我是零碎的新手，它是如此令人困惑。我有一个在ViewPager.中有两个片段的活动ViewPager设置为TabsLayout。我正在使用FragmentStatePagerAdapter。在这些片段的每一个中，我都有一个RecyclerView，它填充了存储在服务器上的项目的列表。
问题1
正在使用相同的数据多次（大约每20秒）重新创建片段。
我想要的
我希望仅当用户导航到每个片段时才重新创建每个片段。这样，它可以包含从Web服务器下载的最新数据。
问题2
当我查看第二个片段时，所有片段的重新播放将我带回到第一个片段。抱歉，我不知道可以使用任何专业术语来形容这一点。每次重新创建片段时，我都会自动发送回第一个片段。第一个片段是第一次创建活动时加载的片段。
我想要的
我希望用户在他/她想要的时间内保持不动的状态，而不会进行自动重新娱乐（嗯，就像我上面所说的那样，仅当用户导航到它时才进行重新娱乐。）< / p>
注意
两个片段都是相同的，所以我只会共享一个片段的代码。
这是我的活动：
public class MainActivity extends AppCompatActivity
implements NavigationView.OnNavigationItemSelectedListener, OneFragment.OnFragmentInteractionListener, TwoFragment.OnFragmentInteractionListener {
private final int MIN_TIME_BW_UPDATES = 0;
private final float MIN_DISTANCE_CHANGE_FOR_UPDATES = 0;
private final long ONE_MEGABYTE = 1024 * 1024;
private static final int TWO_MINUTES = 1000 * 60 * 2;
private final int REQUEST_CHECK_SETTINGS = 1;
private Toolbar toolbar;
private TabLayout tabLayout;
private ViewPager viewPager;
private LocationManager locationManager;
private LocationListener locationListener;
private boolean permission, isGPSEnabled, isNetworkEnabled;
private FirebaseFirestore mDatabase;
private StorageReference storageRef;
private Long act_geo_limit;
private Map<String, Object> user;
private Location currentBestLocation;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
viewPager = (ViewPager) findViewById(R.id.viewpager);
FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
fab.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
startActivity(new Intent(MainActivity.this, CreatPostActivity.class));
}
});
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
drawer.addDrawerListener(toggle);
toggle.syncState();
NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
final View hView = navigationView.getHeaderView(0);
mDatabase = FirebaseFirestore.getInstance();
storageRef = FirebaseStorage.getInstance().getReference();
user = new HashMap<>();
locationManager = (LocationManager) getSystemService(LOCATION_SERVICE);
// Define a listener that responds to location updates
locationListener = new LocationListener() {
public void onLocationChanged(Location location) {
// Called when a new location is found by the network location provider.
makeUseOfNewLocation(location);
TextView loc = hView.findViewById(R.id.location);
try {
List<Address> addressList = getAddressForLocation(MainActivity.this, currentBestLocation);
loc.setText(addressList.get(0).getAddressLine(0));
}catch (Exception e){
Toast.makeText(MainActivity.this, "Please reboot this device", Toast.LENGTH_LONG).show();
e.printStackTrace();
}
mDatabase
.collection("Users")
.document(FirebaseAuth.getInstance().getUid())
.get()
.addOnCompleteListener(new OnCompleteListener<DocumentSnapshot>() {
@Override
public void onComplete(@NonNull Task<DocumentSnapshot> task) {
user = task.getResult().getData();
act_geo_limit = ((Long) user.get("act_geo_limit"));
String p1 = user.get("profile_image_path").toString();
