java.lang.RuntimeException：无法启动活动ComponentInfo {in.jainrishabh.noteelite / in.jainrishabh.noteelite.MapView}：java.lang.NullPointerException：尝试调用虚方法'void com.google.android.gms空对象引用上的.maps.GoogleMap.setOnMapClickListener（com.google.android.gms .maps.GoogleMap $ OnMapClickListener）'
任何人都知道我为什么会得到NullPointer异常
GoogleMap googleMap;
SharedPreferences sharedPreferences;
int locationCount = 0;
private ArrayList<UserDetailsPojo> pojoArrayList;
private float latia;
private float longia;
private Editor editor;
SharedPreferences prefs;
float lat;
float lng;
String lat_temp;
String long_temp;
private ListView userNamesListView;
private ListAdapter userListAdapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_map_view);
prefs = this.getSharedPreferences("sharedpref", Context.MODE_PRIVATE);
latia = prefs.getFloat("latitude", -34);
longia = prefs.getFloat("longitude", 151);
LatLng myLocation = new LatLng(latia, longia);
pojoArrayList = new ArrayList<UserDetailsPojo>();
// For the third argument, we need a List that contains Strings.
//We decided to display undergraduates names on the ListView.
//Therefore we need to create List that contains undergraduates names
userListAdapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, populateList());
//Toast.makeText(getApplicationContext(), "lati is:"+latia, Toast.LENGTH_LONG).show();
// Getting Google Play availability status
int status = GooglePlayServicesUtil.isGooglePlayServicesAvailable(getBaseContext());
// Showing status
if(status!=ConnectionResult.SUCCESS){ // Google Play Services are not available
int requestCode = 10;
Dialog dialog = GooglePlayServicesUtil.getErrorDialog(status, this, requestCode);
dialog.show();
}else { // Google Play Services are available
// Getting reference to the SupportMapFragment of activity_main.xml
MapFragment fm = (MapFragment) getFragmentManager().findFragmentById(R.id.map);
// Getting GoogleMap object from the fragment
googleMap = fm.getMap();
// Enabling MyLocation Layer of Google Map
googleMap.setMyLocationEnabled(true);
// Opening the sharedPreferences object
sharedPreferences = getSharedPreferences("location", -34);
// Getting number of locations already stored
locationCount = sharedPreferences.getInt("locationCount", 151);
// Getting stored zoom level if exists else return 0
String zoom = sharedPreferences.getString("zoom", "0");
// If locations are already saved
if(locationCount!=0){
String lat = "";
String lng = "";
// Iterating through all the locations stored
for(int i=0;i<locationCount;i++){
// Getting the latitude of the i-th location
lat = lat_temp;
// Getting the longitude of the i-th location
lng = long_temp;
// Drawing marker on the map
drawMarker(new LatLng(Double.parseDouble(lat), Double.parseDouble(lng)));
}
// Moving CameraPosition to last clicked position
googleMap.moveCamera(CameraUpdateFactory.newLatLng(new LatLng(Double.parseDouble(lat), Double.parseDouble(lng))));
//googleMap.moveCamera(CameraUpdateFactory.newLatLngZoom(myLocation, 13));
// Setting the zoom level in the map on last position is clicked
googleMap.animateCamera(CameraUpdateFactory.zoomTo(15));
}
}
googleMap.setOnMapClickListener(new OnMapClickListener() {
@Override
public void onMapClick(LatLng point) {
locationCount++;
// Drawing marker on the map
drawMarker(point);
/** Opening the editor object to write data to sharedPreferences */
SharedPreferences.Editor editor = sharedPreferences.edit();
// Storing the latitude for the i-th location
editor.putString("lat"+ Integer.toString((locationCount-1)), Double.toString(point.latitude));
// Storing the longitude for the i-th location
editor.putString("lng"+ Integer.toString((locationCount-1)), Double.toString(point.longitude));
// Storing the count of locations or marker count
editor.putInt("locationCount", locationCount);
/** Storing the zoom level to the shared preferences */
editor.putString("zoom", Float.toString(googleMap.getCameraPosition().zoom));
/** Saving the values stored in the shared preferences */
editor.commit();
Toast.makeText(getBaseContext(), "Marker is added to the Map", Toast.LENGTH_SHORT).show();
}
});
googleMap.setOnMapLongClickListener(new OnMapLongClickListener() {
@Override
public void onMapLongClick(LatLng point) {
// Removing the marker and circle from the Google Map
googleMap.clear();
// Opening the editor object to delete data from sharedPreferences
SharedPreferences.Editor editor = sharedPreferences.edit();
// Clearing the editor
editor.clear();
// Committing the changes
editor.commit();
// Setting locationCount to zero
locationCount=0;
}
});
}
private void drawMarker(LatLng point){
// Creating an instance of MarkerOptions
MarkerOptions markerOptions = new MarkerOptions();
// Setting latitude and longitude for the marker
markerOptions.position(point);
// Adding marker on the Google Map
googleMap.addMarker(markerOptions);
}
@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);
return true;
}
public List<String> populateList(){
// We have to return a List which contains only String values. Lets create a List first
List<String> userNamesList = new ArrayList<String>();
// First we need to make contact with the database we have created using the DbHelper class
AndroidOpenDbHelper openHelperClass = new AndroidOpenDbHelper(this);
// Then we need to get a readable database
SQLiteDatabase sqliteDatabase = openHelperClass.getReadableDatabase();
// We need a a guy to read the database query. Cursor interface will do it for us
//(String table, String[] columns, String selection, String[] selectionArgs, String groupBy, String having, String orderBy)
Cursor cursor = sqliteDatabase.query(AndroidOpenDbHelper.TABLE_USER, null, null, null, null, null, null);
// Above given query, read all the columns and fields of the table
startManagingCursor(cursor);
// Cursor object read all the fields. So we make sure to check it will not miss any by looping through a while loop
while (cursor.moveToNext()) {
// In one loop, cursor read one undergraduate all details
// Assume, we also need to see all the details of each and every undergraduate
// What we have to do is in each loop, read all the values, pass them to the POJO class
//and create a ArrayList of undergraduates
//int Time = cursor.getInt(cursor.getColumnIndex(AndroidOpenDbHelper.COLUMN_TIME));
double latia = cursor.getDouble(cursor.getColumnIndex(AndroidOpenDbHelper.COLUMN_LATI));
double longia = cursor.getDouble(cursor.getColumnIndex(AndroidOpenDbHelper.COLUMN_LONGI));
// Finish reading one raw, now we have to pass them to the POJO
UserDetailsPojo ugPojoClass = new UserDetailsPojo();
ugPojoClass.setLati(latia);
ugPojoClass.setLongi(longia);
// Lets pass that POJO to our ArrayList which contains undergraduates as type
pojoArrayList.add(ugPojoClass);
lat_temp = Double.toString(latia);
long_temp = Double.toString(longia);
Log.d("latis1",lat_temp);
Log.d("longis1",long_temp);
}
// If you don't close the database, you will get an error
// sqliteDatabase.close();
return userNamesList;
}
}
块引用
<fragment
android:id="@+id/map"
android:layout_width="wrap_content"
android:layout_height="700dp"
android:layout_weight="4"
android:name="com.google.android.gms.maps.MapFragment"
/>
这是我的Mapview XML
答案 0 :(得分：0)
您可能在实例化之前引用了googleMap变量。尝试更改第一行的GoogleMap googleMap;
相反。
GoogleMap googleMap = new GoogleMap（）;
此外，请务必在else案例中设置setOnMapClickListener，以使其按预期工作。如果地图对象不存在（即Google Play服务不可用），您也不想设置事件监听器。