我有3个标签：
我有一个主要活动，它有一个TabLayout来显示3个标签：
public class MainActivity extends AppCompatActivity implements MyMapFragment.OnFragmentInteractionListener, SettingsFragment.OnFragmentInteractionListener {
private static final int INDEX_HOME_FRAGMENT = 0;
private static final int INDEX_MAP_FRAGMENT = 1;
private static final int INDEX_SETTINGS_FRAGMENT = 2;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
TabLayout tabLayout = (TabLayout) findViewById(R.id.tab_layout);
tabLayout.addTab(tabLayout.newTab().setText("Home"));
tabLayout.addTab(tabLayout.newTab().setText("Map"));
tabLayout.addTab(tabLayout.newTab().setText("Settings"));
tabLayout.addOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
@Override
public void onTabSelected(TabLayout.Tab tab) {
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
switch(tab.getPosition()) {
case INDEX_HOME_FRAGMENT:
HomeFragment homeFragment = new HomeFragment();
transaction.replace(R.id.frame_layout, homeFragment);
// Commit the transaction
transaction.commit();
break;
case INDEX_MAP_FRAGMENT:
MyMapFragment myMapFragment = new MyMapFragment();
transaction.replace(R.id.frame_layout, myMapFragment);
// Commit the transaction
transaction.commit();
break;
case INDEX_SETTINGS_FRAGMENT:
SettingsFragment settingsFragment = new SettingsFragment();
transaction.replace(R.id.frame_layout, settingsFragment);
// Commit the transaction
transaction.commit();
break;
default:
//error occured here
Log.e("Error occured = ", " TAB_ERROR");
break;
}
}
});
// Check that the activity is using the layout version with
// the fragment_container FrameLayout
if (findViewById(R.id.frame_layout) != null) {
if (savedInstanceState != null) {
return;
}
HomeFragment homeFragment = new HomeFragment();
// Add the fragment to the 'fragment_container' FrameLayout
getSupportFragmentManager().beginTransaction()
.add(R.id.frame_layout, homeFragment ).commit();
}
}
@Override
public void onFragmentInteraction(Uri uri) {
//do nothing
}
}
此活动还会在单击选项卡时进行处理。单击选项卡时，它应显示FrameLayout中的片段 一切正常。唯一的问题是当我点击地图标签时，Google地图会一直刷新 我希望地图在应用程序启动时预加载，因此当用户单击地图选项卡时，已经加载了地图shoudl。当用户离开地图选项卡并返回时，它应该像以前一样保存地图。目前，当用户返回地图选项卡时，地图会重新加载，并且需要一段时间才能加载地图。
这是我的地图片段：
public class MyMapFragment extends SupportMapFragment
implements OnMapReadyCallback,
GoogleApiClient.ConnectionCallbacks,
GoogleApiClient.OnConnectionFailedListener,
LocationListener {
public static final int MY_PERMISSIONS_REQUEST_LOCATION = 99;
GoogleMap mGoogleMap;
LocationRequest mLocationRequest;
GoogleApiClient mGoogleApiClient;
Marker lastOpenned = null;
@Override
public void onResume() {
super.onResume();
setUpMapIfNeeded();
}
private void setUpMapIfNeeded() {
if (mGoogleMap == null) {
getMapAsync(this);
}
}
@Override
public void onPause() {
super.onPause();
//stop location updates when Activity is no longer active
if (mGoogleApiClient != null) {
//LocationServices.FusedLocationApi.removeLocationUpdates(mGoogleApiClient, this);
LocationServices.FusedLocationApi.removeLocationUpdates(mGoogleApiClient,this);
}
}
@Override
public void onMapReady(GoogleMap googleMap) {
mGoogleMap = googleMap;
LatLngBounds.Builder builder = new LatLngBounds.Builder();
mGoogleMap.addMarker(new MarkerOptions()
.position(new LatLng(40.76793169992044, -73.98180484771729))
.title("San Francisco"));
mGoogleMap.addMarker(new MarkerOptions()
.position(new LatLng(41.76793169992044, -72.98180484771729))
.title("Las Vegas"));
builder.include(new LatLng(40.76793169992044, -73.98180484771729));
builder.include(new LatLng(41.76793169992044, -72.98180484771729));
LatLngBounds bounds = builder.build();
mGoogleMap.animateCamera(CameraUpdateFactory.newLatLngBounds(bounds, 200));
mGoogleMap.setOnMarkerClickListener(new GoogleMap.OnMarkerClickListener() {
public boolean onMarkerClick(Marker marker) {
return true;
}
});
//Initialize Google Play Services
if (android.os.Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
if (ContextCompat.checkSelfPermission(getActivity(),
Manifest.permission.ACCESS_FINE_LOCATION)
== PackageManager.PERMISSION_GRANTED) {
//Location Permission already granted
buildGoogleApiClient();
mGoogleMap.setMyLocationEnabled(true);
} else {
//Request Location Permission
checkLocationPermission();
}
} else {
buildGoogleApiClient();
mGoogleMap.setMyLocationEnabled(true);
}
}
protected synchronized void buildGoogleApiClient() {
mGoogleApiClient = new GoogleApiClient.Builder(getActivity())
.addConnectionCallbacks(this)
.addOnConnectionFailedListener(this)
.addApi(LocationServices.API)
.build();
mGoogleApiClient.connect();
}
@Override
public void onConnected(Bundle bundle) {
mLocationRequest = new LocationRequest();
mLocationRequest.setInterval(1000);
mLocationRequest.setFastestInterval(1000);
mLocationRequest.setPriority(LocationRequest.PRIORITY_BALANCED_POWER_ACCURACY);
if (ContextCompat.checkSelfPermission(getActivity(),
Manifest.permission.ACCESS_FINE_LOCATION)
== PackageManager.PERMISSION_GRANTED) {
LocationServices.FusedLocationApi.requestLocationUpdates(mGoogleApiClient, mLocationRequest, this);
}
}
@Override
public void onConnectionSuspended(int i) {
}
@Override
public void onLocationChanged(Location location) {
}
private void checkLocationPermission() {
if (ContextCompat.checkSelfPermission(getActivity(), Manifest.permission.ACCESS_FINE_LOCATION)
!= PackageManager.PERMISSION_GRANTED) {
// Should we show an explanation?