storageRef.child(p1).getBytes(ONE_MEGABYTE).addOnSuccessListener(new OnSuccessListener<byte[]>() {
@Override
public void onSuccess(byte[] bytes) {
Bitmap bitmap = BitmapFactory.decodeByteArray(bytes, 0, bytes.length);
ImageView imageView = hView.findViewById(R.id.imageView);
//Set Profile pic
imageView.setImageBitmap(bitmap);
}
});
TextView userName = hView.findViewById(R.id.user_name);
userName.setText(user.get("user_name").toString());
Bundle bundle=new Bundle();
bundle.putString("latitude", String.valueOf(currentBestLocation.getLatitude()));
bundle.putString("longitude", String.valueOf(currentBestLocation.getLongitude()));
bundle.putString("act_geo_limit", String.valueOf(act_geo_limit));
setupViewPager(viewPager, bundle);
tabLayout = (TabLayout) findViewById(R.id.tabs);
tabLayout.setupWithViewPager(viewPager);
}
});
}
public void onStatusChanged(String provider, int status, Bundle extras) {}
public void onProviderEnabled(String provider) {
}
public void onProviderDisabled(String provider) {
}
};
if (isDevMode()) {
Toast.makeText(this, "Please turn off Developer Options", Toast.LENGTH_LONG).show();
FirebaseAuth.getInstance().signOut();
startActivity(new Intent(MainActivity.this, LoginActivity.class));
} else {
boolean isGpsEnabled = locationManager.isProviderEnabled(LocationManager.GPS_PROVIDER);
boolean isNetworkEnabled = locationManager.isProviderEnabled(LocationManager.NETWORK_PROVIDER);
if (isGpsEnabled || isNetworkEnabled) {
//Toast.makeText(this, "GPS is Enabled in your device", Toast.LENGTH_SHORT).show();
if ( ContextCompat.checkSelfPermission( this, Manifest.permission.ACCESS_FINE_LOCATION ) != PackageManager.PERMISSION_GRANTED ) {
ActivityCompat.requestPermissions(this, new
String[]{Manifest.permission.ACCESS_FINE_LOCATION},REQUEST_CHECK_SETTINGS);
}
} else {
Toast.makeText(this, "Enable Location Services on your device", Toast.LENGTH_SHORT).show();
FirebaseAuth.getInstance().signOut();
startActivity(new Intent(MainActivity.this, LoginActivity.class));
}
}
if (locationManager.isProviderEnabled(LocationManager.NETWORK_PROVIDER)) {
Log.d("NETWORK ENABLED", "TRUE");
isNetworkEnabled = true;
} else {
Log.d("NETWORK ENABLED", "FALSE");
}
if (locationManager.isProviderEnabled(LocationManager.GPS_PROVIDER)) {
Log.d("GPS ENABLED", "TRUE");
isGPSEnabled = true;
} else {
Log.d("GPS ENABLED", "FALSE");
}
currentBestLocation = getLastBestLocation();
if (currentBestLocation != null){
TextView location = hView.findViewById(R.id.location);
try {
List<Address> addressList = getAddressForLocation(this, currentBestLocation);
location.setText(addressList.get(0).getAddressLine(1));
}catch (Exception e){
showRebootAlertToUser();
e.printStackTrace();
}
}
navigationView.setNavigationItemSelectedListener(this);
listenForLocationUpdates();
}
private void showRebootAlertToUser(){
AlertDialog.Builder alertDialogBuilder = new AlertDialog.Builder(this);
alertDialogBuilder.setMessage("GeoCoder Error: Please restart this device.")
.setCancelable(false)
.setNegativeButton("Got it",
new DialogInterface.OnClickListener(){
public void onClick(DialogInterface dialog, int id){
Intent homeIntent = new Intent(Intent.ACTION_MAIN);
homeIntent.addCategory( Intent.CATEGORY_HOME );
homeIntent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(homeIntent);
}
});
AlertDialog alert = alertDialogBuilder.create();
alert.show();
}
@android.annotation.TargetApi(17) public boolean isDevMode() {
return false;
/*
if(Integer.valueOf(android.os.Build.VERSION.SDK) == 16) {
return android.provider.Settings.Secure.getInt(getApplicationContext().getContentResolver(),
android.provider.Settings.Secure.DEVELOPMENT_SETTINGS_ENABLED , 0) != 0;
} else if (Integer.valueOf(android.os.Build.VERSION.SDK) >= 17) {
return android.provider.Settings.Secure.getInt(getApplicationContext().getContentResolver(),
android.provider.Settings.Global.DEVELOPMENT_SETTINGS_ENABLED , 0) != 0;
} else return false;
*/
}
@Override
public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {
switch (requestCode) {
case REQUEST_CHECK_SETTINGS:
if (grantResults.length> 0) {
boolean permission = grantResults[0] == PackageManager.PERMISSION_GRANTED;
if (permission) {
Toast.makeText(getApplicationContext(), "Permission Granted", Toast.LENGTH_LONG).show();
} else {
FirebaseAuth.getInstance().signOut();
startActivity(new Intent(MainActivity.this, LoginActivity.class));
}
}
break;
}
}
public List<Address> getAddressForLocation(Context context, Location location) throws IOException {
if (location == null) {
return null;
}
double latitude = location.getLatitude();
double longitude = location.getLongitude();
int maxResults = 1;
Geocoder gc = new Geocoder(context, Locale.getDefault());
List<Address> addresses = gc.getFromLocation(latitude, longitude, maxResults);
if (addresses.size() > 0) {
return addresses;
} else {
return null;
}
}
protected boolean isBetterLocation(Location location, Location currentBestLocation) {
if (currentBestLocation == null) {
// A new location is always better than no location
return true;
}
// Check whether the new location fix is newer or older
long timeDelta = location.getTime() - currentBestLocation.getTime();
boolean isSignificantlyNewer = timeDelta > TWO_MINUTES;
boolean isSignificantlyOlder = timeDelta < -TWO_MINUTES;
boolean isNewer = timeDelta > 0;
// If it's been more than two minutes since the current location, use the new location,
// because the user has likely moved.
if (isSignificantlyNewer) {
return true;
// If the new location is more than two minutes older, it must be worse.
} else if (isSignificantlyOlder) {
return false;
}
// Check whether the new location fix is more or less accurate
int accuracyDelta = (int) (location.getAccuracy() - currentBestLocation.getAccuracy());
boolean isLessAccurate = accuracyDelta > 0;
boolean isMoreAccurate = accuracyDelta < 0;
boolean isSignificantlyLessAccurate = accuracyDelta > 200;
// Check if the old and new location are from the same provider
boolean isFromSameProvider = isSameProvider(location.getProvider(),
currentBestLocation.getProvider());
// Determine location quality using a combination of timeliness and accuracy
if (isMoreAccurate) {
return true;
} else if (isNewer && !isLessAccurate) {
return true;
} else if (isNewer && !isSignificantlyLessAccurate && isFromSameProvider) {
return true;
}
return false;
}
// Checks whether two providers are the same
private boolean isSameProvider(String provider1, String provider2) {
if (provider1 == null) {
return provider2 == null;
}
return provider1.equals(provider2);
}
/**
* @return the last know best location
*/
private Location getLastBestLocation() {
if ( ContextCompat.checkSelfPermission( this, android.Manifest.permission.ACCESS_COARSE_LOCATION ) == PackageManager.PERMISSION_GRANTED )
{
Location locationGPS = locationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER);
Location locationNet = locationManager.getLastKnownLocation(LocationManager.NETWORK_PROVIDER);
long GPSLocationTime = 0;
if (null != locationGPS) {
GPSLocationTime = locationGPS.getTime();
}
long NetLocationTime = 0;
if (null != locationNet) {
NetLocationTime = locationNet.getTime();
}
if (0 < GPSLocationTime - NetLocationTime) {
return locationGPS;
} else {
return locationNet;
}
}
return null;
}
