//清理坐標數據的視圖和數據    [_bMapView removeAnnotations:_mapAnnotations];    [_mapAnnotations removeAllObjects];    [_carPointArray removeAllObjects];    //聲明解析時對坐標數據的位置區域的篩選，包括經度和緯度的最小值和最大值    CLLocationDegrees minLat;    CLLocationDegrees maxLat;    CLLocationDegrees minLon;    CLLocationDegrees maxLon;    //解析數據    for (int i=0; i<rows.count; i++) {        NSDictionary *row = [rows objectAtIndex:i];        坐標模型類 *item = [[坐標模型類 alloc] initWithJson:row];        if (item.vehicleNo && [item.vehicleNo length]>0) {            標注模型類 *annotation = [[標注模型類 alloc] init];            annotation.coordinate = item.baiduCoordinate;            annotation.item = item;            [_mapAnnotations addObject:annotation];            [_bMapView addAnnotation:annotation];            [annotation release];                        if (i==0) {                //以第一個坐標點做初始值                minLat = item.baiduCoordinate.latitude;                maxLat = item.baiduCoordinate.latitude;                minLon = item.baiduCoordinate.longitude;                maxLon = item.baiduCoordinate.longitude;            }else{                //對比篩選出最小緯度，最大緯度；最小經度，最大經度                minLat = MIN(minLat, item.baiduCoordinate.latitude);                maxLat = MAX(maxLat, item.baiduCoordinate.latitude);                minLon = MIN(minLon, item.baiduCoordinate.longitude);                maxLon = MAX(maxLon, item.baiduCoordinate.longitude);            }                        [_carPointArray addObject:item];        }        [item release];    }    //動態的根據坐標數據的區域，來確定地圖的顯示中心點和縮放級別    if (_carPointArray.count > 0) {        //計算中心點        CLLocationCoordinate2D centCoor;        centCoor.latitude = (CLLocationDegrees)((maxLat+minLat) * 0.5f);        centCoor.longitude = (CLLocationDegrees)((maxLon+minLon) * 0.5f);        BMKCoordinateSpan span;        //計算地理位置的跨度        span.latitudeDelta = maxLat - minLat;        span.longitudeDelta = maxLon - minLon;        //得出數據的坐標區域        BMKCoordinateRegion region = BMKCoordinateRegionMake(centCoor, span);        //百度地圖的坐標范圍轉換成相對視圖的位置        CGRect fitRect = [_bMapView convertRegion:region toRectToView:_bMapView];        //將地圖視圖的位置轉換成地圖的位置        BMKMaPRect fitMapRect = [_bMapView convertRect:fitRect toMapRectFromView:_bMapView];        //設置地圖可視范圍為數據所在的地圖位置        [_bMapView setVisibleMapRect:fitMapRect animated:YES];            }

MKMapRect zoomRect = MKMapRectNull;for (id <MKAnnotation> annotation in mapView.annotations) {    MKMapPoint annotationPoint = MKMapPointForCoordinate(annotation.coordinate);    MKMapRect pointRect = MKMapRectMake(annotationPoint.x, annotationPoint.y, 0, 0);    if (MKMapRectIsNull(zoomRect)) {        zoomRect = pointRect;    } else {        zoomRect = MKMapRectUnion(zoomRect, pointRect);    }}[mapView setVisibleMapRect:zoomRect animated:YES];