谷歌地图（Google Map Android v2）活动在切换USB模式时崩溃

Question

我在这里陷入了一个奇怪的情况，它偶然发生。我目前正在使用适用于Android v2的Google Map API来显示地图片段。一切运行正常，除非用户在USB模式之间切换时应用程序崩溃。

问题是，我无法保存一些对象，因为在这种情况下我无法重写onSaveInstanceState（）。这是Google Maps API中的issue。我得到空指针异常。完整的logcat如下：

04-27 18:45:10.289: E/AndroidRuntime(19982): FATAL EXCEPTION: main 
04-27 18:45:10.289: E/AndroidRuntime(19982): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.octanetech.cortes/com.octanetech.cortes.MapActivity}: java.lang.NullPointerException 
04-27 18:45:10.289: E/AndroidRuntime(19982): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663) 
04-27 18:45:10.289: E/AndroidRuntime(19982): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679) 
04-27 18:45:10.289: E/AndroidRuntime(19982): at android.app.ActivityThread.access$2300(ActivityThread.java:125) 
04-27 18:45:10.289: E/AndroidRuntime(19982): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033) 
04-27 18:45:10.289: E/AndroidRuntime(19982): at android.os.Handler.dispatchMessage(Handler.java:99) 
04-27 18:45:10.289: E/AndroidRuntime(19982): at android.os.Looper.loop(Looper.java:123) 
04-27 18:45:10.289: E/AndroidRuntime(19982): at android.app.ActivityThread.main(ActivityThread.java:4627) 
04-27 18:45:10.289: E/AndroidRuntime(19982): at java.lang.reflect.Method.invokeNative(Native Method) 
04-27 18:45:10.289: E/AndroidRuntime(19982): at java.lang.reflect.Method.invoke(Method.java:521) 
04-27 18:45:10.289: E/AndroidRuntime(19982): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:871) 
04-27 18:45:10.289: E/AndroidRuntime(19982): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:629) 
04-27 18:45:10.289: E/AndroidRuntime(19982): at dalvik.system.NativeStart.main(Native Method) 
04-27 18:45:10.289: E/AndroidRuntime(19982): Caused by: java.lang.NullPointerException 
04-27 18:45:10.289: E/AndroidRuntime(19982): at com.octanetech.cortes.MapActivity.displayPlaces(MapActivity.java:644) 
04-27 18:45:10.289: E/AndroidRuntime(19982): at com.octanetech.cortes.MapActivity.onCreate(MapActivity.java:158) 
04-27 18:45:10.289: E/AndroidRuntime(19982): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047) 
04-27 18:45:10.289: E/AndroidRuntime(19982): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627) 
04-27 18:45:10.289: E/AndroidRuntime(19982): ... 11 more 
04-27 18:45:10.309: W/ActivityManager(2466): Force finishing activity com.octanetech.cortes/.MapActivity 

的应用是越来越崩溃，只有当我恢复地图活动，应用程序的其余部分，否则是工作的罚款。任何帮助将不胜感激。

编辑将修剪MapActivity类：

public class MapActivity extends SherlockFragmentActivity implements LocationListener, OnInfoWindowClickListener, SearchView.OnQueryTextListener, 
    OnMarkerClickListener { 
// private final BitmapDescriptor markerBitmap = null; 
private GoogleMap mMap; 
private CameraPosition cameraPosition; 
Location currentLocation; 
MapView mapView; 
Bitmap beaconImage; 
Geocoder geocoder; 
private Handler mHandler; 
protected Marker marker; 
ActionBar actionBar; 
private Menu menu; 
private boolean menuCreated; 

@Override 
public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 

    actionBar = getSupportActionBar(); 
    actionBar.setDisplayShowTitleEnabled(false); 
    actionBar.setDisplayShowHomeEnabled(false); 
    navigate = new NavigateActivity(this); 
    context = this; 
    currentLocation = new Location("asd"); 
    currentLocation.setLatitude(0); 
    currentLocation.setLongitude(0); 
    setContentView(R.layout.activity_map); 
    mMap = ((SupportMapFragment) getSupportFragmentManager() 
      .findFragmentById(R.id.map)).getMap(); 
    SupportMapFragment f = ((SupportMapFragment) getSupportFragmentManager() 
      .findFragmentById(R.id.map)); 
    f.setRetainInstance(true); 

    mMap.setMyLocationEnabled(true); 

    mMap.setOnInfoWindowClickListener(this); 
    mMap.setOnMarkerClickListener(this); 
    cameraPosition = mMap.getCameraPosition(); 

    geocoder = new Geocoder(this, Locale.getDefault()); 

    displayPlaces(); 

