如何使用 TabLayout 在 ViewPager 中的 Google 地图片段中获取当前位置
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【中文标题】如何使用 TabLayout 在 ViewPager 中的 Google 地图片段中获取当前位置【英文标题】：How to get current location within a Google Maps Fragment in a ViewPager with TabLayout 【发布时间】：2017-07-27 00:26:39 【问题描述】：我设法实现了一个 TabLayout。在其中一个选项卡中是一个谷歌地图片段。我想请求访问用户位置的权限，然后在当前位置上放置一个标记。截至目前，对话框没有出现，我不知道为什么。谁能帮帮我？
public class MapsFragment extends Fragment implements OnMapReadyCallback
GoogleMap mGoogleMap;
MapView mMapView;
View mView;
LocationManager locationManager;
static final int REQUEST_LOCATION = 1;
public MapsFragment()
// Required empty public constructor
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState)
// Inflate the layout for this fragment
mView = inflater.inflate(R.layout.fragment_maps,container,false);
return mView;
@Override
public void onViewCreated(View view, Bundle savedInstanceState)
super.onViewCreated(view, savedInstanceState);
mMapView = (MapView) mView.findViewById(R.id.googleMap);
if(mMapView != null)
mMapView.onCreate(null);
mMapView.onResume();
mMapView.getMapAsync(this);
@Override
public void onMapReady(GoogleMap googleMap)
mGoogleMap = googleMap;
googleMap.setMapType(GoogleMap.MAP_TYPE_NORMAL);
//Initialize Google PLay Services
if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.M)
if(ContextCompat.checkSelfPermission(getContext(),
Manifest.permission.ACCESS_FINE_LOCATION) == PackageManager.PERMISSION_GRANTED)
//Location Permission is gratned
MapsInitializer.initialize(getContext());
mGoogleMap.setMyLocationEnabled(true);
googleMap.addMarker(new MarkerOptions().position(new LatLng(36.652527, -121.797277)).title("CSUMB"));
CameraPosition CSUMB = CameraPosition.builder().target(new LatLng(36.6538, -121.797277)).zoom(16).bearing(0).tilt(45).build();
googleMap.moveCamera(CameraUpdateFactory.newCameraPosition(CSUMB));
void getLocation()
locationManager = (LocationManager)getActivity()
.getSystemService(Context.LOCATION_SERVICE);
getLocation();
if(ActivityCompat.checkSelfPermission(getContext(), Manifest.permission.ACCESS_FINE_LOCATION)
!= PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(getContext(),
Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED)
else
Location location = locationManager.getLastKnownLocation(LocationManager.NETWORK_PROVIDER);
if(location!= null)
double latti = location.getLatitude();
double longi = location.getLongitude();
Toast.makeText(getActivity(),"Location is " + String.valueOf(latti) + ", " + String.valueOf(longi),Toast.LENGTH_LONG);
Log.e("Maps Fragment", "Location is: " + String.valueOf(latti) + ", " + String.valueOf(longi));
else
Log.e("Maps fragment", "Unable to find current location.");
@Override
public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults)
super.onRequestPermissionsResult(requestCode, permissions, grantResults);
switch (requestCode)
case REQUEST_LOCATION:
getLocation();
break;
@Override
public void onResume()
super.onResume();
mMapView.onResume();
@Override
public void onPause()
super.onPause();
mMapView.onPause();
@Override
public void onDestroy()
super.onDestroy();
mMapView.onDestroy();
@Override
public void onLowMemory()
super.onLowMemory();
mMapView.onLowMemory();
【问题讨论】：
【参考方案1】：这与我的other answer here 非常接近，但是，该答案并未解释如何使用带有 TabLayout 的 ViewPager。
首先，将其与其他答案区分开来，您需要使用 instantiateItem() 覆盖在 FragmentPagerAdapter 中保留对当前 Fragment 的引用。
另外，请注意，此处需要在 Activity 中使用 onRequestPermissionsResult() 方法，以便将用户的权限请求响应路由到 Fragment。
这是完整的活动代码：
public class MainActivity extends AppCompatActivity
ViewPager viewPager;
PagerAdapter pagerAdapter;
@Override
protected void onCreate(Bundle savedInstanceState)
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
// Get the ViewPager and set it's PagerAdapter so that it can display items
viewPager = (ViewPager) findViewById(R.id.viewpager);
pagerAdapter = new PagerAdapter(getSupportFragmentManager(), MainActivity.this);
viewPager.setAdapter(pagerAdapter);
// Give the TabLayout the ViewPager
TabLayout tabLayout = (TabLayout) findViewById(R.id.tab_layout);
tabLayout.setupWithViewPager(viewPager);
// Iterate over all tabs and set the custom view
for (int i = 0; i < tabLayout.getTabCount(); i++)
TabLayout.Tab tab = tabLayout.getTabAt(i);
tab.setCustomView(pagerAdapter.getTabView(i));
class PagerAdapter extends FragmentPagerAdapter
String tabTitles[] = new String[] "Tab One", "Tab Two", "Tab Three", ;
public Fragment[] fragments = new Fragment[tabTitles.length];
Context context;
public PagerAdapter(FragmentManager fm, Context context)
super(fm);
this.context = context;
@Override
public int getCount()
return tabTitles.length;
@Override
public Fragment getItem(int position)
switch (position)
case 0:
return new MapFragment();
case 1:
return new BlankFragment();
case 2:
return new BlankFragment();
return null;
