Android Google 地图在片段中不起作用

Question

我在带有 viewpager 的选项卡片段中使用地图，但地图在我的应用程序中显示空指针异常。

我添加了权限<uses-permission android:name="android.permission.INTERNET" /> <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" /> 和 API 密钥正确

<meta-data
            android:name="com.google.android.geo.API_KEY"
            android:value="@string/google_maps_key" />

我的代码是：

import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;


import com.google.android.gms.maps.CameraUpdateFactory;
import com.google.android.gms.maps.GoogleMap;
import com.google.android.gms.maps.OnMapReadyCallback;
import com.google.android.gms.maps.SupportMapFragment;
import com.google.android.gms.maps.model.LatLng;
import com.google.android.gms.maps.model.MarkerOptions;

public class HomeTabFragment2 extends Fragment implements OnMapReadyCallback {

    private GoogleMap mMap;

    public HomeTabFragment2() {
        // Required empty public constructor
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View v=inflater.inflate(R.layout.home_tab_fragment_1, container, false);



        // Obtain the SupportMapFragment and get notified when the map is ready to be used.
        SupportMapFragment mapFragment = (SupportMapFragment) getFragmentManager()
                .findFragmentById(R.id.map);
        mapFragment.getMapAsync(this);
    return v;
    }

    @Override
    public void onMapReady(GoogleMap googleMap) {
        mMap = googleMap;

        // Add a marker in Sydney and move the camera
        LatLng sydney = new LatLng(9.2700, 76.7800);
        mMap.addMarker(new MarkerOptions().position(sydney).title("Marker in Pathanamthitta"));
        mMap.moveCamera(CameraUpdateFactory.newLatLng(sydney));
    }

