一个地图中放多个标签，如何获取一个恰当的缩放级别

今天需要实现一个逻辑，需要在地图中放多个自定义对象，然后需要根据这些点，获取一个合适的缩放级别，可用的函数有这两个 ：

自动调整到一个合适的缩放级别：

MapController::zoomToSpan();

获取一个缩放级别：

MapView::getZoomToBound();

不过有一点要注意，调用这两个函数，都要等到地图加载完成之后，即

MKMapViewListener::onMapLoadFinish() 被调用之后，不然会没有效果。

笔记先做成这样，以后有时间再总结！

代码如下：

package mars.maptest;

import java.util.ArrayList;

import android.util.Log;
import android.app.Activity;
import android.os.Bundle;
import android.os.Message;
import android.graphics.drawable.Drawable;
import android.view.View;
import android.widget.Toast;
import android.graphics.Matrix;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.drawable.BitmapDrawable;
import android.os.Handler;
import android.os.SystemClock;

import com.baidu.mapapi.BMapManager;
import com.baidu.mapapi.map.MapController;
import com.baidu.mapapi.map.MapView;  
import com.baidu.platform.comapi.basestruct.GeoPoint;
import com.baidu.mapapi.map.OverlayItem;
import com.baidu.mapapi.map.ItemizedOverlay;
import com.baidu.mapapi.map.MapPoi;
import com.baidu.mapapi.map.MKMapViewListener;
/*
 * 1. 不知道为什么，如果同时用getZoomToBound()和animateTo()两个函数，一定要把animateTo()放到getZoomToBound()后面，不然会无效.
 * 2. getZoomToBound()函数的参数，应该是两个对角点，一定不要搞错.
 * 3. zoomToSpan()函数的参数是    经纬度差，一定不要弄错.
 * 4. 用2、3两个函数，一定要等到地图初始化完成，即 MKMapViewListener.onMapLoadFinish() 调用完之后再进行调用才能有效.
 */
public class MainActivity extends Activity{

	private BMapManager mBMapMan = null;
	private MapView mMapView = null;
	private MapController mMapController = null;

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);

		mBMapMan=new BMapManager(getApplication());  
		mBMapMan.init(null);

		setContentView(R.layout.main);

		mMapView=(MapView)findViewById(R.id.bmapsView);  
		mMapView.setBuiltInZoomControls(true);  
		//设置启用内置的缩放控件  
		mMapController=mMapView.getController();
	
		mMapView.regMapViewListener(mBMapMan, mapViewListener);
	}
	
	@Override
	protected void onDestroy(){
	        mMapView.destroy();
	        if(mBMapMan!=null){
	                mBMapMan.destroy();
	                mBMapMan=null;
	        }
	        super.onDestroy();
	}
	@Override
	protected void onPause(){
	        mMapView.onPause();
	        if(mBMapMan!=null){
	               mBMapMan.stop();
	        }
	        super.onPause();
	}
	@Override
	protected void onResume(){
	        mMapView.onResume();
	        if(mBMapMan!=null){
	                mBMapMan.start();
	        }
	       super.onResume();
	}
	
	MKMapViewListener mapViewListener = new MKMapViewListener() {

		@Override
		public void onMapMoveFinish() {			
		}					
		@Override
		public void onClickMapPoi(MapPoi arg0) {
		}
		@Override
		public void onGetCurrentMap(Bitmap arg0) {
		}
		@Override
		public void onMapAnimationFinish() {
		}
		@Override
		public void onMapLoadFinish() {				
			Log.i("vvcar","onMapLoadFinish()!");
				
			drawMulCar(mMapView);				
		}
	};

	public void drawMulCar(View v){
		// 116.413251,39.911752   
		// 116.306317,39.965746   
		// 116.658165,40.136296  
		// 116.683462,39.542834  
		// 117.184788,39.13925   
		// 119.613231,39.958225  
		double mLat1 = 39.911752;  
		double mLon1 = 116.413251;  
		double mLat2 = 39.965746;  
		double mLon2 = 116.306317;  
		double mLat3 = 40.136296;  
		double mLon3 = 116.658165;
		
		double mLat4 = 39.542834;  
		double mLon4 = 116.683462;
		double mLat5 = 39.13925;  
		double mLon5 = 117.184788;
		double mLat6 = 39.958225;  
		double mLon6 = 119.613231;
		
		// 用给定的经纬度构造GeoPoint，单位是微度 (度 * 1E6)  
		GeoPoint p1 = new GeoPoint((int) (mLat1 * 1E6), (int) (mLon1 * 1E6));
		GeoPoint p2 = new GeoPoint((int) (mLat2 * 1E6), (int) (mLon2 * 1E6));
		GeoPoint p3 = new GeoPoint((int) (mLat3 * 1E6), (int) (mLon3 * 1E6));
		GeoPoint p4 = new GeoPoint((int) (mLat4 * 1E6), (int) (mLon4 * 1E6));
		GeoPoint p5 = new GeoPoint((int) (mLat5 * 1E6), (int) (mLon5 * 1E6));
		GeoPoint p6 = new GeoPoint((int) (mLat6 * 1E6), (int) (mLon6 * 1E6));
		
		ArrayList<GeoPoint> gpList = new ArrayList<GeoPoint>();
		gpList.clear();
		gpList.add(p1);
		gpList.add(p2);
		gpList.add(p3);
		gpList.add(p4);
		gpList.add(p5);
		gpList.add(p6);
		