} 

public boolean onCreateOptionsMenu(Menu menu) { 
    super.onCreateOptionsMenu(menu); 

    this.menu = menu; 
    MenuInflater inflater = getSupportMenuInflater(); 
    inflater.inflate(R.menu.mapview_menu, menu); 
    MenuItem searchItem = menu.findItem(R.id.action_search); 
    mSearchView = (SearchView) searchItem.getActionView(); 
    setupSearchView(searchItem); 
    menuCreated = true; 
    return true; 
} 

private void setupSearchView(MenuItem searchItem) { 

    if (isAlwaysExpanded()) { 
     mSearchView.setIconifiedByDefault(false); 
    } else { 
     searchItem.setShowAsActionFlags(MenuItem.SHOW_AS_ACTION_IF_ROOM 
       | MenuItem.SHOW_AS_ACTION_COLLAPSE_ACTION_VIEW); 
    } 

    SearchManager searchManager = (SearchManager) getSystemService(Context.SEARCH_SERVICE); 
    if (searchManager != null) { 
    } 

    mSearchView.setOnQueryTextListener(this); 
} 

public boolean onQueryTextChange(String newText) { 
    // mStatusView.setText("Query = " + newText); 
    return false; 
} 

@Override 
public boolean onOptionsItemSelected(MenuItem item) { 
    switch (item.getItemId()) { 
    case R.id.list: 
     // app icon in action bar clicked; go home 
     Intent intent = new Intent(this, SearchActivity.class); 
     intent.removeExtra("search"); 
     intent.addFlags(Intent.FLAG_ACTIVITY_REORDER_TO_FRONT); 
     startActivity(intent); 
     return true; 
    case R.id.bookmark: 
     intent = new Intent(adasd.this, BookmarkActivity.class); 
     intent.setFlags(Intent.FLAG_ACTIVITY_REORDER_TO_FRONT); 
     startActivity(intent); 
     return true; 

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

public boolean onQueryTextSubmit(String query) { 

    // Extras.createActualDialogueBox(context, "error", url.length()+""); 
    // getPlaces(url); 
    Intent intent = new Intent(this, LoadingActivityForPlaces.class); 
    mBeaconOptionsPoppedUp = false; 
    intent.putExtra("key", query); 
    startActivity(intent); 
    Extras.searched = true; 
    return false; 
} 

public boolean onClose() { 

    return false; 
} 

protected boolean isAlwaysExpanded() { 
    return false; 
} 

@Override 
public void onBackPressed() { 
    // do nothing. 
    if (mBeaconOptionsPoppedUp) { 

     mBeaconOptionsPoppedUp = false; 
    } 
} 

@Override 
public void onResume() { 
    super.onResume(); 
    displayPlaces(); 
} 

@Override 
public void onPause() { 
    super.onPause(); 
    Extras.activityPaused(); 
} 

@Override 
protected void onNewIntent(Intent intent) { 
    super.onNewIntent(intent); 

} 

@Override 
public void onSaveInstanceState(Bundle bundle) { 

} 

@Override 
protected void onRestoreInstanceState(Bundle savedInstanceState) { 

} 

private void displayPlaces() { 
    if (!Extras.trialMode) { 
     // TODO Auto-generated method stub 
     if (placesMarkers != null) { 
      removeMarkers(placesMarkers); 
     } 
     placesMarkers = new ArrayList<Marker>(); 
     for (GooglePlace i : Extras.googlePlaces) { 
      Marker m = mMap.addMarker(new MarkerOptions() 
        .position(i.getPosition()).title(i.getTitle()) 
        .snippet(i.getDescription())); 
      if (i.equals(Extras.currentGooglePlace)) { 

       m.showInfoWindow(); 
      } 
      placesMarkers.add(m); 

     } 

     for (GooglePlace i : Extras.cortesPlaces) { 
      Marker m = mMap.addMarker(new MarkerOptions() 
        .position(i.getPosition()).title(i.getTitle()) 
        .snippet(i.getDescription())); 
      if (i.equals(Extras.currentGooglePlace)) { 

       m.showInfoWindow(); 
      } 
      placesMarkers.add(m); 

     } 
    } 
} 

}

以下附加功能是静态对象的类。当访问displayPlaces（）函数时，该应用程序崩溃。 When Extras.GooglePlaces object is access a 空指针异常被引发。我已经在其他一些活动中初始化了这个对象，但是当用户在USB模式之间切换时，它会得到Null，因此会出现空指针异常。

Answer 1

A NullPointerException在您的代码中不是"an issue in Google Maps API"。

我建议不要使用static关键字，除了常量，嵌套类和有时工厂方法。这包括单身反模式。

您将不得不使用您的应用程序体系结构。 chopchop的建议是一个好的开始。您可能需要查看我的回答中的一些问题以解决无关问题：https://*.com/a/16335191/2183804