在尝试了几乎所有方法之后，如果不拉取空对象引用，我似乎无法获取映射。我正在尝试将谷歌地图片段膨胀为片段，但是每次我这样做时，我总是保留一个 getmap 空对象 .
这是我的代码
在这一点上，我迫切需要任何帮助，我已经尝试了几乎所有方法。
错误
java.lang.NullPointerException: Attempt to invoke virtual method 'com.google.android.gms.maps.GoogleMap com.google.android.gms.maps.SupportMapFragment.getMap()' on a null object reference
at com.gnumbu.errolgreen.importedapplication.ViewMapFragment.onViewCreated(ViewMapFragment.java:122)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:971)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1136)
at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:739)
at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1499)
at android.support.v4.app.FragmentManagerImpl.executePendingTransactions(FragmentManager.java:488)
at android.support.v4.app.FragmentPagerAdapter.finishUpdate(FragmentPagerAdapter.java:141)
at android.support.v4.view.ViewPager.populate(ViewPager.java:1073)
at android.support.v4.view.ViewPager.populate(ViewPager.java:919)
at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1441)
at android.view.View.measure(View.java:17430)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5463)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:430)
at android.view.View.measure(View.java:17430)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5463)
at android.support.v7.internal.widget.ActionBarOverlayLayout.onMeasure(ActionBarOverlayLayout.java:453)
at android.view.View.measure(View.java:17430)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5463)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:430)
at android.view.View.measure(View.java:17430)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5463)
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1436)
at android.widget.LinearLayout.measureVertical(LinearLayout.java:722)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:613)
at android.view.View.measure(View.java:17430)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5463)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:430)
at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2560)
at android.view.View.measure(View.java:17430)
at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2001)
at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1166)
at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1372)
at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1054)
at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5779)
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:767)
at android.view.Choreographer.doCallbacks(Choreographer.java:580)
at android.view.Choreographer.doFrame(Choreographer.java:550)
at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:753)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5221)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
片段 java 类
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
if (container == null) {
return null;
}
view = (RelativeLayout) inflater.inflate(R.layout.fragmentmenu_layout, container, false);
// Passing harcoded values for latitude & longitude. Please change as per your need. This is just used to drop a Marker on the Map
latitude = 26.78;
longitude = 72.56;
; // For setting up the MapFragment
return view;
}
/***** Sets up the map if it is possible to do so *****/
public static void setUpMapIfNeeded() {
// Do a null check to confirm that we have not already instantiated the map.
if (mMap == null) {
// Try to obtain the map from the SupportMapFragment.
mMap = ((SupportMapFragment) SectionsPagerAdapter.fragmentManager
.findFragmentById(R.id.mapView)).getMap();
// Check if we were successful in obtaining the map.
if (mMap != null)
setUpMap();
}
}
/**
* This is where we can add markers or lines, add listeners or move the
* camera.
* <p>
* This should only be called once and when we are sure that {@link #mMap}
* is not null.
*/
private static void setUpMap() {
// For showing a move to my loction button
mMap.setMyLocationEnabled(true);
// For dropping a marker at a point on the Map
mMap.addMarker(new MarkerOptions().position(new LatLng(latitude, longitude)).title("My Home").snippet("Home Address"));
// For zooming automatically to the Dropped PIN Location
mMap.animateCamera(CameraUpdateFactory.newLatLngZoom(new LatLng(latitude,
longitude), 12.0f));
}
@Override
public void onViewCreated(View view, Bundle savedInstanceState) {
// TODO Auto-generated method stub
if (mMap != null)
setUpMap();
if (mMap == null) {
// Try to obtain the map from the SupportMapFragment.
mMap = ((SupportMapFragment) MainActivity.fragmentManager
.findFragmentById(R.id.mapView)).getMap(); // getMap is deprecated
// Check if we were successful in obtaining the map.
