在地图上显示点时出错
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【中文标题】在地图上显示点时出错【英文标题】：Error Displaying Point on Maps 【发布时间】：2015-10-23 20:38:52 【问题描述】：我的 android 应用程序有一点问题 我是android编程新手，请帮帮我 这是我的 FirstActivity.java 代码
package com.example.nav;
import android.os.Bundle;
import java.io.IOException;
import java.util.List;
import java.util.Locale;
import android.content.res.TypedArray;
import android.support.v4.app.FragmentActivity;
import android.view.Menu;
import android.content.Intent;
import android.view.Menu;
import android.view.View.OnClickListener;
import android.widget.EditText;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.content.Intent;
import android.location.Location;
import android.location.LocationManager;
import android.provider.Settings;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;
public class FirstActivity extends BaseActivity
private String[] navMenuTitles;
private TypedArray navMenuIcons;
Button btnGPSShowLocation;
Button btnNWShowLocation;
AppLocationService appLocationService;
@Override
protected void onCreate(Bundle savedInstanceState)
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_first);
navMenuTitles = getResources().getStringArray(R.array.nav_drawer_items);
navMenuIcons = getResources().obtainTypedArray(R.array.nav_drawer_icons);
set(navMenuTitles, navMenuIcons);
appLocationService = new AppLocationService(FirstActivity.this);
btnGPSShowLocation = (Button) findViewById(R.id.btnGPSShowLocation);
btnGPSShowLocation.setOnClickListener(new View.OnClickListener()
@Override
public void onClick(View arg0)
Location gpsLocation = appLocationService
.getLocation(LocationManager.GPS_PROVIDER);
if (gpsLocation != null)
double latitude = gpsLocation.getLatitude();
double longitude = gpsLocation.getLongitude();
Toast.makeText(
getApplicationContext(),
"Mobile Location (GPS): \nLatitude: " + latitude
+ "\nLongitude: " + longitude,
Toast.LENGTH_LONG).show();
else
showSettingsAlert("GPS");
);
btnNWShowLocation = (Button) findViewById(R.id.btnNWShowLocation);
btnNWShowLocation.setOnClickListener(new View.OnClickListener()
@Override
public void onClick(View arg0)
Location nwLocation = appLocationService
.getLocation(LocationManager.NETWORK_PROVIDER);
if (nwLocation != null)
double latitude = nwLocation.getLatitude();
double longitude = nwLocation.getLongitude();
Toast.makeText(
getApplicationContext(),
"Mobile Location (NW): \nLatitude: " + latitude
+ "\nLongitude: " + longitude,
Toast.LENGTH_LONG).show();
else
showSettingsAlert("NETWORK");
);
Button btnShow = (Button) findViewById(R.id.btn_show);
btnShow.setOnClickListener(new OnClickListener()
@Override
public void onClick(View arg0)
Location gpsLocation = appLocationService
.getLocation(LocationManager.GPS_PROVIDER);
double latitude = gpsLocation.getLatitude();
double longitude = gpsLocation.getLongitude();
Intent intent = new Intent(getBaseContext(), MapActivity.class);
// Passing latitude and longitude to the MapActiv
intent.putExtra("lat", latitude);
intent.putExtra("lng", longitude);
startActivity(intent);
finish();
);
public void showSettingsAlert(String provider)
AlertDialog.Builder alertDialog = new AlertDialog.Builder(
FirstActivity.this);
alertDialog.setTitle(provider + " SETTINGS");
alertDialog
.setMessage(provider + " is not enabled! Want to go to settings menu?");
alertDialog.setPositiveButton("Settings",
new DialogInterface.OnClickListener()
public void onClick(DialogInterface dialog, int which)
Intent intent = new Intent(
Settings.ACTION_LOCATION_SOURCE_SETTINGS);
FirstActivity.this.startActivity(intent);
);
alertDialog.setNegativeButton("Cancel",
new DialogInterface.OnClickListener()
public void onClick(DialogInterface dialog, int which)
dialog.cancel();
);
alertDialog.show();
@Override
public boolean onCreateOptionsMenu(Menu menu)
getMenuInflater().inflate(R.menu.main, menu);
return true;
这是我的 MapActivity.java 代码
package com.example.nav;
import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
import android.view.Menu;
import com.google.android.gms.maps.CameraUpdate;
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.LatLng;
import com.google.android.gms.maps.model.MarkerOptions;
public class MapActivity extends FragmentActivity
@Override
protected void onCreate(Bundle savedInstanceState)
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_map);
// Receiving latitude from MainActivity screen
double latitude = getIntent().getDoubleExtra("lat", 0);
// Receiving longitude from MainActivity screen
double longitude = getIntent().getDoubleExtra("lng", 0);
LatLng position = new LatLng(latitude, longitude);
// Instantiating MarkerOptions class
MarkerOptions options = new MarkerOptions();
// Setting position for the MarkerOptions
options.position(position);
// Setting title for the MarkerOptions
options.title("Position");
// Setting snippet for the MarkerOptions
options.snippet("Latitude:"+latitude+",Longitude:"+longitude);
// Getting Reference to SupportMapFragment of activity_map.xml
SupportMapFragment fm = (SupportMapFragment)getSupportFragmentManager().findFragmentById(R.id.map);
// Getting reference to google map
GoogleMap googleMap = fm.getMap();
// Adding Marker on the Google Map
googleMap.addMarker(options);
// Creating CameraUpdate object for position
CameraUpdate updatePosition = CameraUpdateFactory.newLatLng(position);
// Creating CameraUpdate object for zoom
CameraUpdate updateZoom = CameraUpdateFactory.zoomBy(4);
// Updating the camera position to the user input latitude and longitude
