如何在android编程中的地图上添加标记

时间：2015-06-18 18:43:33

标签： android google-maps

因此，出于某种原因，当我尝试向地理点添加标记时，标记无法显示在给定位置。我尝试研究可能是什么问题，但出于某种原因我的代码似乎遵循我研究的所有内容。有人能引导我朝正确的方向发展吗？ 

import android.content.Context;
import android.location.Criteria;
import android.location.Geocoder;
import android.location.Location;
import android.location.LocationManager;
import android.support.v4.app.FragmentActivity;
import android.os.Bundle;
import android.util.Log;
import android.widget.Toast;
import com.google.android.gms.maps.CameraUpdateFactory;
import com.google.android.gms.maps.GoogleMap;
import com.google.android.gms.maps.SupportMapFragment;
import com.google.android.gms.maps.model.CameraPosition;
import com.google.android.gms.maps.model.LatLng;
import com.google.android.gms.maps.model.MarkerOptions;

import java.text.DecimalFormat;

public class MapsActivity extends FragmentActivity {

private GoogleMap mMap; // Might be null if Google Play services APK is not available.

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_maps);
    setUpMapIfNeeded();
}

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

/**
 * Sets up the map if it is possible to do so (i.e., the Google Play services APK is correctly
 * installed) and the map has not already been instantiated.. This will ensure that we only ever
 * call {@link #setUpMap()} once when {@link #mMap} is not null.
 * <p/>
 * If it isn't installed {@link SupportMapFragment} (and
 * {@link com.google.android.gms.maps.MapView MapView}) will show a prompt for the user to
 * install/update the Google Play services APK on their device.
 * <p/>
 * A user can return to this FragmentActivity after following the prompt and correctly
 * installing/updating/enabling the Google Play services. Since the FragmentActivity may not
 * have been completely destroyed during this process (it is likely that it would only be
 * stopped or paused), {@link #onCreate(Bundle)} may not be called again so we should call this
 * method in {@link #onResume()} to guarantee that it will be called.
 */
private void setUpMapIfNeeded() {
    // Do a null check to confirm that we have not already instantiated the map.
    if (mMap == null) {
        // Try to obtain the map from the SupportMapFragment.
        mMap = ((SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.map))
                .getMap();
        // Check if we were successful in obtaining the map.
        if (mMap != null) {
            setUpMap();
        }
    }
}

/**
 * This is where we can add markers or lines, add listeners or move the camera. In this case, we
 * just add a marker near Africa.
 * <p/>
 * This should only be called once and when we are sure that {@link #mMap} is not null.
 */

private void setUpMap() {

    mMap.addMarker(new MarkerOptions().position(new LatLng(0, 0)).title("Marker").snippet("Snippet"));

    // Enable MyLocation Layer of Google Map
    mMap.setMyLocationEnabled(true);

    // Get LocationManager object from System Service LOCATION_SERVICE
    LocationManager locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);

    // Create a criteria object to retrieve provider
    Criteria criteria = new Criteria();

    // Get the name of the best provider
    String provider = locationManager.getBestProvider(criteria, true);

    // Get Current Location
    Location myLocation = locationManager.getLastKnownLocation(provider);

    // set map type
    mMap.setMapType(GoogleMap.MAP_TYPE_NORMAL);

    // Get latitude of the current location

    Location location = locationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER);

    if (location != null) {
        double longitude = location.getLongitude();
        double latitude = location.getLatitude();


        // Get longitude of the current location

        // Create a LatLng object for the current location
        LatLng latLng = new LatLng(latitude, longitude);

        // Show the current location in Google Map
        mMap.moveCamera(CameraUpdateFactory.newLatLng(latLng));

        // Zoom in the Google Map
        //LatLng myCoordinates = new LatLng(latitude, longitude);
        //CameraUpdate yourLocation = CameraUpdateFactory.newLatLngZoom(myCoordinates, 20);
        //mMap.animateCamera(yourLocation);
        mMap.animateCamera(CameraUpdateFactory.zoomTo(20));
        mMap.addMarker(new MarkerOptions().position(new LatLng(latitude, longitude)).title("You are here!").snippet("Consider yourself located"));


        LatLng toLatLng = new LatLng(40.6937, 73.9859);

        mMap.addMarker(new MarkerOptions().position( new LatLng(40.6937, 73.9859)).title("You location is here!").snippet("Consider it located"));

    }
}



        public void onFinish() {
            // Your code here to do something after the Map is rendered
        }
    }

1 个答案:

答案 0 :(得分：0)

你提到的主要问题是：

  

标记无法显示在给定位置

看起来主要原因是getLastKnownLocation()返回null，因此它永远不会进入将Marker置于当前位置的代码。

您可以设置位置侦听器，而不是调用该方法，该侦听器将显式请求新位置。

我清理了一下你的代码，并让它运行起来。请注意，我删除了getLastKnownLocation()的使用，并将您在那里的逻辑移至onLocationChanged()回调。

