我正在制作一个应用程序，其中根据用户位置获取数据。我使用底部导航栏，并具有三个名为Home，Notifications和Account的片段。在Home片段中，我实现了FusedLocation Api以获取用户位置，但是问题是应用首次启动时未获得位置信息。当我更改导航并返回到首页导航时，或在启动活动后，单击首页导航，即可轻松获取位置。 这里有什么问题？有人让我知道。
下面是我的代码。
MainActivity.java
BottomNavigationView bottomBar;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
bottomBar = findViewById(R.id.bottomBar);
Home fragment = new Home();
FragmentTransaction fragmentTransaction =
getSupportFragmentManager().beginTransaction();
fragmentTransaction.replace(R.id.frame,fragment);
fragmentTransaction.commit();
bottomBar.setOnNavigationItemSelectedListener(new
BottomNavigationView.OnNavigationItemSelectedListener() {
@Override
public boolean onNavigationItemSelected(@NonNull MenuItem menuItem)
{
switch(menuItem.getItemId()){
case R.id.navigation_home:
Home fragment = new Home();
FragmentTransaction fragmentTransaction =
getSupportFragmentManager().beginTransaction();
fragmentTransaction.replace(R.id.frame,fragment);
fragmentTransaction.commit();
return true;
case R.id.navigation_notifications:
Notification fragment_notif = new Notification();
FragmentTransaction fragmentTransaction1 =
getSupportFragmentManager().beginTransaction();
fragmentTransaction1.replace(R.id.frame,fragment_notif);
fragmentTransaction1.commit();
return true;
case R.id.navigation_account:
Account fragment_acc = new Account();
FragmentTransaction fragmentTransaction2 =
getSupportFragmentManager().beginTransaction();
fragmentTransaction2.replace(R.id.frame,fragment_acc);
fragmentTransaction2.commit();
return true;
}
return false;
}
});
}
Home.java
public class Home extends Fragment implements GoogleApiClient.OnConnectionFailedListener,GoogleApiClient.ConnectionCallbacks,
com.google.android.gms.location.LocationListener{
TextView fragText;
GoogleApiClient mGoogleApiClient;
LocationRequest mLocationRequest;
String str1;
ProgressBar progressBar;
public Home() {
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View view = inflater.inflate(R.layout.fragment_home, container, false);
fragText = view.findViewById(R.id.fragText);
progressBar = view.findViewById(R.id.progressBar);
mGoogleApiClient = new GoogleApiClient.Builder(getActivity())
.addConnectionCallbacks(this)
.addOnConnectionFailedListener(this)
.addApi(LocationServices.API)
.build();
return view;
}
@Override
public void onStart() {
super.onStart();
mGoogleApiClient.connect();
}
@Override
public void onStop() {
super.onStop();
if(mGoogleApiClient.isConnected()){
mGoogleApiClient.disconnect();
}
}
@Override
public void onConnected(@Nullable Bundle bundle) {
mLocationRequest = LocationRequest.create();
mLocationRequest.setPriority(LocationRequest.PRIORITY_HIGH_ACCURACY);
mLocationRequest.setInterval(1000);
if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
if (ActivityCompat.checkSelfPermission(getActivity(), Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED){
ActivityCompat.requestPermissions(getActivity(), new String[]{Manifest.permission.ACCESS_COARSE_LOCATION}, 1);
} else {
LocationServices.FusedLocationApi.requestLocationUpdates(mGoogleApiClient, mLocationRequest, this);
}
}
else{
LocationServices.FusedLocationApi.requestLocationUpdates(mGoogleApiClient, mLocationRequest, this);
}
}
@Override
public void onConnectionSuspended(int i) {
}
@Override
public void onConnectionFailed(@NonNull ConnectionResult connectionResult) {
}
@Override
public void onLocationChanged(Location location) {
progressBar.setVisibility(View.INVISIBLE);
str1 = hereLocation(location.getLatitude(),location.getLongitude());
fragText.setText(str1);
}
@Override
public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
super.onRequestPermissionsResult(requestCode, permissions, grantResults);
if(grantResults.length>0 && grantResults[0] == PackageManager.PERMISSION_GRANTED){
if(ContextCompat.checkSelfPermission(getActivity(),Manifest.permission.ACCESS_COARSE_LOCATION)
== PackageManager.PERMISSION_GRANTED){
LocationServices.FusedLocationApi.requestLocationUpdates(mGoogleApiClient, mLocationRequest, this);
}
else{
progressBar.setVisibility(View.INVISIBLE);
TastyToast.makeText(getActivity(),"Unable to get location",TastyToast.LENGTH_SHORT,TastyToast.ERROR).show();
}
}
}
private String hereLocation(double lat, double lon){
String city = "";
Geocoder geo = new Geocoder(getContext(), Locale.getDefault());
List<Address> addresses;
try {
addresses = geo.getFromLocation(lat,lon,10);
if(addresses.size()>0){
for (Address adr: addresses){
if(adr.getLocality()!=null && adr.getLocality().length()>0){
city = adr.getLocality();
}
}
}
}
catch (IOException e) {
e.printStackTrace();
}
return city;
}
请仔细阅读以上代码，让我现在为什么要面对这个问题。
谢谢