我使用mapview的活动会随机崩溃。我认为所有可能的空变量都被处理，但是十分之一，它们不是。我已经附上了我的活动和错误。
public class HomeActivity extends MapActivity {
boolean pickup = false;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.home);
findViewById(R.id.searchBar).setVisibility(View.VISIBLE);
findViewById(R.id.searchBar).setOnClickListener(new OnClickListener(){
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
//load new dialog thing with only a onSearchRequested() thing, and a bg click that finishes the app
//but also somehow returns the result back to the map??? put intent, here get intent on resume()?? or whatever, debug breakpoints
findViewById(R.id.searchBar).setVisibility(View.GONE);
Intent pseudoSearch = new Intent(HomeGroup.group, PseudoMapSearchActivity.class);
startActivityForResult(pseudoSearch, 0);
}
});
// initialize the map and set the default location
MapView map = (MapView) findViewById(R.id.map);
//map.setBuiltInZoomControls(true);
map.setSatellite(false);
MapController controller = map.getController();
List<Overlay> overlays = map.getOverlays();
Drawable drawable = this.getResources().getDrawable(
R.drawable.origin_pin);
HomeItemizedOverlay overlay = new HomeItemizedOverlay(drawable,
HomeGroup.group);
overlays.clear();
overlays.add(overlay);
controller.setZoom(17);
map.postInvalidate();
final LocationManager locator = (LocationManager) this
.getSystemService(Context.LOCATION_SERVICE);
String provider = "";
// check what location provider is available
if (!locator.isProviderEnabled(LocationManager.GPS_PROVIDER)) {
//provider = LocationManager.GPS_PROVIDER;
//force user to turn on gps
Criteria criteria = new Criteria();
criteria.setAccuracy(Criteria.ACCURACY_FINE);
criteria.setPowerRequirement(Criteria.POWER_HIGH);
LocationManager lm = (LocationManager)getSystemService(Context.LOCATION_SERVICE);
provider = lm.getBestProvider(criteria, true);
} else {
provider = LocationManager.GPS_PROVIDER;
}
// get the current location
if (provider != null) {
//setLocation(locator.getLastKnownLocation(provider));
final LocationListener listener = new LocationListener() {
@Override
public void onLocationChanged(Location location) {
setLocation(location);
locator.removeUpdates(this);
}
@Override
public void onProviderDisabled(String provider) {
}
@Override
public void onProviderEnabled(String provider) {
}
@Override
public void onStatusChanged(String provider, int status,
Bundle extras) {
}
};
locator.requestLocationUpdates(provider, 15000, 0, listener);
} else {
Toast toast = Toast.makeText(HomeActivity.this,
"Location provider could not be found.", Toast.LENGTH_LONG);
toast.show();
}
}
/**
* Performs any action required to update the current location displayed on
* the home map.
*
* @param location
* A {@link Location} object with the new location to display.
*/
private void setLocation(Location location) {
if (location == null) {
return;
}
if(AndroidHelper.pickup == false)
{
MapView map = (MapView) findViewById(R.id.map);
map.setSatellite(false);
MapController controller = map.getController();
List<Overlay> overlays = map.getOverlays();
Drawable drawable = this.getResources().getDrawable(
R.drawable.origin_pin);
HomeItemizedOverlay overlay = new HomeItemizedOverlay(drawable,
HomeGroup.group);
int latitude = (int) (location.getLatitude() * 1e6);
int longitude = (int) (location.getLongitude() * 1e6);
GeoPoint point = new GeoPoint(latitude, longitude);
if(point!=null)
{
OverlayItem item = new OverlayItem(point, "Current Location",
"This is where you are currently located.");
overlay.setOrigin(item);
}
overlays.clear();
overlays.add(overlay);
controller.animateTo(point);
controller.setZoom(18);
map.postInvalidate();
}
}
这是我的HomeItemizedOverlay类
public class HomeItemizedOverlay extends ItemizedOverlay<OverlayItem> {
private Map<Integer, OverlayItem> overlays = null;
private Context context = null;
private static final int ORIGIN = 0;
private static final int DESTINATION = 1;
public HomeItemizedOverlay(Drawable defaultMarker) {
super(boundCenterBottom(defaultMarker));
this.overlays = new HashMap<Integer, OverlayItem>();
}
public HomeItemizedOverlay(Drawable defaultMarker, Context context) {
this(defaultMarker);
this.context = context;
}
/**
* Set an {@link OverlayItem} to be the origin and calls {@link #populate()}
* to create the overlay.
*
* @param item
* An item to add to the overlay.
*/
public void setOrigin(OverlayItem item) {
this.overlays.put(ORIGIN, item);
populate();
}
/**
* Adds an {@link OverlayItem} to be the destination and calls
* {@link #populate()} to create the overlay.
*
* @param item
* An item to add to the overlay.
*/
public void setDestination(OverlayItem item) {
this.overlays.put(DESTINATION, item);
populate();
}
@Override
protected OverlayItem createItem(int i) {
return this.overlays.get(i);
}
@Override
public int size() {
return this.overlays.size();
}
@Override
protected boolean onTap(int index) {
OverlayItem item = this.overlays.get(index);
//think this causes crashes
AlertDialog.Builder dialog = new AlertDialog.Builder(this.context);
dialog.setTitle(item.getTitle());
dialog.setMessage(item.getSnippet());
dialog.show();
return true;
}
}
这个logcat错误没有在我的代码中提到一行，所以我真的不明白它在哪里破解。这种情况大约发生在10次中。
11-15 13:47:13.192: E/AndroidRuntime(3585): FATAL EXCEPTION: main
11-15 13:47:13.192: E/AndroidRuntime(3585): java.lang.NullPointerException
11-15 13:47:13.192: E/AndroidRuntime(3585): at com.google.android.maps.ItemizedOverlay.getItemsAtLocation(ItemizedOverlay.java:617)
11-15 13:47:13.192: E/AndroidRuntime(3585): at com.google.android.maps.ItemizedOverlay.getItemAtLocation(ItemizedOverlay.java:586)
11-15 13:47:13.192: E/AndroidRuntime(3585): at com.google.android.maps.ItemizedOverlay.handleMotionEvent(ItemizedOverlay.java:498)
11-15 13:47:13.192: E/AndroidRuntime(3585): at com.google.android.maps.ItemizedOverlay.onTouchEvent(ItemizedOverlay.java:572)
11-15 13:47:13.192: E/AndroidRuntime(3585): at com.google.android.maps.OverlayBundle.onTouchEvent(OverlayBundle.java:63)
11-15 13:47:13.192: E/AndroidRuntime(3585): at com.google.android.maps.MapView.onTouchEvent(MapView.java:679)
11-15 13:47:13.192: E/AndroidRuntime(3585): at android.view.View.dispatchTouchEvent(View.java:3882)
11-15 13:47:13.192: E/AndroidRuntime(3585): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:903)
11-15 13:47:13.192: E/AndroidRuntime(3585): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:869)
11-15 13:47:13.192: E/AndroidRuntime(3585): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:869)
11-15 13:47:13.192: E/AndroidRuntime(3585): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:869)
11-15 13:47:13.192: E/AndroidRuntime(3585): at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchTouchEvent(PhoneWindow.java:1691)
11-15 13:47:13.192: E/AndroidRuntime(3585): at com.android.internal.policy.impl.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1125)
11-15 13:47:13.192: E/AndroidRuntime(3585): at android.app.Activity.dispatchTouchEvent(Activity.java:2096)
11-15 13:47:13.192: E/AndroidRuntime(3585): at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:1675)
11-15 13:47:13.192: E/AndroidRuntime(3585): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:869)
11-15 13:47:13.192: E/AndroidRuntime(3585): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:869)
11-15 13:47:13.192: E/AndroidRuntime(3585): at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchTouchEvent(PhoneWindow.java:1691)
11-15 13:47:13.192: E/AndroidRuntime(3585): at com.android.internal.policy.impl.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1125)
11-15 13:47:13.192: E/AndroidRuntime(3585): at android.app.Activity.dispatchTouchEvent(Activity.java:2096)
11-15 13:47:13.192: E/AndroidRuntime(3585): at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:1675)
11-15 13:47:13.192: E/AndroidRuntime(3585): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:869)
11-15 13:47:13.192: E/AndroidRuntime(3585): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:869)
11-15 13:47:13.192: E/AndroidRuntime(3585): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:869)
11-15 13:47:13.192: E/AndroidRuntime(3585): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:869)
11-15 13:47:13.192: E/AndroidRuntime(3585): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:869)
11-15 13:47:13.192: E/AndroidRuntime(3585): at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchTouchEvent(PhoneWindow.java:1691)
11-15 13:47:13.192: E/AndroidRuntime(3585): at com.android.internal.policy.impl.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1125)
11-15 13:47:13.192: E/AndroidRuntime(3585): at android.app.Activity.dispatchTouchEvent(Activity.java:2096)
11-15 13:47:13.192: E/AndroidRuntime(3585): at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:1675)
11-15 13:47:13.192: E/AndroidRuntime(3585): at android.view.ViewRoot.deliverPointerEvent(ViewRoot.java:2204)
11-15 13:47:13.192: E/AndroidRuntime(3585): at android.view.ViewRoot.handleMessage(ViewRoot.java:1888)
11-15 13:47:13.192: E/AndroidRuntime(3585): at android.os.Handler.dispatchMessage(Handler.java:99)
11-15 13:47:13.192: E/AndroidRuntime(3585): at android.os.Looper.loop(Looper.java:130)
11-15 13:47:13.192: E/AndroidRuntime(3585): at android.app.ActivityThread.main(ActivityThread.java:3683)
11-15 13:47:13.192: E/AndroidRuntime(3585): at java.lang.reflect.Method.invokeNative(Native Method)
11-15 13:47:13.192: E/AndroidRuntime(3585): at java.lang.reflect.Method.invoke(Method.java:507)
11-15 13:47:13.192: E/AndroidRuntime(3585): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
11-15 13:47:13.192: E/AndroidRuntime(3585): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
11-15 13:47:13.192: E/AndroidRuntime(3585): at dalvik.system.NativeStart.main(Native Method)
答案 0 :(得分：2)
在构造函数中调用populate()后，请立即尝试调用super。还有其他类似问题的投诉http://code.google.com/p/android/issues/detail?id=2035。
populate的javadoc说：
对新的ItemizedOverlay执行所有处理的实用程序方法。子类通过createItem（int）方法提供Items。在调用任何其他内容之前，子类应该在有数据时立即调用它。
老实说不是很有帮助，但我相信你必须在你的构造函数中调用这个方法。