java - NullPointerException:FragmentManagerImpl.execPendingActions(FragmentManager.java:1410)

Question

所以，我有一个使用 Maps fragment 的 fragment 。效果很好，但是当我按回键或退出应用程序时，出现 NullPointerException，我搜索了又搜索，但我不明白它是什么？!

以下是我的日志:

06-17 12:03:59.105: E/AndroidRuntime(32422): FATAL EXCEPTION: main
06-17 12:03:59.105: E/AndroidRuntime(32422): java.lang.NullPointerException
06-17 12:03:59.105: E/AndroidRuntime(32422):    at android.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1410)
06-17 12:03:59.105: E/AndroidRuntime(32422):    at android.app.FragmentManagerImpl$1.run(FragmentManager.java:441)
06-17 12:03:59.105: E/AndroidRuntime(32422):    at android.os.Handler.handleCallback(Handler.java:725)
06-17 12:03:59.105: E/AndroidRuntime(32422):    at android.os.Handler.dispatchMessage(Handler.java:92)
06-17 12:03:59.105: E/AndroidRuntime(32422):    at android.os.Looper.loop(Looper.java:153)
06-17 12:03:59.105: E/AndroidRuntime(32422):    at android.app.ActivityThread.main(ActivityThread.java:5297)
06-17 12:03:59.105: E/AndroidRuntime(32422):    at java.lang.reflect.Method.invokeNative(Native Method)
06-17 12:03:59.105: E/AndroidRuntime(32422):    at java.lang.reflect.Method.invoke(Method.java:511)
06-17 12:03:59.105: E/AndroidRuntime(32422):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:833)
06-17 12:03:59.105: E/AndroidRuntime(32422):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:600)
06-17 12:03:59.105: E/AndroidRuntime(32422):    at dalvik.system.NativeStart.main(Native Method)

Here我认为答案是正确的，但我无法实现它。

感谢您的帮助。

Java 代码:

public class NearMeFragment extends Fragment {

private GoogleMap googleMap;
double latitude = 19.18482;
double longitude = 72.83410;
Context context;
ListFragment lf;
ListView lv;
RestaurantListAdapter adapter;

GPSTracker gps;

public NearMeFragment() {
}

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

    View rootView = inflater.inflate(R.layout.fragment_near_me, container,
            false);


    getActivity().getActionBar().show();

    createMap

    return rootView;
}

public void createMap() {
    try {
        initializeMap();

        for (int i = 0; i < bean.size(); i++) {
            try {
                latitude = Double.valueOf(bean.get(i).getLatitude());
                longitude = Double.valueOf(bean.get(i).getLongitude());
            } catch (NumberFormatException e) {
                latitude = 19.18482;
                longitude = 72.83410;
            }

            LatLng pos = new LatLng(latitude, longitude);

            MarkerOptions marker = new MarkerOptions()
                    .position(pos)
                    .title(bean.get(i).getName())
                    .icon(BitmapDescriptorFactory
                            .fromResource(R.drawable.marker));

            CircleOptions circle = new CircleOptions().center(pos)
                    .radius(Double.valueOf(bean.get(i).getDistance()) * 10)
                    .strokeColor(Color.parseColor("#FFFFFF"))
                    .strokeWidth(5)
                    .fillColor(Color.parseColor("#25f67f21"));

            googleMap.addMarker(marker);
            googleMap.addCircle(circle);
        }

        // CameraPosition cp = new CameraPosition.Builder()
        // .target(new LatLng(latitude, longitude)).zoom(12).build();

        CameraUpdate center = CameraUpdateFactory.newLatLng(new LatLng(
                latitude, longitude));
        CameraUpdate zoom = CameraUpdateFactory.zoomTo(12);

        googleMap.moveCamera(center);
        googleMap.animateCamera(zoom);

        googleMap.setMyLocationEnabled(true);
        googleMap.getUiSettings().setZoomControlsEnabled(true);
        googleMap.getUiSettings().setMyLocationButtonEnabled(false);
        googleMap.getUiSettings().setCompassEnabled(true);
        googleMap.getUiSettings().setZoomGesturesEnabled(true);
        googleMap.getUiSettings().setRotateGesturesEnabled(true);
        googleMap.getUiSettings().setAllGesturesEnabled(true);

    } catch (Exception e) {
        Log.e("TAG", "MSG: " + e);
    }

}

private void initializeMap() {
    if (googleMap == null) {
        googleMap = ((MapFragment) getFragmentManager().findFragmentById(
                R.id.map)).getMap();

        if (googleMap == null) {
            Toast.makeText(NearMeFragment.this.getActivity(),
                    "Sorry! unable to create maps", Toast.LENGTH_LONG)
                    .show();
        }
    }
}

@Override
public void onDestroyView() {
    super.onDestroyView();
    Fragment fragment = ((MapFragment) getFragmentManager()
            .findFragmentById(R.id.map));
    FragmentTransaction ft = getFragmentManager().beginTransaction();
    ft.remove(fragment);
    ft.commit();

}

}

XML 代码:

    <fragment
        android:id="@+id/map"
        android:name="com.google.android.gms.maps.MapFragment"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:clickable="true" />



</FrameLayout>

主要 Activity :

import com.porcupyne.mumbaifoodlovers.R;

import net.simonvt.menudrawer.MenuDrawer;
import android.support.v4.app.Fragment;
import android.widget.SearchView;
import android.widget.TextView;
import android.widget.Toast;
import android.app.Activity;
import android.app.FragmentTransaction;
import android.app.SearchManager;
import android.content.Context;
import android.content.Intent;
import android.content.SharedPreferences;
import android.content.SharedPreferences.Editor;
import android.content.pm.ActivityInfo;
import android.graphics.Color;
import android.os.Bundle;
import android.os.Handler;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup;
import android.view.Window;
import android.widget.ImageButton;
import static com.porcupyne.mumbaifoodlovers.LoginActivity.flag;

  public class MainActivity extends Activity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

            NearMeFragment nmf = new NearMeFragment();
            FragmentTransaction ft = getFragmentManager()
                    .beginTransaction();
            ft.replace(R.id.frame_container, nmf,null);
            ft.commit();
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {

    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.main, menu);

    SearchManager searchManager = (SearchManager) getSystemService(Context.SEARCH_SERVICE);
    SearchView searchView = (SearchView) menu.findItem(R.id.action_search)
            .getActionView();
    searchView.setSearchableInfo(searchManager
            .getSearchableInfo(getComponentName()));
    return super.onCreateOptionsMenu(menu);
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    switch (item.getItemId()) {
    case R.id.action_search:
        return true;

    case android.R.id.home:
        MainFragment mf = new MainFragment();
        FragmentTransaction ft = getFragmentManager().beginTransaction();
        ft.replace(R.id.frame_container, mf);
        ft.commit();
        return true;

    default:
        return super.onOptionsItemSelected(item);
    }
}

/**
 * A placeholder fragment containing a simple view.
 */
public static class PlaceholderFragment extends Fragment {

    public PlaceholderFragment() {
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment_main, container,
                false);
        return rootView;
    }
}

}

Answer 1

试试这个方法:onDestroyView()

@Override
public void onDestroyView ()
{
    try{
      MapFragment fragment = ((MapFragment) getFragmentManager().findFragmentById(R.id.map));
      FragmentTransaction ft = getActivity().getFragmentManager().beginTransaction();
      ft.remove(fragment);
      ft.commit();
    }catch(Exception e){
    }
  super.onDestroyView();  

}

并且您的 Activity 必须Extends Activity