Question

我尝试使用该服务。现在，服务正在运行，...它在任务栏上添加了通知。单击任务栏时，此通知应调用MyActivity.class。但它给出了错误。错误发生后请查看代码错误：

... W / dalvikvm（2384）：threadid = 1：   线程退出与未捕获的异常   （group = 0x4001d7e0）E / AndroidRuntime（   2384）：致命的例外：主要   E / AndroidRuntime（2384）：   java.lang.RuntimeException：无法   开始活动   ComponentInfo {activity.change / activity.change.MyActivity}：   显示java.lang.NullPointerException

...

代码：

public void addNotification()
    {

    String ns = Context.NOTIFICATION_SERVICE;
    NotificationManager mNotificationManager = (NotificationManager) getSystemService(ns);


    int icon = R.drawable.icon; //.drawable.notification_icon;
    CharSequence tickerText = "Hello";
    long when = System.currentTimeMillis();

    Notification notification = new Notification(icon, tickerText, when);
    //notification.defaults=Notification.FLAG_ONLY_ALERT_ONCE+Notification.FLAG_AUTO_CANCEL;
    //notification.defaults=notification.flags
    notification.flags|=Notification.FLAG_AUTO_CANCEL;


    Context context = getApplicationContext();
    CharSequence contentTitle = "UHS Next";
    CharSequence contentText = "Hello World!";
    Intent notificationIntent = new Intent(this, Class_B.class); // I want to call class_B, not A. A has called "this" Service though.
    PendingIntent contentIntent = PendingIntent.getActivity(this, 0, notificationIntent, 0);

    /*
     * PendingIntent mAlarmSender = PendingIntent.getService(AlarmService.this, 0, new Intent(AlarmService.this, AlarmService_Service.class), 0);
     * */

    notification.setLatestEventInfo(context, contentTitle, contentText, contentIntent);


    //private static final int HELLO_ID = 1;  << moved to the global declaration 
    mNotificationManager.notify(HELLO_ID, notification);

}

// Part of error log：

I/WindowManager(   90): Ignoring HOME; event canceled.
D/MyService( 5206): Received message!!
D/dalvikvm(   90): GC_EXTERNAL_ALLOC freed 22585 objects / 1120256 bytes in 79ms
D/dalvikvm( 5206): GC_EXPLICIT freed 3702 objects / 224088 bytes in 77ms
I/ActivityManager(   90): Starting activity: Intent { act=android.intent.action.MAIN 
    cat=[android.intent.category.HOME] flg=0x10200000 
    cmp=com.android.launcher/com.android.launcher2.Launcher }
D/dalvikvm(  172): GC_EXPLICIT freed 36 objects / 1944 bytes in 91ms
I/ActivityManager(   90): Starting activity: 
    Intent { cmp=activity.change/.W2PExampleAndNew bnds=[0,387][480,483] }
W/ActivityManager(   90): startActivity called from non-Activity context; 
    forcing Intent.FLAG_ACTIVITY_NEW_TASK for: 
    Intent { cmp=activity.change/.W2PExampleAndNew bnds=[0,387][480,483] }
V/RenderScript_jni(  171): surfaceDestroyed
D/AndroidRuntime( 5206): Shutting down VM
W/dalvikvm( 5206): threadid=1: thread exiting with uncaught exception (group=0x4001d7e0)
E/AndroidRuntime( 5206): FATAL EXCEPTION: main
E/AndroidRuntime( 5206): java.lang.RuntimeException: Unable to start activity ComponentInfo
    {activity.change/activity.change.W2PExampleAndNew}: java.lang.NullPointerException
E/AndroidRuntime( 5206):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663)
E/AndroidRuntime( 5206):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
E/AndroidRuntime( 5206):    at android.app.ActivityThread.access$2300(ActivityThread.java:125)
E/AndroidRuntime( 5206):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
E/AndroidRuntime( 5206):    at android.os.Handler.dispatchMessage(Handler.java:99)
E/AndroidRuntime( 5206):    at android.os.Looper.loop(Looper.java:123)
E/AndroidRuntime( 5206):    at android.app.ActivityThread.main(ActivityThread.java:4627)
E/AndroidRuntime( 5206):    at java.lang.reflect.Method.invokeNative(Native Method)
E/AndroidRuntime( 5206):    at java.lang.reflect.Method.invoke(Method.java:521)
E/AndroidRuntime( 5206):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:858)
E/AndroidRuntime( 5206):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
E/AndroidRuntime( 5206):    at dalvik.system.NativeStart.main(Native Method)
E/AndroidRuntime( 5206): Caused by: java.lang.NullPointerException
E/AndroidRuntime( 5206):    at activity.change.W2PExampleAndNew.onCreate(W2PExampleAndNew.java:63)
E/AndroidRuntime( 5206):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
E/AndroidRuntime( 5206):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627)
E/AndroidRuntime( 5206):    ... 11 more
W/ActivityManager(   90):   Force finishing activity activity.change/.W2PExampleAndNew
W/ActivityManager(   90): Activity pause timeout for HistoryRecord{44cafc20 activity.change/.W2PExampleAndNew}
V/RenderScript_jni(  171): surfaceCreated
V/RenderScript_jni(  171): surfaceChanged
D/WifiService(   90): acquireWifiLockLocked: WifiLock{NetworkLocationProvider type=2 binder=android.os.Binder@44d28380}
D/LocationMasfClient(   90): getNetworkLocation(): Returning cache location with accuracy 70.0
D/dalvikvm(  465): GC_FOR_MALLOC freed 6095 objects / 509112 bytes in 38ms
W/ActivityManager(   90): Activity destroy timeout for HistoryRecord{44cafc20 activity.change/.W2PExampleAndNew}
D/WifiService(   90): releaseWifiLockLocked: WifiLock{NetworkLocationProvider type=2 binder=android.os.Binder@44d28380}
I/Process ( 5206): Sending signal. PID: 5206 SIG: 9
W/InputManagerService(   90): Window already focused, ignoring focus gain of: 
    com.android.internal.view.IInputMethodClient$Stub$Proxy@44d18b80
I/ActivityManager(   90): Process activity.change (pid 5206) has died.
W/ActivityManager(   90): Scheduling restart of crashed service activity.change/.W2PAndroidService in 5000ms
I/ActivityManager(   90): Start proc activity.change for service activity.change/.W2PAndroidService: pid=5258 uid=10073 gids={1006, 1015, 3003}
D/MyService( 5258): onCreate

Answer 1

确保您在MyActivity中声明了androidManifest.xml个活动。

<强>更新
如果MyActivity是您的主要启动器活动（启动服务），并且您希望从通知中启动Activity_B，则必须在androidManifest.xml中声明这两项活动（请注意launchMode，如果你设置了！）：

<activity android:name="MyActivity" 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="Activity_B" />

此外，指定通知时的Intent应如下所示：

Intent notificationIntent = new Intent(this, Activity_B.class);

<强> DEPR。
您还可以在创建getApplicationContext()时尝试设置this而不是PendingIntent：

PendingIntent contentIntent = PendingIntent.getActivity(
    getApplicationContext(), 0, notificationIntent, 0);

服务如何调用活动？官方的例子不起作用！

1 个答案: