Question

基本上我使用mapview在我的应用程序中显示地图。意味着不像大多数地图应用那样使用片段但是我在向地图添加标记时遇到了问题。请帮帮我。

这是我的编码

private static final int GPS_ERROR_DIALOG_REQUEST = 9001;
MapView mMapView;
GoogleMap map;
Context CTX = this;

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

    if (servicesOK()) {
        setContentView(R.layout.parents);
        mMapView = (MapView) findViewById(R.id.map);
        mMapView.onCreate(savedInstanceState);
        Toast.makeText(this, "Ready to map!", Toast.LENGTH_SHORT).show();
        map.addMarker(new MarkerOptions()
                .position(new LatLng( 4.588946, 101.125293))
                .title("You are here"));
    }
    else
    {
        Toast.makeText(this, "Not ready to map!", Toast.LENGTH_SHORT).show();
    }

    Button AddUser = (Button) findViewById(R.id.user_reg);
    Button KidsDelete = (Button) findViewById(R.id.user_del);

    AddUser.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            startActivity(new Intent(Parents.this, AddUser.class));
        }
    });
    KidsDelete.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            startActivity(new Intent(Parents.this, KidsDelete.class));
        }
    });
}

public boolean servicesOK() {

    int isAvailable = GoogleApiAvailability.getInstance().isGooglePlayServicesAvailable(CTX);

    if (isAvailable == ConnectionResult.SUCCESS) {
        return true;
    } else if (GoogleApiAvailability.getInstance().isUserResolvableError(isAvailable)) {
        Dialog dialog = GoogleApiAvailability.getInstance().getErrorDialog(this, isAvailable, GPS_ERROR_DIALOG_REQUEST);
        dialog.show();
    } else {
        Toast.makeText(this, "Can't connect to Google Play services", Toast.LENGTH_SHORT).show();
    }
    return false;

}

//For mapView
@Override
protected void onDestroy() {
    super.onDestroy();
    mMapView.onDestroy();
}

@Override
public void onLowMemory() {
    super.onLowMemory();
    mMapView.onLowMemory();
}

@Override
protected void onPause() {
    super.onPause();
    mMapView.onPause();
}


@Override
protected void onResume() {
    super.onResume();
    mMapView.onResume();
}

@Override
protected void onSaveInstanceState(Bundle outstate) {
    super.onSaveInstanceState(outstate);
    mMapView.onSaveInstanceState(outstate);
}

这是错误

E/AndroidRuntime: FATAL EXCEPTION: main
                  Process: com.example.moon.mykidstracker, PID: 3031
                  java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.moon.mykidstracker/com.example.moon.mykidstracker.Parents}: java.lang.NullPointerException: Attempt to invoke virtual method 'com.google.android.gms.maps.model.Marker com.google.android.gms.maps.GoogleMap.addMarker(com.google.android.gms.maps.model.MarkerOptions)' on a null object reference
                      at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2416)
                      at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
                      at android.app.ActivityThread.-wrap11(ActivityThread.java)
                      at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
                      at android.os.Handler.dispatchMessage(Handler.java:102)
                      at android.os.Looper.loop(Looper.java:148)
                      at android.app.ActivityThread.main(ActivityThread.java:5417)
                      at java.lang.reflect.Method.invoke(Native Method)
                      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
                      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
                   Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'com.google.android.gms.maps.model.Marker com.google.android.gms.maps.GoogleMap.addMarker(com.google.android.gms.maps.model.MarkerOptions)' on a null object reference
                      at com.example.moon.mykidstracker.Parents.onCreate(Parents.java:35)
                      at android.app.Activity.performCreate(Activity.java:6237)
                      at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1107)
                      at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2369)
                      at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476) 
                      at android.app.ActivityThread.-wrap11(ActivityThread.java) 
                      at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344) 
                      at android.os.Handler.dispatchMessage(Handler.java:102) 
                      at android.os.Looper.loop(Looper.java:148) 
                      at android.app.ActivityThread.main(ActivityThread.java:5417) 
                      at java.lang.reflect.Method.invoke(Native Method) 
                      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) 
                      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)

Answer 1

在您的活动/片段中实施OnMapReadyCallback。

比onMapReady方法

@Override
    public void onMapReady(GoogleMap googleMap) {
        mMap = googleMap;
        if (mMap != null) {
            marker = mMap.addMarker(new MarkerOptions()
                    .position(latLng).title(place_name)
                    .icon(BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_CYAN))
                    .draggable(false).visible(true));
        }
    }

Answer 2

   -----------------------
         map = yourMapView.getMap();

如何将标记添加到MapView

2 个答案: