Java Can'；t定期向服务器更新位置

我正在开发定期更新用户位置的应用程序。我提供了服务，它工作了，我通过广播发送结果

Intent i = new Intent("location_update");
            i.putExtra("lat",location.getLatitude());
            i.putExtra("lang",location.getLongitude());
            sendBroadcast(i);

我在这里也收到了成功的结果：

                latData=String.valueOf(intent.getExtras().get("lat"));
                langData=String.valueOf(intent.getExtras().get("lang"));

到目前为止，一切都很好，但当我试图通过这样的改造来更新数据库lat&lang时

    user.lang= Float.parseFloat(langData);

    user.username= "mohamed";
    user.lang= (float) 15.155;

它给了我空指针异常，这是因为user.lang接收空值！此外，我确信我100%成功地从服务接收到数据，并且为了确保我将数据传递到文本视图，它会定期工作和更改。不管怎样，这是我连接的全部代码

<?php

include 'DB.php';

$data = file_get_contents("php://input");
$obj = json_decode($data);
$db = DB::getInstance();
header('Content-Type: application/json');
if(!isset($obj->{'lang'})){
    print "{\"status\":0,\"message\":\"lang is Missing !\"}" ;
}else if(!isset($obj->{'lat'})){
    print "{\"status\":0,\"message\":\"lat is Missing !\"}" ;
}else if(!isset($obj->{'username'})){
    print "{\"status\":0,\"message\":\"username is Missing !\"}" ;
}else{
    $lang = $obj->{'lang'};
    $lat = $obj->{'lat'};
    $username= $obj->{'username'};




    $update = $db->update('users',
            [
                'lang'     => $lang,
                'lat'    => $lat,
            ])->where('user_name','=',$username)->exec();

        if($update){
            print "{\"status\":1,\"message\":\"\"}" ;
        } else {
            print "{\"status\":0,\"message\":\"Error while updating\"}" ;
        }
    }

主要活动

public class MainActivity2 extends AppCompatActivity {

    private Button btn_start, btn_stop;
    private TextView langLoc, latLoc,idupdate;
    private BroadcastReceiver broadcastReceiver;
    User user = new User();
    String latData , langData;



    @Override
    protected void onResume() {
        super.onResume();

        if(broadcastReceiver == null){
            broadcastReceiver = new BroadcastReceiver() {

                @Override
                public void onReceive(Context context,Intent intent) {



                    latData=String.valueOf(intent.getExtras().get("lat"));
                    langData=String.valueOf(intent.getExtras().get("lang"));
                    //langLoc.setText(langData);
                    //latLoc.setText(latData);




                }
            };
        }
        registerReceiver(broadcastReceiver,new IntentFilter("location_update"));



        user.username= "mohamed";
        //user.lang= Float.parseFloat(langData);

        //user.lat= (float) 15.15;

        /*IncomingData
        User user = Session.getInstance().getUser();
        if (user !=null){
            tv_email.setText(user.username);

        }*/



        Webservice.getInstance().getApi().UpdateuserLocation(user).enqueue(new Callback<MainResponse>() {

            @Override
            public void onResponse(Call<MainResponse> call, Response<MainResponse> response) {



            }

            @Override
            public void onFailure(Call<MainResponse> call, Throwable t) {

            }
        });



    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        if(broadcastReceiver != null){
            unregisterReceiver(broadcastReceiver);
        }
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main22);

        btn_start = (Button) findViewById(R.id.button);
        btn_stop = (Button) findViewById(R.id.button2);
        latLoc = (TextView) findViewById(R.id.lat);
        langLoc = (TextView) findViewById(R.id.lang);


        if(!runtime_permissions())
            enable_buttons();

    }

    private void enable_buttons() {

        btn_start.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                //Service Start
                Intent i =new Intent(getApplicationContext(),GPS_Service.class);
                startService(i);

            }
        });

        btn_stop.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {

                Intent i = new Intent(getApplicationContext(),GPS_Service.class);
                stopService(i);

            }
        });

    }

    private boolean runtime_permissions() {
        if(Build.VERSION.SDK_INT >= 23 && ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED){

            requestPermissions(new String[]{Manifest.permission.ACCESS_FINE_LOCATION, Manifest.permission.ACCESS_COARSE_LOCATION},100);

            return true;
        }
        return false;
    }


    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
        if(requestCode == 100){
            if( grantResults[0] == PackageManager.PERMISSION_GRANTED && grantResults[1] == PackageManager.PERMISSION_GRANTED){
                enable_buttons();
            }else {
                runtime_permissions();
            }
        }
    }

}

---

应用程序将数据发送到服务器并成功更新数据库。

问题在于，在接收器的

onReceive

回调中初始化之前，您的字符串

langData

为空。您需要将

parseFloat

调用移到该位置，以便变量已初始化。然后，一旦初始化变量，您将更新您的用户，然后发出请求

像这样：

            @Override
            public void onReceive(Context context,Intent intent) {
                latData=String.valueOf(intent.getExtras().get("lat"));
                langData=String.valueOf(intent.getExtras().get("lang"));

                user.lang= Float.parseFloat(langData);
                user.lat= Float.parseFloat(latData);

                Webservice.getInstance().getApi().UpdateuserLocation(user).enqueue(new Callback<MainResponse>() {
                     @Override
                     public void onResponse(Call<MainResponse> call, Response<MainResponse> response) {
                     }

                     @Override
                     public void onFailure(Call<MainResponse> call, Throwable t) {
                     }
                });
            }

@覆盖
公共void onReceive（上下文、意图）{
latData=String.valueOf（intent.getExtras（）.get（“lat”））；
langData=String.valueOf（intent.getExtras（）.get（“lang”）；
user.lang=Float.parseFloat（langData）；
user.lat=Float.parseFloat（latData）；
Webservice.getInstance（）.getApi（）.UpdateuserLocation（用户）.enqueue（新回调（）命令）{
@凌驾
公共void onResponse（调用、响应）{
}
@凌驾
失败时公共无效（调用调用，可丢弃的t）{
}
});
}

U如果（broadcastReceiver==null）{broadcastReceiver=new broadcastReceiver（）{@Override public void onReceive（Context Context，Intent Intent）{latData=String.valueOf（Intent.getExtras（）.get（“lat”）；langData=String.valueOf，则表示正确（intent.getExtras（）.get（“lang”）；user.lang=Float.parseFloat（langData）；}}；如果我做得正确，它不会向server@M.Magdy，我编辑了答案以包含代码更改。请参见上文^

            @Override
            public void onReceive(Context context,Intent intent) {
                latData=String.valueOf(intent.getExtras().get("lat"));
                langData=String.valueOf(intent.getExtras().get("lang"));

                user.lang= Float.parseFloat(langData);
                user.lat= Float.parseFloat(latData);

                Webservice.getInstance().getApi().UpdateuserLocation(user).enqueue(new Callback<MainResponse>() {
                     @Override
                     public void onResponse(Call<MainResponse> call, Response<MainResponse> response) {
                     }

                     @Override
                     public void onFailure(Call<MainResponse> call, Throwable t) {
                     }
                });
            }