if (ActivityCompat.shouldShowRequestPermissionRationale(getActivity(),
Manifest.permission.ACCESS_FINE_LOCATION)) {
// Show an explanation to the user *asynchronously* -- don't block
// this thread waiting for the user's response! After the user
// sees the explanation, try again to request the permission.
new AlertDialog.Builder(getActivity())
.setTitle("Location Permission Needed")
.setMessage("This app needs the Location permission, please accept to use location functionality")
.setPositiveButton("OK", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialogInterface, int i) {
//Prompt the user once explanation has been shown
ActivityCompat.requestPermissions(getActivity(),
new String[]{Manifest.permission.ACCESS_FINE_LOCATION},
MY_PERMISSIONS_REQUEST_LOCATION);
}
})
.create()
.show();
} else {
// No explanation needed, we can request the permission.
ActivityCompat.requestPermissions(getActivity(),
new String[]{Manifest.permission.ACCESS_FINE_LOCATION},
MY_PERMISSIONS_REQUEST_LOCATION);
}
}
}
@Override
public void onRequestPermissionsResult(int requestCode,
String permissions[], int[] grantResults) {
switch (requestCode) {
case MY_PERMISSIONS_REQUEST_LOCATION: {
// If request is cancelled, the result arrays are empty.
if (grantResults.length > 0
&& grantResults[0] == PackageManager.PERMISSION_GRANTED) {
// permission was granted, yay! Do the
// location-related task you need to do.
if (ContextCompat.checkSelfPermission(getActivity(),
Manifest.permission.ACCESS_FINE_LOCATION)
== PackageManager.PERMISSION_GRANTED) {
if (mGoogleApiClient == null) {
buildGoogleApiClient();
}
mGoogleMap.setMyLocationEnabled(true);
}
} else {
// permission denied, boo! Disable the
// functionality that depends on this permission.
Toast.makeText(getActivity(), "permission denied", Toast.LENGTH_LONG).show();
}
return;
}
// other 'case' lines to check for other
// permissions this app might request
}
}
@Override
public void onConnectionFailed(@NonNull ConnectionResult connectionResult) {
}
public interface OnFragmentInteractionListener {
// TODO: Update argument type and name
void onFragmentInteraction(Uri uri);
}
}
答案 0 :(得分：0)
I would suggest not making new MyMapFragment() every time you click the tab if you don't want the map to reload.
A simple way to do that is a simple wrapper Fragment holder class.
public class MainActivity extends AppCompatActivity
implements MyMapFragment.OnFragmentInteractionListener, SettingsFragment.OnFragmentInteractionListener {
static class FragmentTab {
String name;
Fragment frag;
public FragmentTab(String name, Fragment f) {
this.name = name;
this.frag = f;
}
}
// These are only created once, not per-click
private List<FragmentTab> tabs = Arrays.asList(
new FragmentTab("Home", new HomeFragment()),
new FragmentTab("Map", new MyMapFragment()),
new FragmentTab("Settings", new SettingsFragment()),
);
Then, you can iterate and index that list to clean up the rest of your code
for (FragmentTab tab : tabs) {
tabLayout.addTab(tabLayout.newTab().setText(tab.name));
}
tabLayout.addOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
@Override
public void onTabSelected(TabLayout.Tab tab) {
getSupportFragmentManager()
.beginTransaction()
.replace(R.id.frame_layout, tabs.get(tab.getPosition()).frag)
.commit();
}
};
A LinkedHashMap<String, Fragment> would also work, but replacing tab.getPosition() for tab.getTitle() (I think)