if (mMap != null)
setUpMap();
getAllFeaturedItems();
captureMapScreen();
}
}
@Override
public void onStart() {
super.onStart();
}
@Override
public void onResume() {
super.onResume();
setUpMapIfNeeded();
}
@Override
public void onPause() {
super.onPause();
}
@Override
public void onStop() {
super.onStop();
}
@Override
public void onLowMemory() {
super.onLowMemory();
}
/**** The mapfragment's id must be removed from the FragmentManager
**** or else if the same it is passed on the next time then
**** app will crash ****/
@Override
public void onDestroyView() {
super.onDestroyView();
if (mMap != null) {
MainActivity.fragmentManager.beginTransaction()
.remove(MainActivity.fragmentManager.findFragmentById(R.id.mapView)).commit();
mMap = null;
}
}
@Override
public void onDestroy() {
super.onDestroy();
}
fragmentmenu_layout.xml
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="match_parent"
android:layout_height="match_parent"
android:translationZ="5dp"
>
<ListView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="@+id/listViewMenu"
android:layout_gravity="center_horizontal"
android:dividerHeight="1sp"
android:translationZ="5dp"
android:divider="@color/background_default"
android:background="@color/background_white"
android:clickable="true"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:layout_below="@+id/screenShotMapView" />
<ImageView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/screenShotMapView"
android:layout_alignParentTop="true"
android:maxWidth="50dp"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:layout_alignParentRight="true"
android:layout_alignParentEnd="true"
android:adjustViewBounds="true"
android:translationZ="5dp"
/>
<fragment
class="com.google.android.gms.maps.MapFragment"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/mapView"
android:layout_alignParentTop="true"
android:layout_alignParentRight="true"
android:layout_alignParentEnd="true"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:adjustViewBounds="true"
android:longClickable="false"
android:visibility="visible"
android:maxHeight="50dp"
android:maxWidth="50dp"
/>
</RelativeLayout>
主要活动.java
public static FragmentManager fragmentManager;
@Override
protected void onCreate(Bundle savedInstanceState) {
// setTheme(R.style.ActionBarTheme);
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// initialising the object of the FragmentManager. Here I'm passing getSupportFragmentManager(). You can pass getFragmentManager() if you are coding for Android 3.0 or above.
// final ActionBar actionBar = getSupportActionBar();
buildGoogleApiClient();
// actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
// actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
mImageBitmap = null;
// Create the adapter that will return a fragment for each section/page
mSectionsPagerAdapter = new SectionsPagerAdapter(
this.getBaseContext(), getSupportFragmentManager());
fragmentManager = getSupportFragmentManager();
// Set up the ViewPager with the sections adapter.
mViewPager = (ViewPager) findViewById(R.id.pager);
mViewPager.setAdapter(mSectionsPagerAdapter);
mViewPager.setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {
@Override
public void onPageSelected(int position) {
// actionBar.setSelectedNavigationItem(position);
}
});
// For each of the sections in the app, add a tab to the action bar.
/*
for (int i = 0; i < mSectionsPagerAdapter.getCount(); i++) {
// Create a tab with text corresponding to the page title defined by
// the adapter. Also specify this Activity object, which implements
// the TabListener interface, as the callback (listener) for when
// this tab is selected.
if (i == 0) {
actionBar.addTab(
actionBar.newTab()
.setIcon(R.drawable.ic_action_view_as_list)
// .setText(mSectionsPagerAdapter.getPageTitle(i))
.setTabListener(this)
);
}
if (i == 1) {
actionBar.addTab(
actionBar.newTab()
.setIcon(R.drawable.ic_action_web_site_dark)
// .setText(mSectionsPagerAdapter.getPageTitle(i))
.setTabListener(this)
);
}
}
*/
mAlbumStorageDirFactory = new BaseAlbumDirFactory();
Intent intent = new Intent(this, SplashScreen.class);
startActivity(intent);
}
不太确定为什么我对此投了这么多票，但是我已经解决了这个问题。
此行
mMap = ((SupportMapFragment) MainActivity.fragmentManager
.findFragmentById(R.id.mapView)).getMap();
需要更改为
mMap = ((SupportMapFragment) getChildFragmentManager()
.findFragmentById(R.id.mapView)).getMap();
android：name= 应该改为 "com.google.android.gms.maps.SupportMapFragment" 即
从
<fragment android:name="com.google.android.gms.maps.MapFragment"
android:layout_width="match_parent"
android:layout_height="match_parent"/>
自
<fragment android:name="com.google.android.gms.maps.SupportMapFragment"
android:layout_width="match_parent"
android:layout_height="match_parent"/>
问题是您正在尝试从SupportMapFragment获取地图，但您使用的是不同类型的MapFragment，这在 xml 中可以清楚地看到
class="com.google.android.gms.maps.MapFragment"
它应该是
class="com.google.android.gms.maps.SupportMapFragment"
使您能够从代码启动类型 SupportMapFragment
我getMap()更改为getMapAsync(OnMapReadyCallback)并且它起作用了。
来源： 支持地图片段