Question

我在osmdroid库中遇到了一些问题。我的应用程序包含一个带有3个片段的滑块，其中一个我试图添加打开的街道地图，但总有这个例外，我不知道如何解决它。我试图在他们的github网站https://github.com/osmdroid/osmdroid上实现这个库。如果我正在使用正常活动，它会起作用，但如果它也适用于片段，它会很棒。

非常感谢！

package ... .map;

import android.os.Bundle;
import android.preference.PreferenceManager;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

import org.osmdroid.api.IMapController;
import org.osmdroid.config.Configuration;
import org.osmdroid.tileprovider.tilesource.TileSourceFactory;
import org.osmdroid.util.GeoPoint;
import org.osmdroid.views.MapView;

import ... .R;

public class TabFragmentMap extends Fragment {

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {

        Configuration.getInstance().load(getContext(), PreferenceManager.getDefaultSharedPreferences(getContext()));

        MapView map = (MapView) getActivity().findViewById(R.id.map);
        map.setTileSource(TileSourceFactory.MAPNIK);

        map.setBuiltInZoomControls(true);
        map.setMultiTouchControls(true);

        IMapController mapController = map.getController();
        mapController.setZoom(9);
        GeoPoint startPoint = new GeoPoint(48.8583, 2.2944);
        mapController.setCenter(startPoint);

        return inflater.inflate(R.layout.tab_fragment_map, container, false);
    }

    @Override
    public void onResume() {
        super.onResume();
        Configuration.getInstance().load(getContext(), PreferenceManager.getDefaultSharedPreferences(getActivity()));
    }
}

并且有布局xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical">

        <org.osmdroid.views.MapView
            android:id="@+id/map"
            android:layout_width="fill_parent"
            android:layout_height="fill_parent" />

</LinearLayout>

引发了我的异常：

java.lang.NullPointerException: Attempt to invoke virtual method 'void org.osmdroid.views.MapView.setTileSource(org.osmdroid.tileprovider.tilesource.ITileSource)' on a null object reference
        at ... .map.TabFragmentMap.onCreateView(TabFragmentMap.java:46)
        at android.support.v4.app.Fragment.performCreateView(Fragment.java:2080)
        at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1108)
        at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1290)
        at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:801)
        at android.support.v4.app.FragmentManagerImpl.execSingleAction(FragmentManager.java:1638)
        at android.support.v4.app.BackStackRecord.commitNowAllowingStateLoss(BackStackRecord.java:679)
        at android.support.v4.app.FragmentStatePagerAdapter.finishUpdate(FragmentStatePagerAdapter.java:166)
        at android.support.v4.view.ViewPager.populate(ViewPager.java:1240)
        at android.support.v4.view.ViewPager.populate(ViewPager.java:1088)
        at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1614)
        at android.view.View.measure(View.java:18930)
        at android.widget.RelativeLayout.measureChildHorizontal(RelativeLayout.java:715)
        at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:461)
        at android.view.View.measure(View.java:18930)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5976)
        at android.widget.FrameLayout.onMeasure(FrameLayout.java:194)
        at android.support.v7.widget.ContentFrameLayout.onMeasure(ContentFrameLayout.java:135)
        at android.view.View.measure(View.java:18930)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5976)
        at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1486)
        at android.widget.LinearLayout.measureVertical(LinearLayout.java:765)
        at android.widget.LinearLayout.onMeasure(LinearLayout.java:647)
        at android.view.View.measure(View.java:18930)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5976)
        at android.widget.FrameLayout.onMeasure(FrameLayout.java:194)
        at android.view.View.measure(View.java:18930)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5976)
        at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1486)
        at android.widget.LinearLayout.measureVertical(LinearLayout.java:765)
        at android.widget.LinearLayout.onMeasure(LinearLayout.java:647)
        at android.view.View.measure(View.java:18930)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5976)
        at android.widget.FrameLayout.onMeasure(FrameLayout.java:194)
        at com.android.internal.policy.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2705)
        at android.view.View.measure(View.java:18930)
        at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2154)
        at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1248)
        at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1484)
        at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1139)
        at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6238)
        at android.view.Choreographer$CallbackRecord.run(Choreographer.java:884)
        at android.view.Choreographer.doCallbacks(Choreographer.java:696)
        at android.view.Choreographer.doFrame(Choreographer.java:631)
        at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:870)
        at android.os.Handler.handleCallback(Handler.java:743)
        at android.os.Handler.dispatchMessage(Handler.java:95)
        at android.os.Looper.loop(Looper.java:150)
        at android.app.ActivityThread.main(ActivityThread.java:5621)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:794)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:684)

Answer 1

您正在当前活动中搜索MapView个实例（通过getActivity()）。但是，视图不包含在您的活动布局中，而是包含在片段布局中。而是尝试搜索片段布局：

View view = inflater.inflate(R.layout.fragment_main, container, false);
MapView map = (MapView) view.findViewById(R.id.map);

片段ITileSource中的Osmdroid对空对象的引用

1 个答案: