mapFragment.getMapAsync 处的 NullPointerException

在解决了与我的标题相关的问题后，我找不到问题的解决方案。我有一个NullPointerException at mapFragment.getMapAsync。下面是我的MapActivity code.

package com.example.jerofad.mylocation;
import android.app.FragmentManager;
import android.support.v4.app.FragmentActivity;
import android.os.Bundle;
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 MapsActivity extends FragmentActivity implements  OnMapReadyCallback {
    private GoogleMap mMap;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_maps);
        // Obtain the SupportMapFragment and get notified when the map is ready to be used.
        SupportMapFragment mapFragment = (SupportMapFragment) this.getSupportFragmentManager()
                .findFragmentById(R.id.map);
        mapFragment.getMapAsync(this);
    }

    @Override
    public void onMapReady(GoogleMap googleMap) {
        mMap = googleMap;
        // Add a marker in Sydney and move the camera
        LatLng sydney = new LatLng(-34, 151);
        mMap.addMarker(new MarkerOptions().position(sydney).title("Marker in Sydney"));
        mMap.moveCamera(CameraUpdateFactory.newLatLng(sydney));
        mMap.getUiSettings().setZoomControlsEnabled(true);
    }
}

我在用google play service 8.4.0。我的 Android 清单如下。

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.jerofad.mylocation">

<!--
     The ACCESS_COARSE/FINE_LOCATION permissions are not required to use
     Google Maps Android API v2, but you must specify either coarse or fine
     location permissions for the 'MyLocation' functionality. 
-->
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION"/>
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="com.google.android.providers.gsf.permission.READ_GSERVICES" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"
    android:maxSdkVersion="22"/>
<permission
    android:name="com.example.jerofad.mylocation.permission.MAPS_RECEIVE"
    android:protectionLevel="signature" />
<uses-permission android:name="com.example.jerofad.mylocation.permission.MAPS_RECEIVE" />
<uses-permission
    android:name="android.permission.READ_EXTERNAL_STORAGE"
    android:maxSdkVersion="22" />
<uses-feature
    android:glEsVersion="0x00020000"
    android:required="true" />

<application
    android:allowBackup="true"
    android:icon="@drawable/mylocation"
    android:label="@string/app_name"
    android:supportsRtl="true"
    android:theme="@style/AppTheme">        
    <meta-data
        android:name="com.google.android.geo.API_KEY"
        android:value="@string/google_maps_key" />
    <meta-data
        android:name="com.google.android.gms.version"
        android:value="@integer/google_play_services_version" />

    <activity
        android:name=".MapsActivity"
        android:label="@string/title_activity_maps">

    </activity>
    <activity
        android:name=".LauncherActivity"
        android:label="@string/title_activity_launcher"
        android:theme="@style/AppTheme.NoActionBar">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
</application>

我该如何修复该错误mapFragment.getMapAsync(this)。提前致谢。这是崩溃日志。

04-25 11:11:49.079 31448-31448/com.example.jerofad.mylocation 
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.jerofad.mylocation, PID: 31448
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.jerofad.mylocation/com.example.jerofad.mylocation.MapsActivity}: java.lang.NullPointerException
   at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2338)
   at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2390)
   at android.app.ActivityThread.access$800(ActivityThread.java:151)
   at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1321)
   at android.os.Handler.dispatchMessage(Handler.java:110)
   at android.os.Looper.loop(Looper.java:193)
   at android.app.ActivityThread.main(ActivityThread.java:5299)
   at java.lang.reflect.Method.invokeNative(Native Method)
   at java.lang.reflect.Method.invoke(Method.java:515)
   at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:825)
   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:641)
   at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
   at com.example.jerofad.mylocation.MapsActivity.onCreate(MapsActivity.java:24)
   at android.app.Activity.performCreate(Activity.java:5423)
   at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1088)
   at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2302)
   at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2390) 
   at android.app.ActivityThread.access$800(ActivityThread.java:151) 
   at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1321) 
   at android.os.Handler.dispatchMessage(Handler.java:110) 
   at android.os.Looper.loop(Looper.java:193) 
   at android.app.ActivityThread.main(ActivityThread.java:5299) 
   at java.lang.reflect.Method.invokeNative(Native Method) 
   at java.lang.reflect.Method.invoke(Method.java:515) 
   at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:825) 
   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:641) 
   at dalvik.system.NativeStart.main(Native Method)

这是activity_maps.xml。

<?xml version="1.0" encoding="utf-8"?>
<fragment xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/map"
    class ="com.google.android.gms.maps.MapFragment"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:name="com.example.jerofad.mylocation.MapsActivity" />

请尝试这个，

暂时删除/注释 SupportMapfragment 行并 尝试这个，

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