Question

有什么方法可以实现缩放监听器，一旦缩放级别改变就可以触发事件。到目前为止，我已经使用onUserinteraction方法手动检查更改缩放级别。另一件事是我想要动态添加/删除叠加层。到目前为止我所做的是onUserinteraction方法，我使用mapOverlays.add（）函数调用一个动态添加叠加的函数，并且实际上添加动态地发生。但不知何故mapOverlays.remove（）函数没有删除叠加

     //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，让我们为OnZoomListener创建界面。请注意，您可以根据需要更改界面，以下只是一个以

开头的框架代码


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，您需要一个子类，只要缩放发生变化，就会调用此OnZoomListener。以下是this SO Answer

的扩展名的骨架代码


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();
        }
    }
}

现在，您可以在布局中使用MyMapView而不是标准MapView。注意：代码包com.so4729255是我用于测试的。


  <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"
        />

最后在代码中添加OnZoomListener。下面的代码只显示Toast以说明使用情况，您可以做任何您需要做的事情


 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();
            }
        });

至于你的第二个问题，正如大家都回答的那样，调用MapView.invalidate()时应该重新映射具有新状态的地图，因为它会强制视图按the API documentation重绘

Answer 2

你必须使用

刷新地图

mapview.invalidate()

postInvalidate在UI线程上发布无效请求，而a 调用invalidate（）会立即使View无效

Answer 3

当缩放级别改变时，地图会重新绘制，所以我只是将这种类型的功能放在我的叠加层绘制方法中，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（）。

Android地图叠加问题

3 个答案: