我在这个网站上看到过很多其他类似的问题，并试图更改我的代码以匹配，但它从未解决问题。
我的应用加载了一些按钮来推送。其中一个打开一个类文件，在屏幕上打开一个地图。该类的代码是：
public class FuelMap extends Activity
{
private final LatLng locBurb = new LatLng(49.27645, -122.917587);
private final LatLng locSura = new LatLng(49.187500, -122.849000);
private GoogleMap map;
@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_fuel_map);
//map = ((MapFragment) getFragmentManager().findFragmentById(R.id.map )).getMap();
// Show the Up button in the action bar.
setupActionBar();
}
/**
* Set up the {@link android.app.ActionBar}, if the API is available.
*/
@TargetApi(Build.VERSION_CODES.HONEYCOMB)
private void setupActionBar()
{
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB)
{
getActionBar().setDisplayHomeAsUpEnabled(true);
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu)
{
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.fuel_map, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item)
{
switch (item.getItemId()) {
case android.R.id.home:
// This ID represents the Home or Up button. In the case of this
// activity, the Up button is shown. Use NavUtils to allow users
// to navigate up one level in the application structure. For
// more details, see the Navigation pattern on Android Design:
//
// http://developer.android.com/design/patterns/navigation.html#up-vs-back
//
NavUtils.navigateUpFromSameTask(this);
return true;
}
return super.onOptionsItemSelected(item);
}
public void OnClickCity(View C)
{
//CameraUpdate update = CameraUpdateFactory.newLatLng(locBurb);
//map.animateCamera(update);
}
public void OnClickBuraby(View B)
{
}
public void OnClickSurray(View S)
{
}
}
但如果我取消注释该行：//map = ((MapFragment) getFragmentManager().findFragmentById(R.id.map )).getMap();
然后应用程序将运行，直到我尝试将其切换到地图。
就像我在开头所说的那样，我已经搜索并经常在这个网站上找到与我的问题相关的答案，但没有一个给我任何结果。我不相信这个问题是由于我可以加载地图而安装Android应用程序所需的谷歌地图的错误。所以任何人都知道可能是什么原因？
-LogCat info
04-16 17:16:10.747: D/AndroidRuntime(11672): Shutting down VM
04-16 17:16:10.747: W/dalvikvm(11672): threadid=1: thread exiting with uncaught exception (group=0x41543300)
04-16 17:16:10.752: E/AndroidRuntime(11672): FATAL EXCEPTION: main
04-16 17:16:10.752: E/AndroidRuntime(11672): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.testing.fuelapptesting/com.testing.fuelapptesting.FuelMap}: java.lang.NullPointerException
04-16 17:16:10.752: E/AndroidRuntime(11672): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2059)
04-16 17:16:10.752: E/AndroidRuntime(11672): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084)
04-16 17:16:10.752: E/AndroidRuntime(11672): at android.app.ActivityThread.access$600(ActivityThread.java:130)
04-16 17:16:10.752: E/AndroidRuntime(11672): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195)
04-16 17:16:10.752: E/AndroidRuntime(11672): at android.os.Handler.dispatchMessage(Handler.java:99)
04-16 17:16:10.752: E/AndroidRuntime(11672): at android.os.Looper.loop(Looper.java:137)
04-16 17:16:10.752: E/AndroidRuntime(11672): at android.app.ActivityThread.main(ActivityThread.java:4745)
04-16 17:16:10.752: E/AndroidRuntime(11672): at java.lang.reflect.Method.invokeNative(Native Method)
04-16 17:16:10.752: E/AndroidRuntime(11672): at java.lang.reflect.Method.invoke(Method.java:511)
04-16 17:16:10.752: E/AndroidRuntime(11672): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
04-16 17:16:10.752: E/AndroidRuntime(11672): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
04-16 17:16:10.752: E/AndroidRuntime(11672): at dalvik.system.NativeStart.main(Native Method)
04-16 17:16:10.752: E/AndroidRuntime(11672): Caused by: java.lang.NullPointerException
04-16 17:16:10.752: E/AndroidRuntime(11672): at com.testing.fuelapptesting.FuelMap.onCreate(FuelMap.java:31)
04-16 17:16:10.752: E/AndroidRuntime(11672): at android.app.Activity.performCreate(Activity.java:5008)
04-16 17:16:10.752: E/AndroidRuntime(11672): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1079)
04-16 17:16:10.752: E/AndroidRuntime(11672): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2023)
04-16 17:16:10.752: E/AndroidRuntime(11672): ... 11 more
04-16 17:16:13.580: I/Process(11672): Sending signal. PID: 11672 SIG: 9
- activity_Fuel_Map布局
