应用程序关闭，它应提交数据

我得到以下代码。我正在尝试将我的坐标提交给电子邮件。应用程序关闭，它应提交数据

但是每次按下按钮，应用程序都会关闭。

public LatLng getLocation() 
    { 
     // Get the location manager 
     LocationManager locationManager = (LocationManager) getSystemService(LOCATION_SERVICE); 
     Criteria criteria = new Criteria(); 
     String bestProvider = locationManager.getBestProvider(criteria, false); 
     Location location = locationManager.getLastKnownLocation(bestProvider); 
     //double lat; 
     //double lon; 
     try { 
      lat = location.getLatitude(); 
      lon = location.getLongitude(); 
      Log.i("logging","lat "+lat+" long "+lon); 
      return new LatLng(lat, lon); 
     } 
     catch (NullPointerException e){ 
      e.printStackTrace(); 
      return null; 
     } 
    } 

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

    final Button button = (Button) findViewById(R.id.addbutton); 
    button.setOnClickListener(new View.OnClickListener() { 
     public void onClick(View v) { 

      final Button button = (Button) findViewById(R.id.addbutton); 
      button.setOnClickListener(new View.OnClickListener() { 
       public void onClick(View v) { 
        LatLng latlng = getLocation(); 


        Intent i = new Intent(Intent.ACTION_SENDTO); 
        //i.setType("message/rfc822"); 
        i.putExtra(Intent.EXTRA_EMAIL , new String[]{"[email protected]"}); 
        i.putExtra(Intent.EXTRA_SUBJECT, "subject of email"); 
        i.putExtra(Intent.EXTRA_TEXT , latlng.latitude+" " + latlng.longitude); 
        try { 
         startActivity(Intent.createChooser(i, "Send mail...")); 
        } catch (android.content.ActivityNotFoundException ex) { 
         makeText(MapsActivity.this, "There are no email clients installed.", LENGTH_SHORT).show(); 
        } 

       } 
      }); 
     } 
    });

如果我按下按钮，将出现从堆栈跟踪以下错误：

E/AndroidRuntime: FATAL EXCEPTION: main 
                       Process: com.example.testingmapingmarker23, PID: 6630 
                       Theme: themes:{default=overlay:system, iconPack:system, fontPkg:system, com.android.systemui=overlay:system, com.android.systemui.navbar=overlay:system} 
                       java.lang.NullPointerException: Attempt to read from field 'double com.google.android.gms.maps.model.LatLng.latitude' on a null object reference 
                        at com.example.testingmapingmarker23.MapsActivity$1$1.onClick(MapsActivity.java:96) 
                        at android.view.View.performClick(View.java:5204) 
                        at android.view.View$PerformClick.run(View.java:21158) 
                        at android.os.Handler.handleCallback(Handler.java:739) 
                        at android.os.Handler.dispatchMessage(Handler.java:95) 
                        at android.os.Looper.loop(Looper.java:148) 
                        at android.app.ActivityThread.main(ActivityThread.java:5461) 
                        at java.lang.reflect.Method.invoke(Native Method) 
                        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) 
                        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)

所以，问题是：究竟是什么问题呢？不知何故坐标也不会通过日志显示。

来源

2017-08-07 MrHarrison

您需要执行某些步骤获得的位置，以便于我，它看起来像你的代码是不完整的。我在下面的答案中提到了一些示例教程中的步骤。看一看。 –

在对此对象执行任何操作之前，您应该先检查latlng。

例如

LatLng latlng = getLocation(); 


Intent i = new Intent(Intent.ACTION_SENDTO); 
//i.setType("message/rfc822"); 
i.putExtra(Intent.EXTRA_EMAIL , new String[]{"[email protected]"}); 
i.putExtra(Intent.EXTRA_SUBJECT, "subject of email"); 
if(latlng != null) { 
    i.putExtra(Intent.EXTRA_TEXT , latlng.latitude+" " + latlng.longitude); 
} else { 
    i.putExtra(Intent.EXTRA_TEXT , "location not available"); 
} 

try { 
    startActivity(Intent.createChooser(i, "Send mail...")); 
} catch (android.content.ActivityNotFoundException ex) { 
    makeText(MapsActivity.this, "There are no email clients installed.", LENGTH_SHORT).show(); 
}

来源

2017-08-07 08:42:58