      setMarkersForZoomLevel16(); 
      break; 
     default: 
      // Hide the markers or remove the overlay from the map view.     
      mapv.getOverlays().clear(); 
    }  

    // Putting this call here rather than at the beginning, ensures that 
    // the Overlay items are drawn over the top of canvas stuff e.g. route lines. 
    super.draw(canvas, mapv, false);   
} 

当您删除叠加层时，请记得调用mapView.invalidate（）。