我对谷歌地图有一个恼人的问题。我测试了它，地图显示正常。但现在我想设置“我的位置已启用”，以便地图自动从手机开始。现在，每次我运行应用程序时都会崩溃。我注意到，当我使用语法GoogleMap时，应用程序崩溃了。 我试图弄清楚这个问题并在网上环顾四周而没有结果。
这是我的Maps.java文件：
package test.test;
import com.google.android.gms.maps.GoogleMap;
import com.google.android.gms.maps.SupportMapFragment;
import android.location.Location;
import android.location.LocationListener;
import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
public class Maps extends FragmentActivity implements LocationListener{
GoogleMap googlemap;
@Override
public void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.maps);
SupportMapFragment mf = (SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.map);
googlemap = mf.getMap();
googlemap.setMyLocationEnabled(true);
googlemap.setMapType(GoogleMap.MAP_TYPE_NORMAL);
}
Maps.xml：
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<fragment
android:id="@+id/map"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:name="com.google.android.gms.maps.SupportMapFragment" />
</LinearLayout>
最后我的androidmanifest：
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="test.test"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="8"
android:targetSdkVersion="16" />
<permission
android:name="test.test.permission.MAPS_RECEIVE"
android:protectionLevel="signature" />
<uses-permission android:name="test.test.permission.MAPS_RECEIVE" />
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="com.google.android.providers.gsf.permission.READ_GSERVICES" />
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
<uses-feature
android:glEsVersion="0x00020000"
android:required="true" />
<application
....
<meta-data
android:name="com.google.android.maps.v2.API_KEY"
android:value="my key is here" />
</application>
以下是错误日志：
FATAL EXCEPTION: main
java.lang.RuntimeException: Unable to start activity ComponentInfo{test.test/test.test.Maps}: java.lang.NullPointerException
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
at android.app.ActivityThread.access$600(ActivityThread.java:141)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:5039)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
at test.test.Maps.onCreate(Maps.java:23)
at android.app.Activity.performCreate(Activity.java:5104)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
... 11 more
答案 0 :(得分：1)
该片段还没有准备就绪，或者设备上的Google Play服务出现了问题。
来自the docs（强调补充）：
<强>返回
GoogleMap。 如果片段的视图尚未准备好，则为空。如果片段生命周期尚未通过onCreateView(LayoutInflater, ViewGroup, Bundle)，则会发生这种情况。如果Google Play服务不可用，也会发生这种情况。如果Google Play服务随后可用且片段已经过onCreateView(LayoutInflater, ViewGroup, Bundle)，则再次调用此方法将初始化并返回GoogleMap。
'maps'演示应用程序显示了一个处理此问题的模式，尝试在创建时和恢复时设置地图：
/**
* This shows how to create a simple activity with a map and a marker on the map.
* <p>
* Notice how we deal with the possibility that the Google Play services APK is not
* installed/enabled/updated on a user's device.
*/
public class BasicMapActivity extends FragmentActivity {
/**
* Note that this may be null if the Google Play services APK is not available.
*/
private GoogleMap mMap;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.basic_demo);
setUpMapIfNeeded();
}
@Override
protected void onResume() {
super.onResume();
setUpMapIfNeeded();
}
/**
* Sets up the map if it is possible to do so (i.e., the Google Play services APK is correctly
* installed) and the map has not already been instantiated.. This will ensure that we only ever
* call {@link #setUpMap()} once when {@link #mMap} is not null.
* <p>
* If it isn't installed {@link SupportMapFragment} (and
* {@link com.google.android.gms.maps.MapView MapView}) will show a prompt for the user to
* install/update the Google Play services APK on their device.
* <p>
* A user can return to this FragmentActivity after following the prompt and correctly
* installing/updating/enabling the Google Play services. Since the FragmentActivity may not have been
* completely destroyed during this process (it is likely that it would only be stopped or
* paused), {@link #onCreate(Bundle)} may not be called again so we should call this method in
* {@link #onResume()} to guarantee that it will be called.
*/
private void setUpMapIfNeeded() {
// Do a null check to confirm that we have not already instantiated the map.
if (mMap == null) {
// Try to obtain the map from the SupportMapFragment.
mMap = ((SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.map))
.getMap();
// Check if we were successful in obtaining the map.
if (mMap != null) {
setUpMap();
}
}
}
/**
* This is where we can add markers or lines, add listeners or move the camera. In this case, we
* just add a marker near Africa.
* <p>
* This should only be called once and when we are sure that {@link #mMap} is not null.
*/
private void setUpMap() {
mMap.addMarker(new MarkerOptions().position(new LatLng(0, 0)).title("Marker"));
}
}