无法定期将位置更新到服务器

Question

我正在开发定期更新用户位置的应用程序。我做了服务并且它起作用了，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);

我也在这里成功收到了结果：

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

到目前为止，一切正常，但是当IAM尝试通过这样的改造来更新数据库lat&lang时

    user.lang= Float.parseFloat(langData);

它给了我空指针异常，那是因为 user.lang 收到空值！此外，我确定 100% 我成功地从服务接收数据，并确保我将数据传递给文本视图，并且它会定期工作和更改。无论如何，这是我的完整连接代码

<?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"}" ;
        }
    }

用户

public class User extends RealmObject{
@SerializedName("username")
public String username;
@SerializedName("password")
public String password;
@SerializedName("email")
public String email;
@SerializedName("lang")
public float lang;
@SerializedName("lat")
public float lat;
@SerializedName("id")
public int id;
public boolean isAdmin;}

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();
            }
        }
    }
}

最后一件事，当我像这样使用户的数据静态时

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

应用将数据发送到服务器，数据库更新成功。

Answer 1

问题是你的字符串langData在接收器的onReceive回调中初始化之前是空的。您需要将parseFloat调用移动到其中，以便初始化变量。然后，一旦初始化了变量，您将更新您的用户，然后触发请求。

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) {
                     }
                });
            }