googleMap.moveCamera(updatePosition);
// Applying zoom to the marker position
googleMap.animateCamera(updateZoom);
@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;
这是我的 appLocationService.java
import android.app.Service;
import android.content.Context;
import android.content.Intent;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.Bundle;
import android.os.IBinder;
public class AppLocationService extends Service implements LocationListener
protected LocationManager locationManager;
Location location;
private static final long MIN_DISTANCE_FOR_UPDATE = 10;
private static final long MIN_TIME_FOR_UPDATE = 1000 * 60 * 2;
public AppLocationService(Context context)
locationManager = (LocationManager) context
.getSystemService(LOCATION_SERVICE);
public Location getLocation(String provider)
if (locationManager.isProviderEnabled(provider))
locationManager.requestLocationUpdates(provider,
MIN_TIME_FOR_UPDATE, MIN_DISTANCE_FOR_UPDATE, this);
if (locationManager != null)
location = locationManager.getLastKnownLocation(provider);
return location;
return null;
@Override
public void onLocationChanged(Location location)
@Override
public void onProviderDisabled(String provider)
@Override
public void onProviderEnabled(String provider)
@Override
public void onStatusChanged(String provider, int status, Bundle extras)
@Override
public IBinder onBind(Intent arg0)
return null;
在这里，我尝试将经纬度从 FirstActivity.java 发送到 MapActivity.java，以便它可以根据纬度和经度在谷歌地图中显示一个点。 但是我得到了一个错误
这是我的清单
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.nav"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="14"
android:targetSdkVersion="17" />
<permission
android:name="com.example.nav.permission.MAPS_RECEIVE"
android:protectionLevel="signature"/>
<uses-permission android:name="com.example.nav.permission.MAPS_RECEIVE"/>
<uses-permission android:name="android.permission.INTERNET"/>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
<uses-permission android:name="com.google.android.providers.gsf.permission.READ_GSERVICES"/>
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION"/>
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION"/>
<uses-feature
android:glEsVersion="0x00020000"
android:required="true"/>
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name=".FirstActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity android:name=".SecondActivity" />
<activity android:name=".MapActivity" />
<meta-data
android:name="com.google.android.maps.v2.API_KEY"
android:value="MY_KEY" />
</application>
这是我的日志
08-01 11:45:52.211: E/AndroidRuntime(2021): java.lang.NullPointerException
08-01 11:45:52.211: E/AndroidRuntime(2021): at com.example.nav.FirstActivity$3.onClick(FirstActivity.java:97)
08-01 11:45:52.211: E/AndroidRuntime(2021): at android.view.View.performClick(View.java:4204)
08-01 11:45:52.211: E/AndroidRuntime(2021): at android.view.View$PerformClick.run(View.java:17355)
08-01 11:45:52.211: E/AndroidRuntime(2021): at android.os.Handler.handleCallback(Handler.java:725)
08-01 11:45:52.211: E/AndroidRuntime(2021): at android.os.Handler.dispatchMessage(Handler.java:92)
08-01 11:45:52.211: E/AndroidRuntime(2021): at android.os.Looper.loop(Looper.java:137)
08-01 11:45:52.211: E/AndroidRuntime(2021): at android.app.ActivityThread.main(ActivityThread.java:5041)
08-01 11:45:52.211: E/AndroidRuntime(2021): at java.lang.reflect.Method.invokeNative(Native Method)
08-01 11:45:52.211: E/AndroidRuntime(2021): at java.lang.reflect.Method.invoke(Method.java:511)
08-01 11:45:52.211: E/AndroidRuntime(2021): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
08-01 11:45:52.211: E/AndroidRuntime(2021): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
08-01 11:45:52.211: E/AndroidRuntime(2021): at dalvik.system.NativeStart.main(Native Method)
【问题讨论】：
【参考方案1】：你得到这个异常变量 gpsLocation 为空。它应该从 appLocationService 获得它的价值。 我可以看到你在
中创建了一个新的 appLocationServiceappLocationService = new AppLocationService(FirstActivity.this);
确保你已经启动了服务（start service() 方法）。
也改变这个：
Button btnShow = (Button) findViewById(R.id.btn_show);
btnShow.setOnClickListener(new OnClickListener()
@Override
public void onClick(View arg0)
Location gpsLocation = appLocationService
.getLocation(LocationManager.GPS_PROVIDER);
double latitude = gpsLocation.getLatitude();
double longitude = gpsLocation.getLongitude();
Intent intent = new Intent(getBaseContext(), MapActivity.class);
// Passing latitude and longitude to the MapActiv
intent.putExtra("lat", latitude);
intent.putExtra("lng", longitude);
startActivity(intent);
finish();
);
到这里：
Button btnShow = (Button) findViewById(R.id.btn_show);
btnShow.setOnClickListener(new OnClickListener()
@Override
public void onClick(View arg0)
Location gpsLocation = appLocationService
.getLocation(LocationManager.GPS_PROVIDER);
if(gpsLocation==null)
//if no location found create one
gpsLocation =new Location("");
gpsLocation.setLatitude(20.75d);
gpsLocation.setLongitude(44.9d);
double latitude = gpsLocation.getLatitude();
double longitude = gpsLocation.getLongitude();
Intent intent = new Intent(getBaseContext(), MapActivity.class);
// Passing latitude and longitude to the MapActiv
intent.putExtra("lat", latitude);
intent.putExtra("lng", longitude);
startActivity(intent);
finish();
);
【讨论】：
谢谢，但我的 appLocationService 没有问题，但我的地图有问题。当我尝试单击将启动地图的第三个按钮时，我的应用程序被强制关闭 我已经解决了，但是地图上的坐标我们没有刷新。我该怎么办？以上是关于在地图上显示点时出错的主要内容，如果未能解决你的问题，请参考以下文章
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