我要做的就是让用户获得他喜欢的类型的列表。例如，如果输入是医院，我的应用程序将使用搜索字符串＆＃34; Hospital＆＃34;打开谷歌地图。但正如使用像geo:0,0?q=hospital uri这样的地理编码的文档中所建议的，uri显示了坐标0纬度附近的所有医院。 0经度。因此，当我尝试使用以下代码首先获取用户坐标时。
放置Decoder.java
package com.kkze.Mappy;
import android.app.Activity;
import android.app.AlertDialog;
import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;
import android.location.Criteria;
import android.location.Location;
import android.location.LocationManager;
import android.net.Uri;
import android.os.Build;
import android.os.Bundle;
import android.provider.Settings;
import android.text.TextUtils;
import android.util.Log;
import android.widget.Toast;
public class PlacesDecoder extends Activity {
Intent intentThatCalled;
public double latitude;
public double longitude;
public LocationManager locationManager;
public Criteria criteria;
public String bestProvider;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
intentThatCalled = getIntent();
String voice2text = intentThatCalled.getStringExtra("v2txt");
getLocation(voice2text);
}
public static boolean isLocationEnabled(Context context)
{
int locationMode = 0;
String locationProviders;
if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT)
{
try
{
locationMode = Settings.Secure.getInt(context.getContentResolver(), Settings.Secure.LOCATION_MODE);
} catch (Settings.SettingNotFoundException e) {
e.printStackTrace();
}
return locationMode != Settings.Secure.LOCATION_MODE_OFF;
}
else
{
locationProviders = Settings.Secure.getString(context.getContentResolver(), Settings.Secure.LOCATION_PROVIDERS_ALLOWED);
return !TextUtils.isEmpty(locationProviders);
}
}
public void getLocation(String voice2txt) {
locationManager = (LocationManager) this.getSystemService(Context.LOCATION_SERVICE);
criteria = new Criteria();
bestProvider = String.valueOf(locationManager.getBestProvider(criteria, true)).toString();
Location location = locationManager.getLastKnownLocation(bestProvider);
if (isLocationEnabled(PlacesDecoder.this)) {
Log.e("TAG", "GPS is on");
latitude = location.getLatitude();
longitude = location.getLongitude();
Toast.makeText(PlacesDecoder.this, "latitude:" + latitude + " longitude:" + longitude, Toast.LENGTH_SHORT).show();
searchNearestPlace(voice2txt);
}
else
{
AlertDialog.Builder notifyLocationServices = new AlertDialog.Builder(PlacesDecoder.this);
notifyLocationServices.setTitle("Switch on Location Services");
notifyLocationServices.setMessage("Location Services must be turned on to complete this action. Also please take note that if on a very weak network connection, such as 'E' Mobile Data or 'Very weak Wifi-Connections' it may take even 15 mins to load. If on a very weak network connection as stated above, location returned to application may be null or nothing and cause the application to crash.");
notifyLocationServices.setPositiveButton("Ok, Open Settings", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
Intent openLocationSettings = new Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS);
PlacesDecoder.this.startActivity(openLocationSettings);
finish();
}
});
notifyLocationServices.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
finish();
}
});
notifyLocationServices.show();
}
}
public void searchNearestPlace(String v2txt) {
Log.e("TAG", "Started");
v2txt = v2txt.toLowerCase();
String[] placesS = {"accounting", "airport", "aquarium", "atm", "attraction", "bakery", "bakeries", "bank", "bar", "cafe", "campground", "casino", "cemetery", "cemeteries", "church", "courthouse", "dentist", "doctor", "electrician", "embassy", "embassies", "establishment", "finance", "florist", "food", "grocery", "groceries", "supermarket", "gym", "health", "hospital", "laundry", "laundries", "lawyer", "library", "libraries", "locksmith", "lodging", "mosque", "museum", "painter", "park", "parking", "pharmacy", "pharmacies", "physiotherapist", "plumber", "police", "restaurant", "school", "spa", "stadium", "storage", "store", "synagog", "synagogue", "university", "universities", "zoo"};
String[] placesM = {"amusement park", "animal care", "animal care", "animal hospital", "art gallery", "art galleries", "beauty salon", "bicycle store", "book store", "bowling alley", "bus station", "car dealer", "car rental", "car repair", "car wash", "city hall", "clothing store", "convenience store", "department store", "electronics store", "electronic store", "fire station", "funeral home", "furniture store", "gas station", "general contractor", "hair care", "hardware store", "hindu temple", "home good store", "homes good store", "home goods store", "homes goods store", "insurance agency", "insurance agencies", "jewelry store", "liquor store", "local government office", "meal delivery", "meal deliveries", "meal takeaway", "movie rental", "movie theater", "moving company", "moving companies", "night club", "pet store", "place of worship", "places of worship", "post office", "real estate agency", "real estate agencies", "roofing contractor", "rv park", "shoe store", "shopping mall", "subway station", "taxi stand", "train station", "travel agency", "travel agencies", "veterinary care"};
