嘿，我是Android的新手在这里我正在使用一个面向地图的项目现在我遇到了一个问题，当我触摸覆盖项时它显示在log-cat中的空指针异常我无法理解它是什么意思。在这里我有两个类MyPlacemapActivity和AddItemizedOverlay有人请帮我解决这个问题，这里是我的班级代码
AddItemizedOverlay.java
public class AddItemizedOverlay extends ItemizedOverlay<OverlayItem> {
private ArrayList<OverlayItem> mapOverlays = new ArrayList<OverlayItem>();
private Context context;
String reference;
private String username;
String p_u_name;
public AddItemizedOverlay(Drawable defaultMarker) {
super(boundCenterBottom(defaultMarker));
}
public AddItemizedOverlay(Drawable defaultMarker, Context context) {
this(defaultMarker);
this.context = context;
}
public AddItemizedOverlay(Drawable defaultMarker, Context context,String StringData) {
this(defaultMarker);
this.context = context;
this.username=StringData;
System.out.println("AdditemizedOverlay:got username:"+username +StringData);
}
@Override
public boolean onTouchEvent(MotionEvent event, MapView mapView)
{
if (event.getAction() == 1) {
GeoPoint geopoint = mapView.getProjection().fromPixels(
(int) event.getX(),
(int) event.getY());
}
return false;
}
@Override
protected OverlayItem createItem(int i) {
return mapOverlays.get(i);
}
@Override
public int size() {
return mapOverlays.size();
}
@Override
protected boolean onTap(int index) {
OverlayItem item = mapOverlays.get(index);
AlertDialog.Builder dialog = new AlertDialog.Builder(this.context);
reference = item.getSnippet();
username = item.getTitle();
dialog.setTitle("");
dialog.setMessage("Do you want ot park here ?");
System.out.println("Inside Additemized:"+reference+username);
dialog.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
SharedPreferences prefs = context.getSharedPreferences("myprefs", 0);
SharedPreferences.Editor editor =prefs.edit();
editor.putString("KEY_REFERENCE", reference);
editor.putString("KEY_USERNAME", username);
editor.commit();
Intent intent = new Intent(context, SinglePlaceActivity.class);
intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
context.startActivity(intent);
}
})
.setNegativeButton("No",new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog,int id) {
// if this button is clicked, just close
// the dialog box and do nothing
dialog.cancel();
// MainActivity.this.finish();
}
});
dialog.show();
return true;
}
public void addOverlay(OverlayItem overlay) {
mapOverlays.add(overlay);
}
public void populateNow(){
this.populate();
}
}
MyPlacemapActivity.java
public class MyPlacemapActivity extends MapActivity {
// Nearest places
PlacesList nearPlaces;
// Map view
MapView mapView;
// Map overlay items
List<Overlay> mapOverlays;
AddItemizedOverlay itemizedOverlay;
MyItemizedOverlay myitemizedoverlay;
FindItemizedOverlay finditemizedoverlay;
GeoPoint geoPoint;
// Map controllers
MapController mc;
Drawable defaultMarker,drawable;
double latitude;
double longitude;
OverlayItem overlayitem;
String p_u_name;
String type,keyword;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.map_places);
SharedPreferences prefs = getSharedPreferences("myprefs", 0);
p_u_name = prefs.getString("KEY_USERNAME", "");
Intent i = getIntent();
// Users current geo location
String user_latitude = i.getStringExtra("user_latitude");
String user_longitude = i.getStringExtra("user_longitude");
type = i.getExtras().getString("KEY_TYPES");
keyword =i.getExtras().getString("KEY_KEYWORD");
System.out.println("sarath"+user_latitude + user_longitude + type);
// Nearplaces list
nearPlaces = (PlacesList) i.getSerializableExtra("near_places");
mapView = (MapView) findViewById(R.id.mapView);
mapView.setBuiltInZoomControls(true);
mapOverlays = mapView.getOverlays();
// Geopoint to place on map
geoPoint = new GeoPoint((int) (Double.parseDouble(user_latitude) * 1E6),(int) (Double.parseDouble(user_longitude) * 1E6));
// Drawable marker icon
Drawable drawable_user = this.getResources().getDrawable(R.drawable.mark_red);
myitemizedoverlay = new MyItemizedOverlay(drawable_user, this);
// Map overlay item
overlayitem = new OverlayItem(geoPoint, "Your Location","That is you!");
myitemizedoverlay.addOverlay(overlayitem);
mapOverlays.add(myitemizedoverlay);
myitemizedoverlay.populateNow();
System.out.println("keyword:"+keyword+"type:"+type);
//----------------------------------------------------------------------------------------------------------
// Drawable marker icon
if(type.equalsIgnoreCase("gas_station")&&keyword.equalsIgnoreCase("gas_station")){
drawable= this.getResources().getDrawable(R.drawable.mark_gasstation);
finditemizedoverlay = new FindItemizedOverlay(drawable);
mc = mapView.getController();
// These values are used to get map boundary area
// The area where you can see all the markers on screen
int minLat = Integer.MAX_VALUE;
int minLong = Integer.MAX_VALUE;
int maxLat = Integer.MIN_VALUE;
int maxLong = Integer.MIN_VALUE;
// check for null in case it is null
if (nearPlaces.results != null) {
// loop through all the places
for (Place mplace : nearPlaces.results) {
latitude = mplace.geometry.location.lat; // latitude
longitude = mplace.geometry.location.lng; // longitude
// Geopoint to place on map
geoPoint = new GeoPoint((int) (latitude * 1E6),
(int) (longitude * 1E6));
// Map overlay item
overlayitem = new OverlayItem(geoPoint,p_u_name,mplace.reference);
finditemizedoverlay.addOverlay(overlayitem);
// calculating map boundary area
minLat = (int) Math.min( geoPoint.getLatitudeE6(), minLat );
minLong = (int) Math.min( geoPoint.getLongitudeE6(), minLong);
maxLat = (int) Math.max( geoPoint.getLatitudeE6(), maxLat );
maxLong = (int) Math.max( geoPoint.getLongitudeE6(), maxLong );
}
mapOverlays.add(finditemizedoverlay);
// showing all overlay items
finditemizedoverlay.populateNow();
}
// Adjusting the zoom level so that you can see all the markers on map
mapView.getController().zoomToSpan(Math.abs( minLat - maxLat ), Math.abs( minLong - maxLong ));
// Showing the center of the map
mc.animateTo(new GeoPoint((maxLat + minLat)/2, (maxLong + minLong)/2 ));
mapView.postInvalidate();
}
else if(type.equalsIgnoreCase("shopping_mall")&&keyword.equalsIgnoreCase("shopping_mall")){
drawable= this.getResources().getDrawable(R.drawable.mark_shopping);
finditemizedoverlay = new FindItemizedOverlay(drawable);
mc = mapView.getController();
// These values are used to get map boundary area
// The area where you can see all the markers on screen
int minLat = Integer.MAX_VALUE;
int minLong = Integer.MAX_VALUE;
int maxLat = Integer.MIN_VALUE;
int maxLong = Integer.MIN_VALUE;
// check for null in case it is null
if (nearPlaces.results != null) {
// loop through all the places
for (Place mplace : nearPlaces.results) {
latitude = mplace.geometry.location.lat; // latitude
longitude = mplace.geometry.location.lng; // longitude
// Geopoint to place on map
geoPoint = new GeoPoint((int) (latitude * 1E6),
(int) (longitude * 1E6));
// Map overlay item
overlayitem = new OverlayItem(geoPoint,p_u_name,mplace.reference);
finditemizedoverlay.addOverlay(overlayitem);
// calculating map boundary area
minLat = (int) Math.min( geoPoint.getLatitudeE6(), minLat );
minLong = (int) Math.min( geoPoint.getLongitudeE6(), minLong);
maxLat = (int) Math.max( geoPoint.getLatitudeE6(), maxLat );
maxLong = (int) Math.max( geoPoint.getLongitudeE6(), maxLong );
}
mapOverlays.add(finditemizedoverlay);
// showing all overlay items
finditemizedoverlay.populateNow();
}
// Adjusting the zoom level so that you can see all the markers on map
mapView.getController().zoomToSpan(Math.abs( minLat - maxLat ), Math.abs( minLong - maxLong ));
// Showing the center of the map
mc.animateTo(new GeoPoint((maxLat + minLat)/2, (maxLong + minLong)/2 ));
mapView.postInvalidate();
}
else if(type.equalsIgnoreCase("restaurant")&&keyword.equalsIgnoreCase("restaurant")){
drawable= this.getResources().getDrawable(R.drawable.mark_restaurant_blue);
finditemizedoverlay = new FindItemizedOverlay(drawable);
mc = mapView.getController();
// These values are used to get map boundary area
// The area where you can see all the markers on screen
int minLat = Integer.MAX_VALUE;
int minLong = Integer.MAX_VALUE;
int maxLat = Integer.MIN_VALUE;
int maxLong = Integer.MIN_VALUE;
// check for null in case it is null
if (nearPlaces.results != null) {
// loop through all the places
for (Place mplace : nearPlaces.results) {
latitude = mplace.geometry.location.lat; // latitude
longitude = mplace.geometry.location.lng; // longitude
// Geopoint to place on map
geoPoint = new GeoPoint((int) (latitude * 1E6),
(int) (longitude * 1E6));
// Map overlay item
overlayitem = new OverlayItem(geoPoint,p_u_name,mplace.reference);
finditemizedoverlay.addOverlay(overlayitem);
// calculating map boundary area
minLat = (int) Math.min( geoPoint.getLatitudeE6(), minLat );
minLong = (int) Math.min( geoPoint.getLongitudeE6(), minLong);
maxLat = (int) Math.max( geoPoint.getLatitudeE6(), maxLat );
maxLong = (int) Math.max( geoPoint.getLongitudeE6(), maxLong );
}
mapOverlays.add(finditemizedoverlay);
// showing all overlay items
