android – java.lang.RuntimeException无法实例化服务：java.lang.NullPointerException

概述我试图创建一个启动服务的活动(在新线程中).它包含一个带有两个editText和一个名为Send的按钮的布局.关键是当我执行MainActivity时,它会抛出： 06-15 22:32:13.312: E/AndroidRuntime(643): FATAL EXCEPTION: main06-15 22:32:13.312: E/AndroidRuntime(643): java.lang. 我试图创建一个启动服务的活动(在新线程中).它包含一个带有两个editText和一个名为Send的按钮的布局.关键是当我执行MainActivity时,它会抛出：

06-15 22:32:13.312: E/AndroIDRuntime(643): FATAL EXCEPTION: main06-15 22:32:13.312: E/AndroIDRuntime(643): java.lang.RuntimeException: Unable to instantiate service hikoki.services.NotificationsService: java.lang.NullPointerException06-15 22:32:13.312: E/AndroIDRuntime(643):  at androID.app.ActivityThread.handleCreateService(ActivityThread.java:2237)06-15 22:32:13.312: E/AndroIDRuntime(643):  at androID.app.ActivityThread.access00(ActivityThread.java:123)06-15 22:32:13.312: E/AndroIDRuntime(643):  at androID.app.ActivityThread$H.handleMessage(ActivityThread.java:1201)06-15 22:32:13.312: E/AndroIDRuntime(643):  at androID.os.Handler.dispatchMessage(Handler.java:99)06-15 22:32:13.312: E/AndroIDRuntime(643):  at androID.os.Looper.loop(Looper.java:137)06-15 22:32:13.312: E/AndroIDRuntime(643):  at androID.app.ActivityThread.main(ActivityThread.java:4424)06-15 22:32:13.312: E/AndroIDRuntime(643):  at java.lang.reflect.Method.invokeNative(Native Method)06-15 22:32:13.312: E/AndroIDRuntime(643):  at java.lang.reflect.Method.invoke(Method.java:511)06-15 22:32:13.312: E/AndroIDRuntime(643):  at com.androID.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)06-15 22:32:13.312: E/AndroIDRuntime(643):  at com.androID.internal.os.ZygoteInit.main(ZygoteInit.java:551)06-15 22:32:13.312: E/AndroIDRuntime(643):  at dalvik.system.NativeStart.main(Native Method)06-15 22:32:13.312: E/AndroIDRuntime(643): Caused by: java.lang.NullPointerException06-15 22:32:13.312: E/AndroIDRuntime(643):  at androID.content.Contextwrapper.getSystemService(Contextwrapper.java:386)06-15 22:32:13.312: E/AndroIDRuntime(643):  at hikoki.services.NotificationsService.<init>(NotificationsService.java:35)06-15 22:32:13.312: E/AndroIDRuntime(643):  at java.lang.class.newInstanceImpl(Native Method)06-15 22:32:13.312: E/AndroIDRuntime(643):  at java.lang.class.newInstance(Class.java:1319)06-15 22:32:13.312: E/AndroIDRuntime(643):  at androID.app.ActivityThread.handleCreateService(ActivityThread.java:2234)06-15 22:32:13.312: E/AndroIDRuntime(643):  ... 10 more

主要活动的代码是这样的：

public class MainActivity extends Activity {    private String TAG = getClass().getSimplename();    @OverrIDe    protected voID onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentVIEw(R.layout.activity_main);        Thread t= new Thread(){            public voID run(){                Intent intent=new Intent(getContext(),NotificationsService.class);                //Intent intent=new Intent("hikoki.services.NotificationsService");                Log.d(TAG,"sending notificationsService");                startService(intent);            }        };        t.start();    }    protected Context getContext() {            return this;    }}

NotificationsService代码在这里：

public class NotificationsService extends IntentService{    private static  int TIME_INTERVAL_MIliS=5000;    private static final int REFRESH=10;    private  notificationmanager noteManager;    private static List<FlightStatusNote> flights= new ArrayList<FlightStatusNote>();    public NotificationsService(){        super("NotificationsService");         noteManager= notificationmanager)getSystemService(Context.NOTIFICATION_SERVICE)    }}

AndroIDManifest是这样的：

<?xml version="1.0" enCoding="utf-8"?><manifest xmlns:androID="http://schemas.androID.com/apk/res/androID"    package="hikoki.services"    androID:versionCode="1"    androID:versionname="1.0" ><uses-sdk    androID:minSdkVersion="15"    androID:targetSdkVersion="17" /><uses-permission androID:name="androID.permission.INTERNET" /><uses-permission androID:name="androID.permission.ACCESS_NETWORK_STATE" /><application    androID:allowBackup="true"    androID:icon="@drawable/ic_launcher"    androID:label="@string/app_name"    androID:theme="@style/Apptheme" >    <activity        androID:name="hikoki.services.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>    <service androID:name=".FlightStatusService"></service>    <service androID:enabled="true" androID:name=".NotificationsService"></service></application></manifest>

解决方法 您不能从初始化程序(如您原来的那样)或构造函数(就像您现在一样)调用getSystemService().请覆盖onCreate(),并在那里调用getSystemService().

基本上,直到调用onCreate()(或者更准确地说,直到你从onCreate()调用super.onCreate()之后),服务上的继承方法还没有准备好供您使用.

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