int index;
for (int i = 0; i <= placesM.length - 1; i++) {
Log.e("TAG", "forM");
if (v2txt.contains(placesM[i])) {
Log.e("TAG", "sensedM?!");
index = i;
Uri gmmIntentUri = Uri.parse("geo:" + latitude + "," + longitude + "?q=" + placesM[index]);
Intent mapIntent = new Intent(Intent.ACTION_VIEW, gmmIntentUri);
mapIntent.setPackage("com.google.android.apps.maps");
startActivity(mapIntent);
finish();
}
}
for (int i = 0; i <= placesS.length - 1; i++) {
Log.e("TAG", "forS");
if (v2txt.contains(placesS[i])) {
Log.e("TAG", "sensedS?!");
index = i;
Uri gmmIntentUri = Uri.parse("geo:" + latitude + "," + longitude + "?q=" + placesS[index]);
Intent mapIntent = new Intent(Intent.ACTION_VIEW, gmmIntentUri);
mapIntent.setPackage("com.google.android.apps.maps");
startActivity(mapIntent);
finish();
}
}
}
}
问题是始终且始终位置返回null。而且我知道，只要启用了位置，另一个应用程序Jarvis就可以轻松完成任务，如果不是，则只是要求用户。但在相同的条件下，我的应用程序总是崩溃。
我做了什么：
它仍然会发生。我是Android的初学者。 拜托，请帮助我。有没有办法解决我的问题？甚至认为其他应用程序设法做到了。
这是我的LogCat。
Process: com.kkze.Mappy, PID: 6742
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.kkze.Mappy/com.kkze.Mappy.PlacesDecoder}: java.lang.NullPointerException: Attempt to invoke virtual method 'double android.location.Location.getLatitude()' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2658)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2723)
at android.app.ActivityThread.access$900(ActivityThread.java:172)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1422)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:145)
at android.app.ActivityThread.main(ActivityThread.java:5832)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1399)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1194)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'double android.location.Location.getLatitude()' on a null object reference
at com.kkze.Mappy.PlacesDecoder.getLocation(PlacesDecoder.java:62)
at com.kkze.Mappy.PlacesDecoder.onCreate(PlacesDecoder.java:32)
at android.app.Activity.performCreate(Activity.java:6221)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1119)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2611)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2723)
at android.app.ActivityThread.access$900(ActivityThread.java:172)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1422)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:145)
at android.app.ActivityThread.main(ActivityThread.java:5832)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1399)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1194)
同时检查位置！= null需要ACCESS_FINE_LOCATION权限，这会弄乱我的应用程序，导致它始终返回null。
答案 0 :(得分：18)
正如Jon Skeet在评论中提到的，getLastKnownLocation()方法可以并且将返回null。主要问题是它没有向操作系统提示请求新的位置锁定，而只是检查是否存在来自某个其他应用程序位置请求的最后已知位置。如果最近没有其他应用程序发出了位置请求，那么您将获得一个返回给您的空位置。
保证您实际获得位置的唯一方法是请求一个，这是通过调用requestLocationUpdates()来完成的。
传递给onLocationChanged()回调方法的位置不会为空，因为回调仅发生在成功的位置锁定上。
请注意，您的应用注册位置更新的整个时间都会导致额外的电池耗尽，因此请务必尽快取消注册位置更新。在第一个位置进入时，您似乎可以取消注册。
此外，您可能需要考虑在等待位置锁定时在此活动中显示进度对话框，以便向用户提供应用正在等待的某些反馈。
以下是代码应如下所示的一般结构：
public class MainActivity extends Activity
implements LocationListener {
Intent intentThatCalled;
public double latitude;
public double longitude;
public LocationManager locationManager;
public Criteria criteria;
public String bestProvider;
String voice2text; //added
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
intentThatCalled = getIntent();
voice2text = intentThatCalled.getStringExtra("v2txt");
getLocation();
}
public static boolean isLocationEnabled(Context context)
{
//...............
return true;
}
protected void getLocation() {
if (isLocationEnabled(MainActivity.this)) {
locationManager = (LocationManager) this.getSystemService(Context.LOCATION_SERVICE);
criteria = new Criteria();
bestProvider = String.valueOf(locationManager.getBestProvider(criteria, true)).toString();
//You can still do this if you like, you might get lucky:
Location location = locationManager.getLastKnownLocation(bestProvider);
if (location != null) {
Log.e("TAG", "GPS is on");
latitude = location.getLatitude();
longitude = location.getLongitude();
Toast.makeText(MainActivity.this, "latitude:" + latitude + " longitude:" + longitude, Toast.LENGTH_SHORT).show();
searchNearestPlace(voice2text);
}
else{
//This is what you need:
locationManager.requestLocationUpdates(bestProvider, 1000, 0, this);
}
}
else
{
//prompt user to enable location....