private void makeUseOfNewLocation(Location location) {
if ( isBetterLocation(location, getLastBestLocation()) ) {
currentBestLocation = location;
//Log.d("LOCATION+++++", "used");
} else {
currentBestLocation = getLastBestLocation();
//Log.d("LOCATION+++++", "reused");
}
}
private void listenForLocationUpdates(){
//Toast.makeText(CreatPostActivity.this, "got in", Toast.LENGTH_LONG).show();
if ( ContextCompat.checkSelfPermission( this, Manifest.permission.ACCESS_FINE_LOCATION ) == PackageManager.PERMISSION_GRANTED ) {
if (!isGPSEnabled && !isNetworkEnabled) {
// No network provider is enabled
} else {
if (isNetworkEnabled) {
//Toast.makeText(CreatPostActivity.this, "Listen enabled", Toast.LENGTH_LONG).show();
locationManager.requestLocationUpdates(
LocationManager.NETWORK_PROVIDER,
MIN_TIME_BW_UPDATES,
MIN_DISTANCE_CHANGE_FOR_UPDATES, locationListener);
}
// If GPS enabled, get latitude/longitude using GPS Services
if (isGPSEnabled) {
locationManager.requestLocationUpdates(
LocationManager.GPS_PROVIDER,
MIN_TIME_BW_UPDATES,
MIN_DISTANCE_CHANGE_FOR_UPDATES, locationListener);
}
}
}
}
private void setupViewPager(ViewPager viewPager, Bundle bundle) {
ViewPagerAdapter adapter = new ViewPagerAdapter(getSupportFragmentManager());
OneFragment oneFragment = new OneFragment();
oneFragment.setArguments(bundle);
TwoFragment twoFragment = new TwoFragment();
twoFragment.setArguments(bundle);
adapter.addFragment(oneFragment, "Popular");
adapter.addFragment(twoFragment, "Recent");
viewPager.setOffscreenPageLimit(2);
viewPager.setAdapter(adapter);
}
@Override
public void onFragmentInteraction(Uri uri) {
}
@Override
public void onPointerCaptureChanged(boolean hasCapture) {
}
class ViewPagerAdapter extends FragmentStatePagerAdapter {
private final List<Fragment> mFragmentList = new ArrayList<>();
private final List<String> mFragmentTitleList = new ArrayList<>();
public ViewPagerAdapter(FragmentManager manager) {
super(manager);
}
@Override
public Fragment getItem(int position) {
Log.d("Taggggggg", "God is good");
return mFragmentList.get(position);
}
@Override
public int getCount() {
return mFragmentList.size();
}
public void addFragment(Fragment fragment, String title) {
mFragmentList.add(fragment);
mFragmentTitleList.add(title);
}
@Override
public CharSequence getPageTitle(int position) {
return mFragmentTitleList.get(position);
}
}
@Override
public void onBackPressed() {
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
if (drawer.isDrawerOpen(GravityCompat.START)) {
drawer.closeDrawer(GravityCompat.START);
} else {
super.onBackPressed();
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
@SuppressWarnings("StatementWithEmptyBody")
@Override
public boolean onNavigationItemSelected(MenuItem item) {
// Handle navigation view item clicks here.
int id = item.getItemId();
if (id == R.id.nav_home) {
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
drawer.closeDrawer(GravityCompat.START);
} else if (id == R.id.nav_wall) {
startActivity(new Intent(this, MyWallActivity.class));
} else if (id == R.id.nav_messages) {
Toast.makeText(this, "This service is not available", Toast.LENGTH_SHORT).show();
} else if (id == R.id.nav_ver) {
startActivity(new Intent(this, AdBriefingActivity.class));
} else if (id == R.id.nav_invite) {
Toast.makeText(this, "This service is not available", Toast.LENGTH_SHORT).show();
}
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
drawer.closeDrawer(GravityCompat.START);
return true;
}
}
这是我的片段之一
public class OneFragment extends Fragment {
// TODO: Rename parameter arguments, choose names that match
// the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
private static final String ARG_PARAM1 = "param1";
private static final String ARG_PARAM2 = "param2";
// TODO: Rename and change types of parameters
private String mParam1;
private String mParam2;
private RecyclerView recycler;
private View view;
private Bundle bundle;
private List<Post> postList,sortedPostList;
private List<String> postIdList;
private PostAdapter adapter;
private GeoQueryDataEventListener listener;
private GeoQuery geoQuery;
private OnFragmentInteractionListener mListener;
public OneFragment() {
// Required empty public constructor
}
/**
* Use this factory method to create a new instance of
* this fragment using the provided parameters.
