mapFragment.getMapAsync（this） - NullPointerException [英] mapFragment.getMapAsync(this) - NullPointerException

问题描述

我使用 com.google.android.gms：play-services-maps：7.5.0 版Google地图服务。当试图调用下面的代码时，我得到 java.lang.NullPointerException：尝试调用虚方法void com.google.android.gms.maps.SupportMapFragment.getMapAsync（com.google.android.gms.maps .OnRide
public View onCreateView 。

I am using com.google.android.gms:play-services-maps:7.5.0 version of Google Maps services. When trying to call the below I get 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.

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    SupportMapFragment mapFragment = (SupportMapFragment) getActivity().getSupportFragmentManager()
            .findFragmentById(R.id.map);
    mapFragment.getMapAsync(this); //error

    return inflater.inflate(R.layout.fragment_example_map, container, false);
}

fragment_example_map.xml文件：

fragment_example_map.xml file:

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="app.ExampleMap">

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

推荐答案

您试图在存在片段之前找到片段。您指出具有该片段的布局是 fragment_example_map.xml 。但是，您正在尝试在膨胀该布局文件之前查找地图片段。这是行不通的。

You are attempting to find a fragment before it exists. You indicate that the layout that has the fragment is fragment_example_map.xml. However, you are trying to find the map fragment before you inflate that layout file. This will not work.

除此之外，您似乎试图从另一个片段中获取地图片段，该片段的 onCreateView（ ）方法。我不知道为什么你要在这里嵌入片段，因为它看起来会让你的代码更复杂，更脆弱，没有明显的好处。

Beyond that, you appear to be trying to get at the map fragment from inside another fragment, in that fragment's onCreateView() method. I do not know why you are nesting fragments here, as it seems like it will make your code more complex and more fragile for no obvious benefit.

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