最近，我从迁移的Eclipse项目到Android工作室。一切设置和工作正常，除了我的一个片段，它使用一个SupportMapFragment。下面findFragmentById（在Eclipse构建时，它的工作），现在返回null :(

Recently I migrated a project from Eclipse to Android Studio. Everything is setup and working fine except for my one fragment which uses a SupportMapFragment. The below findFragmentById (which worked when building in Eclipse) is now returning null :(

public void onActivityCreated(Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);
    SupportMapFragment m = ((SupportMapFragment) getActivity().getSupportFragmentManager().findFragmentById(R.id.safety_map));

XML的片段...

snippet of xml...

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:map="http://schemas.android.com/apk/res-auto"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
     android:orientation="vertical" >

     <fragment
         android:id="@+id/safety_map"
         android:layout_width="fill_parent"
         android:layout_height="fill_parent"
         android:layout_marginBottom="40dp"
         map:cameraTargetLat="@string/livesafe_latitude"
         map:cameraTargetLng="@string/livesafe_longitude"
         map:uiZoomControls="false"
         class="com.google.android.gms.maps.SupportMapFragment"/>

下面是我的build.gradle我的依赖关系：

Here are my dependencies in my build.gradle:

 dependencies {
    //google analytics
    compile 'com.google.apis:google-api-services-analytics:v3-rev103-1.19.0'
    //support library for api 10
    compile 'com.android.support:support-v4:21.0.0'
    //google play services
    compile 'com.google.android.gms:play-services:6.1.11'
    compile project(':facebook')
    compile files('libs/android-support-multidex.jar')
    compile files('libs/aws-android-sdk-1.6.0-debug.jar')
    compile files('libs/FlurryAnalytics_3.3.2.jar')
 }

我并没有改变任何code在XML文件或$ P $在Eclipse pviously工作的片段类。

I haven't changed any code in the xml file or the Fragment class that previously worked in Eclipse.

推荐答案

由你改写的事实来看 Fragment.onActivityCreated（），我认为你的包含地图片段布局是你的片段的布局。在这种情况下， SupportMapFragment 是孩子的您的主机片段片段。当您试图找回它，你使用的活动 FragmentManager 。您应该改用你的片段的 FragmentManager ：

Judging by the fact that you're overriding Fragment.onActivityCreated(), I take it that your layout containing the map fragment is the layout for your Fragment. In that case, the SupportMapFragment is a child fragment of your hosting Fragment. When you attempt to retrieve it, you're using the Activity FragmentManager. You should instead use your Fragment's FragmentManager:

例如，这样的：

SupportMapFragment m = ((SupportMapFragment) getActivity()
        .getSupportFragmentManager().findFragmentById(R.id.safety_map));

变成了：

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