		//准备overlay图像数据，根据实情情况修复  
		Drawable mark3= getResources().getDrawable(R.drawable.car_gray);
		//旋转图片
		BitmapDrawable mark1 = rotateBitmap(R.drawable.car_gray,180);
		BitmapDrawable mark2 = rotateBitmap(R.drawable.car_gray,45);		
				
		//用OverlayItem准备Overlay数据  
		OverlayItem item1 = new OverlayItem(p1,"item1","item1");  
		item1.setMarker(mark1);
		OverlayItem item2 = new OverlayItem(p2,"item2","item2");  
		item2.setMarker(mark1);  
		OverlayItem item3 = new OverlayItem(p3,"item3","item3");  
		item3.setMarker(mark1);
		OverlayItem item4 = new OverlayItem(p4,"item4","item4");  
		item4.setMarker(mark1);
		OverlayItem item5 = new OverlayItem(p5,"item5","item5");  
		item5.setMarker(mark1);
		OverlayItem item6 = new OverlayItem(p6,"item6","item6");  
		item6.setMarker(mark1);
		
		//创建IteminizedOverlay  
		OverlayTest itemOverlay = new OverlayTest(mark1, mMapView);  
		//将IteminizedOverlay添加到MapView中  
		  
		mMapView.getOverlays().clear();  
		mMapView.getOverlays().add(itemOverlay);  

		itemOverlay.addItem(item1);  
		itemOverlay.addItem(item2);  
		itemOverlay.addItem(item3);
		itemOverlay.addItem(item4); 
		itemOverlay.addItem(item5); 
		itemOverlay.addItem(item6);

		GeoPoint pMid = new GeoPoint((int) (mLat1 * 1E6), (int) (mLon1 * 1E6));
		GeoPoint pMax = new GeoPoint((int) (mLat1 * 1E6), (int) (mLon1 * 1E6));
		GeoPoint pMin = new GeoPoint((int) (mLat1 * 1E6), (int) (mLon1 * 1E6));
		
		getCenterAndEdg(gpList,pMid,pMax,pMin);
		Log.i("vvcar","mid point is : " + String.valueOf( pMid.getLongitudeE6()/1E6 ) + "," + String.valueOf( pMid.getLatitudeE6()/1E6 ) );
		Log.i("vvcar","max point is : " + String.valueOf( pMax.getLongitudeE6()/1E6 ) + "," + String.valueOf( pMax.getLatitudeE6()/1E6 ) );
		Log.i("vvcar","min point is : " + String.valueOf( pMin.getLongitudeE6()/1E6 ) + "," + String.valueOf( pMin.getLatitudeE6()/1E6 ) );
		
		//!!!!!这里不知道为什么，如果同时用getZoomToBound()和animateTo()两个函数，一定要把animateTo()放到getZoomToBound()后面，不然会无效
		mMapController.setCenter(pMid);
		float zoomlevel = mMapView.getZoomToBound(pMax,pMin);
		mMapController.setZoom(zoomlevel);
		
		
		mMapView.refresh();				
	}
	
	/*
	 * 输入若干个坐标点，返回这些点的中心店和两个对角点
	 */
	public void getCenterAndEdg(ArrayList<GeoPoint> list,GeoPoint pMid,GeoPoint pMax,GeoPoint pMin){

		double dMidLng = 0;
		double dMidLat = 0;
		double dMaxLng = (list.get(0).getLongitudeE6())/1E6;
		double dMaxLat = (list.get(0).getLatitudeE6())/1E6;
		double dMinLng = (list.get(0).getLongitudeE6())/1E6;
		double dMinLat = (list.get(0).getLatitudeE6())/1E6;

		
		for(int i = 0 ; i<list.size() ; i++ ){

			double dLng = (list.get(i).getLongitudeE6())/1E6;
			double dLat = (list.get(i).getLatitudeE6())/1E6;
			
			Log.i("vvcar","point " + String.valueOf(i) + " info : " + String.valueOf(dLng) + "," + String.valueOf(dLat) );
			
			if( dLng > dMaxLng ){
				dMaxLng = dLng;
			}
			if( dLng < dMinLng ){
				dMinLng = dLng;
			}
			if( dLat > dMaxLat ){
				dMaxLat = dLat;
			}
			if( dLat < dMinLat ){
				dMinLat = dLat;
			}
		}

		//
		dMidLng = (dMaxLng+dMinLng)/2;
		dMidLat = (dMaxLat+dMinLat)/2;

		pMid.setLongitudeE6( (int)(dMidLng * 1E6) );
		pMid.setLatitudeE6( (int)(dMidLat * 1E6) );

		//
		pMax.setLongitudeE6( (int)(dMaxLng * 1E6) );
		pMax.setLatitudeE6( (int)(dMaxLat * 1E6) );
		pMin.setLongitudeE6( (int)(dMinLng * 1E6) );
		pMin.setLatitudeE6( (int)(dMinLat * 1E6) );
	}

	
	class OverlayTest extends ItemizedOverlay<OverlayItem> {

	    //用MapView构造ItemizedOverlay  
	    public OverlayTest(Drawable mark,MapView mapView){
	            super(mark,mapView);  
	    }
	    
	    protected boolean onTap(int index) {
	        //在此处理item点击事件  
	    	Log.i("map", "index is " + String.valueOf(index) );
	        return true;
	    }
	    
	    public boolean onTap(GeoPoint pt, MapView mapView){
	    	//在此处理MapView的点击事件，当返回 true时  
            super.onTap(pt,mapView);
	        Log.i("map","point is " + String.valueOf(pt.getLongitudeE6()) + " , " + String.valueOf(pt.getLatitudeE6()) );
	        //这里不能返回true，返回true就不调用了?
	        return false;
	    }

	}
}