我在这里陷入了一个奇怪的境地，它是偶然发生的。我目前正在使用 Google Map APIs for Android v2 来显示 map fragment 。一切都运行良好，除了当用户在 USB 模式之间切换时应用程序崩溃。
问题是，我无法保存某些对象，因为在这种情况下我无法覆盖 onSaveInstanceState()。这是一个issue在谷歌地图 API 中。我遇到了 Null-Pointer-Exception。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
只有当我恢复 map Activity 时应用程序才会崩溃，否则应用程序的其余部分工作正常。任何帮助将不胜感激。
编辑 添加修剪的 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);
}
}
}
这里的 Extras 是一个带有静态对象的类。应用程序在访问 displayPlaces() 函数时崩溃。当访问 Extras.GooglePlaces 对象时，将抛出一个 Null-pointer-exception。我已经在其他一些 Activity 中初始化了这个对象，但是当用户在 USB 模式之间切换时，它得到 Null 并因此出现空指针异常。
最佳答案
代码中的 NullPointerException 不是“Google Maps API 中的问题”。
我建议不要使用 static 关键字，除了常量、嵌套类和有时是工厂方法。这包括单例反模式。
您将不得不使用您的应用程序架构。 chopchop 的建议是一个好的开始。您可能想在此处检查我对不相关问题的回答中的一些要点:https://stackoverflow.com/a/16335191/2183804
关于android - 谷歌地图(谷歌地图 Android v2) Activity 在切换 USB 模式时崩溃，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/16417839/