0

I am developing an app using the google maps android api. The app displays various tileoverlays that the user can turn on and off. When I rotate my device the overlay remains in place but when I click the button to turn off my overlay my device acts as if the variable that controls my overlay is null. How can I retain control over my tileoverlay under these circumstances.

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    SupportMapFragment mapFragment =
            (SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.map);

    //mMap=null;
    if (savedInstanceState == null) {
        // First incarnation of this activity.
        mapFragment.setRetainInstance(true);
    } else  {
        // Reincarnated activity. The obtained map is the same map instance in the previous
        // activity life cycle. There is no need to reinitialize it.
        mMap = mapFragment.getMap();
    }
    setUpMapIfNeeded();
    setUpFieldsIfNeeded();
}
private void setUpMapIfNeeded() {
        // Do a null check to confirm that we have not already instantiated the map.
        if (mMap == null) {
          // Try to obtain the map from the SupportMapFragment.
             mMap  = ((SupportMapFragment)   getSupportFragmentManager().findFragmentById(R.id.map)).getMap();

          }
        }
      }
 private void setUpFieldsIfNeeded(){            

    if (fieldsOverlay == null) {
        TileProvider tileProvider = new UrlTileProvider(256, 256) {
            @Override
            public synchronized URL getTileUrl(int x, int y, int zoom) {


                //String s = String.format(Locale.US, CMAFieldsRequestFormat, zoom, x, y);  
                String s = String.format(Locale.US, cartoDBFieldsTile, zoom, x, y); 
                s =s.replace(" ", "%20");
                System.out.println(s);
                URL url = null;
                try {
                    url = new URL(s);
                } catch (MalformedURLException e) {
                    throw new AssertionError(e);
                }
                return url;
            }
        };


         fieldsOverlay = mMap.addTileOverlay(
                 new TileOverlayOptions().tileProvider(tileProvider));
         fieldsOverlay.setVisible(false);
         fieldsOverlay.setZIndex(1);}

    }

TLDR: I'm using google maps with a tileOverlay named fieldsOverlay. When I rotate my device the overlay itself is preserved but it is no longer connected to the variable fieldsOverlay. What is the best way to fix this problem.

Thanks

edit: I was able to get the app to appear to function the way I want by running mMap.clear then reinitializing my layer and setting the visibility to a savedInstanceState value when I reincarnate my activity, but this doesn't seem like a good solution.

4

1 回答 1

1

使用SupportMapFragment.setRetainInstace似乎是实现预期结果的快速方法，但实际上并非如此。

首先，它会导致内存泄漏。查看我的gmaps-api-issue进行讨论。

你遇到的问题很正常。TileOverlay重新创建时不会保留您保留的引用Activity。实际上创建了一个新Activity对象。视觉对象应该像普通View的 Android 一样对待：在配置更改时不保留。官方文档中甚至对此有注释，但我现在找不到。

如果你不使用setRetainInstance你不会有没有引用你的对象的问题，因为你必须在旋转时再次创建。

于 2013-08-16T21:59:12.390 回答