android - 在 viewpager 中添加 openstreetmap

Question

我对android studio中的viewpager有一些疑问，

所以我使用 viewpager 和 PagerAdapter 类制作了一个具有 3 个屏幕的 viewpager公共(public)类 MainActivity 扩展 FragmentActivity {

private MapView myOpenMapView;
private MapController myMapController;
ExpandableListAdapter listAdapter;
ExpandableListView expListView;
List<String> listDataHeader;
HashMap<String, List<String>> listDataChild;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    MyPagerAdapter adapter = new MyPagerAdapter();
    ViewPager myPager = (ViewPager) findViewById(R.id.viewpager_layout);
    myPager.setAdapter(adapter);
    myPager.setCurrentItem(1);

    expListView = (ExpandableListView) findViewById(R.id.expandableListView2);
    prepareListData();
    listAdapter = new ExpandableListAdapter(this,listDataHeader,listDataChild);
}
    public class MyPagerAdapter extends PagerAdapter {
            public int getCount() {
                return 3;
            }

            public Object instantiateItem(ViewGroup collection, int position) {
                View view=null;

                LayoutInflater inflater = (LayoutInflater) collection.getContext()
                        .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
                int resId = 0;
                switch (position) {
                    case 0:
                        resId = R.layout.activity_friend;
                        view = inflater.inflate(resId, null);
                        break;
                    case 1:
                        resId = R.layout.fragment_main_page;
                        view = inflater.inflate(resId, null);
                        break;
                    case 2:
                        resId = R.layout.activity_map;
                        view = inflater.inflate(resId, null);
                        myOpenMapView = (MapView) findViewById(R.id.openmapview);
                        //myOpenMapView.setBuiltInZoomControls(true);
                        //myMapController = myOpenMapView.getController();
                        //myMapController.setZoom(4);
                        //myOpenMapView.setTileSource(TileSourceFactory.MAPQUESTOSM);

                        break;
                }
                ((ViewPager) collection).addView(view, 0);
                return view;
            }

            @Override
            public void destroyItem(ViewGroup arg0, int arg1, Object arg2) {
                ((ViewPager) arg0).removeView((View) arg2);
            }

            @Override
            public boolean isViewFromObject(View arg0, Object arg1) {
                return arg0 == ((View) arg1);
            }

            //public boolean isViewFromObject(ViewGroup arg0, Object arg1) {
            // return arg0 == ((View) arg1);
            //}
            @Override
            public Parcelable saveState() {
                return null;
            }
        }

这很好用，现在在我的项目中我想实现一个 openstreetmap，我添加了这段代码

            myOpenMapView = (MapView) findViewById(R.id.openmapview);
            myOpenMapView.setBuiltInZoomControls(true);
            myMapController = myOpenMapView.getController();
            myMapController.setZoom(4);
            myOpenMapView.setTileSource(TileSourceFactory.MAPQUESTOSM); 

如果将此代码放在单独的 Activity 中，则此代码可以正常工作，但出于某种原因，如果它位于 viewpager 的 oncreate 或 pageradapter 类中，则无法正常工作

谁能解释为什么它不起作用以及我该如何解决它？

Answer 1

                    resId = R.layout.activity_map;
                    v = inflater.inflate(resId,null);
                    View map = v.findViewById(R.id.openmapview);
                    myOpenMapView = (MapView)map;
                    myOpenMapView.setBuiltInZoomControls(true);
                    myOpenMapView.setMultiTouchControls(true);
                    myOpenMapView.setClickable(true);
                    myMapController = myOpenMapView.getController();
                    myMapController.setZoom(15);
                    myOpenMapView.getController().setCenter(
                            new GeoPoint(MAP_LATITUDE, MAP_LONGITUDE));
                    myOpenMapView.setTileSource(TileSourceFactory.MAPQUESTOSM);
                    break;

我想通了，

你创建了一个新 View

View map = v.findViewById(R.id.openmapview); 

就这样但是你是从膨胀 View 中创建的

然后你把刚刚获取的id填入map中

myOpenMapView = (MapView)map;

希望对遇到同样问题的人有所帮助