//.................
}
}
@Override
protected void onPause() {
super.onPause();
locationManager.removeUpdates(this);
}
@Override
public void onLocationChanged(Location location) {
//Hey, a non null location! Sweet!
//remove location callback:
locationManager.removeUpdates(this);
//open the map:
latitude = location.getLatitude();
longitude = location.getLongitude();
Toast.makeText(MainActivity.this, "latitude:" + latitude + " longitude:" + longitude, Toast.LENGTH_SHORT).show();
searchNearestPlace(voice2text);
}
@Override
public void onStatusChanged(String provider, int status, Bundle extras) {
}
@Override
public void onProviderEnabled(String provider) {
}
@Override
public void onProviderDisabled(String provider) {
}
public void searchNearestPlace(String v2txt) {
//.....
}
}
答案 1 :(得分：1)
在getLocation方法
if (isLocationEnabled(PlacesDecoder.this) && location != null) {
...
}
答案 2 :(得分：1)
您编写了获取当前位置（latlng）的代码，并且此错误是由于您在真正的android设备上的gps（location）无法打开引起的。 我打开它，它对我有用。希望有用
答案 3 :(得分：0)
出现空指针异常，因为您的应用不会请求当前位置，而是使用最后找到的位置，只是检查您是否已启用您的位置并运行使用您当前位置的任何其他应用。之后，尝试再次运行您的项目。希望这能解决你的问题。
答案 4 :(得分：0)
这是完成保险丝位置概念的另一种方法，我曾经用过这种方法，对我来说是成功的 mFusedLocationClient = LocationServices.getFusedLocationProviderClient（this）;
是声明融合的位置
@SuppressWarnings( {"MissingPermission"})
private void enableLocationComponent() {
System.out.println("on map click is here in permission///////////////");
// Check if permissions are enabled and if not request
if (PermissionsManager.areLocationPermissionsGranted(this)) {
// Activate the MapboxMap LocationComponent to show user location
// Adding in LocationComponentOptions is also an optional parameter
LocationComponent locationComponent = mapboxMap.getLocationComponent();
locationComponent.activateLocationComponent(this);
locationComponent.setLocationComponentEnabled(true);
// Set the component's camera mode
locationComponent.setCameraMode(CameraMode.TRACKING);
mFusedLocationClient.getLastLocation().addOnSuccessListener(this, new OnSuccessListener<Location>() {
@Override
public void onSuccess(Location location) {
originLocation=location;
// Got last known location. In some rare situations this can be null.
if (location != null) {
originLocation=location;
System.out.println(" permission granted location is in iff ++///////////////"+location);
}
}
});
//originLocation = locationComponent.getLastKnownLocation();
System.out.println("origin location is that//////////"+originLocation);
} else {
permissionsManager = new PermissionsManager(this);
permissionsManager.requestLocationPermissions(this);
}
}
@Override
public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
permissionsManager.onRequestPermissionsResult(requestCode, permissions, grantResults);
Toast.makeText(this, "granted", Toast.LENGTH_LONG).show();
}
@Override
public void onExplanationNeeded(List<String> permissionsToExplain) {
Toast.makeText(this, R.string.user_location_permission_explanation, Toast.LENGTH_LONG).show();
}
@Override
public void onPermissionResult(boolean granted) {
if (granted) {
enableLocationComponent();
} else {
Toast.makeText(this, R.string.user_location_permission_not_granted, Toast.LENGTH_LONG).show();``
finish();
}
}
答案 5 :(得分：0)
正如Yash所说，您的应用程序不要求提供当前位置，而是使用最近找到的位置，此错误对我有用的简单解决方法是：打开GPS并在手机上打开google maps应用程序，或者模拟器查看您当前的位置，然后将其关闭。现在，当您打开Current App（正在使用）或运行它时，它不会出现此错误。为我工作。
答案 6 :(得分：0)
我使用.getLastLocation()遇到了同样的问题。然后，我使用mMap.setMyLocationEnabeled(true)，并使用.setMyLocationEnabeled(true)启用的on map location按钮获取GPS位置。之后，下一次.getLastLocation()工作正常。我不知道确切的原因，但我认为地图上的位置按钮一次保存了我的当前位置，下次我使用.getLastLocation()时，它不为null，因为最后一个位置已经存在。