<RelativeLayout 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"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context=".MainActivity" >
<fragment
android:id="@+id/maps"
android:name="com.google.android.gms.maps.MapFragment"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_below="@+id/busCity" />
<TextView
android:id="@+id/map"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/maps"
android:layout_alignParentTop="true"
android:layout_marginLeft="33dp"
android:ems="10"
android:text="Map" >
<requestFocus />
</TextView>
<Button
android:id="@+id/buttBuraby"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@+id/map"
android:layout_toRightOf="@+id/buttCity"
android:onClick="OnClickBuraby"
android:text="Buraby" />
<Button
android:id="@+id/buttSurray"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@+id/map"
android:layout_toRightOf="@+id/buttBuraby"
android:onClick="OnClickSurray"
android:text="Surray" />
<Button
android:id="@+id/buttCity"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignBaseline="@+id/buttBuraby"
android:layout_alignBottom="@+id/buttBuraby"
android:layout_alignLeft="@+id/maps"
android:onClick="OnClickCity"
android:text="City" />
</RelativeLayout>
- 清单文件
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.testing.fuelapptesting"
android:versionCode="1"
android:versionName="1.0" >
<uses-permission android:name="android.permission.INTERNET"/>
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
<uses-permission android:name="com.google.android.providers.gsf.permission.READ_GSERVICES"/>
<!-- The following two permissions are not required to use
Google Maps Android API v2, but are recommended. -->
<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"/>
<uses-sdk
android:minSdkVersion="11"
android:targetSdkVersion="18" />
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name="com.testing.fuelapptesting.MainActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name="com.testing.fuelapptesting.News"
android:label="@string/title_activity_news"
android:parentActivityName="com.testing.fuelapptesting.MainActivity" >
<meta-data
android:name="android.support.PARENT_ACTIVITY"
android:value="com.testing.fuelapptesting.MainActivity" />
</activity>
<activity
android:name="com.testing.fuelapptesting.Messages"
android:label="@string/title_activity_messages" >
</activity>
<activity
android:name="com.testing.fuelapptesting.FuelMap"
android:label="@string/title_activity_fuel_map"
android:parentActivityName="com.testing.fuelapptesting.MainActivity" >
<meta-data
android:name="android.support.PARENT_ACTIVITY"
android:value="com.testing.fuelapptesting.MainActivity" />
</activity>
<activity
android:name="com.testing.fuelapptesting.Scanner"
android:label="@string/title_activity_scanner"
android:parentActivityName="com.testing.fuelapptesting.MainActivity" >
<meta-data
android:name="android.support.PARENT_ACTIVITY"
android:value="com.testing.fuelapptesting.MainActivity" />
</activity>
<meta-data android:name="com.google.android.gms.version"
android:value="@integer/google_play_services_version" />
<meta-data
android:name="com.google.android.maps.v2.API_KEY"
android:value="AIzaSyC8hlQR9rdDGYMEXQCqpMD2PxzQRrpprPg"/>
</application>
</manifest>
答案 0 :(得分：1)
试试此链接：in google maps V2 ... fragment.getMap() returns null
在onCreateView（）中，您尝试加载的地图片段尚未实例化。 希望这能解决问题。您可能需要在地图加载后发布到处理程序..本质上是一个回调。
答案 1 :(得分：0)
我似乎在使用Maps V2，因此您在xml中的声明不正确。
中提到的片段不是FragmentLayout <?xml version="1.0" encoding="utf-8"?>
<fragment xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/map"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:name="com.google.android.gms.maps.MapFragment"/>
答案 2 :(得分：0)
非常感谢所有帮助人员。我最终弄明白了这个问题。这是字母＆＃39;。
在这一行：//map = ((MapFragment) getFragmentManager().findFragmentById(R.id.map )).getMap();我正在拉动名为map的对象。如果查看我的activity_Fuel_Map布局，则地图对象是TextView。
` <TextView
android:id="@+id/map"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/maps"
android:layout_alignParentTop="true"
android:layout_marginLeft="33dp"
android:ems="10"
android:text="Map" >`
所以我不得不将（R.id.map）更改为（R.id.maps）来拉取我的地图片段。
<fragment
android:id="@+id/maps"
android:name="com.google.android.gms.maps.MapFragment"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_below="@+id/busCity" />
再次感谢所有帮助人员。