finditemizedoverlay.populateNow();
}
// Adjusting the zoom level so that you can see all the markers on map
mapView.getController().zoomToSpan(Math.abs( minLat - maxLat ), Math.abs( minLong - maxLong ));
// Showing the center of the map
mc.animateTo(new GeoPoint((maxLat + minLat)/2, (maxLong + minLong)/2 ));
mapView.postInvalidate();
}
else if(type.equalsIgnoreCase("parking")&&keyword.equalsIgnoreCase("garage parking")){
drawable= this.getResources().getDrawable(R.drawable.mark_blue);
itemizedOverlay = new AddItemizedOverlay(drawable);
mc = mapView.getController();
// These values are used to get map boundary area
// The area where you can see all the markers on screen
int minLat = Integer.MAX_VALUE;
int minLong = Integer.MAX_VALUE;
int maxLat = Integer.MIN_VALUE;
int maxLong = Integer.MIN_VALUE;
// check for null in case it is null
if (nearPlaces.results != null) {
// loop through all the places
for (Place mplace : nearPlaces.results) {
latitude = mplace.geometry.location.lat; // latitude
longitude = mplace.geometry.location.lng; // longitude
// Geopoint to place on map
geoPoint = new GeoPoint((int) (latitude * 1E6),
(int) (longitude * 1E6));
// Map overlay item
overlayitem = new OverlayItem(geoPoint,p_u_name,mplace.reference);
System.out.println("inside mymap:"+mplace.reference+p_u_name);
itemizedOverlay.addOverlay(overlayitem);
// calculating map boundary area
minLat = (int) Math.min( geoPoint.getLatitudeE6(), minLat );
minLong = (int) Math.min( geoPoint.getLongitudeE6(), minLong);
maxLat = (int) Math.max( geoPoint.getLatitudeE6(), maxLat );
maxLong = (int) Math.max( geoPoint.getLongitudeE6(), maxLong );
}
mapOverlays.add(itemizedOverlay);
// showing all overlay items
itemizedOverlay.populateNow();
}
// Adjusting the zoom level so that you can see all the markers on map
mapView.getController().zoomToSpan(Math.abs( minLat - maxLat ), Math.abs( minLong - maxLong ));
// Showing the center of the map
mc.animateTo(new GeoPoint((maxLat + minLat)/2, (maxLong + minLong)/2 ));
mapView.postInvalidate();
}
else if(type.equalsIgnoreCase("parking")&&keyword.equalsIgnoreCase("street parking")){
drawable= this.getResources().getDrawable(R.drawable.mark_blue);
itemizedOverlay = new AddItemizedOverlay(drawable);
mc = mapView.getController();
// These values are used to get map boundary area
// The area where you can see all the markers on screen
int minLat = Integer.MAX_VALUE;
int minLong = Integer.MAX_VALUE;
int maxLat = Integer.MIN_VALUE;
int maxLong = Integer.MIN_VALUE;
// check for null in case it is null
if (nearPlaces.results != null) {
// loop through all the places
for (Place mplace : nearPlaces.results) {
latitude = mplace.geometry.location.lat; // latitude
longitude = mplace.geometry.location.lng; // longitude
// Geopoint to place on map
geoPoint = new GeoPoint((int) (latitude * 1E6),
(int) (longitude * 1E6));
// Map overlay item
overlayitem = new OverlayItem(geoPoint,p_u_name,mplace.reference);
System.out.println("inside mymap:"+mplace.reference +p_u_name);
itemizedOverlay.addOverlay(overlayitem);
// calculating map boundary area
minLat = (int) Math.min( geoPoint.getLatitudeE6(), minLat );
minLong = (int) Math.min( geoPoint.getLongitudeE6(), minLong);
maxLat = (int) Math.max( geoPoint.getLatitudeE6(), maxLat );
maxLong = (int) Math.max( geoPoint.getLongitudeE6(), maxLong );
}
mapOverlays.add(itemizedOverlay);
// showing all overlay items
itemizedOverlay.populateNow();
}
// Adjusting the zoom level so that you can see all the markers on map
mapView.getController().zoomToSpan(Math.abs( minLat - maxLat ), Math.abs( minLong - maxLong ));
// Showing the center of the map
mc.animateTo(new GeoPoint((maxLat + minLat)/2, (maxLong + minLong)/2 ));
mapView.postInvalidate();
}
else
{
AlertDialog.Builder builder = new AlertDialog.Builder(MyPlacemapActivity.this);
builder.setTitle("Connection Error.");
builder.setMessage("Try again?.")
.setCancelable(false)
.setPositiveButton("OK", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int id) {
Intent u = new Intent(getApplicationContext(),Find_TabActivity.class);
startActivity(u);
dialog.dismiss();
}
});
AlertDialog alert = builder.create();
alert.show();
}
}
@Override
protected boolean isRouteDisplayed() {
return false;
}
}
答案 0 :(得分：2)
问题出在以下几行：
finditemizedoverlay = new FindItemizedOverlay(drawable);
您正在初始化ItemizedOverlay而未传递onTap()方法创建AletDialo所需的上下文。
您应该将其替换为：
finditemizedoverlay = new FindItemizedOverlay(drawable, this);
Note:如果你把logcat放在你的问题中会有所帮助。
问候。