我还添加了删除之前＆＃34;当前位置的功能＆＃34;标记，并在每次位置更改时添加新的。

另请注意，在非洲附近的赤道上出现的一个标记是由于这条线，所以我只是评论说：

mMap.addMarker(new MarkerOptions().position(new LatLng(0, 0)).title("Marker").snippet("Snippet"));

以下是完整更新的类代码：

import android.content.Context;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.support.v4.app.FragmentActivity;
import android.os.Bundle;
import com.google.android.gms.maps.CameraUpdateFactory;
import com.google.android.gms.maps.GoogleMap;
import com.google.android.gms.maps.SupportMapFragment;
import com.google.android.gms.maps.model.BitmapDescriptorFactory;
import com.google.android.gms.maps.model.LatLng;
import com.google.android.gms.maps.model.Marker;
import com.google.android.gms.maps.model.MarkerOptions;
import android.location.Criteria;

public class MapsActivity extends FragmentActivity implements LocationListener {

    private GoogleMap mMap; // Might be null if Google Play services APK is not available.
    LocationManager locationManager;
    Marker marker;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_maps);
        setUpMapIfNeeded();
    }

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

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

        //remove location listener
        if (locationManager != null){
            locationManager.removeUpdates(this);
        }

    }

    private void setUpMapIfNeeded() {
        // Do a null check to confirm that we have not already instantiated the map.
        if (mMap == null) {
            // Try to obtain the map from the SupportMapFragment.
            mMap = ((SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.map))
                    .getMap();
            // Check if we were successful in obtaining the map.
            if (mMap != null) {
                setUpMap();
            }
        }
    }

    private void setUpMap() {

        //This was the Marker at equator near Africa
        //mMap.addMarker(new MarkerOptions().position(new LatLng(0, 0)).title("Marker").snippet("Snippet"));

        // Enable MyLocation Layer of Google Map
        mMap.setMyLocationEnabled(true);
        mMap.setMapType(GoogleMap.MAP_TYPE_HYBRID);
        mMap.getUiSettings().setZoomControlsEnabled(true);
        mMap.getUiSettings().setMyLocationButtonEnabled(true);
        mMap.getUiSettings().setCompassEnabled(true);
        mMap.getUiSettings().setRotateGesturesEnabled(true);
        mMap.getUiSettings().setZoomGesturesEnabled(true);

        // Get LocationManager object from System Service LOCATION_SERVICE
        locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);

        if (locationManager.isProviderEnabled(LocationManager.NETWORK_PROVIDER)) {
            locationManager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 1000, 0, this);
        }

        if (locationManager.isProviderEnabled(LocationManager.GPS_PROVIDER)) {
            locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 1000, 0, this);
        }


    }



    public void onFinish() {
        // Your code here to do something after the Map is rendered
    }

    @Override
    public void onLocationChanged(Location location) {

        double longitude = location.getLongitude();
        double latitude = location.getLatitude();

        // Create a LatLng object for the current location
        LatLng latLng = new LatLng(latitude, longitude);

        // Show the current location in Google Map
        mMap.moveCamera(CameraUpdateFactory.newLatLng(latLng));
        mMap.animateCamera(CameraUpdateFactory.zoomTo(15));

        if (marker != null) {
            marker.remove();
        }
        marker = mMap.addMarker(new MarkerOptions().position(new LatLng(latitude, longitude))
                .title("You are here!").snippet("Consider yourself located")
                .icon(BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_MAGENTA)));

    }

    @Override
    public void onStatusChanged(String provider, int status, Bundle extras) {

    }

    @Override
    public void onProviderEnabled(String provider) {

    }

    @Override
    public void onProviderDisabled(String provider) {

    }
}

结果：

Map Image

编辑：

你选择了一个有趣的地方来放置你的硬编码标记。

我用这个替换了标记代码：

    LatLng toLatLng = new LatLng(40.6937, 73.9859);

    // Create a LatLng object for the current location
    LatLng latLng = new LatLng(40.6937, 73.9859);

    // Show the current location in Google Map
    mMap.moveCamera(CameraUpdateFactory.newLatLng(latLng));
    mMap.animateCamera(CameraUpdateFactory.zoomTo(15));

    if (marker != null) {
        marker.remove();
    }
    marker = mMap.addMarker(new MarkerOptions().position(new LatLng(40.6937, 73.9859))
            .title("You are here!").snippet("Consider yourself located")
            .icon(BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_MAGENTA)));

它将标记放在给定位置。请注意，由于卫星图像不同，会产生一些奇怪的效果。

初步结果：

initial

放大看看我们在哪里！

zoomed out

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