我正在使用Xamarin(7.1版)开发
Android应用程序.它显示为地图并绘制PolyLines,在OnCameraIdle()中执行此操作.
在OnCreate中以编程方式生成MapFragment.我通过GetMapAsync在OnResume中获取GoogleMap,并在OnMapReady中绑定侦听器.
他们工作正常,但只在一开始.一旦设备旋转(纵向 – >横向或反之亦然),相机移动不会再触发听众.
然而,地图工作 – 我(用户)仍然可以移动相机.我(应用程序)不能再用它了.
这是裸码,只有地图创建和处理.其他(实际绘图)被删除：
public class MapActivity : Activity,IOnMapReadyCallback,GoogleMap.IOnCameraIdleListener,GoogleMap.IOnCameraMoveStartedListener
{
private GoogleMap _map;
private MapFragment _mapFragment;
private void InitializeMap()
{
_mapFragment = MapFragment.NewInstance();
var tx = FragmentManager.BeginTransaction();
tx.Add(Resource.Id.map_placeholder,_mapFragment);
tx.Commit();
}
private void SetMapListeners()
{
Log.Debug("MyApp/ Map","SetMapListeners");
_map.SetOnCameraIdleListener(this);
_map.SetOnCameraMoveStartedListener(this);
}
/* Activity */
protected override void OnCreate(Bundle savedInstanceState)
{
base.OnCreate(savedInstanceState);
Log.Debug("MyApp / Map","OnCreate");
SetContentView(Resource.Layout.Map);
InitializeMap();
}
protected override void OnStart()
{
base.OnStart();
Log.Debug("MyApp / Map","OnStart");
}
protected override void OnResume()
{
base.OnResume();
if (_map == null)
_mapFragment.GetMapAsync(this);
Log.Debug("MyApp / Map","OnResume");
}
protected override void OnPause()
{
base.OnPause();
Log.Debug("MyApp / Map","OnPause");
}
protected override void OnStop()
{
base.OnStop();
Log.Debug("MyApp / Map","OnStop");
}
protected override void OnDestroy()
{
base.OnStop();
Log.Debug("MyApp/ Map","OnDestroy");
}
/* IOnMapReadyCallback */
public void OnMapReady(GoogleMap googleMap)
{
Log.Debug("MyApp / Map","Map is ready!");
_map = googleMap;
SetMapListeners();
}
/* IOnCameraIdleListener */
public void OnCameraIdle()
{
Log.Debug("MyApp / Map","Camera is idle.");
// Drawing routine is called here
}
/* IOnCameraMoveStartedListener */
public void OnCameraMoveStarted(int reason)
{
Log.Debug("MyApp / Map","Camera move started.");
}
}
正如您在以下日志摘录中可以看到的,侦听器在开始时工作,但是一旦设备旋转(至少)一次,它们就会消失.
我也尝试在生命周期中调用SetMapListeners一次,第一次调用OnMapReady,但是没有改变任何东西.
04-03 20:29:06.486 D/MyApp / Map( 7446): OnCreate 04-03 20:29:06.688 I/Google Maps Android API( 7446): Google Play services client version: 10084000 04-03 20:29:06.695 I/Google Maps Android API( 7446): Google Play services package version: 10298438 04-03 20:29:07.394 D/MyApp / Map( 7446): OnStart 04-03 20:29:07.399 D/MyApp / Map( 7446): OnResume 04-03 20:29:07.432 D/MyApp / Map( 7446): Map is ready! 04-03 20:29:07.438 D/MyApp / Map( 7446): SetMapListeners 04-03 20:29:07.568 D/MyApp / Map( 7446): Camera is idle. 04-03 20:29:09.231 D/MyApp / Map( 7446): Camera move started. 04-03 20:29:09.590 D/MyApp / Map( 7446): Camera is idle. 04-03 20:29:12.350 D/MyApp / Map( 7446): Camera move started. 04-03 20:29:12.751 D/MyApp / Map( 7446): Camera is idle. ## Listeners are responding,now rotating the device. 04-03 20:29:15.503 D/MyApp / Map( 7446): OnPause 04-03 20:29:15.508 D/MyApp / Map( 7446): OnStop 04-03 20:29:15.572 D/MyApp / Map( 7446): OnDestroy 04-03 20:29:15.595 I/Google Maps Android API( 7446): Google Play services package version: 10298438 04-03 20:29:15.596 D/MyApp / Map( 7446): OnCreate 04-03 20:29:15.628 I/Google Maps Android API( 7446): Google Play services package version: 10298438 04-03 20:29:15.655 D/MyApp / Map( 7446): OnStart 04-03 20:29:15.655 D/MyApp / Map( 7446): OnResume 04-03 20:29:15.690 D/MyApp / Map( 7446): Map is ready! 04-03 20:29:15.691 D/MyApp / Map( 7446): SetMapListeners ## Map is rotated,camera position was preserved. ## Now moving the camera,but no listeners are responding. 04-03 20:29:24.436 D/MyApp / Map( 7446): OnPause 04-03 20:29:31.288 D/MyApp / Map( 7446): OnStop 04-03 20:29:31.359 D/MyApp / Map( 7446): OnDestroy
对我来说有趣的是,当我切换回上一个活动并再次打开地图时,它会开始新鲜,再次工作.但是,正如您在日志中看到的那样,在旋转设备的同时,活动也被破坏并新创建.据我所知,片段不是,所以也许这是暗示.我不知道.
我也尝试删除OnDestroy中的监听器(通过设置null),但也没有改变任何东西.
你有什么想法我可能做错了吗？
解决方法
尝试检查savedInstanceState以查看您的Activity是否是第一次构建,或者是否只是返回它.您似乎在每次呼叫时都是重叠的片段.
