谷歌地图 - Android应用程序无法加载 - 空对象引用

Question

我目前正在尝试使用Google地图集成开发Android应用.目前我很难找到错误,因为代码来自谷歌网站本身,除了它是一个SupportMapFragment.如果您知道使用SupportMapFragment的实际教程也会很棒.实际,因为我认为.getMap()是折旧的.如果我应该发布整个代码,请告诉我(我是stackoverflow中的新手)

如果尝试使用此代码:

import android.content.Context;
import android.location.Criteria;
import android.location.Location;
import android.location.LocationManager;
import android.os.Bundle;
import android.support.v4.app.FragmentManager;
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 MapsFragment extends SupportMapFragment implements OnMapReadyCallback {

其中一个函数是:

    @Override
     public void onResume() {
    FragmentManager fragmentManager = getActivity().getSupportFragmentManager();
    SupportMapFragment supportMapFragment = (SupportMapFragment) fragmentManager
            .findFragmentById(R.id.map);

    supportMapFragment.getMapAsync(this);
}

错误是: 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

Fragment xml看起来像这样:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/root"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <fragment
        android:id="@+id/map"
        android:name="com.google.android.gms.maps.SupportMapFragment"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>
</RelativeLayout>

Answer 1

看起来你需要使用Fragment's SupportFragmentManager 查看此findFragmentById的答案,支持SupportMapFragment在Android Studio中返回null

Answer 2

地图片段正在Lollipop上运行,您可能需要这样做.

SupportMapFragment supportMapFragment;
if (Build.VERSION.SDK_INT < 21) {
    supportMapFragment = (SupportMapFragment) getActivity()
        .getSupportFragmentManager().findFragmentById(R.id.map);
} else {
    supportMapFragment = (SupportMapFragment) getActivity()
        .getChildFragmentManager().findFragmentById(R.id.map);
}
supportMapFragment.getMapAsync(this);