*
* @param param1 Parameter 1.
* @param param2 Parameter 2.
* @return A new instance of fragment OneFragment.
*/
// TODO: Rename and change types and number of parameters
public static OneFragment newInstance(String param1, String param2) {
OneFragment fragment = new OneFragment();
Bundle args = new Bundle();
args.putString(ARG_PARAM1, param1);
args.putString(ARG_PARAM2, param2);
fragment.setArguments(args);
return fragment;
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (getArguments() != null) {
mParam1 = getArguments().getString(ARG_PARAM1);
mParam2 = getArguments().getString(ARG_PARAM2);
}
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
if (null != view) {
return view;
}
view = inflater.inflate(R.layout.fragment_one, container, false);
recycler = (RecyclerView) view.findViewById(R.id.one_fragment_recycler_view);
LinearLayoutManager manager = new LinearLayoutManager(getContext());
recycler.setLayoutManager(manager);
postList = new ArrayList<>();
sortedPostList = new ArrayList<>();
postIdList = new ArrayList<>();
adapter = new PostAdapter(postList, getContext());
recycler.setAdapter(adapter);
CollectionReference postRef = FirebaseFirestore.getInstance().collection("Posts");
bundle = getArguments();
listener = new GeoQueryDataEventListener() {
@Override
public void onDocumentEntered(DocumentSnapshot documentSnapshot, GeoPoint location) {
// ...
postList.add(documentSnapshot.toObject(Post.class));
}
@Override
public void onDocumentExited(DocumentSnapshot documentSnapshot) {
// ...
}
@Override
public void onDocumentMoved(DocumentSnapshot documentSnapshot, GeoPoint location) {
// ...
}
@Override
public void onDocumentChanged(DocumentSnapshot documentSnapshot, GeoPoint location) {
// ...
}
@Override
public void onGeoQueryReady() {
// ...
//mergeSortPost(postList, 0, postList.size()-1);
adapter.notifyDataSetChanged();
Log.d("TAG______", "Damn it did it again");
}
@Override
public void onGeoQueryError(Exception exception) {
// ...
}
};
loadPostList(postRef);
return view;
}
@Override
public void onAttach(Context context) {
super.onAttach(context);
if (context instanceof OnFragmentInteractionListener) {
mListener = (OnFragmentInteractionListener) context;
} else {
throw new RuntimeException(context.toString()
+ " must implement OnFragmentInteractionListener");
}
}
private void removeListener(){
geoQuery.removeGeoQueryEventListener(listener);
}
private void loadPostList(final CollectionReference postRef) {
GeoFirestore geoFirestore = new GeoFirestore(postRef);
geoQuery = geoFirestore.queryAtLocation(
new GeoPoint(
Double.valueOf(bundle.get("latitude").toString()),
Double.valueOf(bundle.get("longitude").toString())),
Double.valueOf(bundle.get("act_geo_limit").toString())
);
geoQuery.addGeoQueryDataEventListener(listener);
}
@Override
public void onDetach() {
super.onDetach();
removeListener();
}
/**
* This interface must be implemented by activities that contain this
* fragment to allow an interaction in this fragment to be communicated
* to the activity and potentially other fragments contained in that
* activity.
* <p>
* See the Android Training lesson <a href=
* "http://developer.android.com/training/basics/fragments/communicating.html"
* >Communicating with Other Fragments</a> for more information.
*/
public interface OnFragmentInteractionListener {
// TODO: Update argument type and name
void onFragmentInteraction(Uri uri);
}
}