Android：在Play商店發佈後無法獲取當前位置

Question

我使用此代碼獲取當前位置並且工作正常。但在商店發佈後，它不再適用。應用程序保持鎖定在doInBackground函數中。

private class GpsAsync extends AsyncTask<Void, Integer, Boolean> { 
    private ContactLocationListener contactLocationListener; 
    private Location location; 

    @Override 
    protected void onPreExecute() { 
     super.onPreExecute(); 
     contactLocationListener = new ContactLocationListener(); 
     locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, contactLocationListener); 
    } 

    @Override 
    protected Boolean doInBackground(Void... voids) { 
     while (location == null) {} 
     return null; 
    } 

    @Override 
    protected void onPostExecute(Boolean aBoolean) { 
     super.onPostExecute(aBoolean); 
     textViewLatitude.setText(String.valueOf(location.getLatitude())); 
     textViewLongitude.setText(String.valueOf(location.getLongitude())); 
    } 

    public class ContactLocationListener implements LocationListener { 
     @Override 
     public void onLocationChanged(Location loc) { 
      location = loc; 
     } 
     @Override 
     public void onStatusChanged(String s, int i, Bundle bundle) {} 
     @Override 
     public void onProviderEnabled(String s) {} 
     @Override 
     public void onProviderDisabled(String s) {} 
    } 
} 

我的清單：

if (ContextCompat.checkSelfPermission(getActivity(), Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && 
       ActivityCompat.checkSelfPermission(getActivity(), Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) { 
      ActivityCompat.requestPermissions(getActivity(), new String[]{Manifest.permission.ACCESS_FINE_LOCATION}, 50); 
} else { 
    // start GpsAsync 
} 

Answer 1

兩件事情：

1. 在doInBackground while循環導致每次無限循環

   <uses-permission android:name="android.permission.INTERNET" /> 
   <uses-permission android:name="android.permission.CAMERA" /> 
   <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" /> 
   <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" /> 
   <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" /> 
   <uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" /> 
   <uses-feature android:name="android.hardware.location.gps" /> 
   

   我的權限檢查當LocationProvider失敗時提供位置。它通常很危險。更好地使一些「衛士」繞 - 至少簡單的計數器：

   protected Boolean doInBackground(Void... voids) { 
       Integer count = 0 
       while (location == null||count<10000) {count++} 
       return null; 
   } 
   

2. 至於爲什麼提供商位置發佈後返回null問題。有幾種可能的原因，請檢查：

   • 可用並接通設備上的全球定位系統（我猜它可能在不同的設備上進行測試後發佈，其中GPS被關斷）

   • ？可能的權限問題。由於API 23對於位置和其他「危險」服務，除了在聲明中聲明之外，應該由用戶接受一次（第一次調用應用程序時彈出）。如果用戶「拒絕」服務 - GPS提供商將始終返回空值。

   • 此外，考慮的情況下使用 「getBestProvider」 如果GPS不可用，如下面

     LocationManager locationManager; 
     String svcName = Context.LOCATION_SERVICE; 
     locationManager = 
     (LocationManager)getSystemService(svcName); 
     Criteria criteria = new Criteria(); 
     criteria.setAccuracy(Criteria.ACCURACY_FINE); 
     criteria.setPowerRequirement(Criteria.POWER_LOW); 
     criteria.setAltitudeRequired(false); 
     criteria.setBearingRequired(false); 
     criteria.setSpeedRequired(false); 
     criteria.setCostAllowed(true); 
     String provider = locationManager.getBestProvider(criteria, true); 
     locationManager.getLastKnownLocation(provider); 
     l = locationManager.getLastKnownLocation(provider); 
     

代碼從用戶請求許可：

 // first check the permission in manifest: 
     if (ActivityCompat.checkSelfPermission(this, android.Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, android.Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) { 


      // then ask for GPS permission from user: 
      ActivityCompat.requestPermissions(MainActivity.this, new String[]{android.Manifest.permission.ACCESS_COARSE_LOCATION, android.Manifest.permission.ACCESS_FINE_LOCATION}, 1); 
     } 

    /////////////////////////////////////////////////////////////////////////////// 
    ///// NOTE: Even if we declared the permission in manifest, user can decline. 
    /// So we anyway will do try/catch on pemission exception later on! 
    ///////////////////////////////////////////////////////////////////////////////