我在运行项目时遇到此错误。我搜索过，我认为问题与上下文有关，但我不知道如何解决。
我的代码：（我认为错误发生在方法showSettingsAlert（））
public class GPSTracker extends Service implements LocationListener {
private final Context mContext;
private TextView textView;
// flag for GPS status
boolean isGPSEnabled = false;
// flag for network status
boolean isNetworkEnabled = false;
// flag for GPS status
boolean canGetLocation = false;
Location location; // location
double latitude; // latitude
double longitude; // longitude
// The minimum distance to change Updates in meters
private static final long MIN_DISTANCE_CHANGE_FOR_UPDATES = 1000; // 1000 meters
// The minimum time between updates in milliseconds
private static final long MIN_TIME_BW_UPDATES = 60000 * 60 * 1; // 60 minute
// Declaring a Location Manager
protected LocationManager locationManager;
@Override
public int onStartCommand(Intent intent, int flags, int startId) {
getLocation();
return START_STICKY;
}
public Location getLocation() {
try {
locationManager = (LocationManager) mContext.getSystemService(LOCATION_SERVICE);
// getting GPS status
isGPSEnabled = locationManager.isProviderEnabled(LocationManager.GPS_PROVIDER);
// getting network status
isNetworkEnabled = locationManager.isProviderEnabled(LocationManager.NETWORK_PROVIDER);
if (!isGPSEnabled && !isNetworkEnabled) {
// no network provider is enabled
} else {
this.canGetLocation = true;
// First get location from Network Provider
if (isNetworkEnabled) {
locationManager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, MIN_TIME_BW_UPDATES, MIN_DISTANCE_CHANGE_FOR_UPDATES, this);
Log.d("Network", "Network");
if (locationManager != null) {
location = locationManager.getLastKnownLocation(LocationManager.NETWORK_PROVIDER);
if (location != null) {
latitude = location.getLatitude();
longitude = location.getLongitude();
}
}
}
// if GPS Enabled get lat/long using GPS Services
if (isGPSEnabled) {
if (location == null) {
locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, MIN_TIME_BW_UPDATES, MIN_DISTANCE_CHANGE_FOR_UPDATES, this);
Log.d("GPS Enabled", "GPS Enabled");
if (locationManager != null) {
location = locationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER);
if (location != null) {
latitude = location.getLatitude();
longitude = location.getLongitude();
}
}
}
}
}
} catch (Exception e) {
e.printStackTrace();
}
stopUsingGPS();
return location;
}
/**
* Stop using GPS listener
* Calling this function will stop using GPS in your app
* */
public void stopUsingGPS(){
if(locationManager != null){
locationManager.removeUpdates(GPSTracker.this);
}
}
/**
* Function to get latitude
* */
public double getLatitude(){
if(location != null){
latitude = location.getLatitude();
}
// return latitude
return latitude;
}
/**
* Function to get longitude
* */
public double getLongitude(){
if(location != null){
longitude = location.getLongitude();
}
// return longitude
return longitude;
}
/**
* Function to check GPS/wifi enabled
* @return boolean
* */
public boolean canGetLocation() {
return this.canGetLocation;
}
/**
* Function to show settings alert dialog
* On pressing Settings button will lauch Settings Options
* */
public void showSettingsAlert(){
AlertDialog.Builder alertDialog = new AlertDialog.Builder(mContext);
// Setting Dialog Title
alertDialog.setTitle("GPS is settings");
// Setting Dialog Message
alertDialog.setMessage("GPS is not enabled. Do you want to go to settings menu?");
// On pressing Settings button
alertDialog.setPositiveButton("Settings", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog,int which) {
Intent intent = new Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS);
mContext.startActivity(intent);
}
});
// on pressing cancel button
alertDialog.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
dialog.cancel();
}
});
// Showing Alert Message
alertDialog.show();
}
@Override
public void onLocationChanged(Location location) {
textView.append("\n "+location.getLatitude()+" "+location.getLongitude());
}
@Override
public void onProviderDisabled(String provider) {
Intent intent = new Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS);
mContext.startActivity(intent);
}
@Override
public void onProviderEnabled(String provider) {
}
@Override
public void onStatusChanged(String provider, int status, Bundle extras) {
}
@Override
public IBinder onBind(Intent arg0) {
return null;
}
}
这是我的Logcat：
10-25 20:29:30.277 10524-10524/com.example.nunog.myapplication12 E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.nunog.myapplication12, PID: 10524
java.lang.RuntimeException: Unable to start service com.example.nunog.myapplication12.Anomaly@424d1620 with Intent { cmp=com.example.nunog.myapplication12/.Anomaly (has extras) }: android.view.WindowManager$BadTokenException: Unable to add window -- token null is not for an application
at android.app.ActivityThread.handleServiceArgs(ActivityThread.java:3006)
at android.app.ActivityThread.access$2200(ActivityThread.java:174)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1404)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:146)
at android.app.ActivityThread.main(ActivityThread.java:5593)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1283)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1099)
at dalvik.system.NativeStart.main(Native Method)
Caused by: android.view.WindowManager$BadTokenException: Unable to add window -- token null is not for an application
at android.view.ViewRootImpl.setView(ViewRootImpl.java:775)
at android.view.WindowManagerGlobal.addView(WindowManagerGlobal.java:278)
at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:69)
at android.app.Dialog.show(Dialog.java:301)
at android.app.AlertDialog$Builder.show(AlertDialog.java:957)
at com.example.nunog.myapplication12.GPSTracker.showSettingsAlert(GPSTracker.java:176)
编辑：我已经尝试在我的AlertDialog（）中使用 this 而不是 mContext ，但是当我这样做时，我得到一个NullPointerException。
答案 0 :(得分：0)
您只能使用Bobbake4已经评论的活动创建警报对话框。
另一个答案可以帮助您：https://stackoverflow.com/a/22627480/2972104
答案 1 :(得分：0)
创建类的构造函数并传递Activity of Activity
private Context mContext;
public GPSTracker(Context context) {
mContext = context;
}
像你这样在你的班级制作对象
GPSTracker tracker = new GPSTracker(YourActivity.this);
答案 2 :(得分：-2)
你的mContext为null，使用Activity来显示alertDialog，不在Service中，Service是后台任务，它不能用于UI