}

我的 Logcat：

1-01 23:58:24.139 5673-5673/com.example.rubin E/AndroidRuntime: FATAL EXCEPTION: main
11-01 23:58:24.139 5673-5673/com.example.rubin E/AndroidRuntime: Process: com.example.rubin, PID: 5673
11-01 23:58:24.139 5673-5673/com.example.rubin E/AndroidRuntime: java.lang.NullPointerException: Attempt to invoke virtual method 'void com.google.android.gms.maps.SupportMapFragment.getMapAsync(com.google.android.gms.maps.OnMapReadyCallback)' on a null object reference
11-01 23:58:24.139 5673-5673/com.example.rubin E/AndroidRuntime:     at com.example.rubin.HomeTabFragment2.onCreateView(HomeTabFragment2.java:34)
11-01 23:58:24.139 5673-5673/com.example.rubin E/AndroidRuntime:     at android.support.v4.app.Fragment.performCreateView(Fragment.java:1965)
11-01 23:58:24.139 5673-5673/com.example.rubin E/AndroidRuntime:     at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1078)
11-01 23:58:24.139 5673-5673/com.example.rubin E/AndroidRuntime:     at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1259)
11-01 23:58:24.139 5673-5673/com.example.rubin E/AndroidRuntime:     at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:738)
11-01 23:58:24.139 5673-5673/com.example.rubin E/AndroidRuntime:     at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1624)
11-01 23:58:24.139 5673-5673/com.example.rubin E/AndroidRuntime:     at android.support.v4.app.FragmentManagerImpl.executePendingTransactions(FragmentManager.java:570)
11-01 23:58:24.139 5673-5673/com.example.rubin E/AndroidRuntime:     at android.support.v4.app.FragmentStatePagerAdapter.finishUpdate(FragmentStatePagerAdapter.java:163)
11-01 23:58:24.139 5673-5673/com.example.rubin E/AndroidRuntime:     at android.support.v4.view.ViewPager.populate(ViewPager.java:1106)
11-01 23:58:24.139 5673-5673/com.example.rubin E/AndroidRuntime:     at android.support.v4.view.ViewPager.populate(ViewPager.java:952)
11-01 23:58:24.139 5673-5673/com.example.rubin E/AndroidRuntime:     at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1474)
11-01 23:58:24.139 5673-5673/com.example.rubin E/AndroidRuntime:     at android.view.View.measure(View.java:17547)
11-01 23:58:24.139 5673-5673/com.example.rubin E/AndroidRuntime:     at android.widget.RelativeLayout.measureChildHorizontal(RelativeLayout.java:727)
11-01 23:58:24.139 5673-5673/com.example.rubin E/AndroidRuntime:     at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:463)
11-01 23:58:24.139 5673-5673/com.example.rubin E/AndroidRuntime:     at android.view.View.measure(View.java:17547)
11-01 23:58:24.139 5673-5673/com.example.rubin E/AndroidRuntime:     at android.widget.RelativeLayout.measureChildHorizontal(RelativeLayout.java:727)
11-01 23:58:24.139 5673-5673/com.example.rubin E/AndroidRuntime:     at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:463)
11-01 23:58:24.139 5673-5673/com.example.rubin E/AndroidRuntime:     at android.view.View.measure(View.java:17547)
11-01 23:58:24.139 5673-5673/com.example.rubin E/AndroidRuntime:     at android.widget.RelativeLayout.measureChildHorizontal(RelativeLayout.java:727)
11-01 23:58:24.139 5673-5673/com.example.rubin E/AndroidRuntime:     at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:463)
11-01 23:58:24.139 5673-5673/com.example.rubin E/AndroidRuntime:     at android.view.View.measure(View.java:17547)
11-01 23:58:24.139 5673-5673/com.example.rubin E/AndroidRuntime:     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5535)
11-01 23:58:24.139 5673-5673/com.example.rubin E/AndroidRuntime:     at android.support.design.widget.CoordinatorLayout.onMeasureChild(CoordinatorLayout.java:610)
11-01 23:58:24.139 5673-5673/com.example.rubin E/AndroidRuntime:     at android.support.design.widget.CoordinatorLayout.onMeasure(CoordinatorLayout.java:677)
11-01 23:58:24.139 5673-5673/com.example.rubin E/AndroidRuntime:     at android.view.View.measure(View.java:17547)
11-01 23:58:24.139 5673-5673/com.example.rubin E/AndroidRuntime:     at android.support.v4.widget.DrawerLayout.onMeasure(DrawerLayout.java:940)
11-01 23:58:24.139 5673-5673/com.example.rubin E/AndroidRuntime:     at android.view.View.measure(View.java:17547)
11-01 23:58:24.139 5673-5673/com.example.rubin E/AndroidRuntime:     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5535)
11-01 23:58:24.139 5673-5673/com.example.rubin E/AndroidRuntime:     at android.widget.FrameLayout.onMeasure(FrameLayout.java:436)
11-01 23:58:24.139 5673-5673/com.example.rubin E/AndroidRuntime:     at android.support.v7.internal.widget.ContentFrameLayout.onMeasure(ContentFrameLayout.java:135)
11-01 23:58:24.139 5673-5673/com.example.rubin E/AndroidRuntime:     at android.view.View.measure(View.java:17547)
11-01 23:58:24.139 5673-5673/com.example.rubin E/AndroidRuntime:     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5535)
11-01 23:58:24.139 5673-5673/com.example.rubin E/AndroidRuntime:     at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1436)
11-01 23:58:24.139 5673-5673/com.example.rubin E/AndroidRuntime:     at android.widget.LinearLayout.measureVertical(LinearLayout.java:722)
11-01 23:58:24.139 5673-5673/com.example.rubin E/AndroidRuntime:     at android.widget.LinearLayout.onMeasure(LinearLayout.java:613)
11-01 23:58:24.139 5673-5673/com.example.rubin E/AndroidRuntime:     at android.view.View.measure(View.java:17547)
11-01 23:58:24.139 5673-5673/com.example.rubin E/AndroidRuntime:     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5535)
11-01 23:58:24.139 5673-5673/com.example.rubin E/AndroidRuntime:     at android.widget.FrameLayout.onMeasure(FrameLayout.java:436)
11-01 23:58:24.139 5673-5673/com.example.rubin E/AndroidRuntime:     at android.view.View.measure(View.java:17547)
11-01 23:58:24.139 5673-5673/com.example.rubin E/AndroidRuntime:     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5535)
11-01 23:58:24.139 5673-5673/com.example.rubin E/AndroidRuntime:     at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1436)
11-01 23:58:24.139 5673-5673/com.example.rubin E/AndroidRuntime:     at android.widget.LinearLayout.measureVertical(LinearLayout.java:722)
11-01 23:58:24.139 5673-5673/com.example.rubin E/AndroidRuntime:     at android.widget.LinearLayout.onMeasure(LinearLayout.java:613)
11-01 23:58:24.139 5673-5673/com.example.rubin E/AndroidRuntime:     at android.view.View.measure(View.java:17547)
11-01 23:58:24.139 5673-5673/com.example.rubin E/AndroidRuntime:     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5535)
11-01 23:58:24.139 5673-5673/com.example.rubin E/AndroidRuntime:     at android.widget.FrameLayout.onMeasure(FrameLayout.java:436)
11-01 23:58:24.139 5673-5673/com.example.rubin E/AndroidRuntime:     at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2615)
11-01 23:58:24.139 5673-5673/com.example.rubin E/AndroidRuntime:     at android.view.View.measure(View.java:17547)
11-01 23:58:24.139 5673-5673/com.example.rubin E/AndroidRuntime:     at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2015)
11-01 23:58:24.139 5673-5673/com.example.rubin E/AndroidRuntime:     at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1173)
11-01 23:58:24.139 5673-5673/com.example.rubin E/AndroidRuntime:     at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1379)
11-01 23:58:24.139 5673-5673/com.example.rubin E/AndroidRuntime:     at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1061)
11-01 23:58:24.139 5673-5673/com.example.rubin E/AndroidRuntime:     at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5885)
11-01 23:58:24.139 5673-5673/com.example.rubin E/AndroidRuntime:    at android.view.Choreogra

当我将片段更改为片段活动时，它的效果非常好。 但我无法弄清楚它将如何在片段中工作。请帮我。

Answer 1

你的 logcat 抛出

AndroidRuntime: java.lang.NullPointerException: 尝试调用 虚方法'void com.google.android.gms.maps.SupportMapFragment.getMapAsync(com.google.android.gms.maps.OnMapReadyCallback)' 在空对象引用上

你可以试试getSupportFragmentManager或getChildFragmentManager

SupportMapFragment m = ((SupportMapFragment)
        .getSupportFragmentManager().findFragmentById(R.id.map));

或（完美解决方案）

 SupportMapFragment m = ((SupportMapFragment) getChildFragmentManager().findFragmentById(R.id.map));

public final FragmentManager getChildFragmentManager()

在 API 级别 17 中添加返回一个私有 FragmentManager 用于放置和 管理此 Fragment 内部的 Fragments。

更多详情可以查看

findFragmentById for SupportMapFragment returns null in Android Studio

Answer 2

尝试更改以下行：

 SupportMapFragment mapFragment = (SupportMapFragment) getFragmentManager()
            .findFragmentById(R.id.map);

到：

SupportMapFragment mapFragment = (SupportMapFragment)v.getFragmentManager()
            .findFragmentById(R.id.map);