当前，我的地图应用程序从Web服务器获取坐标，并将这些值放在Google地图“ LatLng”中。第一次输入可正常使用，但是，当我按下后退按钮并再次重新输入活动而应用程序崩溃时，它似乎来自服务器方法的getLocation不会再次开始。我已经在下面提供了代码。我仍然是学习Java和android studio的初学者。
主要活动
public class MainActivity extends AppCompatActivity implements View.OnClickListener {
Retrofit.Builder builder = new Retrofit.Builder()
.baseUrl("https://teamdronex.com/")
.addConverterFactory(GsonConverterFactory.create());
Retrofit retrofit = builder.build();
UserClient userClient = retrofit.create(UserClient.class);
@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);
}
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_Map:
getMap();
break;
}
}
private static String token;
private void login() {
Login login = new Login("johndoe@example.com", "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 getMap() {
Intent intent = new Intent(MainActivity.this, GMap.class);
startActivity(intent);
}
}
#Gmap Activity
public class GMap extends FragmentActivity implements OnMapReadyCallback {
private GoogleMap mMap;
private String lat;
private String lng;
public GMap(){
this.getLocation();
}
Retrofit.Builder builder = new Retrofit.Builder()
.baseUrl("https://teamdronex.com/")
.addConverterFactory(GsonConverterFactory.create());
Retrofit retrofit = builder.build();
UserClient userClient = retrofit.create(UserClient.class);
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_gmap);
// Obtain the SupportMapFragment and get notified when the map is ready to be used.
SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager()
.findFragmentById(R.id.map);
mapFragment.getMapAsync(this);
}
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()) {
lat = response.body().getGps_latitude();
lng = response.body().getGps_longitude();
Log.e("Lat","INSIDE getLocation");
Log.e("Lat","lat"+ lat);
} else {
Toast.makeText(GMap.this, "login not correct", Toast.LENGTH_SHORT).show();
}
}
@Override
public void onFailure(Call<Location> call, Throwable t) {
Toast.makeText(GMap.this, "error", Toast.LENGTH_SHORT).show();
}
});
}
@Override
public void onMapReady(GoogleMap googleMap) {
Log.e("result","smt " + this.lat);
double Lat = Double.parseDouble(this.lat);
double Lng = Double.parseDouble(this.lng);
mMap = googleMap;
LatLng sydney = new LatLng(Lat, Lng);
mMap.addMarker(new MarkerOptions().position(sydney).title("Home"));
mMap.moveCamera(CameraUpdateFactory.newLatLng(sydney));
CameraUpdate zoom=CameraUpdateFactory.zoomTo(17);
mMap.animateCamera(zoom);
}
}