@Override
public CharSequence getPageTitle(int position)
// Generate title based on item position
return tabTitles[position];
public View getTabView(int position)
View tab = LayoutInflater.from(MainActivity.this).inflate(R.layout.custom_tab, null);
TextView tv = (TextView) tab.findViewById(R.id.custom_text);
tv.setText(tabTitles[position]);
return tab;
//This populates your Fragment reference array:
@Override
public Object instantiateItem(ViewGroup container, int position)
Fragment createdFragment = (Fragment) super.instantiateItem(container, position);
fragments[position] = createdFragment;
return createdFragment;
@Override
public void onRequestPermissionsResult(int requestCode,
String permissions[], int[] grantResults)
if (requestCode == MapFragment.MY_PERMISSIONS_REQUEST_LOCATION)
MapFragment mapFragment = (MapFragment) pagerAdapter.fragments[0];
if (mapFragment != null)
mapFragment.onRequestPermissionsResult(requestCode, permissions, grantResults);
else
super.onRequestPermissionsResult(requestCode, permissions, grantResults);
activity_main.xml：
<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_
android:layout_
android:fitsSystemWindows="true"
tools:context=".MainActivity">
<android.support.design.widget.AppBarLayout
android:layout_
android:layout_
android:theme="@style/AppTheme.AppBarOverlay"
android:elevation="6dp">
<android.support.v7.widget.Toolbar
android:id="@+id/toolbar"
android:layout_
android:layout_
android:background="?attr/colorPrimary"
android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"
app:popupTheme="@style/ThemeOverlay.AppCompat.Light"
android:elevation="0dp" />
<android.support.design.widget.TabLayout
android:id="@+id/tab_layout"
app:tabMode="fixed"
android:layout_
android:layout_
android:layout_below="@+id/toolbar"
android:background="?attr/colorPrimary"
android:elevation="0dp"
app:tabTextColor="#d3d3d3"
app:tabSelectedTextColor="#ffffff"
app:tabIndicatorColor="#ff00ff"
android:minHeight="?attr/actionBarSize"
/>
</android.support.design.widget.AppBarLayout>
<android.support.v4.view.ViewPager
android:id="@+id/viewpager"
android:layout_
android:layout_
app:layout_behavior="@string/appbar_scrolling_view_behavior"
/>
</android.support.design.widget.CoordinatorLayout>
custom_tab.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_
android:layout_>
<TextView
android:id="@+id/custom_text"
android:layout_
android:layout_
android:background="?attr/selectableItemBackground"
android:gravity="center"
android:textSize="16dip"
android:textColor="#ffffff"
android:maxLines="1"
/>
</LinearLayout>
对于地图片段，使用与其他答案基本相同的代码：
public class MapFragment extends SupportMapFragment
implements OnMapReadyCallback,
GoogleApiClient.ConnectionCallbacks,
GoogleApiClient.OnConnectionFailedListener,
LocationListener
GoogleMap mGoogleMap;
LocationRequest mLocationRequest;
GoogleApiClient mGoogleApiClient;
Location mLastLocation;
Marker mCurrLocationMarker;
@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);
@Override
public void onMapReady(GoogleMap googleMap)
mGoogleMap=googleMap;
mGoogleMap.setMapType(GoogleMap.MAP_TYPE_HYBRID);
//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 onConnectionFailed(ConnectionResult connectionResult)
@Override
public void onLocationChanged(Location location)
mLastLocation = location;
if (mCurrLocationMarker != null)
mCurrLocationMarker.remove();
//Place current location marker
LatLng latLng = new LatLng(location.getLatitude(), location.getLongitude());
MarkerOptions markerOptions = new MarkerOptions();
markerOptions.position(latLng);
markerOptions.title("Current Position");
markerOptions.icon(BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_MAGENTA));
mCurrLocationMarker = mGoogleMap.addMarker(markerOptions);
//move map camera
mGoogleMap.moveCamera(CameraUpdateFactory.newLatLng(latLng));
mGoogleMap.animateCamera(CameraUpdateFactory.zoomTo(11));
//optionally, stop location updates if only current location is needed
if (mGoogleApiClient != null)
LocationServices.FusedLocationApi.removeLocationUpdates(mGoogleApiClient, this);
public static final int MY_PERMISSIONS_REQUEST_LOCATION = 99;
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
结果
一、位置权限提示：
一旦用户在运行时接受了权限，就显示用户的当前位置：
【讨论】：
你能解释一下为什么我们需要一个片段引用数组吗？ @TheLearner 需要通过调用mapFragment.onRequestPermissionsResult() 将用户的权限选择从活动传递到片段。请记住，当用户滑动时，ViewPager 会根据需要创建和重新创建 Fragment，默认情况下，它会保持当前 Fragment 和两侧的 Fragment 处于活动状态。因此，为了获得对当前活动 Fragments 的引用，需要 instantiateItem() 覆盖。
感谢您的解释。由于某种原因，我收到一个错误：PagerAdapter.getTabView(int)' on an null object reference at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2947)
没关系，我能弄明白，但我的 getTabView 永远不会被调用；/
我理解您的代码，但永远不会调用 getTabView 方法。我忘了提到我也在使用导航抽屉，但我认为这不会引起问题。你能帮我看看我的代码吗？以上是关于如何使用 TabLayout 在 ViewPager 中的 Google 地图片段中获取当前位置的主要内容，如果未能解决你的问题，请参考以下文章