java - 地图停止单击按钮时（尝试调用虚拟方法'java.lang.String java.lang.String.trim()）

Question

我正在尝试从服务器检索纬度和经度并将其显示在我的谷歌地图活动中。但是我从服务器获得的值是 String ，所以我从 String 更改为 Double，以便能够在谷歌地图位置中使用。我已经得到了位置，但是当我单击显示地图时，应用程序停止工作，并且我在 logact 中遇到错误。请看一下。

#Main Activity
 @Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    findViewById(R.id.btn_login).setOnClickListener(this);
    findViewById(R.id.btn_secret).setOnClickListener(this);
    findViewById(R.id.btn_Location).setOnClickListener(this);
}
public void onClick(View v) {
    switch (v.getId()) {
        case R.id.btn_login:
            login();
            break;
        case R.id.btn_secret:
            getSecret();
            break;
        case R.id.btn_Location:
            getLocation();
            break;
        case R.id.btn_Map:
            getMap();
            break;
    }

}

private static String token;
private  String lat;
private  String lng;



public String getLat() {
    return this.lat;
}

public String  getLng(){
    return this.lng;
}


private void login() {
    Login login = new Login("[e-mail]", "aaaaaa");
    Call<User> call = userClient.login(login);

    call.enqueue(new Callback<User>() {
        @Override
        public void onResponse(Call<User> call, Response<User> response) {
            if (response.isSuccessful()) {
                Toast.makeText(MainActivity.this, response.body().getToken(), Toast.LENGTH_SHORT).show();
                token = response.body().getToken();
            } else {
                Toast.makeText(MainActivity.this, "login not correct", Toast.LENGTH_SHORT).show();

            }
        }

        @Override
        public void onFailure(Call<User> call, Throwable t) {
            Toast.makeText(MainActivity.this, "error", Toast.LENGTH_SHORT).show();
        }
    });
}

private void getSecret() {
    Call<ResponseBody> call = userClient.getSecret(token);

    call.enqueue(new Callback<ResponseBody>() {
        @Override
        public void onResponse(Call<ResponseBody> call, Response<ResponseBody> response) {
            if (response.isSuccessful()) {
                try {
                    Toast.makeText(MainActivity.this, response.body().string(), Toast.LENGTH_SHORT).show();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            } else {
                Toast.makeText(MainActivity.this, "token is not correct", Toast.LENGTH_SHORT).show();

            }
        }

        @Override
        public void onFailure(Call<ResponseBody> call, Throwable t) {
            Toast.makeText(MainActivity.this, "error", Toast.LENGTH_SHORT).show();

        }
    });
}

private void getLocation() {
    Call<Location> call = userClient.getLocation();

    call.enqueue(new Callback<Location>() {
        @Override
        public void onResponse(Call<Location> call, Response<Location> response) {
            if (response.isSuccessful()) {
                Toast.makeText(MainActivity.this, response.body().getGps_latitude(), Toast.LENGTH_SHORT).show();
                Toast.makeText(MainActivity.this, response.body().getGps_longitude(), Toast.LENGTH_LONG).show();
                lat = response.body().getGps_latitude();
                lng = response.body().getGps_longitude();

            } else {
                Toast.makeText(MainActivity.this, "login not correct", Toast.LENGTH_SHORT).show();

            }
        }

        @Override
        public void onFailure(Call<Location> call, Throwable t) {
            Toast.makeText(MainActivity.this, "error", Toast.LENGTH_SHORT).show();

        }

    });


}

private void getMap(){
    Intent intent = new Intent(this,GMap.class);
    startActivity(intent);
}

}

#Map Activity
@Override
public void onMapReady(GoogleMap googleMap) {
    mMap = googleMap;

    MainActivity mainActivity = new MainActivity();


    double Lat = Double.parseDouble(mainActivity.getLat());
    double Lng = Double.parseDouble(mainActivity.getLng());

    LatLng sydney = new LatLng(Lat, Lng);
    mMap.addMarker(new MarkerOptions().position(sydney).title("Home"));
    mMap.moveCamera(CameraUpdateFactory.newLatLng(sydney));
}



#Error Logcat
java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String java.lang.String.trim()' on a null object reference
    at sun.misc.FloatingDecimal.readJavaFormatString(FloatingDecimal.java:1838)
    at sun.misc.FloatingDecimal.parseDouble(FloatingDecimal.java:110)
    at java.lang.Double.parseDouble(Double.java:539)
    at com.example.login_retro.Api.model.GMap.onMapReady(GMap.java:48)
    at com.google.android.gms.maps.zzak.zza(Unknown Source:2)
    at com.google.android.gms.maps.internal.zzaq.dispatchTransaction(Unknown Source:12)
    at com.google.android.gms.internal.maps.zzb.onTransact(Unknown Source:12)
    at android.os.Binder.transact(Binder.java:628)
    at fv.b(:com.google.android.gms.dynamite_mapsdynamite@15180051@15.1.80 (040408-237499370):14)
    at com.google.android.gms.maps.internal.bd.a(:com.google.android.gms.dynamite_mapsdynamite@15180051@15.1.80 (040408-237499370):4)
    at com.google.maps.api.android.lib6.impl.bk.run(:com.google.android.gms.dynamite_mapsdynamite@15180051@15.1.80 (040408-237499370):4)
    at android.os.Handler.handleCallback(Handler.java:809)
    at android.os.Handler.dispatchMessage(Handler.java:102)
    at android.os.Looper.loop(Looper.java:166)
    at android.app.ActivityThread.main(ActivityThread.java:7383)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:469)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:963)

标签： javaandroid